Thermal performance and comfort conditions analysis of a vernacular Palafitic timber building in Portuguese Coastline context
Abstract
The palafitic timber constructions of the central Portuguese coastline are an example of the adaptation to site-specific conditions (climate and sand landscape morphodynamics) using the available endogenous resources. Thus, in a context of environmental awareness and climate change, it is relevant to understand their features/strategies and how they perform. This work analyses the energy performance and thermal condition evaluation of a vernacular timber building–palheiro–from Praia de Mira, through in situ measurements, subjective analysis and energy simulation provided by DesignBuilder/EnergyPlus. The results show a good or satisfactory thermal performance during most of the seasons by passive means only. Despite, it was not possible to guarantee thermal comfort conditions for the occupants during winter. In the energy performance analysis, five scenarios, with different external walls, were compared. In the two scenarios that satisfy the maximum U-value for the climate zone, the current conventional building had a slightly better performance on heating and cooling (less 1.1 and 1.4 kWh/m2, respectively) than the timber building. However, the difference between the two construction solutions is not substantial in the annual energy demand (2.5 kWh/m2, 7.3%), indicating that timber structures are suitable in this mild climate area.
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sustainability Article Thermal Performance and Comfort Conditions Analysis of a Vernacular Palafitic Timber Building in Portuguese Coastline Context Jorge Fernandes 1,* , Ricardo Mateus 1, Helena Gervásio 2, Sandra Monteiro Silva 1, Jorge Branco 1and Manuela Almeida 1 1Institute for Sustainability and Innovation in Structural Engineering (ISISE), Department of Civil Engineering, University of Minho, 4800-058 Guimarães, Portugal; [email protected] (R.M.); [email protected] (S.M.S.); [email protected] (J.B.); [email protected] (M.A.) 2Institute for Sustainability and Innovation in Structural Engineering (ISISE), Faculdade de Ciências e Tecnologia, University of Coimbra, 3030-788 Coimbra, Portugal; [email protected] *Correspondence: [email protected] Received: 30 October 2020; Accepted: 11 December 2020; Published: 15 December 2020 Abstract: The palafitic timber constructions of the central Portuguese coastline are an example of the adaptation to site-specific conditions (climate and sand landscape morphodynamics) using the available endogenous resources. Thus, in a context of environmental awareness and climate change, it is relevant to understand their features/strategies and how they perform. This work analyses the energy performance and thermal condition evaluation of a vernacular timber building–palheiro–from Praia de Mira, through in situ measurements, subjective analysis and energy simulation provided by DesignBuilder/EnergyPlus. The results show a good or satisfactory thermal performance during most of the seasons by passive means only. Despite, it was not possible to guarantee thermal comfort conditions for the occupants during winter. In the energy performance analysis, five scenarios, with different external walls, were compared. In the two scenarios that satisfy the maximum U-value for the climate zone, the current conventional building had a slightly better performance on heating and cooling (less 1.1 and 1.4 kWh/m 2 , respectively) than the timber building. However, the difference between the two construction solutions is not substantial in the annual energy demand (2.5 kWh/m 2 , 7.3%), indicating that timber structures are suitable in this mild climate area. Keywords: Portuguese vernacular buildings; timber building; thermal comfort; energy and microclimatic performance; energy building simulation 1. Introduction The rise of environmental awareness has brought to light several problems regarding the environmental impacts and energy efficiency of the building sector. Thus, pulled by an ecological demand from society, the sector is slowly changing to the sustainability paradigm. As one of the largest economic sectors, buildings are a key sector to implement holistic measures aiming performance levels beyond “sustainability”, as the concept of the regenerative and restorative building. To force this change, representative institutions must define long-term goals and the directives to achieve them. For example, the European Union has set the goals of achieving net-zero greenhouse gas emissions and fully decarbonize the building stock by 2050, facilitating the cost-effective transformation of existing buildings into nearly zero-energy buildings (nZEB) [ 1 , 2 ]. Nevertheless, the problems of the building sector do not resume to carbon emissions and there is also the need to improve the overall Sustainability 2020,12, 10484; doi:10.3390/su122410484 www.mdpi.com/journal/sustainability
Sustainability 2020,12, 10484 2 of 33 environmental performance by adopting materials with lower environmental impacts and those that are more compatible, for instance, with the local environmental/climate context [3]. Nowadays, the advantages of timber construction in the framework of sustainable construction lie in the fact that it is a renewable, reusable, recyclable and biodegradable resource and, as such, fit into a cradle-to-cradle life cycle. Due to this fact, the use of timber in construction has been increasing, particularly throughout Europe [ 4 , 5 ]. When compared with conventional materials, timber allows reducing the overall time for construction [ 4 ]. It can also result in a reduction of greenhouse gas emissions of around 25%, mainly related to the replacement of the reinforced concrete structure, as shown by [ 6 ]. Furthermore, it is a sequestering carbon material, since, as the timber product remains functional, carbon stays out of the atmosphere [ 7 , 8 ]. If used in its natural form, that is, without artificial treatments that improve its properties (e.g., glued laminates), wood is a material that needs low processing to be used in construction prone to prefabrication—which contributes to reducing construction time and waste. Even waste can be crushed and recycled as raw material for other engineered wood products, such as particle and oriented strand-boards or just used as an energy source (biomass) [ 7 ]. However, when chemical glues, surface treatments and impregnating agents are used, timber waste products can be hazardous [ 7 ]. As timber requires low processing to be applied in construction, timber buildings have a relatively low embodied energy. In some cases, the embodied energy could be reduced even more if sawmill systems such as those used on Madeira Island continued to be used, taking advantage of the energy from water streams [ 9 ]. The reuse of timber has a long tradition in Scandinavian countries, where the components can be easily dismantled and reassembled without any waste [ 7 ]. The sequential exploitation of a resource during its use, by reuse and recycling, improves the efficiency of the raw material use and in the case of pine, its service life could be extended from about 75 to more than 350 years [8]. The use of construction materials from local sources or with low transportation demand, is essential in the scope of sustainable buildings and timber is no exception. The study by Coelho et al. [ 10 ] on the life cycle assessment of a timber building reveals the importance of using local resources of raw material and production to reduce the transport needs that affect the environmental performance of this type of construction. In the scope of thermal and energy performance, several authors highlight that the lack of thermal mass of lightweight timber constructions can lead to overheating, even in mild summers [ 4 , 5 , 11 ]. In this topic, it is more common to find studies for countries with cold winters and mild summers than for temperate climates, like the Mediterranean. Adekunle and Nikopoulou [ 4 , 11 ] investigated the indoor thermal conditions and overheating risk in two timber buildings in the southeast of England. The authors concluded that these buildings perform better in winter than summer and found that the lack of thermal mass of these constructions increased the risk of overheating, even in England’s mild summer conditions. This issue is a drawback for timber construction and is reported by several authors. The study of Pajek et al. [ 5 ] dealt with this issue and focused on improving the thermal performance of lightweight timber building envelopes during the cooling season in three European countries (Finland, Austria and Spain). The authors concluded that enhanced lightweight envelopes (e.g., with clay boards, Phase Change Materials, etc.) could improve thermal comfort in lightweight buildings and reduce their energy demand for cooling. The results of the study showed that, concerning thermal performance, lightweight, well-insulated constructions behave much better in mild summer climates (as the ones in Northern and Central European locations), where outdoor temperatures during the summer are not as high as in Southern Europe. However, the authors also concluded that in Southern European locations, such as Madrid, thermal comfort in this type of buildings is more difficult to achieve during summer, despite the enhancements and natural cooling. In the same line, the study of Tonelli and Grimaudo [ 12 ] aimed at improving thermal inertia of timber constructions to better address summer conditions in the Mediterranean climate, namely in Italy. The authors state that timber constructions in warm temperate climates fail to dissipate the heat and therefore have overheating risks. Since heavy constructions perform better in this type of climate,
Sustainability 2020,12, 10484 3 of 33 the authors developed a prototype of timber-framed construction with an inner layer of additional heat inertial storage, in direct contact with the indoor environment and a cross-ventilation strategy for night cooling to remove the thermal gains during the day. However, the authors have not presented thermal performance results. From the literature review it was verified that there is a lack of quantitative studies on the thermal performance of vernacular timber buildings, particularly for temperate climates. In Portugal, the study of the vernacular architecture within the scope of sustainability is still in the first stages. Regarding the vernacular timber architecture from the coast, analyzing the state-of-art, it is possible to conclude that there are no quantitative studies on the thermal performance of these type of buildings, covering all seasons. Timber is a ubiquitous building material in Portuguese vernacular architecture. Depending on the local availability of this resource, its use in construction goes from the occasional use as a structural element (e.g., roof) to the entire dwelling. Regarding the latter, the examples of the palheiros built in the coast of mainland Portugal, the Avieiros in the banks of Tagus River and the houses of Santana in Madeira Island stand out (Figure 1). The abundant forest in these places and at the same time, the lack of other materials promoted the use of timber as a building material. In addition, the use of timber in these places was consistent with the climatic conditions, since it shows good behavior for the humidity of the sea or river basins [13]. Sustainability 2020, 12, x FOR PEER REVIEW 3 of 33 In the same line, the study of Tonelli and Grimaudo [12] aimed at improving thermal inertia of timber constructions to better address summer conditions in the Mediterranean climate, namely in Italy. The authors state that timber constructions in warm temperate climates fail to dissipate the heat and therefore have overheating risks. Since heavy constructions perform better in this type of climate, the authors developed a prototype of timber-framed construction with an inner layer of additional heat inertial storage, in direct contact with the indoor environment and a cross-ventilation strategy for night cooling to remove the thermal gains during the day. However, the authors have not presented thermal performance results. From the literature review it was verified that there is a lack of quantitative studies on the thermal performance of vernacular timber buildings, particularly for temperate climates. In Portugal, the study of the vernacular architecture within the scope of sustainability is still in the first stages. Regarding the vernacular timber architecture from the coast, analyzing the state-ofart, it is possible to conclude that there are no quantitative studies on the thermal performance of these type of buildings, covering all seasons. Timber is a ubiquitous building material in Portuguese vernacular architecture. Depending on the local availability of this resource, its use in construction goes from the occasional use as a structural element (e.g., roof) to the entire dwelling. Regarding the latter, the examples of the palheiros built in the coast of mainland Portugal, the Avieiros in the banks of Tagus River and the houses of Santana in Madeira Island stand out (Figure 1). The abundant forest in these places and at the same time, the lack of other materials promoted the use of timber as a building material. In addition, the use of timber in these places was consistent with the climatic conditions, since it shows good behavior for the humidity of the sea or river basins [13]. (a) (b) (c) Figure 1. (a) Palheiro from Praia de Mira (probably in the 1950s) (anonymous author; image edited); (b) house of Santana, Madeira [13]; (c) Avieiro’s house. The transposition of the Energy Performance Building Directive (EPBD-recast) [14] into national legislation [15] has defined requirements which can limit and constrain the use of vernacular building elements as they had so far been used. Stricter thermal requirements, namely the thermal transmittance coefficient (U-value) and the low thermal inertia that characterizes the timber structures, hinders buildings’ thermal performance in Southern European countries, mainly during the cooling season due to the overheating risk. Thus, the study of the real thermal performance of such buildings is necessary to understand whether this type of constructions can meet current energy and comfort requirements. As an example, according to the Portuguese legal requirements for external vertical opaque elements, the U-values must be lower than 0.35–0.50 W/(m2·°C), depending on the climatic zone [5]. For a timber wall (pine) to achieve this thermal performance, without an additional thermal insulation layer, it is necessary to have a 33 cm-thick massive timber wall (U = 0.50 W/(m2·°C) [16]). By using a thermal insulation layer (e.g., ≈8 cm of ICB-Insulation Cork Board), it is possible to reduce the wall’s thickness at least by half. This solution is compatible with the traditional timber-framed cavity walls. Although most of these vernacular timber cavity walls have just an air Figure 1. ( a )Palheiro from Praia de Mira (probably in the 1950s) (anonymous author; image edited); (b) house of Santana, Madeira [13]; (c)Avieiro’s house. The transposition of the Energy Performance Building Directive (EPBD-recast) [ 14 ] into national legislation [ 15 ] has defined requirements which can limit and constrain the use of vernacular building elements as they had so far been used. Stricter thermal requirements, namely the thermal transmittance coefficient (U-value) and the low thermal inertia that characterizes the timber structures, hinders buildings’ thermal performance in Southern European countries, mainly during the cooling season due to the overheating risk. Thus, the study of the real thermal performance of such buildings is necessary to understand whether this type of constructions can meet current energy and comfort requirements. As an example, according to the Portuguese legal requirements for external vertical opaque elements, the U-values must be lower than 0.35–0.50 W/(m 2·◦ C), depending on the climatic zone [ 5 ]. For a timber wall (pine) to achieve this thermal performance, without an additional thermal insulation layer, it is necessary to have a 33 cm-thick massive timber wall (U =0.50 W/(m 2·◦ C) [ 16 ]). By using a thermal insulation layer (e.g., ≈ 8 cm of ICB-Insulation Cork Board), it is possible to reduce the wall’s thickness at least by half. This solution is compatible with the traditional timber-framed cavity walls. Although most of these vernacular timber cavity walls have just an air gap, there are records of palheiros in Leirosa (near Figueira da Foz), in which the cavity was filled with reeds to provide an “insulation” layer (Figure 2).
Sustainability 2020,12, 10484 4 of 33 Sustainability 2020, 12, x FOR PEER REVIEW 4 of 33 gap, there are records of palheiros in Leirosa (near Figueira da Foz), in which the cavity was filled with reeds to provide an “insulation” layer (Figure 2). Figure 2. Reeds used as a thermal insulation layer of a timber wall (Leirosa, Figueira da Foz). It is also essential to analyze possible limitations posed by the thermal regulation in the design of new and refurbished timber buildings. Besides the low thermal inertia of this type of vernacular buildings, it is also relevant to analyze the combined effect of other climate-responsive strategies that might also influence their thermal performance. Also, it is still missing to analyze this type of buildings in line with the standards of comfort and specifically using the adaptive comfort model. The preservation of this kind of passive solution is essential to preserve the heritage, culture, history and identity of the regions. Thus, this work aimed at contributing to this field by analyzing the thermal performance of a vernacular timber building located on the central coast of mainland Portugal. The study examines how vernacular timber building techniques suit the specific local conditions. The performance of a vernacular timber building, a palheiro from Praia de Mira, considering thermal comfort and energy efficiency, was analyzed through in situ measurements of hygrothermal parameters that characterize the indoor thermal environment and affect occupants’ thermal comfort and subjective analysis of the thermal conditions. This study was coupled with energy simulation provided by DesignBuilder/EnergyPlus that was used to investigate the energy performance of the building. The purpose of the simulations is to compare, under the same conditions, the impact of different vernacular and conventional solutions on the energy performance for heating/cooling. As an outcome, this research will contribute to a better understanding of the properties of this type of architecture, by assessing the impacts of using the studied vernacular design principles and building materials in improving the thermal behavior of both new and retrofitted buildings. 2. Materials and Methods To evaluate indoor thermal performance, in situ assessments of a case study (described in Section 3) were carried. These assessments were divided into short and long-term monitoring. In these assessments, the hygrothermal parameters that characterize the indoor thermal environment and affect the body/environment heat exchange (air temperature, relative humidity, mean radiant temperature and air velocity) were measured. 2.1. Short-Term Monitoring Short-term monitoring was carried out, at least one day per season and consisted of objective measurements and subjective evaluation: • Objective measurements—with the purpose of quantitatively assess the thermal comfort conditions in a room. A thermal microclimate station (model Delta OHM 32.1) that measures air temperature, relative humidity, mean radiant temperature and air velocity (Table 1), in Figure 2. Reeds used as a thermal insulation layer of a timber wall (Leirosa, Figueira da Foz). It is also essential to analyze possible limitations posed by the thermal regulation in the design of new and refurbished timber buildings. Besides the low thermal inertia of this type of vernacular buildings, it is also relevant to analyze the combined effect of other climate-responsive strategies that might also influence their thermal performance. Also, it is still missing to analyze this type of buildings in line with the standards of comfort and specifically using the adaptive comfort model. The preservation of this kind of passive solution is essential to preserve the heritage, culture, history and identity of the regions. Thus, this work aimed at contributing to this field by analyzing the thermal performance of a vernacular timber building located on the central coast of mainland Portugal. The study examines how vernacular timber building techniques suit the specific local conditions. The performance of a vernacular timber building, a palheiro from Praia de Mira, considering thermal comfort and energy efficiency, was analyzed through in situ measurements of hygrothermal parameters that characterize the indoor thermal environment and affect occupants’ thermal comfort and subjective analysis of the thermal conditions. This study was coupled with energy simulation provided by DesignBuilder/EnergyPlus that was used to investigate the energy performance of the building. The purpose of the simulations is to compare, under the same conditions, the impact of different vernacular and conventional solutions on the energy performance for heating/cooling. As an outcome, this research will contribute to a better understanding of the properties of this type of architecture, by assessing the impacts of using the studied vernacular design principles and building materials in improving the thermal behavior of both new and retrofitted buildings. 2. Materials and Methods To evaluate indoor thermal performance, in situ assessments of a case study (described in Section 3) were carried. These assessments were divided into short and long-term monitoring. In these assessments, the hygrothermal parameters that characterize the indoor thermal environment and affect the body/environment heat exchange (air temperature, relative humidity, mean radiant temperature and air velocity) were measured. 2.1. Short-Term Monitoring Short-term monitoring was carried out, at least one day per season and consisted of objective measurements and subjective evaluation: • Objective measurements—with the purpose of quantitatively assess the thermal comfort conditions in a room. A thermal microclimate station (model Delta OHM 32.1) that measures air temperature, relative humidity, mean radiant temperature and air velocity (Table 1), in compliance with standards ISO 7726 [ 17 ], ISO 7730 [ 18 ] and ASHRAE 55 [ 19 ], was used for this purpose. The measurements were performed in several rooms, especially where occupant’s stay for more
Sustainability 2020,12, 10484 5 of 33 extended periods. The measuring equipment was placed according to occupants’ distribution in the room. The measurements were performed considering that the occupants were seated, as recommended in ASHRAE 55 [ 19 ]. The data recorded in these measurements was used to determine the operative temperature (the analysis procedure is explained below in this section). • Subjective evaluation—to assess the occupants’ perceived indoor environmental quality, using surveys. The survey was based in the “Thermal Environment Survey” from ASHRAE 55 [ 19 ] and was used to determine occupants’ satisfaction according to ASHRAE 55 [ 19 ] thermal sensation scale. Table 1. Location and characteristics of measurement equipment used. Equipment Specifications, Measurement Range and Accuracy Location Thermal microclimate station (Delta OHM 32.1) Sustainability 2020, 12, x FOR PEER REVIEW 5 of 33 compliance with standards ISO 7726 [17], ISO 7730 [18] and ASHRAE 55 [19], was used for this purpose. The measurements were performed in several rooms, especially where occupant’s stay for more extended periods. The measuring equipment was placed according to occupants’ distribution in the room. The measurements were performed considering that the occupants were seated, as recommended in ASHRAE 55 [19]. The data recorded in these measurements was used to determine the operative temperature (the analysis procedure is explained below in this section). •Subjective evaluation — to assess the occupants’ perceived indoor environmental quality, using surveys. The survey was based in the “Thermal Environment Survey” from ASHRAE 55 [19] and was used to determine occupants’ satisfaction according to ASHRAE 55 [19] thermal sensation scale. Table 1. Location and characteristics of measurement equipment used. Equipment Specifications, Measurement Range and Accuracy Location Thermal microclimate station (Delta OHM 32.1) Probes installed: 1. Globe temperature probe Ø150 mm (range from −10 to 100 °C); 2. Omnidirectional hot-wire probe for wind speed measurement (range from 0 to 5 m/s); 3. Combined temperature and relative humidity probe (range from −10 to 80 °C and 5–98% RH); 4. Two-sensor probe for measuring natural wet bulb temperature and dry bulb temperature (range from 4 to 80 °C). Reception Thermo-hygrometer and datalogger (Klimalogg Pro, TFA 30.3039.IT) + Wireless thermo-hygrometer transmitters (model TFA 30.3180.IT) connected to the datalogger Datalogger: •Temperature accuracy of ±1 °C and a measuring range between 0 and 50 °C with 0.1 °C resolution; •Relative humidity accuracy of ± 3% and measuring range between 1 and 99% with 1% resolution. •Transmitters: •Temperature accuracy of ±1 °C and measuring range between 39.6 °C and +59.9 °C with 0.1 °C resolution; •Relative humidity accuracy of ± 3% and measuring range of 1–99% with 1% resolution. Datalogger: Reception Transmitters: Exhibition room “Classroom” “Dining room” 1 2 3 4 Probes installed: 1. Globe temperature probe Ø150 mm (range from − 10 to 100 ◦C); 2. Omnidirectional hot-wire probe for wind speed measurement (range from 0 to 5 m/s); 3. Combined temperature and relative humidity probe (range from − 10 to 80 ◦ C and 5–98% RH); 4. Two-sensor probe for measuring natural wet bulb temperature and dry bulb temperature (range from 4 to 80 ◦C). Reception Thermo-hygrometer and datalogger (Klimalogg Pro, TFA 30.3039.IT) +Wireless thermo-hygrometer transmitters (model TFA 30.3180.IT) connected to the datalogger Sustainability 2020, 12, x FOR PEER REVIEW 5 of 33 compliance with standards ISO 7726 [17], ISO 7730 [18] and ASHRAE 55 [19], was used for this purpose. The measurements were performed in several rooms, especially where occupant’s stay for more extended periods. The measuring equipment was placed according to occupants’ distribution in the room. The measurements were performed considering that the occupants were seated, as recommended in ASHRAE 55 [19]. The data recorded in these measurements was used to determine the operative temperature (the analysis procedure is explained below in this section). •Subjective evaluation — to assess the occupants’ perceived indoor environmental quality, using surveys. The survey was based in the “Thermal Environment Survey” from ASHRAE 55 [19] and was used to determine occupants’ satisfaction according to ASHRAE 55 [19] thermal sensation scale. Table 1. Location and characteristics of measurement equipment used. Equipment Specifications, Measurement Range and Accuracy Location Thermal microclimate station (Delta OHM 32.1) Probes installed: 1. Globe temperature probe Ø150 mm (range from −10 to 100 °C); 2. Omnidirectional hot-wire probe for wind speed measurement (range from 0 to 5 m/s); 3. Combined temperature and relative humidity probe (range from −10 to 80 °C and 5–98% RH); 4. Two-sensor probe for measuring natural wet bulb temperature and dry bulb temperature (range from 4 to 80 °C). Reception Thermo-hygrometer and datalogger (Klimalogg Pro, TFA 30.3039.IT) + Wireless thermo-hygrometer transmitters (model TFA 30.3180.IT) connected to the datalogger Datalogger: •Temperature accuracy of ±1 °C and a measuring range between 0 and 50 °C with 0.1 °C resolution; •Relative humidity accuracy of ± 3% and measuring range between 1 and 99% with 1% resolution. •Transmitters: •Temperature accuracy of ±1 °C and measuring range between 39.6 °C and +59.9 °C with 0.1 °C resolution; •Relative humidity accuracy of ± 3% and measuring range of 1–99% with 1% resolution. Datalogger: Reception Transmitters: Exhibition room “Classroom” “Dining room” 1 2 3 4 Datalogger: •Temperature accuracy of ±1 ◦C and a measuring range between 0 and 50 ◦C with 0.1 ◦C resolution; •Relative humidity accuracy of ± 3% and measuring range between 1 and 99% with 1% resolution. •Transmitters: •Temperature accuracy of ±1◦C and measuring range between 39.6 ◦ C and +59.9 ◦ C with 0.1 ◦C resolution; •Relative humidity accuracy of ± 3% and measuring range of 1–99% with 1% resolution. Datalogger: Reception Transmitters: Exhibition room “Classroom” “Dining room”
Sustainability 2020,12, 10484 6 of 33 Table 1. Cont. Equipment Specifications, Measurement Range and Accuracy Location Weather station Sustainability 2020, 12, x FOR PEER REVIEW 6 of 33 Probes installed: 1. Pyranometer (solar radiation sensor) CMP3-L, Kipp and Zonen 2. Air temperature, relative humidity, wind speed and direction, precipitation and absolute pressure sensor (WXT520, Vaisala) 3. Datalogger (CR800, Campbell Scientific, Inc.) 4. Photovoltaic panel + battery (power source) Outdoor 2.2. Long-Term Monitoring Long-term monitoring was carried out to measure the indoor and outdoor air temperatures and relative humidity throughout the measurement period. For this, thermo-hygrometer sensors were installed in the most representative rooms of the case study and outdoors (Table 1). Local weather data was measured using a portable weather station (Table 1), installed close to the case study (approx. 300 m). The measurements were carried out during different monitoring campaigns for all seasons, in compliance with specified procedures and standards (ISO 7726 [17], ISO 7730 [18] and ASHRAE 55 [19]). The monitoring campaigns were carried out for periods of at least 25 days and with the sensors recording data in periods of 30 min. Results on indoor environmental parameters were correlated with the outdoor parameters. During the measurement period, occupants filled an occupancy table where recorded how they used the building, that is, if they used the heating or cooling systems, promoted ventilation, among others. These occupancy records were useful to understand, for example, sudden changes in air temperature and relative humidity profiles. 2.3. Thermal Comfort Model The main purpose of a building is to alleviate the adverse weather conditions by offering protection and trying to guarantee healthy and comfortable conditions. This concept can be quantifiable in terms of thermal comfort assessed through objective and subjective evaluations. For the objective evaluation, an adaptive model of thermal comfort was used in the analysis of thermal comfort conditions since this is the adequate model for naturally conditioned buildings. The chosen model was the Portuguese adaptive model of thermal comfort since it is the most representative of the Portuguese reality [20,21]. This model is an adaptation to the Portuguese context of the models specified in standards ASHRAE 55 [19,22] and EN 15251 [23]. It considers the typical climate and ways of living and how buildings are conventionally designed and used. According to this model [21]: (i) occupants may tolerate broader temperature ranges than those indicated for mechanically heated and/or cooled buildings; and (ii) the outdoor temperature has a strong influence on occupants’ thermal perception/sensation. In the application of the proposed model to the case study, the following conditions were met, as preconized: (i) the occupants have activity levels that result in metabolic rates (met) ranging from 1.0 to 1.3 met (sedentary activity levels); (ii) occupants are free to adapt the thermal insulation of their clothing (clo); (iii) air velocity is below 0.6 m/s; (iv) indoor operative temperature is bounded between 10 °C and 35 °C; and (v) outdoor running mean temperature is between 5 °C and 30 °C. The building has no air-conditioning system or its use is sporadic. Therefore, in the analysis of the case study, the adaptive model for building without mechanical systems was applied. 4 3 1 2 Probes installed: 1. Pyranometer (solar radiation sensor) CMP3-L, Kipp and Zonen 2. Air temperature, relative humidity, wind speed and direction, precipitation and absolute pressure sensor (WXT520, Vaisala) 3. Datalogger (CR800, Campbell Scientific, Inc.) 4. Photovoltaic panel +battery (power source) Outdoor 2.2. Long-Term Monitoring Long-term monitoring was carried out to measure the indoor and outdoor air temperatures and relative humidity throughout the measurement period. For this, thermo-hygrometer sensors were installed in the most representative rooms of the case study and outdoors (Table 1). Local weather data was measured using a portable weather station (Table 1), installed close to the case study (approx. 300 m). The measurements were carried out during different monitoring campaigns for all seasons, in compliance with specified procedures and standards (ISO 7726 [ 17 ], ISO 7730 [ 18 ] and ASHRAE 55 [ 19 ]). The monitoring campaigns were carried out for periods of at least 25 days and with the sensors recording data in periods of 30 min. Results on indoor environmental parameters were correlated with the outdoor parameters. During the measurement period, occupants filled an occupancy table where recorded how they used the building, that is, if they used the heating or cooling systems, promoted ventilation, among others. These occupancy records were useful to understand, for example, sudden changes in air temperature and relative humidity profiles. 2.3. Thermal Comfort Model The main purpose of a building is to alleviate the adverse weather conditions by offering protection and trying to guarantee healthy and comfortable conditions. This concept can be quantifiable in terms of thermal comfort assessed through objective and subjective evaluations. For the objective evaluation, an adaptive model of thermal comfort was used in the analysis of thermal comfort conditions since this is the adequate model for naturally conditioned buildings. The chosen model was the Portuguese adaptive model of thermal comfort since it is the most representative of the Portuguese reality [ 20 , 21 ]. This model is an adaptation to the Portuguese context of the models specified in standards ASHRAE 55 [ 19 , 22 ] and EN 15251 [ 23 ]. It considers the typical climate and ways of living and how buildings are conventionally designed and used. According to this model [ 21 ]: (i) occupants may tolerate broader temperature ranges than those indicated for mechanically heated and/or cooled buildings; and (ii) the outdoor temperature has a strong influence on occupants’ thermal perception/sensation. In the application of the proposed model to the case study, the following conditions were met, as preconized: (i) the occupants have activity levels that result in metabolic rates (met) ranging from 1.0 to 1.3 met (sedentary activity levels); (ii) occupants are free to adapt the thermal insulation of their clothing (clo); (iii) air velocity is below 0.6 m/s; (iv) indoor operative temperature is bounded between 10 ◦ C and 35 ◦ C; and (v) outdoor running mean temperature is between 5 ◦ C and 30 ◦ C. The building
Sustainability 2020,12, 10484 7 of 33 has no air-conditioning system or its use is sporadic. Therefore, in the analysis of the case study, the adaptive model for building without mechanical systems was applied. As an individual takes approximately one week to be fully adjusted to the changes in outdoor climate, the thermal comfort temperature (operative temperature, Θo ) is obtained from the exponentially weighted running mean of the outdoor temperature during the last seven days (outdoor running mean temperature, Θrm ) [ 21 , 23 ]. The calculation of the exponentially weighted running mean of the outdoor temperature in the previous seven days is done using Equation (1) [21,23]. Θrm =(Tn−1+0.8Tn−2+0.6Tn−3+0.5Tn−4+0.4Tn−5+0.3Tn−6+0.2Tn−7)/3.8, (1) where: Θrm (◦C)—exponentially weighted running mean of the outdoor air temperature; Tn−i(◦C)—outdoor mean air temperature of the previous day (i). In this model, two comfort temperatures ranges are defined, one to be applied in spaces with active air-conditioning systems and the other in non-air-conditioned spaces (spaces that do not have air-conditioning system or where the system is turned off). The comfort operative temperature limits defined in this model are for 90% of acceptability and these limits are up to 3 ◦ C above or below the estimated comfort temperature, both for non-air-conditioned spaces ( Θo =0.43 Θrm +15.6) and air-conditioned spaces (Θo=0.30Θrm +17.9) [21]. The operative temperature was calculated based on the results obtained in the measurements performed with the Thermal Microclimate Station (Table 1). With the operative temperature ( Θo ) and the outdoor running mean temperature ( Θrm ) is possible to represent, in the adaptive chart, the point that characterizes the thermal environment conditions in the moment of measurement. 2.4. Energy Performance Model The use of dynamic simulation programs for the analysis of the thermal and energy behavior of buildings such as the energy use and indoor thermal comfort conditions is essential. In this paper, DesignBuilder/EnergyPlus software (version 6) (EnergyPlus version 8.9) [ 24 ] was the energy performance simulation program adopted. It requires the following input data for the calculation of the heat balance: climate data, geometry, properties of materials, zoning, internal loads, heating, ventilation and air conditioning (HVAC) systems and natural ventilation/infiltration. The components libraries on the materials and structures were developed by using the data (such as conductivity, specific heat, density, thermal diffusivity) obtained from technical publications [ 16 , 25 ] and DesignBuilder materials library. The characteristics of the model are presented in the following section. The energy simulation under dynamic conditions, due to the wide range of options and variables managed, is a useful tool to predict the performance of buildings. Since the range of options and variables is wide, modelling and inputs can be very time-consuming. Therefore, to simplify the simulation and analysis processes, the method considered was to replicate the case study and its characteristics (construction systems; operation schedules, etc.) but simplifying and keeping all the variables (e.g., internal heat gains) as stable and unchanged as possible. The simulation model was calibrated using the data measured near de case study using a portable weather station. During the analyzed periods for all seasons was found a convergence between the real and the simulated indoor temperature. However, the weather data measured in the same period of the indoor monitoring does not fulfil a whole year. The influence of climate conditions on the building performance is significant and therefore it is essential to use reliable weather data for energy modelling [ 26 ]. For this reason, the weather data files from the EnergyPlus weather database [ 27 ] for the closest location were used in the simulations. In the model, the numerical simulation was carried for one year to quantify the energy performance of the vernacular timber construction solution and the conventional brick wall solution, under seasonal external environmental conditions (summer, winter, spring and autumn). To establish the comparison
Sustainability 2020,12, 10484 8 of 33 between strategies/building solutions simulations, a Base Model was created, which replicates the original conditions of the case study. In the Scenario Models all the features and conditions are the same as the Base Model, except for the one that it is being evaluated in each one (e.g., to assess the influence of the thermal transmittance and inertia of external walls, only this building element is changed between scenarios). In all scenarios defined, only the external wall solution was changed, being all the other conditions kept constant. 3. Description of the Case Study 3.1. Site and Climate The case study is located in the village of Praia de Mira, in Mira’s municipality, district of Coimbra, Portugal (Figure 3a). Praia de Mira, as other coastline settlements from the 19th century, had at first a seasonal occupation of fishermen during the fishing season (from Spring to Autumn) [28]. Sustainability 2020, 12, x FOR PEER REVIEW 8 of 33 in each one (e.g., to assess the influence of the thermal transmittance and inertia of external walls, only this building element is changed between scenarios). In all scenarios defined, only the external wall solution was changed, being all the other conditions kept constant. 3. Description of the Case Study 3.1. Site and Climate The case study is located in the village of Praia de Mira, in Mira’s municipality, district of Coimbra, Portugal (Figure 3a). Praia de Mira, as other coastline settlements from the 19th century, had at first a seasonal occupation of fishermen during the fishing season (from Spring to Autumn) [28]. (a) (b) Figure 3. Case study’s location. (a) country context; (b) case study position in Praia de Mira’s current urban layout. The original name of the village was Palheiros de Mira due to the type of constructions that existed there, the palheiros (named after the material originally used to roof the building, that is, straw (palha) from a plant (estormo–Ammophila arenaria) abundant in coastal sands [28–30]). In a zone of dunes and pine forests, without adequate stone for construction and where timber abounds, the palheiro was the temporary building needed for fishermen coming from other locations during the fishing season [29–31]. Palheiros are palafitic timber buildings adjusted to the humid environment and a shifting landscape of dunes continually changing by the action of wind [13,29,32]. The village was strategically implanted next to a freshwater lagoon and sheltered by the dunes from north and west quadrants (Figure 3b). Praia de Mira was the shoreline settlement where timber construction had its best expression, due to the dimension of the village and for the size of the buildings (with three storeys in some cases) [28,30]. In the construction technique (“Type of Mira” [33]) used in the coastline between Costa Nova and Leirosa, the plumbs of the structure were built on a frame or a grid of beams, that in turn was on a dense mesh of pillars inserted in the ground (Figure 1a). Figure 3. Case study’s location. ( a ) country context; ( b ) case study position in Praia de Mira’s current urban layout. The original name of the village was Palheiros de Mira due to the type of constructions that existed there, the palheiros (named after the material originally used to roof the building, that is, straw (palha) from a plant (estormo–Ammophila arenaria) abundant in coastal sands [ 28 – 30 ]). In a zone of dunes and pine forests, without adequate stone for construction and where timber abounds, the palheiro was the temporary building needed for fishermen coming from other locations during the fishing season [ 29 – 31 ]. Palheiros are palafitic timber buildings adjusted to the humid environment and a shifting landscape of dunes continually changing by the action of wind [13,29,32]. The village was strategically implanted next to a freshwater lagoon and sheltered by the dunes from north and west quadrants (Figure 3b). Praia de Mira was the shoreline settlement where timber construction had its best expression, due to the dimension of the village and for the size of the buildings (with three storeys in some cases) [ 28 , 30 ]. In the construction technique (“Type of Mira” [ 33 ]) used in the coastline between Costa Nova and Leirosa, the plumbs of the structure were built on a frame or a grid of beams, that in turn was on a dense mesh of pillars inserted in the ground (Figure 1a). However, it was also here where this type of construction has seen the fastest decline, due to the approval of the urbanization plan for Praia de Mira in the late 1940s. This plan considered that these buildings did not comply with modern requirements of hygiene and that the fishing activity was interfering with the touristic operation. The urbanization plan prohibited the construction and conservation of timber buildings, which contributed to their systematic and accelerated
Sustainability 2020,12, 10484 9 of 33 destruction [ 28 , 34 ]. The plan also considered the fishing activity as interfering with the touristic operation. The connotation of these constructions with poverty and underdevelopment also led to the change of the name from “Palheiros de Mira” to “Praia de Mira” [ 28 ]. This prohibition contributed to foster the use of industrial materials in the village and to the replacement of timber constructions by conventional constructions of hollow concrete and clay bricks, making this type of traditional construction to disappear gradually [ 17 , 18 ]. Nowadays, the buildings with concrete structure and clay bricks walls are the norm, even in the seafront (Figure 4). There are few existing timber examples and most of them are in poor condition, in some cases, wholly corseted between concrete buildings (Figure 4c). Sustainability 2020, 12, x FOR PEER REVIEW 9 of 33 However, it was also here where this type of construction has seen the fastest decline, due to the approval of the urbanization plan for Praia de Mira in the late 1940s. This plan considered that these buildings did not comply with modern requirements of hygiene and that the fishing activity was interfering with the touristic operation. The urbanization plan prohibited the construction and conservation of timber buildings, which contributed to their systematic and accelerated destruction [28,34]. The plan also considered the fishing activity as interfering with the touristic operation. The connotation of these constructions with poverty and underdevelopment also led to the change of the name from “Palheiros de Mira” to “Praia de Mira” [28]. This prohibition contributed to foster the use of industrial materials in the village and to the replacement of timber constructions by conventional constructions of hollow concrete and clay bricks, making this type of traditional construction to disappear gradually [17,18]. Nowadays, the buildings with concrete structure and clay bricks walls are the norm, even in the seafront (Figure 4). There are few existing timber examples and most of them are in poor condition, in some cases, wholly corseted between concrete buildings (Figure 4c). (a) (b) (c) Figure 4. (a) Main street in the 1950s (anonymous author); (b) Main street in 2016; (c) Palheiro corseted between taller conventional buildings. Concerning climate context, the central coastal region of Portugal has a temperate climate–Type C, sub-type Csb (temperate with dry or temperate summer), according to Köppen-Geiger Climate Classification (Figure 5a) [35]. The annual average mean temperature is below 15 °C [35]. The average mean temperature is 10 °C in winter, while is 20 °C in summer (Figure 5b) [35]. Winter is the most severe season in this area. The summer is mild, with an average maximum temperature below 25 °C [35] (Figure 5d). The influence of the Atlantic Ocean is an important feature affecting local climate parameters, as moderating temperature variation, higher relative humidity values, precipitation and wind speed [36]. Thus, in the case of Praia de Mira, it is visible a lower annual thermal variation than in other zones of the country (Figure 5b,c), a higher average relative humidity (79%) and higher wind speed and more frequent wind than in inner areas of the territory [37]. Figure 4. ( a ) Main street in the 1950s (anonymous author); ( b ) Main street in 2016; ( c )Palheiro corseted between taller conventional buildings. Concerning climate context, the central coastal region of Portugal has a temperate climate–Type C, sub-type Csb (temperate with dry or temperate summer), according to Köppen-Geiger Climate Classification (Figure 5a) [ 35 ]. The annual average mean temperature is below 15 ◦ C [ 35 ]. The average mean temperature is 10 ◦ C in winter, while is 20 ◦ C in summer (Figure 5b) [ 35 ]. Winter is the most severe season in this area. The summer is mild, with an average maximum temperature below 25 ◦ C [ 35 ] (Figure 5d). The influence of the Atlantic Ocean is an important feature affecting local climate parameters, as moderating temperature variation, higher relative humidity values, precipitation and wind speed [ 36 ]. Thus, in the case of Praia de Mira, it is visible a lower annual thermal variation than in other zones of the country (Figure 5b,c), a higher average relative humidity (79%) and higher wind speed and more frequent wind than in inner areas of the territory [37].
Sustainability 2020,12, 10484 16 of 33 and winter. During the monitoring campaign, the building was, most of the time, kept in a free-running mode. The main activities reported by the occupants are synthesized in Table 3. Table 3. Building occupancy profile. Season Use and Description Winter heating/cooling Heating (for all season). The pattern is: two oil-filled radiators in the reception (9 a.m.–5 p.m). ventilation Windows and doors closed. The main entrance door is sporadically opened when visitors enter/exit the building. shading The curtains were usually closed on the ground floor. The upper floor windows do not have curtains. Spring heating/cooling Sporadic use of heating in spring cold days (1 oil-filled radiator). ventilation Main entrance door and reception window open during the day (9 a.m.–5 p.m.), particularly from May forward (sporadically closed in cool days). shading The curtains were usually closed on the ground floor. The upper floor windows do not have curtains. Summer heating/cooling No cooling system was used. ventilation Main entrance door and reception window open during the day (9 a.m.–5 p.m.) shading The curtains were usually closed on the ground floor. The upper floor windows do not have curtains. Autumn heating/cooling Heating (more frequent from middle October forward). The pattern is: One oil-filled radiator in the reception (9 a.m.–5 p.m.), occasionally, two. ventilation Windows and doors closed. The main entrance door is sporadically opened to enter/exit the building. shading The curtains were usually closed on the ground floor. The upper floor windows do not have curtains. 4. Thermal Monitoring and Indoor Comfort Evaluation In this section, the thermal performance of the case study and the effectiveness of this type of construction in mitigating the effects of this specific climate are analyzed. The thermal performance monitoring and indoor comfort evaluation were carried out for the four seasons. The monitoring data is presented for approximately 30 representative days of each season. 4.1. Winter The Winter monitoring was carried from 21st December 2014 to 19th March 2015. During the representative period analyzed (21st January to 21st February 2015), the outdoor mean air temperature was of 10 ◦ C (Table 4). The daily maximum and minimum values were very variable, the maximum temperature was often below 15 ◦ C and the minimum usually around or below 5 ◦ C, reaching on some days nearly 0 ◦C (Figure 11a). The daily temperature amplitude was frequently around 10 ◦C. Indoors, the temperature profiles show an irregular daily variation following the outdoor trend (Figure 11a). In the reception, it is possible to see several peaks of maximum temperature values, in some days considerably higher than in the other rooms, due to heat gains related to occupation, office equipment and, mainly, because of the use of heating devices (oil-filled radiators). Since the reception is not an enclosed room, that is, it has no doors dividing it from the exhibition rooms, it is difficult to achieve stable temperature values above 18 ◦ C during the day, even with the two oil-filled radiators.
Sustainability 2020,12, 10484 17 of 33 Table 4. Comparison between outdoor and indoor air temperatures and relative humidity values during Winter. Winter Outdoor Reception “Dining Room” Room Exhibition Room “Classroom” Temperature (◦C) Mean 10.0 14.0 12.4 13.2 13.3 Maximum 17.0 20.7 19.9 18.4 18.8 Minimum −0.3 6.6 5.5 6.4 6.4 Relative Humidity (%) Mean 76.3 62.6 68.5 66.3 66.7 Maximum 94.5 79.0 74.0 77.0 79.0 Minimum 32.9 37.0 54.0 53.0 50.0 Sustainability 2020, 12, x FOR PEER REVIEW 17 of 33 (a) (b) Figure 11. Winter monitoring: (a) Indoor and outdoor air temperature profiles; (b) Indoor and outdoor air relative humidity profiles. Indoors, the temperature profiles show an irregular daily variation following the outdoor trend (Figure 11a). In the reception, it is possible to see several peaks of maximum temperature values, in some days considerably higher than in the other rooms, due to heat gains related to occupation, office equipment and, mainly, because of the use of heating devices (oil-filled radiators). Since the reception is not an enclosed room, that is, it has no doors dividing it from the exhibition rooms, it is difficult to achieve stable temperature values above 18 °C during the day, even with the two oil-filled radiators. In most of the days, the indoor peak temperature is around or below 18 °C, showing a low quality of the thermal environment. The other rooms have similar temperature profiles. The “dining room” has the lowest mean and minimum values but at the same time the highest maximum temperature, after the reception. This occurs because this room has a higher floor and glazed area (almost the double), it has façades facing north (without solar gains) and west without shading devices, receiving direct solar radiation at the end of the day. The other rooms, “classroom” (first floor) and the exhibition room (ground floor), have the same orientation (east and south) and a similar thermal behavior (slightly better than in the “dining room” due to a better solar exposure). In the night period, when the building is not occupied, the indoor temperature of all rooms is low (minimum values less than 10 °C). Nevertheless, minimum values are considerably higher than the minimum outdoor values. The low thermal inertia of the building elements, together with single-glazed windows with no external solar protection, are the main reasons to explain the considerable indoor daily thermal variation. In what relative humidity is concerned, maximum outdoor values were high and frequently around 90% (Figure 11b), with a mean value of 76.3%. Indoors, the relative humidity profiles are -5 0 5 10 15 20 25 30 21 /0 1/1 5 22 /0 1/1 5 23 /0 1/1 5 24 /0 1/1 5 25 /0 1/1 5 26 /0 1/1 5 27 /0 1/1 5 28 /0 1/1 5 29 /0 1/1 5 30 /0 1/1 5 31 /0 1/1 5 01 /0 2/1 5 02 /0 2/1 5 03 /0 2/1 5 04 /0 2/1 5 05 /0 2/1 5 06 /0 2/1 5 07 /0 2/1 5 08 /0 2/1 5 09 /0 2/1 5 10 /0 2/1 5 11 /0 2/1 5 12 /0 2/1 5 13 /0 2/1 5 14 /0 2/1 5 15 /0 2/1 5 16 /0 2/1 5 17 /0 2/1 5 18 /0 2/1 5 19 /0 2/1 5 20 /0 2/1 5 21 /0 2/1 5 Temperature (°C) Outdoor Exhibition room - ground gloor Dinning room School room Reception 0 10 20 30 40 50 60 70 80 90 100 21/01/15 22/01/15 23/01/15 24/01/15 25/01/15 26/01/15 27/01/15 28/01/15 29/01/15 30/01/15 31/01/15 01/02/15 02/02/15 03/02/15 04/02/15 05/02/15 06/02/15 07/02/15 08/02/15 09/02/15 10/02/15 11/02/15 12/02/15 13/02/15 14/02/15 15/02/15 16/02/15 17/02/15 18/02/15 19/02/15 20/02/15 21/02/15 Relative Humidity (%) Outdoor Exhibition room - ground floor Dinning room School room Reception Figure 11. Winter monitoring: ( a ) Indoor and outdoor air temperature profiles; ( b ) Indoor and outdoor air relative humidity profiles. In most of the days, the indoor peak temperature is around or below 18 ◦ C, showing a low quality of the thermal environment. The other rooms have similar temperature profiles. The “dining room” has the lowest mean and minimum values but at the same time the highest maximum temperature, after the reception. This occurs because this room has a higher floor and glazed area (almost the double), it has façades facing north (without solar gains) and west without shading devices, receiving direct solar radiation at the end of the day. The other rooms, “classroom” (first floor) and the exhibition
Sustainability 2020,12, 10484 18 of 33 room (ground floor), have the same orientation (east and south) and a similar thermal behavior (slightly better than in the “dining room” due to a better solar exposure). In the night period, when the building is not occupied, the indoor temperature of all rooms is low (minimum values less than 10 ◦ C). Nevertheless, minimum values are considerably higher than the minimum outdoor values. The low thermal inertia of the building elements, together with single-glazed windows with no external solar protection, are the main reasons to explain the considerable indoor daily thermal variation. In what relative humidity is concerned, maximum outdoor values were high and frequently around 90% (Figure 11b), with a mean value of 76.3%. Indoors, the relative humidity profiles are similar for all rooms, being relatively stable (with mean values below 70%) and with low daily variation, except for the reception (Figure 11b). The reception, due to the occupation, heating during the museum’s opening hours but also for being in contact with the main entrance, shows a higher daily variation on the relative humidity. The influence of using the portable dehumidifier to reduce moisture content indoors during the winter is not perceptible, being the profile very similar to the other seasons, as it will be shown below. Even though it is a museum, the collection does not require special humidity limits. Thus, taking into consideration the design criteria for the humidity in occupied spaces recommended by EN 16798-1 standard [ 48 ], the values recorded are most of the time within the limits for an existing building (Category III—20–70%) or close and considerably below the outdoor values. Concerning thermal comfort, during the measurement, the occupants were using the oil-filled radiators to heat the reception area. The results showed low thermal comfort conditions in the reception, below the lower limit (Figure 12). In the context of a cold week ( Θrm of 7.6 ◦ C), even when the heating system was on, it was not possible to reach adequate thermal comfort conditions. From the measurements, it was also possible to conclude that the other rooms were also below the thermal comfort limits. Sustainability 2020, 12, x FOR PEER REVIEW 18 of 33 similar for all rooms, being relatively stable (with mean values below 70%) and with low daily variation, except for the reception (Figure 11b). The reception, due to the occupation, heating during the museum’s opening hours but also for being in contact with the main entrance, shows a higher daily variation on the relative humidity. The influence of using the portable dehumidifier to reduce moisture content indoors during the winter is not perceptible, being the profile very similar to the other seasons, as it will be shown below. Even though it is a museum, the collection does not require special humidity limits. Thus, taking into consideration the design criteria for the humidity in occupied spaces recommended by EN 167981 standard [48], the values recorded are most of the time within the limits for an existing building (Category III—20–70%) or close and considerably below the outdoor values. Concerning thermal comfort, during the measurement, the occupants were using the oil-filled radiators to heat the reception area. The results showed low thermal comfort conditions in the reception, below the lower limit (Figure 12). In the context of a cold week (Θ rm of 7.6 °C), even when the heating system was on, it was not possible to reach adequate thermal comfort conditions. From the measurements, it was also possible to conclude that the other rooms were also below the thermal comfort limits. Figure 12. Adaptive comfort chart. Thermal comfort temperature (operative temperature) in the reception during one representative winter day (red dot). In the survey, one occupant (1.2 met; 1.62 clo) considered to be “cold” and the other (1.6 met; 1.19 clo) as being “slightly cool.” Although without the same thermal sensation, the two occupants describe a condition of thermal discomfort, in accordance with the objective measurements. The difference between the two occupants might be because the occupant who answered as being “cold” has a physiological reason (hyperthyroidism), beyond the different metabolic rate and clothing insulation, which might have conditioned his thermal sensation. The hormones produced by the thyroid regulate how the body uses and stores energy, also called “metabolism” [49]. This can explain the high level of clothing insulation (including a scarf and a blanket) this occupant had. From the results for the winter, it is possible to conclude that the building has a low thermal quality, even with thermally insulated elements and an appropriate heating system is required to achieve thermal comfort conditions during the winter season. The use of the two oil-filled radiators is not enough since they do not have the calorific power to rapidly increase air temperature to thermal comfort levels in the reception (opened to exhibition area). Though not energy-efficient equipment, the occupants use the radiators close to them to minimize the sensation of discomfort. Moreover, the non-continuous use of heating and the lack of thermal inertia of the building elements do not allow the indoor temperature to be more stable and within the comfort limits. Moreover, the low airtightness of windows and the sporadic opening of entrance door also influence the heat losses. Figure 12. Adaptive comfort chart. Thermal comfort temperature (operative temperature) in the reception during one representative winter day (red dot). In the survey, one occupant (1.2 met; 1.62 clo) considered to be “cold” and the other (1.6 met; 1.19 clo) as being “slightly cool.” Although without the same thermal sensation, the two occupants describe a condition of thermal discomfort, in accordance with the objective measurements. The difference between the two occupants might be because the occupant who answered as being “cold” has a physiological reason (hyperthyroidism), beyond the different metabolic rate and clothing insulation, which might have conditioned his thermal sensation. The hormones produced by the thyroid regulate how the body uses and stores energy, also called “metabolism” [ 49 ]. This can explain the high level of clothing insulation (including a scarf and a blanket) this occupant had.
Sustainability 2020,12, 10484 19 of 33 From the results for the winter, it is possible to conclude that the building has a low thermal quality, even with thermally insulated elements and an appropriate heating system is required to achieve thermal comfort conditions during the winter season. The use of the two oil-filled radiators is not enough since they do not have the calorific power to rapidly increase air temperature to thermal comfort levels in the reception (opened to exhibition area). Though not energy-efficient equipment, the occupants use the radiators close to them to minimize the sensation of discomfort. Moreover, the non-continuous use of heating and the lack of thermal inertia of the building elements do not allow the indoor temperature to be more stable and within the comfort limits. Moreover, the low airtightness of windows and the sporadic opening of entrance door also influence the heat losses. 4.2. Spring The Spring monitoring was carried from 21 March to 20 June 2015. During the representative monitoring period analyzed (15 April to 16 May 2015), the outdoor mean air temperature was of about 15.7 ◦ C, with maximum values often around 18 ◦ C and minimum values frequently above 10 ◦ C (Table 5; Figure 13a). Table 5. Comparison between outdoor and indoor air temperatures and relative humidity values during Spring. Spring Outdoor Reception “Dining Room” Exhibition Room “Classroom” Temperature (◦C) Mean 15.7 19.1 19.0 19.1 19.6 Maximum 22.6 23.5 23.9 22.3 22.8 Minimum 7.7 14.9 14.4 15.2 14.5 Relative Humidity (%) Mean 77.2 64.6 66.2 65.5 65.1 Maximum 92.2 80.0 73.0 75.0 79.0 Minimum 41.1 46.0 58.0 56.0 54.0 The indoor air temperature profiles for all rooms are very similar, with a mean temperature around 19 ◦ C and almost the same daily variation ( ≈ 4 ◦ C) (Figure 13a; Table 5). Indoor temperature variation follows the outdoor temperature profile but with higher minimum and maximum values. From the Spring further, since the heating system is no longer used, the reception area has a pattern similar to the other rooms. During the analyzed period, the percentage of time with the temperature above 18 ◦C in all rooms was between 73–82%, the “dining room” had the lowest value. Regarding relative humidity, the outdoor day/night variation was high ( ≈ 40%), frequently with maximum values around 90% and a minimum between 50 and 60% (Figure 13b; Table 5). Indoors, the relative humidity profiles for all rooms are more stable than outdoors, showing almost no daily variation. The mean values are similar for all rooms, around 65%. During the analyzed period, the percentage of time with relative humidity values between 20–70% (Category III) in all rooms was higher than 80%, not exceeding by far the upper limit. The thermal comfort assessment was performed on two days, one in mid-April and the other in mid-May. The results show different comfort conditions between the two days. In mid-April, the reception had a thermal comfort condition below the lower limit of the comfort range and in mid-May had a thermal condition in the center of the comfort range (Figure 14).
Sustainability 2020,12, 10484 20 of 33 Sustainability 2020, 12, x FOR PEER REVIEW 19 of 33 4.2. Spring The Spring monitoring was carried from 21st March to 20th June 2015. During the representative monitoring period analyzed (15th April to 16th May 2015), the outdoor mean air temperature was of about 15.7 °C, with maximum values often around 18 °C and minimum values frequently above 10 °C (Table 5; Figure 13a). Table 5. Comparison between outdoor and indoor air temperatures and relative humidity values during Spring. Spring Outdoor Reception “Dining Room” Exhibition Room “Classroom” Temperature (°C) Mean 15.7 19.1 19.0 19.1 19.6 Maximum 22.6 23.5 23.9 22.3 22.8 Minimum 7.7 14.9 14.4 15.2 14.5 Relative Humidity (%) Mean 77.2 64.6 66.2 65.5 65.1 Maximum 92.2 80.0 73.0 75.0 79.0 Minimum 41.1 46.0 58.0 56.0 54.0 (a) (b) Figure 13. Spring monitoring: (a) Indoor and outdoor air temperature profiles; (b) Indoor and outdoor air relative humidity profiles. The indoor air temperature profiles for all rooms are very similar, with a mean temperature around 19 °C and almost the same daily variation (≈4 °C) (Figure 13a; Table 5). Indoor temperature variation follows the outdoor temperature profile but with higher minimum and maximum values. -5 0 5 10 15 20 25 30 15 /0 4/15 16 /0 4/15 17 /0 4/15 18 /0 4/15 19 /0 4/15 20 /0 4/15 21 /0 4/15 22 /0 4/15 23 /0 4/15 24 /0 4/15 25 /0 4/15 26 /0 4/15 27 /0 4/15 28 /0 4/15 29 /0 4/15 30 /0 4/15 01 /0 5/15 02 /0 5/15 03 /0 5/15 04 /0 5/15 05 /0 5/15 06 /0 5/15 07 /0 5/15 08 /0 5/15 09 /0 5/15 10 /0 5/15 11 /0 5/15 12 /0 5/15 13 /0 5/15 14 /0 5/15 15 /0 5/15 16 /0 5/15 Temperature (°C) Outdoor Exhibition room - ground gloor Dining room School room Reception 0 10 20 30 40 50 60 70 80 90 100 15 /0 4/1 5 16 /0 4/1 5 17 /0 4/1 5 18 /0 4/1 5 19 /0 4/1 5 20 /0 4/1 5 21 /0 4/1 5 22 /0 4/1 5 23 /0 4/1 5 24 /0 4/1 5 25 /0 4/1 5 26 /0 4/1 5 27 /0 4/1 5 28 /0 4/1 5 29 /0 4/1 5 30 /0 4/1 5 01 /0 5/1 5 02 /0 5/1 5 03 /0 5/1 5 04 /0 5/1 5 05 /0 5/1 5 06 /0 5/1 5 07 /0 5/1 5 08 /0 5/1 5 09 /0 5/1 5 10 /0 5/1 5 11 /0 5/1 5 12 /0 5/1 5 13 /0 5/1 5 14 /0 5/1 5 15 /0 5/1 5 16 /0 5/1 5 Relative Humidity (%) Outdoor Exhibition room - ground floor Dining room School room Reception Figure 13. Spring monitoring: ( a ) Indoor and outdoor air temperature profiles; ( b ) Indoor and outdoor air relative humidity profiles. Sustainability 2020, 12, x FOR PEER REVIEW 20 of 33 From the Spring further, since the heating system is no longer used, the reception area has a pattern similar to the other rooms. During the analyzed period, the percentage of time with the temperature above 18 °C in all rooms was between 73–82%, the “dining room” had the lowest value. Regarding relative humidity, the outdoor day/night variation was high (≈40%), frequently with maximum values around 90% and a minimum between 50 and 60% (Figure 13b; Table 5). Indoors, the relative humidity profiles for all rooms are more stable than outdoors, showing almost no daily variation. The mean values are similar for all rooms, around 65%. During the analyzed period, the percentage of time with relative humidity values between 20–70% (Category III) in all rooms was higher than 80%, not exceeding by far the upper limit. The thermal comfort assessment was performed on two days, one in mid-April and the other in mid-May. The results show different comfort conditions between the two days. In mid-April, the reception had a thermal comfort condition below the lower limit of the comfort range and in midMay had a thermal condition in the center of the comfort range (Figure 14). (a) (b) Figure 14. Adaptive comfort chart. Thermal comfort temperature (operative temperature) in the reception during two representative spring days. (a) mid-April and (b) mid-May. In the survey carried out in mid-April, two occupants (1.2 and 1.6 met; 1.21 and 0.69 clo) referred as being “neutral” (comfortable) and one as being “cool” (1.20 met; 1.42 clo). In this measurement, the occupants feeling “neutral” had differences in metabolic rate and clothing insulation, where the occupant with less clothing had the highest metabolic rate and vice versa. The occupant feeling “cool,” as in the winter measurement, had higher clothing insulation and a significantly different thermal sensation. A physiological factor might have influenced the perceived thermal comfort of this occupant. It must also be noted that, even with an operative temperature of 18 °C, the thermal condition measured (Figure 14a) is below the lower limit of the comfort range. It might indicate that this limit is not always sufficient to assure a comfort condition and that it also depends on external conditions. In mid-May, the adaptive comfort chart (Figure 14b) showed thermal comfort conditions in the center of the comfort range. In this period three occupants answered as being “neutral” (comfortable) (1.2–1.6 met; 0.43–0.47 clo) and one as being “slightly cool” (1.2 met; 1.04 clo). The results from the subjective evaluation showed occupants’ “neutrality,” which follows the results from the objective measurements. As in previous monitoring, the occupant feeling uncomfortable had higher clothing insulation (the double) and a considerable different thermal sensation, indicating the influence of the physiological disorder on the perceived thermal sensation. The difference between the two days of the monitoring was visible in the significantly different thermal conditions, where the increase in the outdoor running mean temperature was less than 2 °C. Still, indoors the operative temperature increased more than 4 °C. This difference was due to the increase in the number of hours with incident solar radiation and with more intensity in May. Figure 14. Adaptive comfort chart. Thermal comfort temperature (operative temperature) in the reception during two representative spring days. (a) mid-April and (b) mid-May. In the survey carried out in mid-April, two occupants (1.2 and 1.6 met; 1.21 and 0.69 clo) referred as being “neutral” (comfortable) and one as being “cool” (1.20 met; 1.42 clo). In this measurement, the occupants feeling “neutral” had differences in metabolic rate and clothing insulation, where the occupant with less clothing had the highest metabolic rate and vice versa. The occupant feeling “cool,” as in the winter measurement, had higher clothing insulation and a significantly different thermal sensation. A physiological factor might have influenced the perceived thermal comfort of this occupant.
Sustainability 2020,12, 10484 21 of 33 It must also be noted that, even with an operative temperature of 18 ◦ C, the thermal condition measured (Figure 14a) is below the lower limit of the comfort range. It might indicate that this limit is not always sufficient to assure a comfort condition and that it also depends on external conditions. In mid-May, the adaptive comfort chart (Figure 14b) showed thermal comfort conditions in the center of the comfort range. In this period three occupants answered as being “neutral” (comfortable) (1.2–1.6 met; 0.43–0.47 clo) and one as being “slightly cool” (1.2 met; 1.04 clo). The results from the subjective evaluation showed occupants’ “neutrality,” which follows the results from the objective measurements. As in previous monitoring, the occupant feeling uncomfortable had higher clothing insulation (the double) and a considerable different thermal sensation, indicating the influence of the physiological disorder on the perceived thermal sensation. The difference between the two days of the monitoring was visible in the significantly different thermal conditions, where the increase in the outdoor running mean temperature was less than 2 ◦ C. Still, indoors the operative temperature increased more than 4 ◦ C. This difference was due to the increase in the number of hours with incident solar radiation and with more intensity in May. 4.3. Summer Summer monitoring was carried from 21 June to 20 September 2015. During the representative monitoring period analyzed (15 July to 16 August 2015), the outdoor mean air temperature was of about 19 ◦ C, with maximum values often around 22–23 ◦ C and minimum values frequently above 15 ◦C (Table 6; Figure 15a). Table 6. Comparison between outdoor and indoor air temperatures and relative humidity values during Summer. Summer Outdoor Reception “Dining Room” Exhibition Room “Classroom” Temperature (◦C) Mean 19.2 22.9 23.0 23.2 23.6 Maximum 27.3 27.2 27.8 26.6 27.2 Minimum 10.7 18.6 18.2 18.9 18.9 Relative Humidity (%) Mean 79.9 65.8 66.0 66.1 65.8 Maximum 92.3 76.0 70.0 71.0 71.0 Minimum 37.1 56.0 60.0 60.0 58.0 Regarding indoor temperature, as in previous seasons, the mean, maximum and minimum values were very similar for all the monitored rooms (Table 6). During the analyzed period, all the rooms were above 18 ◦C and below 25 ◦C for 85–90% of the time. The mean temperature was around 23–24 ◦ C and often there was a daily variation of 4–5 ◦ C (Table 6; Figure 15a). The “classroom” had the highest mean temperature, while the “dining room” had the highest and lowest maximum and minimum temperature, respectively (Table 6). The solar exposure of the two rooms influenced these values. The “classroom” has façades and windows facing east and south, receiving solar radiation during the morning and part of the afternoon. The “dining room” has north and west oriented façades and is the room with the highest number of windows (2 at north and 3 at west façade walls, ≈ 1 m 2 each), with the highest mean daily temperature variation. Having at the same time a façade receiving intense direct solar radiation during all the afternoon and a “cooler” façade with windows that almost do not receive direct solar radiation in this season. The reception had the lowest mean temperature record and an average daily temperature variation (around 4.5 ◦ C) similar to that of the “dining room.” In the reception, this variation was due to the direct contact with the outdoor environment and ventilation through the always-open entrance door during the opening hours.
Sustainability 2020,12, 10484 22 of 33 Sustainability 2020, 12, x FOR PEER REVIEW 21 of 33 4.3. Summer Summer monitoring was carried from 21st June to 20th September 2015. During the representative monitoring period analyzed (15th July to 16th August 2015), the outdoor mean air temperature was of about 19 °C, with maximum values often around 22–23 °C and minimum values frequently above 15 °C (Table 6; Figure 15a). Table 6. Comparison between outdoor and indoor air temperatures and relative humidity values during Summer. Summe r Outdoo r Reception “Dining Room” Exhibition Room “Classroom” Temperature (°C) Mean 19.2 22.9 23.0 23.2 23.6 Maximum 27.3 27.2 27.8 26.6 27.2 Minimum 10.7 18.6 18.2 18.9 18.9 Relative Humidity (%) Mean 79.9 65.8 66.0 66.1 65.8 Maximum 92.3 76.0 70.0 71.0 71.0 Minimum 37.1 56.0 60.0 60.0 58.0 (a) (b) Figure 15. Summer monitoring: (a) Indoor and outdoor air temperature profiles; (b) Indoor and outdoor air relative humidity profiles. Regarding indoor temperature, as in previous seasons, the mean, maximum and minimum values were very similar for all the monitored rooms (Table 6). During the analyzed period, all the rooms were above 18 °C and below 25 °C for 85–90% of the time. The mean temperature was around 23–24 °C and often there was a daily variation of 4–5 °C (Table 6; Figure 15a). The “classroom” had the highest mean temperature, while the “dining room” -5 0 5 10 15 20 25 30 15/0 7/1 5 16/0 7/1 5 17/0 7/1 5 18/0 7/1 5 19/0 7/1 5 20/0 7/1 5 21/0 7/1 5 22/0 7/1 5 23/0 7/1 5 24/0 7/1 5 25/0 7/1 5 26/0 7/1 5 27/0 7/1 5 28/0 7/1 5 29/0 7/1 5 30/0 7/1 5 31/0 7/1 5 01/0 8/1 5 02/0 8/1 5 03/0 8/1 5 04/0 8/1 5 05/0 8/1 5 06/0 8/1 5 07/0 8/1 5 08/0 8/1 5 09/0 8/1 5 10/0 8/1 5 11/0 8/1 5 12/0 8/1 5 13/0 8/1 5 14/0 8/1 5 15/0 8/1 5 16/0 8/1 5 Temperature (°C) Outdoor Exhibition room - ground gloor Dining room School room Reception 0 10 20 30 40 50 60 70 80 90 100 15/07/15 16/07/15 17/07/15 18/07/15 19/07/15 20/07/15 21/07/15 22/07/15 23/07/15 24/07/15 25/07/15 26/07/15 27/07/15 28/07/15 29/07/15 30/07/15 31/07/15 01/08/15 02/08/15 03/08/15 04/08/15 05/08/15 06/08/15 07/08/15 08/08/15 09/08/15 10/08/15 11/08/15 12/08/15 13/08/15 14/08/15 15/08/15 16/08/15 Relative Humidity (%) Outdoor Exhibition room - ground floor Dining room School room Reception Figure 15. Summer monitoring: ( a ) Indoor and outdoor air temperature profiles; ( b ) Indoor and outdoor air relative humidity profiles. For the relative humidity, as in previous seasons, the outdoor profile had a higher outdoor day/night variation (about 20–30%), where the mean was of 80% and maximum and minimum values often around 90 and 70%, respectively (Table 6; Figure 15b). In contrast, indoor spaces had more stable relative humidity profiles, with small variations and average values around 66%. In the reception, it is possible to see some peaks in the pattern that matches with the opening hours of the museum. Nevertheless, during the analyzed period, the percentage of time with relative humidity values between 20–70% (Category III) in all rooms was higher than 85% (in some rooms more than 95%), not exceeding by far the upper limit. Indoor relative humidity profiles were very stable, within acceptable values and below outdoor values. Regarding the thermal comfort assessment, the results for this season show that the reception had thermal comfort conditions in the center of the comfort range (Figure 16). In the survey, the two occupants answered as being “neutral” (comfortable) (1.2 met; 0.44 and 0.46 clo) as the objective measurement indicated. In this measurement, the occupant who has a physiological disorder was not present. Therefore, it was not possible to verify the impact of the illness on the thermal sensation during summer.
Sustainability 2020,12, 10484 23 of 33 Sustainability 2020, 12, x FOR PEER REVIEW 22 of 33 had the highest and lowest maximum and minimum temperature, respectively (Table 6). The solar exposure of the two rooms influenced these values. The “classroom” has façades and windows facing east and south, receiving solar radiation during the morning and part of the afternoon. The “dining room” has north and west oriented façades and is the room with the highest number of windows (2 at north and 3 at west façade walls, ≈1 m 2 each), with the highest mean daily temperature variation. Having at the same time a façade receiving intense direct solar radiation during all the afternoon and a “cooler” façade with windows that almost do not receive direct solar radiation in this season. The reception had the lowest mean temperature record and an average daily temperature variation (around 4.5 °C) similar to that of the “dining room.” In the reception, this variation was due to the direct contact with the outdoor environment and ventilation through the always-open entrance door during the opening hours. For the relative humidity, as in previous seasons, the outdoor profile had a higher outdoor day/night variation (about 20–30%), where the mean was of 80% and maximum and minimum values often around 90 and 70%, respectively (Table 6; Figure 15b). In contrast, indoor spaces had more stable relative humidity profiles, with small variations and average values around 66%. In the reception, it is possible to see some peaks in the pattern that matches with the opening hours of the museum. Nevertheless, during the analyzed period, the percentage of time with relative humidity values between 20–70% (Category III) in all rooms was higher than 85% (in some rooms more than 95%), not exceeding by far the upper limit. Indoor relative humidity profiles were very stable, within acceptable values and below outdoor values. Regarding the thermal comfort assessment, the results for this season show that the reception had thermal comfort conditions in the center of the comfort range (Figure 16). In the survey, the two occupants answered as being “neutral” (comfortable) (1.2 met; 0.44 and 0.46 clo) as the objective measurement indicated. In this measurement, the occupant who has a physiological disorder was not present. Therefore, it was not possible to verify the impact of the illness on the thermal sensation during summer. Figure 16. Adaptive comfort chart. Thermal comfort temperature (operative temperature) in the reception during one representative summer day. From the results for this season, it was possible to see that the building showed good comfort conditions without the use of cooling systems. Even the lower capacity to regulate the influence of outdoor thermal variations in the indoor environment (as shown in Figure 15a), as the building is a lightweight construction and due to its location in a zone with a mild summer climate (often with minimum temperatures above 15 °C and maximum temperatures lower than 25 °C) allowed the building to have good thermal conditions in a free-running mode during summer. In coastline areas from countries with temperate climates, the low thermal mass of constructions is compensated by the presence of the sea, which allows a natural regulation of thermal variations [50]. Additionally, the low occupancy density, office equipment and lighting led to low internal heat gains and did not affect Figure 16. Adaptive comfort chart. Thermal comfort temperature (operative temperature) in the reception during one representative summer day. From the results for this season, it was possible to see that the building showed good comfort conditions without the use of cooling systems. Even the lower capacity to regulate the influence of outdoor thermal variations in the indoor environment (as shown in Figure 15a), as the building is a lightweight construction and due to its location in a zone with a mild summer climate (often with minimum temperatures above 15 ◦ C and maximum temperatures lower than 25 ◦ C) allowed the building to have good thermal conditions in a free-running mode during summer. In coastline areas from countries with temperate climates, the low thermal mass of constructions is compensated by the presence of the sea, which allows a natural regulation of thermal variations [ 50 ]. Additionally, the low occupancy density, office equipment and lighting led to low internal heat gains and did not affect the thermal environment considerably. Besides, the promotion of natural ventilation, due to the permanent opening of the entrance door, also allows removing thermal loads. 4.4. Autumn The Autumn monitoring was carried from 21st September to 20th December 2015. During the representative monitoring period analyzed (15th October to 16th November 2015), the outdoor mean air temperature was 16.5 ◦ C (Table 7). In this season, maximum and minimum values are very variable throughout the days but the maximum was often above 20 ◦ C and the minimum frequently between 10 ◦ C and 15 ◦ C (Table 8; Figure 17a). It is visible the difference between the first and the second parts of the analyzed period, with maximum and minimum temperature values decreasing in the second half. Table 7. Comparison between outdoor and indoor air temperatures and relative humidity values during Autumn. Autumn Outdoor Reception “Dining Room” Exhibition Room “Classroom” Temperature (◦C) Mean 16.5 19.3 18.8 19.3 19.7 Maximum 25.8 24.4 25.4 24.3 25.6 Minimum 8.5 14.8 14.3 15.0 14.9 Relative Humidity (%) Mean 80.3 69.0 68.3 68.2 69.1 Maximum 93.3 80.0 72.0 76.0 81.0 Minimum 34.1 50.0 57.0 53.0 51.0
Sustainability 2020,12, 10484 24 of 33 Table 8. Building energy simulation conditions and input information. Weather Data (EPW) [27] Porto Climate zone [15] Heating Degree Day (HDD) 1 Summer mean outdoor temperature I2-V2 (Winter–I; Summer–V |1-Mild; 2-Medium; 3–Harsh) 1304 20.9 ◦C Internal heat gains [15]7 W/m2 Maximum U-value for external walls [15]0.40 W/(m2·◦C) Air change rate Minimum 0.6 ach Heating/Cooling temperature setpoint [15,48] 18–25 ◦C Operation Schedules Internal gains On 9 a.m. to 5 p.m. Windows opening Off24/7 Windows shading Ground floor: On 24/7 Upper floor: No solar protection Doors opening Main entrance and first floor east façade balcony Summer: Open 9 a.m. to 5 p.m. All other days: Closed. HVAC (simple 2) (18–25 ◦C) On 7:30 a.m. to 5 p.m. Mechanical ventilation (to assure the minimum 0.6 ach) On 24/7 1 HDD is a weather-based technical index designed to describe the amount of energy needed to heat a building to a comfortable temperature, taking into consideration the outdoor temperature [ 51 , 52 ]. In the Portuguese thermal performance regulation, the comfortable baseline temperature is 18 ◦ Celsius [ 15 ]. Thus the HDD indicates the daily average outdoor temperature lower than the baseline; 2 The heating/cooling system was modelled using ideal loads and the corresponding energy consumption is modelled as a post-process [24]. Sustainability 2020, 12, x FOR PEER REVIEW 23 of 33 the thermal environment considerably. Besides, the promotion of natural ventilation, due to the permanent opening of the entrance door, also allows removing thermal loads. 4.4. Autumn The Autumn monitoring was carried from 21st September to 20th December 2015. During the representative monitoring period analyzed (15th October to 16th November 2015), the outdoor mean air temperature was 16.5 °C (Table 7). In this season, maximum and minimum values are very variable throughout the days but the maximum was often above 20 °C and the minimum frequently between 10 °C and 15 °C (Table 8; Figure 17a). It is visible the difference between the first and the second parts of the analyzed period, with maximum and minimum temperature values decreasing in the second half. Table 7. Comparison between outdoor and indoor air temperatures and relative humidity values during Autumn. Autumn Outdoor Reception “Dining Room” Exhibition Room “Classroom” Temperature (°C) Mean 16.5 19.3 18.8 19.3 19.7 Maximum 25.8 24.4 25.4 24.3 25.6 Minimum 8.5 14.8 14.3 15.0 14.9 Relative Humidity (%) Mean 80.3 69.0 68.3 68.2 69.1 Maximum 93.3 80.0 72.0 76.0 81.0 Minimum 34.1 50.0 57.0 53.0 51.0 (a) (b) Figure 17. Autumn monitoring: (a) Indoor and outdoor air temperature profiles; (b) Indoor and outdoor air relative humidity profiles. -5 0 5 10 15 20 25 30 15 /1 0/1 5 16 /1 0/1 5 17 /1 0/1 5 18 /1 0/1 5 19 /1 0/1 5 20 /1 0/1 5 21 /1 0/1 5 22 /1 0/1 5 23 /1 0/1 5 24 /1 0/1 5 25 /1 0/1 5 25 /1 0/1 5 26 /1 0/1 5 27 /1 0/1 5 28 /1 0/1 5 29 /1 0/1 5 30 /1 0/1 5 31 /1 0/1 5 01 /1 1/1 5 02 /1 1/1 5 03 /1 1/1 5 04 /1 1/1 5 05 /1 1/1 5 06 /1 1/1 5 07 /1 1/1 5 08 /1 1/1 5 09 /1 1/1 5 10 /1 1/1 5 11 /1 1/1 5 12 /1 1/1 5 13 /1 1/1 5 14 /1 1/1 5 15 /1 1/1 5 Temperature (°C) Outdoor Exhibition room - ground gloor Dining room School room Reception 0 10 20 30 40 50 60 70 80 90 100 15 /1 0/1 5 16 /1 0/1 5 17 /1 0/1 5 18 /1 0/1 5 19 /1 0/1 5 20 /1 0/1 5 21 /1 0/1 5 22 /1 0/1 5 23 /1 0/1 5 24 /1 0/1 5 25 /1 0/1 5 25 /1 0/1 5 26 /1 0/1 5 27 /1 0/1 5 28 /1 0/1 5 29 /1 0/1 5 30 /1 0/1 5 31 /1 0/1 5 01 /1 1/1 5 02 /1 1/1 5 03 /1 1/1 5 04 /1 1/1 5 05 /1 1/1 5 06 /1 1/1 5 07 /1 1/1 5 08 /1 1/1 5 09 /1 1/1 5 10 /1 1/1 5 11 /1 1/1 5 12 /1 1/1 5 13 /1 1/1 5 14 /1 1/1 5 15 /1 1/1 5 Relative Humidity (%) Outdoor Exhibition room - ground floor Dining room School room Reception Figure 17. Autumn monitoring: ( a ) Indoor and outdoor air temperature profiles; ( b ) Indoor and outdoor air relative humidity profiles.
Sustainability 2020,12, 10484 25 of 33 As in previous seasons, indoor temperature profiles were very similar for all the monitored rooms (Table 7; Figure 17a). Indoor temperature variation followed the outdoor trend, being the maximum daily values close to outdoor while minimum daily values were always higher (around 6 ◦ C) (Figure 17a). In Figure 17a it is visible the difference between the first and the second parts of the analyzed period, with maximum and minimum temperature values decreasing in the second half, both outdoors and indoors. The mean indoor temperature was between 18.8–19.7 ◦ C (Table 7). During the analyzed period, the temperature in all the rooms was always below 25 ◦ C and above 18 ◦ C for 70–81% of the time. Regarding relative humidity, the outdoor day/night variation was more regular during the second part of the analyzed period ( ≈ 20%), frequently with maximum values around 90% and minimum between 60 and 70% (Figure 17b; Table 7). Indoors, the relative humidity profiles for all rooms are more stable than outdoors showing minor daily variations. In the first half of the measured period, it is visible a sudden drop in indoor relative humidity, following the two days with the lowest values of outdoor relative humidity. After this event, outdoor relative humidity went back to typical values but indoors took almost five days to increase to previous values, around 70%. The mean values are similar for all rooms and about 70% (Table 7). In the case of the reception, some higher peaks are visible, which coincide with the opening hours of the museum. During the analyzed period, although the percentage of time with relative humidity values between 20–70% (Category III) in all rooms was around 50–60%, the upper limit was not exceeded by far. Nevertheless, it has to be highlighted the relative stability of indoor moisture, due to the capacity of timber structures to regulate the moisture (i.e., ability to absorb and release humidity) [7,45]. In the thermal comfort assessment, the results for Autumn show that the reception had a thermal comfort condition below but close to, the lower limit of the comfort range (Figure 18). In the survey, the two occupants answered as being “neutral” (comfortable) (1.2–1.6 met; 0.86 and 0.69 clo, respectively). Although the survey results do not confirm the objective measurement, the thermal condition point is close to the limit. The inversely proportional relationship between the metabolic rate and the cloth insulation of the two occupants has influenced their thermal sensation, showing the adaptation of the two to satisfy their comfort needs. A decrease of one of these variables could have been sufficient to change their answers. In this measurement, the occupant that has a physiological disorder was not working. Sustainability 2020, 12, x FOR PEER REVIEW 24 of 33 As in previous seasons, indoor temperature profiles were very similar for all the monitored rooms (Table 7; Figure 17a). Indoor temperature variation followed the outdoor trend, being the maximum daily values close to outdoor while minimum daily values were always higher (around 6 °C) (Figure 17a). In Figure 17a it is visible the difference between the first and the second parts of the analyzed period, with maximum and minimum temperature values decreasing in the second half, both outdoors and indoors. The mean indoor temperature was between 18.8–19.7 °C (Table 7). During the analyzed period, the temperature in all the rooms was always below 25 °C and above 18 °C for 70–81% of the time. Regarding relative humidity, the outdoor day/night variation was more regular during the second part of the analyzed period (≈20%), frequently with maximum values around 90% and minimum between 60 and 70% (Figure 17b; Table 7). Indoors, the relative humidity profiles for all rooms are more stable than outdoors showing minor daily variations. In the first half of the measured period, it is visible a sudden drop in indoor relative humidity, following the two days with the lowest values of outdoor relative humidity. After this event, outdoor relative humidity went back to typical values but indoors took almost five days to increase to previous values, around 70%. The mean values are similar for all rooms and about 70% (Table 7). In the case of the reception, some higher peaks are visible, which coincide with the opening hours of the museum. During the analyzed period, although the percentage of time with relative humidity values between 20–70% (Category III) in all rooms was around 50–60%, the upper limit was not exceeded by far. Nevertheless, it has to be highlighted the relative stability of indoor moisture, due to the capacity of timber structures to regulate the moisture (i.e., ability to absorb and release humidity) [7,45]. In the thermal comfort assessment, the results for Autumn show that the reception had a thermal comfort condition below but close to, the lower limit of the comfort range (Figure 18). In the survey, the two occupants answered as being “neutral” (comfortable) (1.2–1.6 met; 0.86 and 0.69 clo, respectively). Although the survey results do not confirm the objective measurement, the thermal condition point is close to the limit. The inversely proportional relationship between the metabolic rate and the cloth insulation of the two occupants has influenced their thermal sensation, showing the adaptation of the two to satisfy their comfort needs. A decrease of one of these variables could have been sufficient to change their answers. In this measurement, the occupant that has a physiological disorder was not working. Figure 18. Adaptive comfort chart. Thermal comfort temperature (operative temperature) in the reception during one representative autumn day. Additionally, as in Spring, it must also be noted that even with an operative temperature of 19.6 °C, the thermal condition measured (Figure 18) was below the lower limit of the comfort range. This condition shows that the design value of 18 °C for heating (Category III), is a minimum and that is not always sufficient to assure a comfort condition, being dependent on the external conditions. 10 15 20 25 30 35 0 5 10 15 20 25 30 35 Θ o - Operative temperature (ºC) Θ rm - Outdoor running mean temperature (ºC) Upper limit Θ o = 0.43Θ rm +15.6+3 Lower limit Θ o = 0.43Θ rm +15.6-3 Operation status of the heating/cooling system: OFF Figure 18. Adaptive comfort chart. Thermal comfort temperature (operative temperature) in the reception during one representative autumn day. Additionally, as in Spring, it must also be noted that even with an operative temperature of 19.6 ◦ C, the thermal condition measured (Figure 18) was below the lower limit of the comfort range. This condition shows that the design value of 18 ◦ C for heating (Category III), is a minimum and that is not always sufficient to assure a comfort condition, being dependent on the external conditions.
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