Towards finding the optimal location of a ventilation inlet in a roof monitor skylight, using visual and thermal performance criteria, for dwellings in a Mediterranean climate

1 Towards an optimization of window design, using comfort criteria, for dwellings with vertical skylights in a Mediterranean climate Authors’ names and affiliations: Miguel Angel Campano, Universidad de Sevilla, Lecturer. Ignacio Acosta, Universidad de Sevilla, Lecturer PhD. Jesica Fernández-Agüera, Universidad de Sevilla, Lecturer. Juan José Sendra, Universidad de Sevilla, Professor. Corresponding Author: Miguel Angel Campano, Universidad de Sevilla, Lecturer. Tel. number: +34 954 55 65 95 Email: mcamp[email protected] Permanent address: Instituto Universitario de Arquitectura y Ciencias de la Construcción, Universidad de Sevilla, 41012 Seville. Spain Abstract The main aim of this work is to study the behaviour of a vertical skylight under comfort criteria, simultaneously providing both lighting and outdoor air inlet for a living room or a master bedroom in a house with an underfloor heating/cooling system. The air is introduced into the venue through an aerator placed in the joinery of the skylight window and located - for the purposes of this study - in different positions in the joinery. In order to evaluate the comfort variations caused by this change of position, a series of numerical indicators - both lighting and thermal - are applied to a set of simulation models, generating a complete analysis to determine the optimal positions of the aerator. These models are located in a Mediterranean climate context, with extreme calculation conditions (overcast sky in winter and clear sky in summer). The simulation tools Daylight Visualizer 2.5 and Design Builder 2.42 have been selected for the generation of these models. This work concludes that the optimal position of the aerator is in the side of the joinery of the skylight window, ensuring that both lighting and thermal comfort conditions are maximized. Keywords: Skylight, daylighting, lighting software, CFD, thermal comfort, Mediterranean climate. 1. Introduction and objective 1.1. State of the art The vertical skylight is a key element in contemporary architecture, as it allows a homogeneous distribution of daylight [1] while permitting natural ventilation of inner spaces [2]. Nonetheless, it is hard to find studies which combine both these functions, as they are generally focused solely on the effects of daylighting on thermal comfort and illumination levels, ignoring the thermal influence of the ventilation. In the first case, corresponding to the effects of daylighting, Treado et al., among other authors, offered in-depth research on open skylights [3], analyzing their advantages and drawbacks. Among their conclusions they highlighted the fact that skylights are the most efficient openings in terms of daylighting, as an entire room can be adequately illuminated using 2% of the ceiling 2 surface. They also concluded that lighting through skylights is more efficient than through windows, both in terms of levels of illuminance and uniformity. More recently, the National Research Council of Canada developed SkyVision, a simulation program devoted exclusively to open or focal skylights [4]. Despite its limitations in terms of types of skylight, since it only covers open skylights, the program obtains very precise results, as shown by Laouadi and Arsenault [5]. These results demonstrate the efficiency of this type of skylight, even in overcast sky conditions, while in clear sky conditions considerable thermal gains can be obtained within the room. Laouadi [6] concluded that this type of skylight was ideal for cold climates with low solar radiation. Despite the fact that vertical skylights are highly representative of contemporary architecture, few studies have been carried out on the luminous distribution they generate. Lam [1] is one of the few authors to have carried out in-depth studies on their behaviour for daylighting, concluding that this type of skylight provides the lowest and steadiest light levels with minimum annual heat gain. Among recent studies on vertical skylights it is worth highlighting research carried out by García-Hansen et al. [2]. Using the level of illuminance measurements within the rooms, the authors deduced the thermal gains produced, and subsequently calculated the Solar Saving Factor, which demonstrates the thermal behaviour of the skylight. The value of this factor is an indicator of the correct operation of this type of skylight, particularly for high latitudes. Although numerous studies have shown the efficiency of this type of skylight, little attention appears to have been paid to the efficiency of the design in making the most of daylight. In the case of the effects of ventilation, recent studies have tended to focus on the analysis of the efficiency of ventilation and not on its influence on thermal comfort [7]. In this way, atria [8] and windows [9,10] are analyzed in order to optimize their size or location, but no skylights are analyzed. Because of the usefulness of lightscoop skylights in achieving the suitable conditions of thermal and lighting comfort, research on this architectural element is under development at present. Evidence of this can be found in research by Acosta et al. [11,12], which established the optimal proportions and shapes for lightscoop skylights, in order to obtain the maximum exploitation of daylight. 1.2. Objective The main objective of this research is to determine the appropriate position for an aerator situated in the joinery of a skylight window in a Mediterranean climate, in order to obtain the best conditions for lighting and thermal comfort inside the room. Using the research by Acosta et al. [11,12] on proportions and forms of lightscoop skylights as a starting point, a multidisciplinary analysis is proposed in order to study the various positions of an aerator in the joinery of a vertical skylightin a standard living room of a heated house, and with proportions already optimized using lighting parameters. North orientation of the skylight window is selected in order to avoid direct solar radiation. This analysis on the thermal and lighting comfort resulting from the position of the aerator is performed using indicators from both fields and, in the case of thermal comfort, generating spatial models based on CFD, using parameters from Spanish standard CTE DB HS3 [13]. Thus, the aim is to determine the optimal location of the aerator in the joinery, following the parameters for comfort mentioned above. 2. Calculation Methodology 2.1. Choosing the base model for calculation The characteristics of the base model for the study are as follows: a 25 m2 living room, part of a single family dwelling for five occupants. Dimensions are 5.00 m x 5.00 m, with a height of 3.00 m and a vertical skylight on its roof. The skylight window is 3 2.50 m long and 1.25 m high, including the joinery. As explained in the objectives of the study, the window is oriented to the North, in order to avoid direct sunlight. Solar radiation produces a high thermal load, therefore, except in high latitudes, skylights windows are oriented to avoid sunlight [11]. The skylight is connected to the room through an opening of 2.50 x 1.00 m. As well as by its south-facing exterior wall, the venue is defined by vertical partitions in contact with other thermal treated rooms of the house, which is why they are considered adiabatic walls (Fig. 1). Figure 1: Characteristics of the calculation model. Dimensions in cm. From the base calculation model (Fig. 1) a set of computational models is generated by varying the position of the aerator in the joinery of the skylight window (Fig. 2): upper, lower, left and right side. 4 Figure 2: Positions of the aerator in the window joinery (inner view). Dimensions in cm. As regards lighting comfort conditions, the internal surfaces of the courtyard are ideal diffuse reflectors; therefore, the Lambertian reflection of daylight is directly proportional to the cosine of the angle between the observer's line of sight and the surface normal. The transmittance of all surfaces in the calculation model is completely void and daylight propagates exclusively through the opening in the skylight. Each surface has a different reflectance: the ceiling has an index of 0.9, the walls 0.7, and the floor 0.5, normal values in the design of interiors (Table 1). The opening in the skylight has a 4 mm double glazed window with a 6 mm air chamber. The solar factor of the window is 0.673. The building data on the thermal envelope comply with the current national standard for limiting energy demand and are shown in Table 1. ELEMENT REFLECTANCE FOR INNER SURFACE INTERREFLECTION FOR INNER SURFACE WEIGHT PER UNIT AREA (kg/m2) TRANSMITTANCE (W/m2ꞏK) SOLAR FACTOR Façade 0.7 1.0 306 0.819 - Vertical partitions 0.7 1.0 25 1.786 (adiabatic) - Roof 0.9 1.0 771 0.495 - Ground floor 0.5 1.0 889 1.776 - Insulated door 0.7 1.0 28 2.801 - Fenestration Double glazed window (4/6/4) without thermal break 3.146 0.673 Table 1: Envelope of the calculation model. The skylight design has been made considering the dimensions required to guarantee an approximate value of 1.00% for the Daylight Factor, so that under overcast conditions minimum values close to 100 lux of illuminance can be obtained for the latitude considered. However, in the study performed the relative values will be compared in eachcase, meaning that under overcast sky conditions, lighting indicators will be assessed using the minimum obtained. As it is part of a home, the room is ventilated using a mechanical extraction system through the kitchen and the bathrooms, with inlet openings for outdoor air in the rest of the rooms. In order to allow air to circulate between the different types of venues due to generated depression, a passage opening is placed at the top of the doors which connect rooms, as can be seen in figure 1 [14]. 5 In the room under study, the outdoor inlet is performed using an aerator placed in four different positions within the joinery of the vertical skylight (Fig. 2): horizontally centred upper side, horizontally centred lower side, vertically centred left side, and vertically centred right side. This door is studied in two different positions (Fig. 1): door 1, centred on the north wall, and door 2, centred on the west wall (the position on the west wall can be considered equivalent to the position on the east wall given that the room is symmetrical). Thus, there are eight combinations of air inlet positions with their respective air flows. A triple value of 0.0, 0.4 and 0.8 ACH is proposed as outdoor air change rate of the venue under study, in order to obtain a more precise definition of the influence of the air flow with respect to the relative position of the aerator in the window joinery. These values are obtained as follows:  Value of 0.0 ACH is chosen to set a reference point for the different comparisons in order to define the behaviour of the venue without the interaction of ventilation flow.  The outdoor air change rate of 0.8 ACH is obtained by applying the Document of Indoor air quality (DB-HS3), which is part of the Spanish Technical Building Code [13] and provides a minimum ventilation rate of 10.8 m3/h per occupant for living rooms and dining rooms, based on an occupancy of 5 people.  The ventilation rate of 0.4 ACH, midpoint between the above rates, is within the usual values of ventilation used in European standards [15,16]. The thermal treatment system of the venue is a hot/cold water pipeline radiant floor system, used both for cooling and heating and covering the entire floor surface (a suitable diffusion layer enabling constant thermal emission will be considered in the hypothesis). The set temperature is 20 ºC for winter and 25 ºC for summer (table 2). The thermal emission of the occupants is not included in the calculations for this study of thermal distribution, in order to ensure a clearer and more accurate characterization of the variations in air behaviour in the room as a result of the aerator position. ELEMENT 21st of December 21st of June Desired DF Maximum Value Maximum Value Thermal control 20 ºC set temperature 25 ºC set temperature Radiant floor Hot water pipeline radiant floor Cold water pipeline radiant floor Occupants / Furniture None Openings Four aerator positions in the joinery of the skylight (Fig. 2) Ventilation rate of 0.0 / 0.4 / 0.8 air change per hour through the skylight aerator Room door Two positions for the door in the room. Outlet Aerator above door Area occupied According to EN 7730 on Ergonomics of the thermal environment [17] Table 2: Elements included in the calculations. The number of models performed for each seasonal cycle (winter and summer) is four for lighting comfort and twenty for thermal comfort (table 3), considering the four different positions of the aerator in the window joinery as described above. The door position is not critical in the study of lighting comfort, since it has the same reflection and inter-reflection values as vertical partitions, although it is relevant in the thermal study, due to the change of location of its air passage opening. Finally, the use of a triple value for outdoor air rate to obtain a more accurate definition of its influence on thermal analysis almost triples the number of calculation models in this area of comfort. 6 TYPE OF ANALYSIS NUMBER OF CALCULATIONS TOTAL LOWER AERATOR UPPER AERATOR LEFT AERATOR RIGHT AERATOR LUMINICAL 2 (Winter + Summer) 2 (Winter + Summer) 2 (Winter + Summer) 2 (Winter + Summer) 8 THERMAL 0.0 ACH 2 (W+S) 2 (W+S) 2 (W+S) 2 (W+S) 40 0.4 ACH Door P1 Door P2 Door P1 Door P2 Door P1 Door P2 Door P1 Door P2 2 (W+S) 2 (W+S) 2 (W+S) 2 (W+S) 2 (W+S) 2 (W+S) 2 (W+S) 2 (W+S) 0.8 ACH Door P1 Door P2 Door P1 Door P2 Door P1 Door P2 Door P1 Door P2 2 (W+S) 2 (W+S) 2 (W+S) 2 (W+S) 2 (W+S) 2 (W+S) 2 (W+S) 2 (W+S) Table 3: Number of calculations per type of analysis. 2.2. Choosing the calculation conditions The building under study was assumed to be located in Seville, a city with typical Mediterranean climate conditions whichcorresponds to Csa in the Koppen climate classification [18] and is also part of zone B4 (according to Spanish climatic zoning), with moderately cold winters and hot summers [19] as can be seen in Table 4. Location Seville (Spain) Koppen climate classification Csa Time zone GTM +1:00 Longitude/Latitude -5.99º (W) / 37.38º (N) Elevation above sea level 7.0 m Calculation date 21st of December (Winter solstice) 21st of June (Summer solstice) Sky conditions CIE Standard Overcast Sky (1) CIE Standard Clear Sky (12) Exterior calculation template 7.8 ºC 34.4 ºC Relative humidity for calculation 68.6 % 33.2 % Climatic date template ESP Seville.swec Table 4: Location data. For models calculated with winter conditions, the sky is assumed to be completely overcast, and the definition of Standard Overcast Sky, developed by Perez et al. [20] and accepted by the CIE [21], is used. According to this definition, the ratio of the luminance La of an arbitrary sky element to the zenith luminance Lz is: La/Lz = (f(χ)ꞏφ(Z))/(f(Zs)ꞏφ(0)) (1) where: f(χ) = 1 f(Zs) = 1 φ(Z) = 1+4ꞏexp(-0.7/cosZ) φ(0) = 1+4ꞏexp(-0.7). Z = π/2-γ where γcorresponds to the angle of elevation of the sky element. 7 The Standard Overcast Sky model, also known as CIE sky type 1, determines a sky luminance similar to that of the Traditional Overcast Sky developed by Moon-Spencer [22],in which there is a luminance gradation toward the zenith, while azimuthal uniformity is maintained. In the models with summer conditions, the sky is assumed to be completely clear, with low luminance turbidity. Therefore, the definition of Perez et al. corresponding to Standard Clear Sky, sky type 12 according to the CIE, is used in this study. According to this definition, the ratio of the luminance La of an arbitrary sky element to the zenith luminance Lz is: La/Lz = (f(χ)ꞏφ(Z))/(f(Zs)ꞏφ(0)) where: f(χ) = 1+10ꞏ(exp(-3χ)-exp(-3π/2))+0.45ꞏcos2χ f(Zs) = 1+10ꞏ(exp(-3ZS)-exp(-3π/2))+ 0.45ꞏcos2ZS φ(Z) = 1-1ꞏexp(-0.32/cosZ) φ(0) = 1-1ꞏexp(-0.32). Z = π/2-γ ZS = π/2-γS χ = arccos(cosZSꞏcosZ+sinZSꞏsinZꞏcos|α-αS| and γ corresponds to the angle of elevation of the sky element. The Sky models developed by Perez et al. represent a realistic model of the luminance produced under different climatic conditions, as observed in recent studies [23]. 2.3. Choosing calculation programs Daylight Visualizer The simulation software used to evaluate comfort conditions of illumination is Velux Daylight Visualizer 2.5. This tool has been validated in the calculation of the sky component [24] using the CIE test cases [25], showing an average error of 1.28% for the rendering quality used in this type of trial. The choice of the lighting simulation software is based on a previous study on the different possibilities of simulation applied to buildings [26]. The calculation parameters used in the simulation program are shown in Table 5: Ambient On Trace level 10 Ambient trace level 4 Ambient precision 1.7 Ambient complexity 7 Ambient feature size 0 Table 5: Parameters of the calculation program Velux Daylight Visualizer 2.5. 8 Design Builder When the energy model of the room under study is generated for its subsequent simulation, a simplification is performed for the process of obtaining boundary conditions of each scenario considered by using nodal calculation, in order to obtain a higher speed in the calculation.At this point CFD techniques are used to calculate the internal energy distribution by using CFD techniques. These boundary conditions, generated using nodal calculation, relate to the radiant temperature of the envelope of the venue (door, window, walls, floor and ceiling) and the initial temperature of the indoor air. The software chosen both for nodal calculations and for CFD is Design Builder 2.42.026. This program was designed as the nodal simulation engine EnergyPlus by the U.S. Department of Energy and incorporates a steady-state type CFD module, a simulation tool with low computational needs but reliable results, which calculates snap-shots of the model studied using nodal simulation data as boundary conditions. For the purposes of CFD simulation, the boundary conditions for each scenario were obtained from the previous nodal calculation, also provided by the Design Builder program. This informatics tool is validated by the University of Northumbria (Newcastle) [27], but in order to check its reliability in this type of work a calibration process was performed by Campano et al. [28] using a real model with similar characteristics: a climatic chamber 2.40 m wide, 2.35 m high and 2.40 m deep, with a highly insulated envelope (considered adiabatic). Starting from homogeneous indoor conditions, a constant warm air flow is introduced in the venue placing its inlet at the lower centre of the wall which contains the door of the climatic chamber. In order to perform the thermal measurements inside the climatic chamber, eighty type J thermocouple sensors, are distributed throughout four columns in the venue, as can be seen in figure 3. Figure 3: Type J thermocouples disposed for the thermal measurements in the venue. A comparison between the measurement points of the real model and the simulation model (figure 4) - applying ISO 7726which requires a maximum variation of ±0.5º C - provides an average difference of 0.26 %, with a standard deviation of 0.63%, and a maximum error of 1.05%. 9 Figure 4: 3D thermal contours of simulation model These results validated "Design Builder" software as an accurate tool for developing thermal analysis of venues with warm air flows. A two-equation (Standard k-ε) turbulence model was chosen as CFD calculation conditions (Table 6) since it is the most complete model included in this software, despite its assumption of a fully turbulent flow. A Renormalization Group (RNG) kε model could solve laminar flow with greater accuracy, but the relative deviation between the results of both models is acceptable for this type of indoor environment [29, 30]. In addition, "Upwind" was chosen as a second-order discretization method as it is simpler to calculate hypotheses with air as the sole working fluid, under non-extreme conditions, without significant losses in the expected results. A hexahedral structure with straight, uniform sides was chosen when designing the mesh. The sides have a maximum spacing of 0.05 m, which is progressively reduced near surfaces and objects until it reaches 0.0125 m, using a junction tolerance of 0.0065 m and a maximum ratio between the edges of the resulting cells of 1 to 10. Thus, the total number of cells in the model amounts to 4715552. In order to study the grid independence of the models, two comparison trials were generated with meshes which contained 2934920 and 6572350 cells. It was concluded that the result for the grid with 2934920 cells tended to give higher air temperature values in comparison to the two finer grids. The result for the grid with 5572350 cells did not affect the overall results significantly, although it increased computational time, as is to be expected from these grid densities. Hence in this simulation the grid number is 4715552 . The maximum number of iterations for each simulation was established at 10000. 16 In this position, a relative increase in the Daylight Factors of up to 30% compared to other locations of the aerator is obtained. Similarly, the lateral position of the aerator allows a relative increase close to 15%in the thermal comfort indicators compared to its worst location, placed in the lower part of the window joinery of the skylight. The assessment of comfort indicators has been carried out considering the unfavourable conditions of the winter season. However, as shown in Table 8, the lateral position of the aerator in the window joinery of the skylight also produces the most favourable lighting comfort indicators in summer conditions. In contrast, there are no significant variations between models in the case of thermal comfort indicators in summer (Table 11). 5. References [1] W.M.C. Lam, Sunlighting as formgiver for architecture, New York: Van Nostrand Reinhold Company Inc., (1986) 148. [2] V. Garcia-Hansen, A. Esteves, A. Pattini, Passive solar systems for heating, daylighting and ventilation for rooms without an equator-facing façade, Renewable Energy 26 (2002) 91-111. [3] S. Treado, G. Gillete, T. Kusuda, Daylighting with Windows, Skylights, and Clerestories, Energy and Buildings 6 (1984) 319-330. [4] A. Laouadi, A. Galasiu, M. Atif, A New software tool for predicting skylight performance, International Daylighting 5 (2003) 15-18. [5] A. Laouadi, C. Arsenault, Validation of skylight performance assessment software. ASHRAE Transactions 112 (2006) 113. [6] A. Laouadi, et al., Methodology towards developing skylight design tools for thermal and energy performance of atriums in cold climates. Building and Environment 38 (2003) 117-127. [7] G.M. Stavrakakis, P.L. Zervas, H. Sarimveis , N. Markatos, Optimization of window-openings design for thermal comfort in naturally ventilated buildings. Applied Mathematical Modelling 36 (2012) 193–211. [8] S. Hussain, P. Oosthuizen, Numerical investigations of buoyancy-driven natural ventilation in a simple atrium building and its effect on the thermal comfort conditions. Applied Thermal Engineering 40 (2012) 358-372. [9] G. Fracastoro, G. Mutani, M. Perino, Experimental and theoretical analysis of natural ventilation by windows opening. Energy and Buildings 34 (2002) 817–827. [10] J. Laverge, X. Pattyn, A. Janssens, Performance assessment of residential mechanical exhaust ventilation systems dimensioned in accordance with Belgian, British, Dutch, French and ASHRAE standards. Building and Environment 59 (2013) 177-186. [11] I. Acosta, J. Navarro, J.J. Sendra, P. Esquivias, Daylighting design with lightscoop skylights: Towards an optimization of proportion and spacing under overcast sky conditions, Energy and Buildings 49 (2012) 394-401. [12] I. Acosta, J. Navarro, J.J. Sendra, Daylighting design with lightscoop skylights: Towards an optimization of shape under overcast sky conditions, Energy and Buildings (2013) doi:10.1016/j.enbuild.2013.01.006. [13] Ministerio de Fomento del Gobierno de España. Código Técnico de la Edificación. Documento Básico. Salubridad. CTEDB-HS (2006) Available: http://www.codigotecnico.org [14] A. Meiss, J. Feijó, Effect of openings location on the ventilation efficiency in dwellings, Informes de la Construcción 63 (2011) 53-60. [15] Å Blomsterberg, T. Carlsson, C. Svensson, J. Kronvall, Air flows in dwellings-simulations and measurements, Energy and Buildings 30 (1999) 87-95. [16] C. Dimitroulopoulou, Ventilation in european dwellings: A review, Building and Environment 47 (2012) 109-25. 17 [17] CEN, Ergonomics of the thermal environment. Analytical determination and interpretation of thermal comfort using calculation of the PMV and PPD indices and local thermal comfort criteria. ISO 7730:2005. Bruxelles: CEN, 2005. [18]M. Kottek, J. Grieser, C. Beck, B. Rudolf, F. Rubel, World Map of the Köppen-Geiger climate classification updated. Meteorologische Zeitschrift 15 (2006) 259-263. [19] F.J.S. De la Flor, S.A. Domínguez, J.L.M. Félix, R.G. Falcón, Climatic zoning and its application to Spanish building energy performance regulations. Energy Build 40 (2008) 1984–1990. [20] R. Perez, R. Seals, J. Michalsky, All-Weather Model for Sky Luminance Distribution - Preliminary Configuration and Validation, Solar Energy 50 (3) (1993) 235-245. [21] CIE: Spatial Distribution of Daylight - Luminance Distributions of Various Reference Skies. Commission Internationale de l’Éclairage (1994). CIE 110:1994. [22] P. Moon, D.E. Spencer, Illumination from a Non-Uniform Sky. Illuminating Engineering 37 (1942) 707-726. [23] S. Darula, R. Kittler, H. Kambezidis, A. Bartzokas, Guidelines for more realistic daylight exterior conditions in energy conscious design. Computer adaptation and examples, SK-GR 013/1998 (2000), ICA SAS Bratislava, NOA Athens. [24] R. Labayrade, M. Fontoynont, C. Mouret, P. Avouac, Assessment of Velux Daylight Visualizer 2 against CIE 171:2006 test cases. Département Génie Civil et Bâtiment (2009). [25] CIE: Test cases to assess the accuracy of lighting computer programs. Commission Internationale de l’Éclairage (2006). CIE 171:2006. [26] C.E. Ochoa, M.B.C. Aries, J.L.M. Hensen, State of the art in lighting simulation for building science: a literature review, Journal of Building Performance Simulation 5 (2011) 209-233. [27] School of Built and Natural Environment of Northumbria University. (2011). An Inter-program Analysis of Computational Dynamics Based on PHOENICS and Design Builder Software. Available: http://www.designbuilder.co.uk/component/option,com_docman/task,doc_download/gid,39/Itemid,30/. Last accessed 20th March 2012. [28] M.A. Campano, A. Pinto, I. Acosta, Validation using a real model of a CFD thermal simulation of an insulated venue with a warm air inlet. Proceedings of the 5th International Congress on Energy and Environment Engineering and Management, Lisbon (2013) 206. [29] A. Stamou, I. Katsiris, Verification of a CFD model for indoor airflow and heat transfer. Building and Environment 41 (2006) 1171-1181. [30] J. Srebric, et al., CFD boundary conditions for contaminant dispersion, heat transfer and airflow simulations around human occupants in indoor environments, Building and Environment 43 (2008) 294-303. [31] CEN, Ergonomics of the thermal environment. Determination and interpretation of cold stress when using required clothing insulation (IREQ) and local cooling effects. ISO 11079:2007. Bruxelles: CEN, 2007. [32] CIE: International lighting vocabulary. Commission Internationale de l’Éclairage (2011). CIE S 017:2011. [33] M.A. Campano, J.J. Sendra, S. Domínguez, Analysis of thermal emissions from radiators in classrooms in Mediterranean climates. Procedia Engineering 21 (2011) 106-113. [34] P.O. Fanger, Thermal Comfort Analysis and applications in environmental engineering. New York: Mc Graw Hill, 1972.