Thermal and Daylight Evaluation of Building Zones

1876-6102 © 2015 The Authors. Published by Elsevier Ltd. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/). Peer-review under responsibility of the CENTRO CONGRESSI INTERNAZIONALE SRL doi: 10.1016/j.egypro.2015.11.626 Energy Procedia 78 ( 2015 ) 2784 – 2789 ScienceDirect 6th International Building Physics Conference, IBPC 2015 Thermal and Daylight Evaluation of Building Zones Hasim Altana,b,*, Jitka Mohelnikovac, Petr Hofmanc aBritish University in Dubai, Sustainable Design of the Built Environment, Faculty of Engineering & IT, Dubai 345015, United Arab Emirates bWelsh School of Architecture, Cardiff University, Cardiff CF10 3NB, United Kingdom cBrno University of Technology, Faculty of Civil Engineering, Veveri 331/95, 602 00 Brno, Czech Republic Abstract An analysis of thermal balance and daylight level in building residential zones is presented in the article. The evaluation is focused on influence of façade thermal insulation layers and multi glass pane windows on reduction of solar gains and daylight level in internal spaces. The evaluation was carried out as a computer simulation study run in software DesignBuilder. The simulation outputs provided information about optimal façade design for energy efficiency and convenient daylighting in buildings under temperate climatic conditions. © 2015 The Authors. Published by Elsevier Ltd. Peer-review under responsibility of the CENTRO CONGRESSI INTERNAZIONALE SRL. Keywords: thermal evaluation; daylighting; indoor comfort; energy savings 1. Introduction Trends in building industry towards energy efficiency have positive influence on reduction of energy consumption in buildings [1,2]. Thermal and visual comfort has high importance for new buildings design and retrofit of existing ones. The aspects need be considered in early design stages of building projects [3,4]. High insulation quality of building envelopes lead to design of peripheral walls and roofs with additional thermal insulation layers and windows with double or triple glazed units which are used for many residential and commercial buildings [5]. Sustainable building design requires energy efficiency and indoor climate comfort [6,7]. It practically means that the building energy savings need to be considered carefully together with design requirements to all aspect of indoor environment. The problem * Corresponding author. Tel.: +971-4-279-1448; fax: +971-4-279-1490. E-mail address: [email protected]; [email protected] Available online at www.sciencedirect.com © 2015 The Authors. Published by Elsevier Ltd. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/). Peer-review under responsibility of the CENTRO CONGRESSI INTERNAZIONALE SRL Hasim Altan et al. / Energy Procedia 78 ( 2015 ) 2784 – 2789 2785 of coupling of thermal and daylight evaluation was solved in research focused on thermal performance and natural ventilation and daylighting [8,9] or in studies of one window size and shading effect [10,11]. Despite of improvements in glazing and framing quality modern windows represent thermal bridges in buildings. Window design for highly insulated façades requires solution of many problematic details at window sill and jambs. These details can be solved with additive layers of thermal insulation around the window perimeter. This solution can be positive from thermal solution point of view but in many cases insulation layers create obstructions for solar radiation transmittance [12]. Computer simulations are convenient for building optimization toward the constructional design and building services as well as indoor climate and energy efficiency [13,14]. Coupling of both the thermal and daylight evaluations due to computer simulations is a reasonable concept for the façade and window design strategy. The DesignBuilder [15] simulation study is focused on evaluation of influence of thermally insulated façade on energy efficiency and daylighting in several residential zones. 2. Assignment of Building Zones The comparative study of thermal and daylight analysis in rooms of a common residential building was carried out. The study was focused on evaluation of façade thermal insulation and windows quality and their influence on the heat losses and solar gain and daylight level. The study was completed on way of design model simulated in software DesignBuilder, version 3.4.041 [15]. Simulations were run for a residential area divided into four identical zones - rooms of floor area 14.6 m2, per each, the zone clearance height is 2.6 m. Every zone has two windows – located in its external walls (windows position is in the middle of external walls), Figure 1. The total area of windows per one zone is 2.5 m2. External walls of the zones were designed into different thermal insulation and window glazing thermal properties, Table 1. A contact thermal insulation layer on the masonry influences the overall heat transfer coefficient U [Wm-2K-1] of the external wall. The layer of extruded polystyrene (EPS) was selected in several thicknesses for the façade thermal insulation and elimination of heat losses of the studied zones. Windows were also designed in adequate quality to the thermally insulated façade. Window glazing was selected into two options in dependence on thermal insulation properties as double and triple glazed units, Table 2. Window frames of all windows are positioned on the external side of the masonry and the thermal insulation layer overlaps the whole window perimeter. Simulations were completed in the several combinations of façade insulation and window glazing. The design combinations were selected in accordance with standard recommendations for thermal protection of buildings in the region with temperate climate [16]. Other constructions on every zone's envelope are roof separating partitions and horizontal floor structures of upper and lower floors with the same indoor temperature as in zones. Table 1. Design combinations of thermal insulation layers and windows. Facade thermal insulation - EPS 45 mm 70 mm 100 mm 135 mm 200 mm 245 mm 300 mm 400 mm U [Wm-2K-1] of masonry + EPS 0.30 0.25 0.21 0.18 0.14 0.12 0.10 0.08 Window glazed unit DGU DGU DGU TGU TGU TGU TGU TGU Recommended for buildings [16] Common buildings Low energy buildings Passive buildings Nearly zero energy buildings 3. Simulation Results The energy balance of solar gains and heat losses and also daylight level were studied with respect to the individual zone and its orientation. The study was completed for the location in the region with temperate climatic conditions, in the central Europe, Prague at latitude 50°. The heating season from October to March was considered for the heat losses and heating energy demands, in total 250 days per heating season, it means 6000 hours for permanently heated buildings. Indoor temperature is Ti = 20 °C in all zones. Annual balance of energy demand for heating considering heat losses and solar gains were simulated. The simulation study gives results for a comparison of influence of the insulated peripheral 2786 Hasim Altan et al. / Energy Procedia 78 ( 2015 ) 2784 – 2789 Zone 1 Zone 4 walls and windows on heat losses and solar gains in kWh/year and average Daylight Factor [20, 21] as a percentage of average internal illuminance related to external horizontal illuminance for overcast sky conditions. Fig. 1. Zones 1, 2, 3, and 4 with windows in the thermally insulated envelope. Orientation of windows gives better solar gains to Zone 1 and Zone 2 compared to other zones with windows facing to the North. Results for individual zones are presented in Figure 2 for variations with thickness of thermal insulation (EPS) from 100 to 400 mm. The Daylight Factor reduction in dependence on the thickness of the façade thermal insulation layer is obvious. The thermal insulation layer increased by 300 mm together with better windows reduces the Daylight Factor in zones about forty percent. Solar gain Heat loss Daylight Factor 700 kWh/year 600 kWh/year 500 kWh/year 400 kWh/year 300 kWh/year 200 kWh/year 100 kWh/year 0,40% Zone 1 (Zone 2) 0 kWh/year 100 mm 200 mm 300 mm 400 mm Thickness of thermal insulation 0,00% Zone 3 (Zone 4) Solar gain Heat loss Daylight Factor 600 kWh/year 1,20% Zone 3 (Zone 4) 500 kWh/year 1,00% Facade insulation Solar gain Heat loss Daylight Factor 400 kWh/year 0,80% and glazing 100 mm kWh/year % 300 kWh/year 200 kWh/year 100 kWh/year 0 kWh/year 100 mm 200 mm 300 mm 400 mm Thickness of thermal insulation 0,60% 0,40% 0,20% 0,00% EPS, DGU 406 492 1.14 400 mm EPS, TGU 255 325 0.64 Reduced by 37 % 34 % 44 % Fig. 2. Comparison of solar gains, heat losses and average Daylight Factors in Zone 1, 2, 3 and 4. Table 2. Window properties [19,20,21]. Window glazing: DGU – double glazed unit: Ug = 1.1 Wm-2K-1, solar factor g =0,56, light transmittance Wv= 0,78, TGU – triple glazed unit: Ug = 0.5 Wm-2K-1, solar factor g =0,47, light transmittance Wv= 0,69, Windows frame Uf = 1.0 Wm-2K-1 Zone 1 (Zone 2) 1,20% 1,00% Facade Solar Heat Daylight insulation gain loss Factor 0,80% and glazing kWh/year % 0,60% 100 mm EPS, DGU 572 453 1.12 400 mm 0,20% EPS, TGU 331 306 0.65 Reduced by 42 % 32.5 % 42 % Hasim Altan et al. / Energy Procedia 78 ( 2015 ) 2784 – 2789 2787 Daylighting in the zones was simulated in for date of 21st March and time 10:00 in two alternatives of daylight external conditions: firstly for overcast sky conditions with average external horizontal illuminance of 10,000 lux and secondly for sunny sky conditions. Daylighting in zones were simulated for daylight factor DF [%] distribution for the overcast sky [15,20,21] and for internal illuminance in lux simulated for clear sky [20,21]. Daylighting was evaluated for a working plane in position of 0.85 m over the zones floor level. The daylight simulation models were completed for the following inputs: external surfaces - dark ground of reflectance 0.1 [21], no external obstructions. Internal surfaces reflectance [21]: walls 0.5, floor 0.3, soffit 0.7, no internal obstructions and furniture. The average daylight factor requirement in accordance with BS 8206-2 [20] is 1.5 % for living rooms in residential buildings. Standard [21] gives design recommendations for side-lit rooms with visual activities as writing and reading for minimal daylight factor 1.5 %. For this reason a part of every zone where daylight factor DF t1.5 % was considered as a daylit area in this study. Fig. 3. Daylight level on the working plane in Zones 1, 2, 3 and 4, simulated in DesignBuilder for the 21st March, 10:00, location Prague. a) Overcast sky conditions - peripheral wall with 45 mm external insulation (EPS) and windows with double glazed units (DGU). b) Clear sky conditions - peripheral wall with 45 mm external insulation (EPS) and windows with double glazed units (DGU). c) Overcast sky conditions - peripheral wall with 300 mm external insulation (EPS) and windows with double glazed units (DGU). d) Clear sky conditions - peripheral wall with 300 mm external insulation (EPS) and windows with double glazed units (DGU). [%] [%] 2788 Hasim Altan et al. / Energy Procedia 78 ( 2015 ) 2784 – 2789 The daylight distribution is similar for all zones for the overcast sky conditions because of diffusive daylight but the daylight illuminance level is decreased in dependence on thickness of the façade insulation and type of window glazing. This effect is presented in comparison of DF [%] colour scales selected from simulations for Zone 4, Figure 4. Fig. 4. Daylight level in Zone 4, overcast sky, 21st March, 10:00, a) 100 mm EPS, DGU, b) 200 mm EPS, TGU, c) 300 mm EPS, TGU, d) 400 mm EPS, TGU The clear sky simulations give result with uneven distribution of illuminance on the working plane because of different orientation has influence on the solar gains [21]. In case of sunny sky minimal illuminance t150 lux was selected as a criterion for the well daylit area in individual zones, Figure 5 (21st March, 10:00). Thermal insulation influence on the daylit area is also evident in this case. The zone daylit area on the working plane with daylight factor DF ! 1.5 % determined for overcast sky conditions compared to the heating energy in kWh per heating season for individual solution of façade insulation is shown in Figure 6. The heating energy reduction due to the thermal insulation of the studied building zones in given climatic conditions is efficient for the thermal insulation thickness up to 150 – 12,0 11,0 10,0 9,0 8,0 7,0 6,0 5,0 4,0 3,0 100 mm EPS, DGU 200 mm EPS, TGU 300 mm EPS, TGU 400 mm EPS, TGU 200 mm. The thermal insulation overlapping the window more than 200 mm has influence on gain and of daylight level reduction which can be in annual profile significant. 600 kWh/year Fig. 5. Daylit area of zones with indoor illuminance t150 lux. 5,00 m² 500 kWh/year 4,50 m² 4,00 m² 400 kWh/year 3,50 m² 3,00 m² 300 kWh/year 2,50 m² 200 kWh/year 2,00 m² 1,50 m² 100 kWh/year 0 kWh/year 45 mm EPS, 70 mm EPS, 100 mm EPS, 135 mm EPS, 200 mm EPS, 245 mm EPS, 300 mm EPS, 400 mm EPS, 1,00 m² 0,50 m² 0,00 m² double glazed unit double glazed unit double glazed unit triple glazed unit triple glazed unit triple glazed unit triple glazed unit triple glazed unit Fig. 6. Influence of façade insulation and window glazing on reduction of heating energy and daylit area in zones. [%] [%] [%] [%] D ay lit a rea [m 2 ] Hasim Altan et al. / Energy Procedia 78 ( 2015 ) 2784 – 2789 2789 4. Conclusions The evaluation was focused on an analysis of façade thermal insulation and window quality influence on reduction of solar gains and daylight level in internal residential zones. Buildings with thermally insulated envelopes and multi glass pane windows are recommended for energy efficiency. The massive thermal insulation has positive influence on reduction of heat losses but it creates obstructions for solar gains and daylight access into interiors. It was proven that more than 300 mm of thermal insulation layer overlapping the windows and in combination with triple glazed units could diminish daylight level in the studied interior by forty percent. The façade thermal insulation can be efficient up to thickness of about 150 - 200 mm. The insulation layers of thickness more than 200 mm represent in the given climatic conditions less efficient solution because solar gain reduction. An oblique cut of thermal insulation layer around the window perimeter can be a partial solution for better transmittance of solar radiation. On the other hand the diminished parts of façade thermal insulation can bring problems with thermal bridges. The coupling of thermal and daylight analysis in early stages of building design could be useful for optimization of energy efficient occupancy together with indoor thermal and visual comfort for habitants. Acknowledgements The presented study was supported by the project TE02000077, Smart Regions—Buildings and Settlements Information Modeling, Technology and Infrastructure for Sustainable Development. References [1] Perez-Lombard L, Ortiz J, Pout C. A Review on Buildings Energy Consumption Information. Energy and Buildings. 2008;40/3:394-398. [2] Marszal AJ, Heiselberg P, Bourrelle JS, Musall E, Voss K, Sartori I, Napolitano, A. Zero Energy Building: A Review of Definitions and Calculation Methodologies. Energy and Buildings. 2011;43/4:971-979. [3] Ianni M, Sanchez de Leon M. Applying Energy Performance-Based Design in Early Design Stages, eCAADe 2013: Computation and Performance – Proceedings of the 31st International Conference on Education and Research in Computer Aided Architectural Design in Europe, Delft, The Netherlands, 2013. [4] Tzempelikos AA, Athienitis AK, Karava P. Simulation of Façade and Envelope Design Options for a New Institutional Building. CISBAT 2005, Solar Energy, 2007;81/9:1088-1103. [5] Ariosto T, Memari A. Comparative Study of Energy Efficiency of Glazing Systems for Residential and Commercial Buildings. AEI 2013: 2013. p. 409-418. [6] ed. Mumovic D, Santamouris A Handbook of Sustainable Building Design and Engineering: An Integrated Approach to Energy, Health and Operational Performance, Earthscan, TaylorFrancis, 2009. p. 51-63. [7] Reinhart CF, Mardaljevic J, Rogers Z. Dynamic Daylight Performance Metrics for Sustainable Building Design LEUKOS: The Journal of the Illuminating Engineering Society of North America, Volume 3, Issue 1, 2006, p. 7-31. [8] You W, Qin MH, Ding WW. Improving building facade design using integrated simulation of daylighting, thermal performance and natural ventilation. Building Simulation. 2013;6:269-282. [9] Liu S, Liu J, Yang Q, Pei J, Lai D, Cao X, Chao J, Zhou C. Coupled Simulation of Natural Ventilation and Daylighting for a Residential Community Design. Energy and Buildings.2014;68:686-695. [10] David M, Donn M, Garde F, Lenoir A. Assessment of the Thermal and Visual Efficiency of Solar Shades. Building and Environment, 2011;46/7:1489-1496. [11] Du J. Window Systems and Energy Performance in One-Family Houses: Size and Shading Effects. In: Proceeding of Building Simulation and Optimization, 2014. UCL London, 2014. p. 209-216. [12] Kalousek M, Mohelníkova J. Influence of Window on Solar Gains and Daylight Level. Advanced Materials Research, EnviBUILD 2014. p. 1041. [13] Al-Homoud, MS. Computer-aided Building Energy Analysis Techniques. Building and Environment, 2001;36/4:421-433. [14] Hong T, Chou SK, Bong TY. Building Simulation: An Overview of Developments and Information Sources. Building and Environment, 2000;35/4:347-361. [15] http://www.designbuilder.co.uk/component/option,com_docman/task,doc_details/gid,52/Itemid,30/. [16] CZ standard CSN 730540-2: 2011 Thermal Protection of Buildings. Part 2-Requirements (in Czech). [17] AGS glass, www.YourGlass.cz (25/01/2015). [18] EN 673 2011 Glass in Building - Determination of Thermal Transmittance (U value) - Calculation Method. [19] EN 410:2011 Glass in Building. Determination of Luminous and Solar Characteristics of Glazing. [20] BS 8206-2:2008 Lighting for Buildings – Part 2: Code of Practice for Daylighting. [21] CZ Standard CSN 730580-1: 2007, Z1:2011 Daylighting in Buildings-Part 1: Basic Requirements.