Thermal rehabilitation of buildings facades with exterior insulation systems

Transcription

1 Thermal rehabilitation of buildings facades with exterior insulation systems Bruno André Pirão Freire Supervisor: Prof. António Heleno Domingues Moret Rodrigues June 2015

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3 Thermal rehabilitation of buildings facades with exterior insulation systems 1. Introduction In the early of the XXI century, residential and services buildings sectors were responsible for 40% of final energy consumption in the European Union, which led to the introduction of legislation to ensure that they gradually consume less energy. In that way, the European Commission published Directive 2002/91/EC [1] related to energy performance of buildings (EPBD - Energy Performance of Buildings Directive), with the main objective to adopt: (i) a methodology of calculation of the integrated energy performance of buildings; (ii) minimum requirements on the energy performance of new buildings and large existing buildings that are subject to major renovation; (iii) energy certification of buildings; (iv) the regular inspection of boilers and of air conditioning systems. In 2010, this directive was recast by Directive 2010/31/EU (EPBD recast) [2], which aims to strengthen those previous provisions and implement new measures to ensure the following objectives in 2020: 20% reduction in emissions of greenhouse gas effect; increase by 20% the renewable energy production and; 20% increase in energy efficiency. In addition to improve the objectives previously defined by Directive 2002/91/EC, this reformulation introduced an approach for calculating cost-optimal levels of minimum requirements for the energy performance of new and existing buildings that are present in the Commission Delegated Regulation (EU) Nº244/2012 [3]. This approach is based on a comparative methodology related to climatic conditions, investment costs, maintenance and operating costs (including energy costs and savings, the category of building concerned, earnings from energy produced), where applicable, and disposal costs, where applicable. As a result of reduction in the number of new buildings and the expansion potential of the rehabilitation of existing buildings in Portugal [4], is intended to perform an analysis of the performance of some external thermal insulation composite systems (ETICS), since they have potential to improve the thermal and energy performance of existing buildings. This analysis will be based on a case study building in Lisbon through dynamic simulation of its thermal and energy behaviour, generated by EnergyPlus software, and subsequent application of European methodology for calculating cost-optimal levels associated with each of the ETICS systems under study. 2. Case study definition The case study is defined by a building in need of thermal rehabilitation and built before the first regulation about building thermal performance characteristics (RCCTE) [5]. The chosen case study is an entire floor of a residential building with 10 floors, built in 1967, with four apartments per floor and four outer facades (Figure 1). This will allow a performance analysis according to the cardinal points because each apartment is directed to each of the cardinal points (North, South, East and West). In addition, there are two similar buildings in the adjacent plots (Figure 2), which allow the possibility of repeat the building rehabilitation strategy. In this case, the building in study is located in Lisbon area, more precisely in Olivais neighbourhood, and is integrated into winter climate zone I1 and summer climate zone V2, according to the current regulation [6] (Figure 3). The energy performance analysis of the chosen floor and apartments will be realized before thermal rehabilitation, preserving the original exterior walls construction characteristics, and after thermal rehabilitation, which will be tested with various ETICS solutions according to the different solar orientations. 1

4 Thermal rehabilitation of buildings facades with exterior insulation systems Figure 1 - Building exterior perspective. Figure 2 - Building location. Figure 3 - Winter and summer climate zoning for case study [6] Geometry The chosen floor of the building has four apartments, each one with three bedrooms, called AP01-E AP02-N, AP03-O and AP04-S, which solar orientations are East, North, West and South, respectively (Figure 4). All apartments are symmetric and each one has 74.13m 2 of floor area and a ceiling height of 2.8m. The opaque facade of each apartment occupies approximately 77% of outside area and the remaining 23% are glazing. AP02-N AP03-O AP01-E AP04-S Figure 4 - Floor plan and three-dimensional modeling of the case study floor Building elements characterization About the building facade is assumed two facades solutions before the building thermal rehabilitation. One of them is composed by the existing solution of double masonry brick wall with air gap between them and without thermal insulation () and the other solution is composed by a single masonry brick wall (), which is a solution that exists in many buildings built before the first RCCTE. The present study will focus on the performance of ETICS solutions in rehabilitation applied only to exterior walls, since the remaining construction elements (glazing, interior walls, floors and ceilings) will maintain its original constitution and will not be implemented any rehabilitation solution in these elements. In that way, Table 1 shows the heat transfer coefficients of different construction elements that will be part of the dynamic simulations in order to analyze the building energy performance. Table 1 - Heat transfer coefficients of existent construction elements. Exterior walls Floors and Interior walls Glazing ceilings U (W/m 2.ºC)

5 Thermal rehabilitation of buildings facades with exterior insulation systems 2.3. Characterization of rehabilitation solutions with ETICS The following simulations of thermal rehabilitation of facades with ETICS will show different types of insulation applied to these systems such as expanded polystyrene (EPS), extruded polystyrene (XPS), mineral wool (MW) and insulation cork board (ICB). These rehabilitation solutions will be applied with thermal insulation thicknesses of 20, 40, 60, 80 and 100mm to each of the original solutions ( and ). Table 2 presents the heat transfer coefficients of each thermal rehabilitation solutions applied in the original solutions. Table 2 - Heat transfer coefficients of rehabilitation solutions with ETICS to each of original solutions. ETICS with expanded polystyrene ETICS with extruded polystyrene ETICS with mineral wool ETICS with insulation cork board Exterior double wall Thick. (mm) U (W/m 2.ºC) Exterior single wall EPS XPS MW ICB EPS XPS MW ICB Thick. (mm) U (W/m 2.ºC) Energy needs The purpose of this section is to calculate nominal energy needs per m 2 in heating and cooling seasons to each of the original solutions and thermal rehabilitation with ETICS solutions. The calculation of these energy needs is made by modeling the building floor chosen, with all the definitions described above, and perform a dynamic simulation with EnergyPlus software. In that way, is intended to compare the results of the original solutions and to respective rehabilitation solutions. The weather file used for the dynamic simulation was the Lisbon weather data [7] and the heating season length was defined in 5.3 months and the cooling season length in 4 months (June, July, August and September). Heating and cooling set-points are assumed to be 18ºC and 25ºC, respectively and according to the thermal regulation [6] Usage patterns For energy needs simulation, internal gains were defined by the number of occupants living daily in each apartment, lighting and equipments. The current energy performance regulation for residential buildings [6] establishes a permanent average value of 4W/m 2 for internal gains without considering specific usage patterns but, in this simulation, internal gains were calculated from a daily usage patterns for an increase approach between the simulation and reality [8] (Figure 5). The average number of occupants per m 2, the average of annual energy consumption for lighting and equipments in residential buildings are defined according to the survey Inquérito ao Consumo de Energia no Sector Doméstico 2010 [9]. For ventilation, it is assumed that takes place equally in all fractions and without mechanical systems. The ventilation rate was determined through simplified criteria of previous regulation (RCCTE), assuming that the case study has unrated windows/doors frames for air permeability, windows blind box 3

6 Energy needs (kwh/m 2 ) Power (W/m 2 ) Thermal rehabilitation of buildings facades with exterior insulation systems and the absence of air intake devices in the facade. Table 3 presents the usage patterns, lighting and equipment power and the rate of air renewal. Table 3 - Internal gains usage patterns and air renewal rate [9]. Occupation (number of occupants) 3 Occupation period Every day from 18h to 8h (activity period from 18h to 24h and from 7h to 8h; sleeping period from 24h to 7h) Total daily gain (Wh/m 2 ) 51 Average power per hour (W/m 2 ) 2.13 Lighting Every day from 18h to 24h Consumption per hour (Wh) 149 Daily consumption per m 2 (Wh/m 2 ) 8.35 Average power per hour (W/m 2 ) 0.35 Every day 24 hours (usage pattern 1: from Equipment 24h to 7am; usage pattern 2: from 7h to 18h; usage pattern 3: from 18h to 24h) Daily consumption per m 2 (Wh/m 2 ) 46 Average power per hour (W/m 2 ) 1.92 Daily internal gains per m 2 (Wh/m 2 ) 105 Average internal gains per hour (W/m 2 ) 4.40 Hourly air renewal rate (R ph ) Hours of the day (h) Occupants Equipment Lighting Figure 5 - Internal gains usage patterns through the day. Heating and cooling equipments will also work only when the occupants are at home, which makes its operation restricted to the schedule from 18h to 8h. For the calculation of the energy needs for cooling season it is assumed the use of shading devices (exterior shutters of plastic rulers) that are activated when the incident solar radiation on the glazing exceeds 300W/m 2, although this option is disabled for heating season Energy needs in heating season Figure 6 presents the energy needs in kwh/m 2 in heating season for each apartment, with the original solution and respective rehabilitation solutions with ETICS AP01-E AP02-N AP03-O AP04-S Apartments EPS20 EPS40 EPS60 EPS80 EPS100 XPS20 XPS40 XPS60 XPS80 XPS100 MW20 MW40 MW60 MW80 MW100 ICB20 ICB40 ICB60 ICB80 ICB100 Figure 6 - Energy needs for heating in all apartments for and rehabilitation solutions with ETICS. The annual energy savings in relation to solution ranges, on average, between 11% and 25%, for thicknesses of 20mm and 100mm respectively, and for the apartment with more energy needs in heating 4

7 Energy needs (kwh/m 2 ) Energy needs (kwh/m 2 ) Thermal rehabilitation of buildings facades with exterior insulation systems season (AP02-N). For the apartment with lower energy needs in heating season (AP04-S), the annual savings is located on average between 12% and 27% for thicknesses of 20mm and 100mm respectively. With regard to the solution (Figure 7), energy savings for the apartment with more energy needs in heating season (AP02-N) ranges on average between 14% and 29% to 20mm and 100mm thicknesses respectively. For the apartment with lower energy needs in heating season (AP04-S), annual savings are located on average between 16% and 32% for 20mm and 100mm thicknesses respectively AP01-E AP02-N AP03-O AP04-S Apartments EPS20 EPS40 EPS60 EPS80 EPS100 XPS20 XPS40 XPS60 XPS80 XPS100 MW20 MW40 MW60 MW80 MW100 ICB20 ICB40 ICB60 ICB80 ICB100 Figure 7 - Energy needs for heating in all apartments for and rehabilitation solutions with ETICS Energy needs in cooling season Figures 8 and 9 presents energy needs for cooling season relative to, and respective rehabilitation solutions with ETICS. As can be seen, the largest energy savings in this season takes place in AP01-E and AP04-S apartments, which have higher energy needs during this period. For the other two apartments, AP02-N and AP03-O, the reduction in energy needs with rehabilitation solutions is relatively low and there are no wide variations between energy needs of different rehabilitation solutions with differents thicknesses. In these figures it is also concluded that rehabilitation solutions with ETICS are less effective in decreasing energy needs in cooling season compared to heating season AP01-E AP02-N AP03-O AP04-S Apartments EPS20 EPS40 EPS60 EPS80 EPS100 XPS20 XPS40 XPS60 XPS80 XPS100 MW20 MW40 MW60 MW80 MW100 ICB20 ICB40 ICB60 ICB80 ICB100 Figure 8 - Energy needs for cooling in all apartments for and rehabilitation solutions with ETICS. 5

8 Energy needs (kwh/m 2 ) Thermal rehabilitation of buildings facades with exterior insulation systems AP01-E AP02-N AP03-O AP04-S Apartments EPS20 EPS40 EPS60 EPS80 EPS100 XPS20 XPS40 XPS60 XPS80 XPS100 MW20 MW40 MW60 MW80 MW100 ICB20 ICB40 ICB60 ICB80 ICB100 Figure 9 Energy needs for cooling in all apartments for and rehabilitation solutions with ETICS. 4. Cost-optimal analysis As mentioned above, EPBD 2010 provides that Member States shall ensure implementations with the minimum requirements related to energy performance in order to achieve cost-optimal levels [2], [3]. The optimal cost is obtained from the global costs associated with the improved energy performance measures for a period of 30 years. The global cost of a rehabilitation solution is given by the sum of construction costs, which take place in the year when project starts, with the deferred costs in time, for a calculation period of 30 years, related to energy (heating and cooling) necessary to ensure the indoor thermal comfort, and maintenance work to ensure the performance quality of the solution during the period established. The global cost (C g ) is obtained by the following expression [3]: C g ( ) CI Ca, ird ( i) Vf, i 1 (1) where means the calculation period; C I means initial investment cost for measure of energy efficiency; R d (i) means discount factor for year i; V f,τ means residual value of measure at the end of the calculation period (discounted to the starting year τ 0 ) and C a,i means annual cost during year i for measure of energy efficiency as [3]: C a,i = C e,i + C m,i (2) where C e,i means energy cost for year i and C m,i means maintenance cost of rehabilitation solution for year i. The discount factor R d (i) is obtained based on discount rate r, which is defined as 3%, and according with the following expression [3]: i 1 R d (i) = ( 1 + r/100 ) (3) where (i) means the number of years from the starting períod. 6

9 Global cost per floor area ( /m2) Global cost per floor area ( /m 2 ) Thermal rehabilitation of buildings facades with exterior insulation systems To calculate the energy costs for a period of 30 years, were obtained the annual heating and cooling energy needs for the case study and the different rehabilitation solutions applied (Table 2). It is possible to calculate the final energy (annual) from the ratio between energy needs (from heating and cooling) and energy efficiency EER/COP of HVAC equipments for heating and cooling. Assuming that all the apartments in study have the same type of air conditioning system, corresponding to thermal production units of air conditioning systems with efficiency class C, is obtained, for systems with split units, multissplit and VRF, a minimum EER of 2.80 and a minimum COP of 3.20 [6]. From the calculation of the annual final energy is obtained the primary energy through the conversion factor of energy used (2.5 in case of electricity). Then, the results were normalized by the floor area of the case study. The price of electricity for the calculation was analyzed from a simple tariff of low voltage, higher than 3.45 kva and lower than 6.9 kva, and the value used was /kwh based on reference prices of liberalized electricity market published by ERSE for 2014 and for the tariff "EDP Comercial Casa" [10]. This price was updated according to European Commission forecast for energy prices and respective interest rate [11]. Maintenance costs used for each ETICS solutions correspond to a ten-year period costs according to CYPE Gerador de Preços [12]. For construction costs were considered the cost of the material used and his installation, for each rehabilitation measures adopted [13]. In Figures 10, 11 and 12 are presented cost-optimal graphs for different rehabilitation solutions with ETICS compared to the original solutions and. In each graph is indicated the insulation thickness value considered optimum for each rehabilitation solution. AP01-E AP02-N ICB ICB MW MW XPS XPS40 28 EPS EPS XPS MW ICB 28 EPS EPS XPS MW ICB Figure 10 Cost-optimal graphs for and rehabilitation solutions with ETICS, for the apartments AP01-E and AP02-N. 7

10 Global cost per floor area ( /m 2 ) Global cost per floor area ( /m 2 ) Global cost per floor area ( /m 2 ) Global cost per floor area ( /m 2 ) Global cost per floor area ( /m 2 ) Global cost per floor area ( /m 2 ) Thermal rehabilitation of buildings facades with exterior insulation systems 45 AP03-O 46 AP04-S MW40 ICB ICB20 MW XPS XPS EPS EPS EPS XPS MW ICB Primaty energy kwh/(m2.ano) EPS XPS MW ICB Figure 11 Cost-optimal graphs for and rehabilitation solutions with ETICS, for the apartments AP03-O and AP04-S. 44 AP01-E 42 AP02-N ICB40 MW40 XPS ICB40 MW40 XPS EPS EPS XPS MW ICB 26 EPS EPS XPS MW ICB AP03-O ICB40 36 MW XPS EPS EPS XPS MW ICB AP04-S ICB MW XPS EPS EPS XPS MW ICB Figure 12 - Cost-optimal graphs for and rehabilitation solutions with ETICS, for the apartments AP01-E, AP02-N, AP03-O and AP04-S. 8

11 Thermal rehabilitation of buildings facades with exterior insulation systems 5. Conclusions According to the cost-optimal graphics it is concluded that, for solution, only apartments oriented to east and north (AP01-E and AP02-N) may benefit from savings, from a financial point of view, through rehabilitation solutions with ETICS. In case of apartment AP01-E, only ETICS solution with EPS is below the reference value with a cost-optimal corresponding to 40mm insulation thickness (EPS40). In AP02-N apartment, ETICS solutions with EPS, XPS and MW are those producing savings compared to the original solution with the cost-optimal situated in 60mm thickness in case of EPS (EPS60) and 40mm thickness in case of XPS (XPS40) and MW (MW40). In the other apartments, oriented to west and south (AP03-O and AP04-S), all presented rehabilitation solutions are above the reference value for original solution. For solution, the conclusion is similar to solution where only apartments oriented to east and north (AP01-E and AP02-N) benefit from rehabilitation ETICS solutions, establishing savings from a financial point of view and for a period of 30 years. The difference between them is that in solution, and for AP01-E apartment, rehabilitation solutions with EPS and XPS are beneficial and, for AP02-N apartment, all rehabilitation solutions with ETICS analyzed (with EPS, XPS, MW and ICB) are below the reference value of solution. In case of AP01-E apartment, the cost-optimal was obtained from ETICS with EPS and XPS solutions with 40mm insulation thickness (EPS40 and XPS40). For AP02-N apartment, cost-optimal was defined, in case of EPS and XPS with 60mm thickness (EPS60 and XPS60) and for MW and ICB solutions was set to 40mm insulation thickness (MW40 and ICB40). In the others apartments, AP03-O and AP04-S, none of the rehabilitation solutions with ETICS obtained a value lower than the original solution. With these results it is concluded that rehabilitation solutions with ETICS systems applied to this particular building are more effective in apartments with highest energy needs for heating, having this heating season an important weight in calculation of primary energy. It is also expected that the progressive increase of air conditioning systems efficiency and the reduction of reference comfort temperature (from 20 C in the previous legislation to 18 C in the current regulation), give rise a reduction of benefits from rehabilitation measures with ETICS, from a financial point of view, and may influence the choice of the type of insulation to be implemented. 6. References [1] Comissão Europeia, Directiva 2002/91/CE do Parlamento Europeu e do Conselho de 16 de Dezembro de 2002 relativa ao desempenho energético dos edifícios, Jornal Oficial das Comunidades Europeias, p. 7, [2] Comissão Europeia, Directiva 2010/31/UE do Parlamento Europeu e do Conselho de 19 de Maio de 2010 relativa ao desempenho energético dos edifícios, Jornal Oficial da União Europeia, p. 23,

12 Thermal rehabilitation of buildings facades with exterior insulation systems [3] Comissão Europeia, Regulamento Delegado (UE) N.º 244/2012 da Comissão de 16 de Janeiro de 2012 que complementa a Diretiva 2010/31/UE do Parlamento Europeu e do Conselho, Jornal Oficial da União Europeia, p. 19, [4] Instituto Nacional de Estatística, Estatísticas da Construção e Habitação 2010, Lisboa: Instituto Nacional de Estatística, 2011, p. 93. [5] Ministério das Obras Públicas, Transportes e Comunicações, Decreto-Lei nº 40/90 de 6 de Fevereiro, Regulamento das Características do Comportamento Térmico dos Edifícios, RCCTE, Diário da República - 1ª Série, p. 15, [6] Ministério da Economia e do Emprego, Decreto-Lei nº 118/2013 de 20 de Agosto de 2013, Regulamento de Desempenho Energético dos Edifícios de Habitação, REH, Diário da República - 1ª Série, p. 18, [7] INETI, Lisbon weather file, [Online]. Available: o_region_6/country=prt/cname=portugal. [Acedido em 2 Junho 2014]. [8] N. Pereira, Energy-Efficient Retrofit of Residential Buildings, Lisbon 1960's - 70's case study, Lisboa: Intituto Superior Técnico, 2012, pp [9] INE e DGEG, Inquérito ao Consumo de Energia no Sector Doméstico 2010, Lisboa: Instituto Nacional de Estatística e Direcção-Geral de Energia e Geologia, 2011, p [10] INE; DGEG, Inquérito ao Consumo de Energia no Sector Doméstico 2010, Instituto Nacional de Estatística e Direcção-Geral de Energia e Geologia, Lisboa, [11] ERSE, Entidade Reguladora dos Serviços Energéticos, Preços de referência no mercado liberalizado de energia elétrica e gás natural em Portugal Continental, Agosto [Online]. Available: [Acedido em 20 Setembro 2014]. [12] European Commission, EU Energy, Transport and GHG Emissions, Trends to 2050, Reference Scenario 2013, Luxembourg: Publications Office of the European Union, 2014, pp [13] CYPE Ingenieros, S.A., Gerador de preços, [Online]. Available: [Acedido em 29 Setembro 2014]. [14] Saint-Gobain Weber Portugal, S.A., Simulador de Cálculo, [Online]. Available: [Acedido em 23 Julho 2014]. 10