SUMMER THERMAL COMFORT REQUIREMENTS AND COMPLIANCE ASSESSMENT FRAMEWORKS

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1 fact sheet # Authors Kalle Kuusk, (TUT) with contributions from: Susanne Geissler (OEGNB); Arnold Janssens (UGent); Marina Kyprianou Dracou (CYI); Nikolaos Stathopoulos (ENTPE); Theoni Karlessi (NKUA); Horia Petran (NIRD URBAN-INCERC); José L. Molina (USE); Pär Johansson (Chalmers) Technology Summer thermal comfort Aspect Status on the ground Country All focus countries SUMMER THERMAL COMFORT REQUIREMENTS AND COMPLIANCE ASSESSMENT FRAMEWORKS Summer thermal comfort is somehow addressed in most of the building codes. As it is quite a new issue, it is not fully established and more effort is needed for successful implementation. Residential buildings Non-residential buildings Specific buildings: New buildings Existing buildings Austria OIB-RL (OIB Guideline 6 on Heat Protection and Energy Saving) and the associated Calculation Guideline have been issued by OIB (Österreichisches Institut für Bautechnik Austrian Institute of Construction Engineering - This organisation is an association (Non Profit Organisation) where all Austrian provinces are members, and it is the objective to harmonize the legislation which is the responsibility of the Austrian provinces, such as the building code. Therefore, all provinces have participated in developing the agreed OIB RL-6 which is the harmonized basis for the building codes at the provinces level. The building code which is a law at the province level references the agreed OIB-RL 6. The OIB-RL6 references Austrian Standards, thus becoming part of the legislation. OIB-RL 6 has been revised: first version 2007, revised version 2011, and another revised version 2015 [1]. OIB-RL6 states that in non-residential buildings, cooling energy demand must be below 1 kwh/m 3.a conditioned area, referring to reference climate (new construction) and 2 kwh/m 3.a respectively (major renovation). The proof is a calculation according to Austrian Standard ÖNORM B ( ): Thermal insulation in building construction Part 6: Principles and verification methods Heating demand and cooling demand - National application, national specifications and national supplements to ÖNORM EN ISO [2] Supplement 1: Single family house Examples for validation of the heating demand Supplement 2: Multi-family house Examples for validation of the heating demand Supplement 3: Non-residential building Example for validation of the heating and cooling demand Supplement 4: Single family house and multi-family house Examples for validation of the calculation of the heating demand of a lowest-energy building, which can be heated by air (passive house) For residential buildings there is no specific requirement referring to cooling energy demand. However, summer thermal comfort is addressed by the requirement of avoiding overheating according to ÖNORM B The proof is a calculation according to Austrian Standard ÖNORM B ( ) Thermal protection in building construction Part 3: Prevention of summerly overheating [3]. The

2 calculation is based on the choice of the most exposed room, the assumption that night ventilation is used to cool the building, and the fact that shading devices are used. In practice, shading devices might be not installed due to cost cutting reasons, and night ventilation might not be possible due to security reasons. There is no verification of actual indoor temperatures compared with the calculated ones. The fact that summers tend to become hotter and that sales figures of individual cooling devices are increasing indicates that there might be a problem concerning cooling energy consumption in residential buildings. QUALICHECK fact sheet #31 2 Belgium In Belgium the implementation of the EPBD is the responsibility of the three regions (Brussels, Flanders and Wallonia). In this section only the EPBD regulations in the Flanders region are discussed, which came into force in 2006 in the EBP legislation (Energy Performance and Indoor Climate). The requirements concern both energy efficiency of the building and indoor climate (summer comfort and ventilation). The separate requirement for overheating only applies to new or renovated residential buildings. The requirement has to be met, even when the building is equipped with a cooling system when the building is completed. For non-residential buildings there is no sub-requirement for summer thermal comfort. In these cases designers are encouraged to take measures to improve summer comfort by taking a fictitious cooling energy need into account in the calculation of the E-level, even when the building is not equipped with an active cooling system. Overheating assessment method In most European countries the methodology to calculate heating and cooling energy use to be taken into account in the determination of the energy performance of a building, is based on the European standard EN ISO Apart from the calculation of heating and cooling energy use, the standard also defines a quasi-steady-state calculation method to assess overheating in buildings (Annex I4). However, only few countries have included this method in their national energy performance calculation methods or building codes. The Flemish region of Belgium has adopted the method to determine a so-called overheating indicator of a building. According to the regional energy performance decree, the calculated value of the overheating indicator should be lower than a certain threshold value, otherwise the builder is charged to pay a fine. The overheating indicator (expressed in Kelvin-hours [Kh]) is based on the normalized monthly excess heat gains in relation to the indoor set-point temperature. The excess heat gains depend on the overall monthly heat gains (internal and solar), and a utilization factor which depends on the thermal capacity of the building and the ratio of heat losses to heat gains. For the overheating indicator a threshold value and a maximum value are defined. If the indicator is below the threshold value, no overheating is expected and the probability that active cooling will be installed afterwards is assumed nihil. If the indicator is above the maximum value, the design is non-compliant and needs to be revised. Between the threshold and maximum value, a risk for summer overheating is assumed, and a probability that the occupant will install an active cooling system afterwards is considered. The probability increases from 0 at the lower overheating threshold value to 1 at overheating values above the maximum value. In dwellings not equipped with an active cooling system, a fictitious energy use for cooling is included in the overall primary energy consumption in this case, depending on the predicted cooling need, the value of the overheating indicator and the associated probability of installing an active cooling system. In case the dwelling is equipped with active cooling at the moment of completion, the energy use for cooling is fully taken into account, independent of the overheating indicator value. In Belgium, the energy performance of new and renovated buildings is assessed at the moment of completion of the works by an EPB-assessor, who collects the as-built information, creates the necessary input in the EPB-software, and evaluates whether the building meets the requirements, including the overheating requirements. The EPB-declarations with the results are uploaded to a database, managed by the regional authorities. In case requirements are not met, the builder is charged with a fine proportional to the size and severity of the error.

3 Figure 1 shows the distribution of overheating indicators reported to the authorities as a function of the year of the building permit (125,000 reports, VEA 2015). Both the lower (8,000 Kh) and maximum (17,500 Kh) threshold for overheating are indicated. The figure shows a good compliance to overheating requirements, certainly in more recent projects. Older projects had more difficulties to comply (more projects above the maximum threshold in early years). Apparently architects have learned to optimize their designs over time eg by implementing solar control measures. Figure 1: distribution of declared values of overheating indicator in dwellings as a function of the year of the building permit (Source: VEA (Flemish Energy Agency), 2015, EPB-cijfers en statistieken in Dutch) Cyprus The verification of energy efficiency for the new buildings and buildings undergoing major renovation is based on the calculated primary energy use per square meter per year. The primary energy use is calculated for the building on according to its standardized use, and applied to the building as a whole: including energy needs for space heating, domestic hot water, cooling, lighting, ventilation, and electrical appliances. Requirements for buildings energy performance and calculation methodology are given in Cyprus legislation. The Methodology for Calculating the Energy Efficiency of a Building and the Building Insulation Guide (2 nd Edition) determine the method of calculating the energy performance of buildings, which must be followed by all the qualified building energy assessors. Also, the SBEMcy software program is used for calculating the energy performance of a building and issuing the EPC. and compliance verification process There are no regulations for summer comfort in Cyprus and therefore no compliance and verification process exist. Estonia The verification of energy efficiency for the new buildings is based on the calculated primary energy use. The primary energy use is calculated for the building on according to its standardized use, and applied to the building as a whole: including energy needs for space heating, domestic hot water, cooling, lighting, ventilation, and electrical appliances. Requirements for buildings energy performance and calculation methodology are given in Estonian legislation [4],[5]. Besides energy performance, legislation also regulates summer thermal comfort and sets a limit for maximum indoor temperature. Estonian regulation sets a limit for maximum indoor temperature excess, expressed in degree-hours ( Ch) over a given base temperature. For residential buildings, the base temperature, is tb = +27 C and the excess limit is 150 Ch, for non-residential buildings the values are +25 C and 100 Ch respectively. The 3

4 calculation period is set in the summertime from July 1st till August 31st, including only occupied hours of the building. In buildings with cooling system, specific temperature simulation reporting is not required. Only exception is for detached houses where temperature simulation is not required if specified requirements for window size, shading and openable windows are fulfilled. In the building design process, dynamic indoor temperature simulations are required to produce summer thermal comfort compliance verification certificate as a part of the EPC. The simulation methodology and standardized input data for the compliance assessment procedure is described in detail in the regulation [5]. The simulation models use a single zone method, meaning that only selected rooms are modelled individually with no connections to other rooms. In case of residential buildings, at least two critical rooms are required to simulate, one bedroom and one living room, which have the biggest potential to score high temperatures. Important difference between modelling residential and non-residential buildings is the use of window airing. Cooling with the opening of windows is not taken into account in non-residential buildings. In residential buildings, the opening of windows to the airing position is taken into account. France The 2012 thermal regulation (RT 2012) came into force on January 1st 2013 as a revision of the former RT2005 code. It is the regulation that authorizes or not the construction of a new building (from a thermal point of view); it applies for the residential and tertiary sector. Thermal regulatory calculations must be performed using standardized formulas which are incorporated in a CSTB (Scientific and Technical Centre for Building) approved software. RT 2012 thermal regulation considers three major aspects of the building which must be respected simultaneously: structure and envelope of the building, maximum permitted annual consumption of primary energy and summer thermal comfort. Concerning summer thermal comfort requirements, the compliance with a maximum temperature value is requested. The principle is as follows: the highest indoor temperature Tic (Conventional Indoor Temperature) during a consecutive five hot summer days, must be lower or equal to a maximum reference temperature value called Tic ref: Tic Tic ref. More specifically, the Tic value corresponds to the maximum hourly operative temperature during a period of occupancy. The Tic value is calculated using the Th-BCE 2012 method, taking into account the characteristics of the building as well as its location (climatic zone and altitude). The reference temperature value Tic ref corresponds to the maximum hourly operative temperature as calculated for the reference building. The respect of the aforementioned requirement is mentioned in the thermal report, as seen in Figure 2. QUALICHECK fact sheet #31 4 Figure 2: Excerpt of a typical thermal study report, respect of thermal comfort requirement is mandatory (shown here in red circle).

5 The current thermal comfort assessment method has not changed since the last Thermal Regulation It is expected to evolve in the near future by introducing a new indicator called Dies (Duration of Statistical Summer Discomfort). The new method is expected to take into account the duration and the intensity of the thermal discomfort of the occupant, proposing an adaptive approach according to exterior air temperature. At the end of construction, a Declaration Attesting Completion and Compliance of Works must be delivered to the planning department if the local Town Hall. This declaration certifies that the undertaken work is compliant with the Thermal Regulation RT2012, thermal comfort requirements included. It can be established by a technical controller, an architect, an accredited certification body or a diagnostician of energy performance. The certificate insures the correct consideration of the thermal regulation by verifying the three requirements of the RT2012: bioclimatic need, primary energy consumption and summer thermal comfort. After the deliverance of this certificate no further control or inspection is required by the current French legislation. However, controls of construction regulations (CRC) are performed annually on a sample of new buildings. They aim to raise stakeholder s awareness concerning the respect of construction regulations, improve the quality of buildings and the understanding of legislation. Controls are performed at a departmental level, depending in particular on regional policy on quality construction. Controllers are commissioned state officials or local authorities. Controllers may exercise the right of a site visit and of communication of technical documents during construction and up to 3 years after its completion. Each year a sample of new buildings is therefore controlled, based partly on a random draw and partly on local control policy. In case of non-conformities, an official report is addressed to a public prosecutor who will decide the legal consequences. This may include closure of the case, closure of the case upon regularization of the situation, or prosecution specifying the required sanction (fines, demolition...). Greece The assessment of energy efficiency for the new buildings and buildings undergoing major renovation is based on the calculated primary energy use per square meter per year. The primary energy use is calculated for the building according to its standardized use. The methodology includes energy needs for space heating, domestic hot water, cooling, lighting, ventilation, and electrical appliances. In order to issue the building permit and the energy performance study, the reference values of Τ.Ο.Τ.Ε.Ε /2010 concerning temperature, relative humidity and ventilation according to building use and climatic zone are taken into account, so summer thermal comfort requirements are met. These values are also considered for the energy classification of the building and the issue of EPC. There are no regulations in Greece for compliance verification process concerning summer thermal comfort after the building construction. However most of new constructions are equipped with BMS system that records indoor conditions and this data can be used for verification but it is not obligatory. Romania The energy performance calculation methodology is set by [6], while the design of the ventilation and cooling systems are regulated within [7]. The technical regulation (code) I (design, installation and operation of ventilation and air conditioned systems) provides requirements for indoor environment in terms of comfort and air quality (according to EN standards, which are approved identically as Romanian standards). There is no specific requirement referring to cooling energy demand, while summer thermal comfort is addressed by the requirement of avoiding overheating in qualitative terms. In order to achieve economic ventilation, the compliance with the regulation aims to reduce the building heat load, to 5

6 achieve as possible natural ventilation, control ventilation and cooling of the building during the night in summer, and achieving a balanced circulation of air within the building. In order to assess the need for installing a cooling system for a particular building, the methodology [6] provides calculation procedures for estimating the room temperature of an unconditioned space in summer. The calculation is performed for the hottest day of the year and the results are presented as maximum operative temperature averaged for 3 consecutive hour steps. However, the decision of installing space cooling system is left to the building owner, while the overheating in summer is not a mandatory check in the energy performance certificate or in the design documentation. There is no verification of actual indoor temperatures compared with the assumed ones. Nevertheless, last years showed that summers tend to become hotter, while sales figures of individual cooling devices are increasing, so requirements concerning cooling energy consumption and checking indoor temperatures in unconditioned spaces (to avoid overheating) are needed together with adequate verification procedures. QUALICHECK fact sheet #31 Spain The verification of energy efficiency for the new buildings is based on the calculated non-renewable primary energy use. The energy use is calculated for the building according to its standardized use, and applied to the building as a whole: including energy needs for space heating, domestic hot water, cooling, and, in case of tertiary building, lighting. For residential buildings, there are given limits according the Climatic Zone and the size of the building. For Tertiary buildings, the non-renewable primary energy use must be at maximum 65% of the nonrenewable primary energy use of the reference building. Roughly, reference building is built with the same shape as the original building but the envelope elements are substituted by given elements defined in the legislation. There are fixed values for the seasonal efficiencies of the Heating, Cooling and Domestic Hot Water systems. For renovated existing buildings (more than 25% of the envelope area), the requirement is limited to a limit of the joint net energy demand for heating and cooling, which must be below the value obtained for the reference building. Requirements for buildings energy performance and calculation methodology are given in Spanish legislation [8], [9]. The methodology requires the hourly dynamic calculation of net energy demand, and the hourly simulation of the technical systems for calculation the non-renewable primary energy consumption. It must be realized that the climate in a significant part of Spain is hot enough for making unavoidable the use of active systems for getting reasonable indoor conditions. This is the reason for not having included special requirements for summer thermal comfort, but in addition to the previously cited limit of energy consumption, the net energy demand of both heating and cooling must be below given limits. Summer climate Zones for Spain are named with numbers from 1 (the coldest) to 4 (the hottest). The limits for net energy demand for cooling are: 15 kwh/m 2.year for the 1, 2 and 3 zones; and 20 kwh/m 2.year for the zone 4. Residential buildings are considered ventilated during nights (00:00 to 08:00 hours), in the summer months (June to September) at 4 renovations per hour. There are no special compliance checking for the Summer Thermal Comfort in Spain. It is included in the common procedures for checking the compliance, which are defined in the legislation. Inspections could be made when getting the initial EPC (from the project data), of the final EPC, after the construction process. 6

7 Sweden The energy performance of building in Sweden is given as the summation of energy for heating, cooling, operation of HVAC systems and domestic hot water. The energy use should be equal to or lower than a defined maximum value in a reference year and in a reference climate zone, assuming a normal use of the building (hot water, indoor temperature, internal loads, airing, etc). Contrary to most countries in the EU, the Swedish energy performance certificates (EPCs) are based on measurements of the actual energy use in the building. The measured energy use is corrected for the climate variability by using a reference year, e.g. 30-year average. The energy use should also be corrected for non-normal use. The EPCs, based on the measured energy use, have to be issued within two years after commissioning of a building. The energy use should be measured during a period of 12 consecutive months. The Swedish recommendations for thermal comfort are defined by the Public Health Agency of Sweden s (Folkhälsomyndigheten) general advices on the indoor temperature [3]. However, there are no legal requirements to comply with the recommendations. The indoor temperature is one of the factors that influences the thermal comfort for people in buildings. The guidelines for the indoor temperature applies to the entire occupied zone inside the building which is defined as 1 meter from the outer wall, 0.6 m from the inner wall, from 0.1 m above the floor to 2 meters above the floor. During summer time, the indoor temperature in dwellings and work places should be between 20 and 26 C if the work is light and deskbound [10], [11]. The ventilation systems and comfort cooling are usually not designed to meet the upper limit at extreme outdoor temperatures. These are present only during few extremely hot days, and shorter periods of elevated ambient temperatures (heat wave). According to the definitions by the Swedish Meteorological and Hydrological Institute (SMHI), heat wave occurs when the outdoor temperature is 25 C or more for at least 5 days in a row. During these few days it is allowed that it becomes so hot that it is not experienced as comfortable [11]. Conclusions and remarks Summer thermal comfort is somehow addressed in most of the building codes. As it is quite a new issue, it is not fully established and more effort is needed for successful implementation. Analysis showed that there are four main types of approaches for summer thermal comfort requirements in building codes (Table 1): indoor temperature based requirements (Austria, France); indoor temperature excesses based requirements (Belgium, Estonia); maximum cooling energy need based requirements (Spain); summer thermal comfort is regulated within the overall indoor climate requirements (Cyprus, Greece, Romania, Sweden). Table 1. and compliance procedures in building codes Compliance procedure Country Temperature YES Cooling energy NO (overall indoor climate requirements) YES NO Austria X (residential) X (tertiary) x Belgium X (residential) x Cyprus x x Estonia x x France x X (on a sample) Greece x x Romania x x Spain x x Sweden x x 7

8 In most of the studied countries, there are no specific procedure (Table 1) for compliance and verification process (except in Belgium and sample control in France) In Belgium, the energy performance of buildings is assessed at the moment of completion of the works by an EPB-assessor, who evaluates whether the building meets the requirements, including the overheating requirements. In France, no control or inspection is required, but controls of construction regulations are performed annually on a sample of new buildings. References [1] OIB-RL (OIB Guideline 6 on Heat Protection and Energy Saving) and the associated Calculation Guideline, issued by OIB Austrian Institute of Construction Engineering [2] Austrian Standard ÖNORM B ( ) Thermal insulation in building construction Part 6: Principles and verification methods Heating demand and cooling demand - National application, national specifications and national supplements to ÖNORM EN ISO [3] Austrian Standard ÖNORM B ( ) Thermal protection in building construction Part 3: Prevention of summerly overheating. [4] Minimum requirements for energy performance of buildings. Estonian Government s Ordinance No. 68. RT I, , 4, [5] Methodology for calculating the energy performance of buildings. Ministry of Economic Affairs and Communications s Ordinance No. 63. RT I, , 1, [6] Ministry Order 157/2007 (MDRAP) for the approval of the calculation methodology for the energy performance of buildings: MC 001/ Building Envelope, MC 001/ Energy Performance of Building Systems, MC 001/ Building Energy Audit and Energy Performance Certificate (with further amendments and additional parts). [7] Ministry Order 1659/2011 (MDRT) for the approval of the technical regulation I-5 for the design, execution and operation of ventilation and air conditioning system in buildings. [8] Real Decreto 314/2006, de 17 de marzo, por el que se aprueba el Código Técnico de la Edificación. BOE núm. 74, 28 marzo Documento básico CTE-HE Ahorro de Energía. BOE 12/09/2013 and BOE 08/11/2013. [9] Real Decreto 235/2013, de 5 de abril, por el que se aprueba el procedimiento básico para la certificación de la eficiencia energética de los edificios. BOE Núm. 89,13 de abril de [10] Folkhälsomyndighetens allmänna råd om temperatur inomhus [The Public Health Agency of Sweden s general advices on indoor temperature]. Public Health Agency of Sweden FoHMFS 2014:17, [11] Arbetsplatsens utformning. Arbetsmiljöverkets föreskrifter om arbetsplatsens utformning samt allmänna råd om tillämpningen av föreskrifterna [Workplace Design. The Swedish Work Environment Authority s regulations on workplace design and general advices on the application of the regulations]. Swedish Work Environment Authority AFS 2009:2, QUALICHECK fact sheet #31 The sole responsibility for the content of this publication lies with the authors. It does not necessarily reflect the opinion of the European Union. Neither the EASME nor the European Commission are responsible for any use that may be made of the information contained therein. 8