Thermal bridges calculation rules and accounting in energy calculation in 9 focus countries

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Kuusk Tallinn University of Technology Brussels, 15 th

1 Thermal bridges calculation rules and accounting in energy calculation in 9 focus countries Jarek Kurnitski, Kalle Kuusk Tallinn University of Technology Brussels, 15 th December 2016 IEE/13/610/SIO /03/ /02/ /04/2014

2 Introduction EPBD Annex I states that the methodology for calculating the energy performance of buildings must take into consideration thermal bridges A variety of regulations and thermal bridges calculation practices can be expected to be used in Member States QualiCheck project studied thermal bridges calculation rules and practices in 9 focus countries

3 Heat losses through opaque walls Heat losses through window-wall thermal bridges 14 MWh/a 19 MWh/a

4 Calculation rules Five main types of systems for thermal bridges calculations in building codes were found: Thermal bridges values must be calculated (France) Thermal bridges values are based on simple basic rules (Belgium) Thermal bridges values are based on tabulated values (Estonia) Thermal bridges values are given in energy calculation software (Austria, Cyprus, Greece, Spain) Thermal bridges values are taken into account in mean U-values (Sweden, Romania) 4

5 Calculated values France Thermal bridges must be calculated for all new constructions Overall linear thermal transmission ratio (thermal bridges) of the whole building must be less than 0.28 W/(m².floor.K). Thermal bridges between intermediate floors and facades must be less than 0.6 W/(m.K). The thermal bridges values are calculated using a RT 2012* software. *Réglementation Thermique

6 Calculated values Compliance to thermal bridge requirements is mandatory in the thermal report 6

7 Simple basic rules Belgium Three main options to take thermal bridges into account: Detailed calculation method based on linear thermal transmittance values. Pragmatic method based on simple basic rules and default transmittance values. Penalisation method when no attention is paid to thermal bridges. Mainly the pragmatic approach was taken up by the building industry, since it is based on simple rules which do not require any calculation of linear thermal transmittance values. 7

8 Simple basic rules Belgium The basic rules aim to guarantee a continuous insulation layer within the building envelope. Simplicity allows designers, contractors and EPBreporters to control, mainly in a visual manner, whether a details fulfils the requirements. This way the pragmatic approach also increases the awareness of good thermal detailing in the building industry. 8

9 Simple basic rules Possibilities for the assessment of thermal bridges 9

10 Tabulated values Estonia Linear thermal transmittance of thermal bridges should be calculated by the designer: It is advisable to calculate the linear thermal transmittance of thermal bridges according to standards (ISO 10211, EN ISO 10077, EN ISO 14683, ISO 15099). In the absence of more specific data, it is allowed to use tabulated values in Energy calculations, given in the regulation (common approach). 10

11 Tabulated values Estonia: Tabulated values Välispiirete geomeetriliste külmasildade lisakonduktansid Välispiirde tüüp lisakonduktanss W/(m K) Välissein-välissein Puitsõrestiksein 0,06 Soojustatud kivisein 0,08 Massiivne kivisein, U < 0,5 W/(m 2 K) 0,07 Massiivne kivisein, U > 0,5 W/(m 2 K) 0,22 Katuslagi-välissein Puitsõrestiksein 0,07 Soojustatud kivisein ja katuslaes mineraalvattsoojustus 0,09 Soojustatud kivisein ja katuslaes keramsiitsoojustus 0,13 Massiivne kivisein, U < 0,5 W/(m 2 K) 0,08 Massiivne kivisein, U > 0,5 W/(m 2 K) 0,30 Põrand-välissein Plaat pinnasel ja puitsõrestiksein 0,12 Plaat pinnasel ja soojustatud kivisein 0,15 Plaat pinnasel ja massiivne kivisein, U < 0,5 W/(m 2 K) 0,11 Plaat pinnasel ja massiivne kivisein, U > 0,5 W/(m 2 K) 0,25 Alt tuulutatud põrand ja puitsõrestiksein 0,11 Alt tuulutatud põrand ja soojustatud kivisein 0,17 Alt tuulutatud põrand ja massiivne kivisein, U < 0,5 W/(m 2 K) 0,12 Alt tuulutatud põrand ja massiivne kivisein, U > 0,5 W/(m 2 K) 0,30 Akna seinakinnitus 0,03 It was found that in some cases tabulated values are too good no motivation to calculate

12 Tabulated values Estonia: conservative tabulated values from 2013 to push to thermal bridge calculation Joonkülmasilla soojusläbivus, W/(m K) Uus hoone Oluliselt rekonstrueeritav hoone Välisseina välisnurk 0,1 0,2 Välisseina sisenurk -0,1-0,2 Välisseina ja siseseina liitekoht Välisseina ja vahelae liitekoht Katuse ja välisseina liitekoht Põrand-pinnasel ja välisseina liitekoht Alt tuulutatud põranda ja välisseina liitekoht Akna liitumine välisseinaga (aken soojustuse kihis, raam kaetud soojustusega min. 40% soojustuse paksusest) Akna liitumine välisseinaga (aken kandekonstruktsiooni kihis) Rõdu liitumine välisseinaga 0,1 0,1 0,1 0,2 0,2 0,2 0,3 0,3 0,3 0,3 0,1 0,1 0,2 0,3 0,3 0,5 Result: many complaints that the values are too high, only sometimes calculated

13 Austria Austrian Standard ÖNORM B (p. 13): Default EPC calculation with general formula and predefined ψ-values from Table 1 in Austrian Standard ÖNORM B :2010 Reference ψ-values from thermal bridge catalogues or in line with Austrian Standard ÖNORM EN ISO 14683:2007 [3] Detailed calculation according to Austrian Standard ÖNORM EN ISO 10211:2007

14 Energy calculation software Austria If a standard calculation with the general formula is conducted by the use of EPC software, conductance surcharge values for thermal bridges will be computed autonomously without the need of user input. If detailed calculation method is selected, thermal bridges will have to be entered individually with their linear thermal transmittance value and associated effective length. 14

15 Mean U-values Romania For calculation of transmission losses, the mean U-values are calculated for building components and for the whole building envelope. Mean U-values includes linear and point thermal bridges calculation. For preliminary design the use of correction factors based simplified calculation of thermal bridges effect is allowed. For later stages of design documentation psi values for thermal bridges must be calculated or selected from already calculated tables. 15

16 Compliance and verification In most of the studied countries, there are no specific procedure for compliance and verification process (except in Belgium, sample control in France and U-values based control in Romania) 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. In France, no control or inspection is required, but controls of construction regulations are performed annually on a sample of new buildings. In Romania, building permit documentation contains the U-values compliance report. 16

17 Conclusions Thermal bridges calculation rules are addressed in the building codes of all studied countries Most common solution seems to be some simplified approach where calculations of thermal bridges are not required In many cases tabulated or default values in energy calculation software are used Compliance and verification processes are often missing. How tabulated or default values correspond to the real values of as built solutions in construction site, is unknown In highly insulated buildings a correct thermal bridge accounting is evidently important more attention is needed either to implement reliable simplified method or general calculation method the calculation is still relatively easy procedure compared to energy simulations required in some countries should be a defined task in the design process 17

18 The sole responsibility for the content of this presentation 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.

QUALICHECK STUDY AUSTRIA - ASSESSMENT OF EPC INPUT DATA BASED ON RECALCULATION AND ON-SITE VALIDATION

QUALICHECK STUDY AUSTRIA - ASSESSMENT OF EPC INPUT DATA BASED ON RECALCULATION AND ON-SITE VALIDATION Authors Susanne Geissler, Peter Wallisch (OEGNB) Lukas Maul (University of Applied Sciences Technikum Wien) fact sheet #12 2016.6 Technology All technologies Aspect Status on the ground Country Austria