An additional facade board's effect on the energy performance of an apartment building : A verification of the requirements for nearly zero-energy buildings for 2021

Increasing the energy efficiency of buildings and the introduction of more strict regulations are small but important steps towards a better climate. Today the housing and services sector stands for nearly 40 % of Sweden’s energy use. To push the development towards more energy efficient buildings in Europe, all the new buildings are required to be nearly zero-energy buildings by 2021. The purpose of this project was to evaluate whether the use of an additional facade board on an apartment building results in putting the energy performance within the current energy performance requirements, and also within the future requirements for nearly zero-energy buildings (NZEBs). The facade boards that were tested in this project are manufactured by Kingspan and Isover. The different boards were tested in thicknesses of 30 and 50 mm. The aim of the project was to calculate the building’s average heat transfer coefficient, specific energy use and primary energy number (PET) using COMSOL Multiphysics (CM) and IDA Indoor Climate and Energy (IDA ICE). The results were then about to be controlled against the current energy performance requirements together with the future requirements for NZEBs. The approach of this project consisted of the use of the softwares CM and IDA ICE. Because IDA ICE requires input of the thermal bridges of the building, CM was used to simulate these. This was done in order to achieve more reliable values than if an assumption was made or a standard value was used. A model of the building was then created in IDA ICE where its energy performance and average heat transfer coefficient were obtained from simulations over a normal year. The results obtained from the simulations in CM seemed credible as the use of the best facade board caused the values of the thermal bridges to end up at ”Good” according to IDA ICE’s built in scale. The simulations in IDA ICE showed that the specific energy use of the bulding without an additional facade board was 55,9 kWh/m2,year compared to Boverket’s current requirements at 80 kWh/m2,year. With the 50 mm Kingspan facade board, the board with the best result, the specific energy use was reduced to 53 kWh/m2,year, an improvement of 5,2 %. For the case without an additional facade board, the PET was 66,6 kWh/m2,year compared to the NZEBs requirements for 2018 at 85 kWh/m2,year together with the requirements for year 2021 at 65 kWh/m2,year. By using the 50 mm Kingspan facade board the PET was reduced to 63,3 kWh/m2,year, an improvement of 5,0 %. This resulted in putting the PET below the NZEB requirements for 2021. The facade board that resulted in the least energy savings, Isover P31 30 mm, had an improvement of 2,5 and 2,7 % for the specific energy use and the PET respectively. This facade board also resulted in putting the PET below the NZEB requirements for 2021. The most obvious conclusions that could be drawn from the simulations was that the specific energy use was below the current energy performance requirements with a great margin, both with and without an additional facadeboard. The PET was well below theNZEB requirements for 2018 and was also belowthe NZEB requirements for 2021 using any of the tested facade boards. The building’s average heat transfer coefficient was also well below both today’s energy performance requirements and the NZEB requirements for 2018 and 2021. A use of an additional facade board resulted in an energy saving of around 2,5 and 5 % in the worst and the best case, respectively. Due to the neglect of the ring wall under the bulding, the energy performance is most probably slightly high. However, this is not of utmost relevance since the company normally does not use this kind of solution for their standard buildings. Other uncertainties about the choice of airflows in property spaces may have influenced the results in the other direction. If there are any other obvious energy saving measures than using an additional facade board, these should be taken into account primarily as a facade board can only reduce the energy use marginally