Global effort to reduce energy consumption in buildings has continuously increased to prevent environmental pollutions which lead to global warming and abnormal climate change. In advanced countries, building energy use has reached almost 40% of total energy consumption. In the case of Korea, it accounts for 25% of domestic energy consumption.
More than 60% of the building energy is used for heating and cooling loads. Building insulation plays an important role in building heating and cooling. Thus the insulation performance of building should be acknowledged and regulation for building insulation should be strengthened gradually. The Korean government has set goals to meet passive house standard by 2015 and zero-energy building construction by 2025. So, inevitably insulation regulation will be reinforced more strictly. This means building insulation would need to perform at a higher standard. High efficiency insulation such as vacuum insulation panel is also required to satisfy the reinforced insulation regulation.
Vacuum insulation panel (VIP) is a highly efficient insulation which has higher insulation performance, that is about 7~8 times better than conventional insulation. Using VIP reduces insulation thickness and creates wider effective inner space. However, VIP is a non-homogenous insulation material. It is composed of materials which have different thermal conductivities. Consequently, when VIP is installed in building, it causes various thermal bridges which occur between core and envelope materials, airgap between panels, and between construction materials of building and VIP.
In this study, analysis of the thermal bridge effect caused by VIP installation method in building, using Physibel BISCO simulation program has been done. In all, four types of installation methods using wood lath, anchor, joiner and PVC-rail were simulated. Results showed that insulation performance of VIP wall were different for the VIP installation methods. Considering the thermal bridges, the joiner method showed the least deterioration in the insulation performance of the wall, followed by PVC-rail, wood lath, and anchor fixing method.
Also, the energy performance of a reference building constructed with VIP was simulated using DesignBuilder energy simulation program; for two cases of VIP with and without thermal bridge. The reference building was a 3-story wooden building, thus joiner and wood lath methods were adopted and examined.
The building case which was considered with thermal bridge caused almost 10% rise in heating and cooling load as compared to building case where thermal bridge was not considered. Also the building with thermal bridge effects had at most 7% higher total building energy consumption than building without thermal bridge. In addition, the total building energy consumption for wood lath method was 6% higher than joiner method. The VIP installation methods affected thermal bridge magnitude and consequent building energy performance, which created different heating and cooling loads.
In conclusion it was clearly seen that when VIP is installed in a building, thermal bridge should be considered when analyzing overall insulation performance; because thermal bridge of VIPs can cause degradation of insulation performance. In the future, research to minimize thermal bridge of VIP for use in building is essential. Additionally, research on cost-benefit economics is also required for aggressive adoption of VIP in building.