The impact of prefabricated wall insulation (PWI) panels on building energy performance: Numerical simulation and experimental validation

External wall insulation to reduce the heat loss of building envelope is evident to energy conservation and energy costs. However, traditional insulation methods require long installation time and high labour cost which significantly increase the initial investment of the retrofit work and the thermal quality is usually affected by the in-situ weather conditions when it is installed. Besides, most of the conventional insulation materials have high embodied energy consumption and carbon emissions. This paper advances the current knowledge on the use of prefabricated wall insulation (PWI) panels in building renovation by analysing the heating and cooling energy performance of five PWI panels in a 1940s detached masonry house. Five PWI panels are proposed and designed in the framework of the ongoing SureFit H2020 project, using the core materials of vacuum insulation materials, starch-aerogel insulation materials, silica-aerogel insulation materials and breathing insulation membrane, and incorporated with extruded polystyrene insulation layers. The thermal resistances of the five composite PWI panels are numerical simulated with R-value varied between 3.0 and 5.5 m2K/W. Meanwhile, a hot-box environmental chamber method is applied to experimentally test their U-values and the temperature distribution between layers under the ISO-9869 standard of 30℃ temperature differences (C-5/H25). Comparing with the experimental results, the numerical calculation results are validated with maximum difference of 6.39%. The dynamic energy simulations reveal that the proposed solutions allow reducing the energy need for space heating by 55% - 58%. However, the space cooling demand increases by 70% - 77%, which is still minor due to the baseline space cooling demand of only 1.63 MWh in the UK climate. Moreover, the future work suggests that the increased air-conditioning electricity could be compensated with the sufficient PV power generation in summer.