Using Simulation to Adapt Designs of Zero Carbon Homes Against a Warming Climate

Session 17 Paper 1, CIBSE Technical Symposium, Liverpool John Moores University, Liverpool
11-12 April 2013

Improved standards of air tightness, greater reliance on ventilation and increased levels of insulation especially in new build low and zero carbon homes in the UK, could lead to a rise in instances of overheating unless this is addressed during the early stage design. Indeed recent reports from DECC and the wider industry suggest that instances of overheating are already increasing, to be further exacerbated by predicted warming and climate impacts. This paper uses a dynamic simulation based approach to systematically evaluate the potential for incorporating adaptation strategies into the designs of zero carbon homes in the UK.

The approach adopted is based on risk analysis, which involves assessing the climate change impacts, exposure of the buildings and the needs and vulnerability of the occupants, to arrive at technically-feasible and practical adaptable measures, appropriate for a flagship eco-town development located in Bicester, Oxfordshire. Thermal models of ten house archetypes are built in IES and tested for current and future overheating using IES ApacheSim. A set of future weather data derived from UK Climate Projections 2009 is used to assess the risk of overheating under current climate and 2030s, 2050s and 2080s under a high emissions scenario and 50% probability. Modelling results of indoor temperature are compared with CIBSE Guide A and BS EN 15251 Standard overheating metrics. To tackle overheating, twenty seven individual passive design measures (ventilation, shading, fabric and orientation) are tested in IES model and the most effective measures are combined into three adaptation packages to conduct further testing. Detailed specifications of selected adaptation packages are then discussed with the project team, and incorporated into the design. The practical application of this work is that it creates a replicable methodological approach for adapting new low energy house designs against future climate change. It also helps policy makers and designers to understand the effectiveness of adaption measures in avoiding overheating now, and in the future.