How to Prevent a Passive House from Overheating: An Industry Case Study Using Parametric Design to Propose Compliance Strategies

Abstract

The airtight, well-insulated building fabric of a Passive House can reduce operational energy consumption but can also present a risk of overheating during summer. PHPP, the Excel tool used to model Passive Houses, considers the whole building as a single thermal zone; a simplification that might be partly responsible for the tool's limited ability to predict overheating risk. The current study on a real-world project provides insights on two topics. First, we compare PHPP's overheating assessment with that of CIBSE's TM59 standard that requires dynamic energy modelling at a room level. Our results support the claim that PHPP underestimates overheating; in our case, glazing SHGC and air change rate were some of the most important parameters affecting compliance, as were some other, rarely analysed factors like ratio of external wall to room volume. Second, we report on the effectiveness of using parametric design for compliance modelling of this kind, and found that parameter studies, coupled with appropriate data visualisation, are an effective way to build intuition on a design problem of this kind.