Risks of overheating in highly insulated English houses: an investigation into the design process, comfort performance and occupant behaviour
When exploring the topic of overheating in buildings, the notion is commonly applied to future overheating, as a consequence of climate change. By contrast, this thesis is concerned with present-day overheating, as it is experienced in highly insulated houses. This can be claimed to be an unintended consequence of decarbonising the built environment, which has led to high levels of insulation and airtightness in the design of new homes in the UK. However, evidence of overheating in such homes point at possible inadequacies in the design and regulatory processes leading to highly insulated homes. Such design and processes have tended to focus only on winter comfort and carbon reduction from space heating demand. With a view of addressing the design problems leading to uncomfortably warm homes, this project is devoted to finding evidence of present-day overheating in highly insulated houses. This is pursued by an in-depth, multi case study, in which a mixed method approach to research is carried out in four (different typologies of) English houses -one of which is retrofitted while the other three were built as new. In this research, these houses have undergone longitudinal environmental monitoring and user perspective data gathering, across the four seasons of the year. In addition, in-depth semi-structured interviews with architects and designers of such houses were also carried out. A number of design factors have been found to lead to overheating, mostly resulting from a design process in which the main (physical) factors, such as control of solar gain and provision of adequate ventilation, are largely overlooked. This overlooking has, in turn, originated a potential demand for cooling, especially when no other forms of adaption are provided within the houses. Monitoring has shown that HIHs can be warmer environments: overheating was found in some instances and with different degrees of severity. However, it was also found that assessments may underestimate overheating (no consideration of vulnerable occupants throughout building lifespan). In some cases, it was found that occupants were adopting adaptive behaviour. The interview with designers revealed a generalised limitation in knowledge, where the fabric first approach adopted in low-carbon design focused on winter comfort mostly. For, the role of thermal comfort (the means to deliver it through design, as well as to achieve it by the occupants) was found to be central in HIHs, as comfort is (ought to be) delivered entirely by design. In summary, then, the research findings presented in this thesis indicate that today overheating in HIHs is the result of innovation in architecture, which requires immediate feedback from real-world research to guide regulatory bodies and designers.
- PhD