Does improving the building fabric increase the risk of overheating in mid-terrace dwellings in the UK?

Abstract

In response to the human-induced climate change, the building sector has been experiencing a deep transformation to deliver low carbon dwellings. According to emissions shares, these have mainly focused on cutting down the heating demand in northern countries by increasing the insulation and the airtightness. At the same time, the latest projections show not only that the Earth is warming but also that extreme events will be more frequent and severe, for which raises in morbidity and mortality are expected. Consequently, research and governments have considered fundamental the evaluation of current practices to ensure adequate resilience for these scenarios. A clear concern arises: do the strategies that lower heating demand increase the risk of overheating? The answer is not clear. Advances in the field have identified most influential parameters, but opinions are divided regarding the performance of building fabric.To overcome the limitations identified, this project has integrated under the same study a wide range of constructions designed to meet 1995 and 2006 Building Regulations and FEES and PH standards. In addition, it has encompassed different locations, thermal mass, glazing ratios, shading strategies, occupancy profiles, infiltration levels, availability of purge ventilation and orientations, resulting in a total of 13824 simulations. Such approach has two main problems: simulations aimed at the study of overheating should provide accurate temperature predictions and different standards entail different conditions. The first was addressed through the validation of the model based on a real, highly insulated mid-terrace, the most common type of dwelling that overheats. The second was solved through parametric building simulation. The proposed method has been able to contextualize different cases according to each construction standard, ensuring that simulations remained relevant.Results show that improved building fabric achieves lower overheating risk as long as purge ventilation is available. When it is not, leakier and less insulated dwellings perform better given that external temperatures in the UK are generally below the maximum comfort temperature. Yet, this situation features a risk unlikely to be stand in reality. The tests conducted for the climate change projection in London 2080 stress the benefits of greater insulation and airtightness following the rise of the external temperatures, achieving significantly less duration and severity of discomfort. In addition, it is demonstrated that current overheating criteria can depict different trends, making them potentially unsuitable for research. Finally, the evaluation of annual energy demand for space heating and cooling shows that improvements in the first do not translate in increases of the second for the majority of cases, situation further corroborated for the climate change projection considered.

Date of Award	8 Dec 2015
Original language	English
Awarding Institution	University of Bath
Sponsors	La Caixa Foundation
Supervisor	Sukumar Natarajan (Supervisor) & Alfonso Ramallo Gonzalez (Supervisor)