Preventing the overheating of English suburban homes in a warming climate

Abstract

As the impacts of climate change become more prominent within the next 50 years and beyond, the risk of overheating in homes is a concern. This is specifically relevant in the UK's suburbs where 84% of the population reside. To assess this future impact and the effectiveness of adaptive retrofitting, probabilistic climate change data for the 2030s and 2050s are used to assess the overheating risk in six suburban house archetypes in three cities in the UK: Bristol, Oxford and Stockport. The risks of overheating in typical constructions are assessed and the possibility of preventing overheating through the use of adaptation packages is evaluated through dynamic thermal simulation. Homes in Oxford show the greatest risk of overheating. The most effective (passive) package for tackling future overheating tends to combine fabric improvements and internal heat gain reduction. To assist planners and policy-makers in assessing and preventing overheating risk at a stock level, this adaptation package is further evaluated in selected neighbourhoods across the three case study cities, using the geographical information system (GIS)-based DECoRuM-Adapt (Domestic Energy, Carbon Counting and Carbon Reduction Model) model. The implications for public policy are that the existing housing stock must be future-proofed for a warming climate, particularly retrofit programmes (e.g. the Green Deal) and any upgrading of building regulations.

Etant donné que les répercussions du changement climatique vont devenir de plus en plus importantes au cours des cinquante prochaines années et au-delà, le risque de surchauffe dans les habitations constitue un sujet de préoccupation. Ceci revêt une pertinence particulière dans les banlieues du Royaume-Uni dans lesquelles réside 84 % de la population. Afin d'évaluer cet impact futur et l'efficacité du réaménagement adaptatif, les données probabilistes relatives au changement climatique pour les années 2030 et 2050 sont utilisées pour évaluer le risque de surchauffe dans six archétypes de maisons suburbaines situés dans trois villes du Royaume-Uni : Bristol, Oxford et Stockport. Les risques de surchauffe dans des constructions types sont évalués et la possibilité de prévenir l'excès de chaleur par le recours à des trains de mesures d'adaptation est évaluée au moyen d'une simulation thermique dynamique. Les habitations situées à Oxford présentent le plus grand risque de surchauffe. Les mesures (passives) les plus efficaces pour s'attaquer aux futurs excès de chaleur tendent à combiner les améliorations apportées à l'enveloppe des bâtiments et une réduction interne du gain de chaleur. Afin d'aider les planificateurs et les décideurs à évaluer et à prévenir le risque de surchauffe au niveau du parc bâti, cet ensemble de mesures d'adaptation est évalué de manière plus poussée dans des quartiers sélectionnés sur les trois villes faisant l'objet de l'étude de cas, en utilisant le modèle DECoRuM-Adapt (Domestic Energy, Carbon Counting and Carbon Reduction Model – modèle d'énergie domestique, de comptabilisation du carbone, et de réduction du carbone), basé sur un système d'information géographique (SIG). Les implications pour les politiques publiques sont que la pérennité future du parc de logements existant doit être assurée en termes de réchauffement climatique, en recourant en particulier à des programmes de réaménagement (par ex. le New Deal vert) et à toute mise à jour de la réglementation du bâtiment.

Mots clés: adaptation, changement climatique, logement, atténuation, surchauffe, réaménagement, suburbain

Keywords:

• adaptation
• climate change
• housing
• mitigation
• overheating
• retrofit
• suburban

Acknowledgements

The authors gratefully acknowledge the support of the Engineering and Physical Science Research Council (EPSRC) for financially supporting the SNACC project of which there were three principle investigators at three universities: Rajat Gupta at Oxford Brookes University - Grant Reference No. EP/G060959/1, Katie Williams at the University of the West of England - Grant Reference No. EP/G061289/1, and Glen Bramley at Heriot-Watt University - Grant Reference No. EP/G061238/1. The authors also gratefully acknowledge the PROMETHEUS team at the University of Exeter for its work in creating the future weather files which were used in this research.

Notes

SNACC is a UK Engineering and Physical Sciences Research Council (EPSRC)-funded three-year consortium-based project with the objective ‘to identify effective, practical and acceptable means of suburban re-design in response to climate change projections‘.

The emissions scenarios represent different paths of economic, technological, energy intensity and social change in the 21st century. The Intergovernmental Panel on Climate Change (IPCC) suggests that the emissions scenarios do not relationally have probabilities and that they are non-interventionist. The Medium emissions scenario (SRES A1B) represents a future of very rapid economic growth and population increase with an intermediate use of non-fossil fuel energy sources; the High emissions scenario (SRES A1FI) represents the same scenario but with intensive fossil fuel use (Warren, 2010).

Probabilities used by the IPCC and UKCP09 represent the relative degree to which a possible climate outcome is supported by the evidence. In the cumulative distribution curve, 50% probability is the median of the distribution (also referred to as the central estimate) and 90% probability provides a value where an outcome is very unlikely to be greater than the projected value (Murphy et al., 2010).

The DSY represents a year with a hot, but not extreme, summer. It is a single year of hourly data that was selected from 1961 to 1990 for the current condition and UKCP09 generated 30-year datasets for future climate periods. The DSY format is typically used by UK building professionals to assess summer overheating levels (Eames et al., 2011).

The Green Deal is a UK government initiative that provides private investment in the carbon reduction of the existing building stock. Energy efficiency improvements will be offered by the private sector to homeowners and businesses at little or no upfront cost with payment recouped through customers’ energy bills (Department of Energy and Climate Change (DECC), 2012).

The UK Building Research Establishment's Domestic Energy Model (BREDEM-12) combined with the government-approved Standard Assessment Procedure (SAP) 2009 home energy rating methodology are the underlying energy models in DECoRuM, which calculate annual energy use, fuel costs and CO₂ emissions (Gupta, 2008).

FEES is a performance metric developed by task groups to be implemented in 2016 as a consultation for the improvement of building regulations. FEES resulted in individual standards developed for different dwelling types. For details, see Zero Carbon Hub (2009).