Adapting UK Dwellings for Heat Waves

The emphasis for UK dwelling refurbishment to date has centred on reducing heating energy use. However, there has been increasing evidence pointing to the need for a more holistic approach. Many existing dwellings already experience overheating during hot weather periods. Climate change projections predict increases in both the frequency and severity of extreme weather events including heat waves such as the one in August 2003, which is estimated to have claimed the lives of over 35,000 people throughout Europe, including 2,000 in the UK. Demand for housing exceeds the supply of new stock and it is estimated that over 70% of the dwellings that will be in use in 2050 have already been built. Therefore existing dwellings will require adaptation to provide more comfortable and safe environments, to reduce both summertime overheating and heating energy use. In this research, dynamic thermal simulation computer modelling was used to assess and rank the effectiveness of selected single and combined passive interventions (adaptations) on dwelling overheating during a heat wave period. Simulations were also carried out to assess the effect of those interventions on annual space heating energy use. Four distinct dwelling types were selected to represent the housing stock in London and South East England, producing seven modelling variants: 19th century end and mid-terraced houses; 1930s semi-detached house; 1960s ground, mid and top floor flats and a modern detached house. Simulations were carried out for two different occupancy profiles and four building orientations and the cost of interventions was also considered in the analysis. The first occupancy profile assumed a ‘typical’ family who left the dwellings unoccupied during the daytime, the second assumed residents who were at home all the time (e.g. elderly or infirm). Of the dwelling types studied the 1960s mid and top floor flats and the modern (2006) detached house (Tier 2) experienced more than twice as much overheating as the other dwelling types (Tier 1). Tier 2 dwellings were “harder to treat” and unlike Tier 1 dwellings their overheating exposure could not be eliminated using the selected passive interventions. It was possible to substantially reduce overheating and annual heating energy use of Tier 1 dwellings at moderate cost, whereas the costs for retrofitting Tier 2 dwellings were estimated to be many times higher. The results demonstrated that overheating exposure can be significantly greater for residents who have to stay at home during the daytime and they should not, where possible, be housed in the most vulnerable dwellings. External window shutters were found to be the single most effective intervention for overheating reduction in most of the dwelling types considered, typically resulting in a 50% reduction in overheating exposure. The exception was the 19th century terraced houses, where applying a solar reflective (high albedo) coating to the solid external walls was often more effective. In some cases the addition of insulation increased overheating and external wall insulation consistently outperformed internal wall insulation when considering the effect on overheating, though the latter could be effective as an element of combined interventions. Adaptation should therefore be considered together with mitigation, both in design practice and in regulations. If existing dwellings (for example the 19th century terraced houses) are retrofitted for energy efficiency, without considering summer use, overheating could increase dramatically. Subsequent corrective measures could be costly and energy efficiency may suffer as a result. This research builds on previous publications and research to generate systematic, quantitative and holistic guidance for retrofitting UK dwellings to reduce overheating risk during heat waves, whilst minimising annual space heating energy use and considering the cost of retrofit. An interactive retrofit advice toolkit has been developed (and made publicly available) as part of the research, which allows selection of the best performing interventions within a given budget. Recommendations for further development of the research are also suggested.The research was carried out as part of the CREW project (Community Resilience to Extreme Weather), EPSRC grant no. EP/F036442/

Adapting dwellings for heat waves.

The research presented in this paper investigates combinations of interventions for adapting dwellings to help adequately cope with future heat waves. The effectiveness of a series of passive heat wave mitigating interventions was assessed for Victorian (late 19th century) terraced houses in the UK, using dynamic thermal simulation coupled to a nodal airflow model. The interventions comprised a range of additions and modifications to solar shading, insulation and ventilation. It was found that for a predicted test reference weather year in the 2080s, the overheating problem could be addressed by purely passive means. The most effective interventions for reducing overheating were found to be wall insulation (where external performs better than internal) and measures to reduce solar heat gain, such as external window shutters and painting the external walls a lighter colour. Other interventions were found to be less effective, such as a lighter coloured roof and increased levels of loft insulation. Further research is proposed to investigate the effect of different heat wave durations and also more extreme weather years, where additional low energy interventions (for example fans) may be necessary

Assessment of interventions to reduce dwelling overheating during heat waves considering annual energy use and cost.

Climate change projections indicate that the UK is expected to experience more frequent and more intense heat wave periods over the coming decades. Buildings frequently experience overheating even under the present climate, resulting in discomfort, health complaints and even mortality. Current house building rates are low, resulting in a need to adapt the existing building stock to provide more comfortable and safe environments. Dynamic thermal simulation computer modelling was used to assess and rank the effectiveness of selected single and combined interventions (adaptations) in reducing overheating during a heat wave period for a range of dwelling types, orientations and occupancy profiles. It is shown that solar protection interventions, such as window shutters and solar reflective coatings, can be amongst the most effective at reducing overheating during heat wave periods, but with a corresponding increase in annual space heating energy use. Whereas the addition of wall insulation, though beneficial for reducing energy use, may in some cases actually increase summer overheating. The results and guidance are presented in a way that allows identification of parts of the building stock most at risk and rapid selection of the best performing interventions in terms of overheating reduction, cost and annual energy use. It is also shown that above certain cost levels there is a diminishing return in both overheating performance and energy use reduction. The results of this research will provide important information to support refurbishment decisions of both individual house owners and landlords responsible for multiple properties, such as housing associations and local authorities

Building orientation and occupancy patterns and their effect on interventions to reduce overheating in dwellings during heat waves.

Multi-zone dynamic thermal simulation linked to a nodal airflow model, was used to assess and rank the effectiveness of selected passive heat wave mitigating interventions for reducing overheating during a heat wave period. The simulations were carried out for Victorian terraced houses in South East England using two different occupancy profiles: a family and an elderly couple and two different building orientations: front north facing and south facing. The ranking of interventions for bedrooms, where occupied hours are similar, remain broadly the same for both orientations and occupancy profiles, the most effective being the addition of external wall insulation in all cases. However in living rooms, which are unoccupied during daytime hours for the family but occupied for the elderly couple, the ranking order changes significantly. For elderly occupancy external window shutters replace external wall insulation as the most effective intervention when the living rooms face north and are the most effective for both occupancy profiles when the building is rotated to face south. Adding internal wall insulation reduces overheating in living rooms for the family occupancy scenario, but is found to increase overheating for elderly occupancy compared to the base case. When considering interventions to reduce overheating in dwellings, it is therefore critical to take into account the residents and their corresponding occupancy profile as well as building orientation

Heat wave adaptations for UK dwellings and development of a retrofit toolkit

Purpose – Dwelling retrofit strategies generally concentrate on measures to reduce energy use and carbon emissions. However, climate change projections predict increases in both the frequency and severity of extreme weather events, including heat waves. It is predicted that by the 2040s severe heat waves similar to the European one in August 2003 may be expected to occur every year. Future guidance therefore needs to combine mitigation with adaptation in order to provide safe and comfortable dwellings, whilst also reducing heating energy use, within the available retrofit budget. The paper aims to discuss these issues. Design/methodology/approach – The research presented here used dynamic thermal simulation (EnergyPlus) to model a range of passive interventions on selected dwelling types to predict the effect on both dwelling overheating during a heat wave and annual space heating energy use. The interventions include modifications and additions to solar control, insulation and ventilation. Findings – Results demonstrate the effectiveness of interventions that reduce solar heat gains, with external shutters fitted to windows being the most effective single intervention in many cases. Solar reflective coatings also reduce overheating but lead to increased winter heating energy use, whilst wall insulation reduces heating energy use but can, in some cases, lead to increased overheating. The choice of wall insulation type is shown to be very important, with external insulation consistently performing better than internal for overheating reduction. The modelling further demonstrates that combined interventions can significantly reduce or in many cases eliminate overheating. Overheating exposure was found to vary significantly (up to a factor of ten times) between dwelling types. It can be significantly greater for residents who have to stay at home during the daytime, such as the elderly or infirm, and different interventions are sometimes more suitable in these cases. Originality/value – An innovative modelling methodology integrating overheating reduction, heating energy use and intervention cost has been developed and implemented for adapting UK dwellings to future heat waves. Other innovations include an automated approach for large volumes of simulations (over 180,000); a unique graphical interpretation method for presenting single and combined intervention results; and a user-friendly, interactive retrofit toolkit, which is available online for public access and free of charge

The surgical safety checklist and patient outcomes after surgery: a prospective observational cohort study, systematic review and meta-analysis

© 2017 British Journal of Anaesthesia Background: The surgical safety checklist is widely used to improve the quality of perioperative care. However, clinicians continue to debate the clinical effectiveness of this tool. Methods: Prospective analysis of data from the International Surgical Outcomes Study (ISOS), an international observational study of elective in-patient surgery, accompanied by a systematic review and meta-analysis of published literature. The exposure was surgical safety checklist use. The primary outcome was in-hospital mortality and the secondary outcome was postoperative complications. In the ISOS cohort, a multivariable multi-level generalized linear model was used to test associations. To further contextualise these findings, we included the results from the ISOS cohort in a meta-analysis. Results are reported as odds ratios (OR) with 95% confidence intervals. Results: We included 44 814 patients from 497 hospitals in 27 countries in the ISOS analysis. There were 40 245 (89.8%) patients exposed to the checklist, whilst 7508 (16.8%) sustained ≥1 postoperative complications and 207 (0.5%) died before hospital discharge. Checklist exposure was associated with reduced mortality [odds ratio (OR) 0.49 (0.32–0.77); P\u3c0.01], but no difference in complication rates [OR 1.02 (0.88–1.19); P=0.75]. In a systematic review, we screened 3732 records and identified 11 eligible studies of 453 292 patients including the ISOS cohort. Checklist exposure was associated with both reduced postoperative mortality [OR 0.75 (0.62–0.92); P\u3c0.01; I2=87%] and reduced complication rates [OR 0.73 (0.61–0.88); P\u3c0.01; I2=89%). Conclusions: Patients exposed to a surgical safety checklist experience better postoperative outcomes, but this could simply reflect wider quality of care in hospitals where checklist use is routine

Prospective observational cohort study on grading the severity of postoperative complications in global surgery research

Background The Clavien–Dindo classification is perhaps the most widely used approach for reporting postoperative complications in clinical trials. This system classifies complication severity by the treatment provided. However, it is unclear whether the Clavien–Dindo system can be used internationally in studies across differing healthcare systems in high- (HICs) and low- and middle-income countries (LMICs). Methods This was a secondary analysis of the International Surgical Outcomes Study (ISOS), a prospective observational cohort study of elective surgery in adults. Data collection occurred over a 7-day period. Severity of complications was graded using Clavien–Dindo and the simpler ISOS grading (mild, moderate or severe, based on guided investigator judgement). Severity grading was compared using the intraclass correlation coefficient (ICC). Data are presented as frequencies and ICC values (with 95 per cent c.i.). The analysis was stratified by income status of the country, comparing HICs with LMICs. Results A total of 44 814 patients were recruited from 474 hospitals in 27 countries (19 HICs and 8 LMICs). Some 7508 patients (16·8 per cent) experienced at least one postoperative complication, equivalent to 11 664 complications in total. Using the ISOS classification, 5504 of 11 664 complications (47·2 per cent) were graded as mild, 4244 (36·4 per cent) as moderate and 1916 (16·4 per cent) as severe. Using Clavien–Dindo, 6781 of 11 664 complications (58·1 per cent) were graded as I or II, 1740 (14·9 per cent) as III, 2408 (20·6 per cent) as IV and 735 (6·3 per cent) as V. Agreement between classification systems was poor overall (ICC 0·41, 95 per cent c.i. 0·20 to 0·55), and in LMICs (ICC 0·23, 0·05 to 0·38) and HICs (ICC 0·46, 0·25 to 0·59). Conclusion Caution is recommended when using a treatment approach to grade complications in global surgery studies, as this may introduce bias unintentionally