Risks of overheating in highly insulated English houses : an investigation into the design process, comfort performance and occupant behaviour (original) (raw)
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Investigating the potential of overheating in UK dwellings as a consequence of extant climate change
Energy Policy, 2010
Dynamic simulation is used with defined domestic building variants to investigate internal temperatures of UK dwellings. Factors such as a warming climate and varying internal heat gains are estimated to examine whether UK domestic buildings are likely to be prone to overheating in the future, and therefore require mechanical air conditioning. The study suggests that the ability, or inability, of the occupant to adapt to bedroom temperature is paramount in the understanding of the conditions for overheating. While this is difficult to quantify (and a range of comfort temperatures are proposed), the effect of changing the building construction and geographical location can result in significantly different thermal conditions. As might be expected, the problem appears most noticeable for buildings in the south of the UK and with lightweight constructions. Even with a window-opening schedule applied to such a scenario, the average internal temperature is simulated as being over 28 1C for almost 12% of the year. A different metric, defined as ''cooling nights'', suggests that there might be a cooling problem in bedroom areas for approximately a third of the year. In the North of the UK, and also for solid wall dwellings, this problem diminishes significantly.
Unintended consequences of sustainable architecture: Evaluating overheating risks in new dwellings
2016
Governmental strategies to reduce heating demand from dwellings have led to a range of problems relating to ventilation and occupant comfort. In fact, growing evidence of uncomfortably warm homes has been appearing in UK consistently in the few last years. This paper discusses the overheating risk in four highly insulated homes in the UK where a mixed methods approach has been deployed to characterise areas of overheating risk, which have been found to occur with different degree of severity and different sources of risk, all related to design and
National survey of summertime temperatures and overheating risk in English homes
This paper presents one of the first national scale studies of summertime temperatures in English dwellings. Living room and bedroom temperatures were recorded in 207 homes across the England during the cool summer of 2007. Data was also collected by face-to-face household interviews. Fourteen homes (7%) were observed to be heated for part or all of the analysis period (July to August). Based on the BSEN15251 adaptive thermal comfort model, the 193 free-running dwellings would, in general, to be considered as uncomfortably cool. Over 72% of living rooms and bedrooms had more than 5% of hours below the BSEN15251 Cat II lower threshold, with over 50% having more than 5% of hours below the Cat III threshold. Detached homes and those built before 1919 were significantly cooler (p < 0.05) than those of other type and age. Static criteria revealed that, despite the cool summer, 21% of the bedrooms had more than 5% of night time hours over 26 C; which is a recommended upper limit for bedrooms. The bedrooms of modern homes, i.e. those built after 1990 or with cavity walls, were significantly warmer (p < 0.05). The bedrooms in homes built prior to 1919 were significantly cooler (p < 0.05). The living rooms of flats were significantly warmer than the living rooms in the other dwelling types (p < 0.05). The incidence of warm bedrooms in modern homes, even during a cool summer, is of concern, especially as there is a strong trend towards even better insulation standards in new homes and the energy-efficient retrofitting of existing homes.
Empirical assessment of summertime overheating risk in new, retrofitted and existing UK dwellings
Healthy, Intelligent and Resilient Buildings and Urban Environments
This paper statistically assesses the hourly internal summertime temperature datasets gathered during the summer of 2013 (May to September), from 63 dwellings across the UK. The sample consisted of unmodified dwellings (existing); dwellings with varying levels of fabric improvements (retrofitted) and dwellings constructed to higher levels of the Code for Sustainable Homes (new). Indoor and outdoor temperature data from bedrooms and living rooms from these homes were collected at five-minute intervals using temperature sensors. These data were processed and analysed for summertime overheating, using both static criteria (CIBSE Guide A) and the criteria associated with the EN15251 adaptive thermal comfort model (CIBSE TM52). The results show that despite a relatively cool summer, sufficiently high temperatures were found in a high proportion of dwellings, which were found to be overheated according to the CIBSE static temperature criteria, although the prevalence of overheating was found to be much lower when assessed by the adaptive method. Considerably higher temperatures were found in bedrooms, much higher than living rooms. Interestingly, dwellings with higher levels of insulation experienced overheating twice as frequently as uninsulated dwellings. Given the prevalence of overheating found across the sample, it is necessary to carefully consider this risk during the design and retrofit of homes, to avoid the growth of domestic airconditioning in future.
Overheating in dwellings: a matched pair of test houses with synthetic occupants
CIBSE Technical Symposium, London, UK, 12-13 April 2018, 2018
Summertime overheating is increasingly prevalent in both new and existing UK dwellings. High internal temperatures can be dangerous to vulnerable occupants, disrupt sleep and cause thermal discomfort. The mitigation or exacerbation of overheating through simple occupant interventions like window opening and blind use needs better understanding if homes are to be comfortable and safe in summer without the use of air conditioning. This paper describes the adaptation of two adjoining, semi-detached houses to create a matched pair of test houses for full-scale, side-by-side overheating experiments under real weather conditions. Synthetic occupancy was installed to allow dynamic remote control of actuated windows, motorised curtains, automated internal doors and internal heat gains. The houses were instrumented with calibrated sensors to measure the internal and external environment. The results of the experiments conducted in summer 2017 will be presented in a future paper. These instru...
Building and Environment, 2012
Cities are expected to experience an increasing risk of overheating due to climate change and the urban heat island phenomenon. Although external factors, such as urban morphology and greening, may influence the spatio-temporal variation of overheating risk, the individual building characteristics are also likely to be important. This paper presents the results of EnergyPlus dynamic thermal simulations of 3456 combinations of dwelling types and characteristics selected to represent the London domestic stock. Two Design Summer Year weather files were used to represent the current and future climate: the CIBSE 1984e2004 and a UKCP09 future weather file (50th percentile of external temperature, 2050s, medium emissions scenario). Appreciable variation between dwelling types but generally greater variation within dwelling type was found depending on such factors as orientation, surrounding buildings and insulation levels. Under the current climate, the insulation levels had considerable impact on indoor temperatures, with combined retrofitting of roof insulation and window upgrades reducing daytime living room temperatures during the warmest continuous 5-day period of modelling by, on average, 0.76 C (%95C.I. 0.63, 0.89 C) for mean temperature and 1.30 C (%95C.I. 1.05, 1.54 C) for maximum temperature. On the other hand, internally retrofitted walls and floors tended to increase daytime living room temperatures, with a combined effect of 0.46 C (%95C.I. 0.33, 0.60 C) increase in mean temperature and 0.71 C (%95C.I. 0.47, 0.96) increase in maximum temperature. Within the context of a changing climate, knowledge of insulation characteristics after retrofitting is crucial for the accurate identification of dwellings with greatest overheating potential.
2013
The aim of the report was to produce recommendations for occupants to undertake, concerning passive changes to the building design and changing occupant activity to reduce overheating in 19651980 semi-detached dwellings. To do so, interventions in these two topics were tested to reduce overheating on a post 2010 Building Regulations base case. This base case and interventions simulations were developed using IES software. To measure the level of overheating, internally, a degree hours over the CIBSE overheating threshold (CIBSE, 2006) method was used. The basic upgrades to the building implementing the 2010 Building Regulation were found to decrease the total degree hours. When changed to two elderly (vulnerable) occupants, the total degree hours decreased overall. Other interventions that were found to decrease the total degree hours below the 2010 Building Regulation model were the updated appliances/occupancy trends, the cross ventilation strategy, north orientation and most prominently, the nigh time ventilation. A combined model of these interventions were then able to remove all degree hours beyond the threshold, even in a heat wave simulation; for both occupancy types. As well as the combined intervention model, external wall paint shutters and curtains (sourced from previous research) are recommended for reducing overheating, based on ease-of-use and cost.
Impact of standard construction specification on thermal comfort in UK dwellings
The quest for enhanced thermal comfort for dwellings encompasses the holistic utilization of improved building fabric, impact of weather variation and amongst passive cooling design consideration the provision of appropriate ventilation and shading strategy. Whilst thermal comfort is prime to dwellings considerations, limited research has been done in this area with the attention focused mostly on non-dwellings. This paper examines the current and future thermal comfort implications of four different standard construction specifications which show a progressive increase in thermal mass and airtightness and is underpinned by the newly developed CIBSE adaptive thermal comfort method for assessing the risk of overheating in naturally ventilated dwellings. Interactive investigation on the impact of building fabric variation, natural ventilation scenarios, external shading and varying occupants’ characteristics to analyse dwellings thermal comfort based on non-heating season of current and future weather patterns of London and Birmingham is conducted. The overheating analysis focus on the whole building and individual zones. The findings from the thermal analysis simulation are illustrated graphically coupled with statistical analysis of data collected from the simulation. The results indicate that, judicious integrated approach of improved design options could substantially reduce the operating temperatures in dwellings and enhance thermal comfort.
A critical review of the impact of global warming on overheating in buildings
2018
Over the last century global average temperatures have increased up to 1°F. Indeed, since records of comprehensive global temperatures were available as early as 1880, the evidence suggests that 2001-2010 decade has been shown to be the warmest. This change is having a direct impact in terms of an increase in extremely hot days and warm nights and a decrease in cold days. Evidence suggests that different parts of the world are warming at a faster rate than others. However, research predicts that the long-term impact of global warming is only set to increase. One of the major contributors of global warming is the impact of carbon emissions and in an effort to reduce these emissions the UK Government implemented changes to UK regulations, such as Part L conservation of heat and power that dictates improved thermal insulation and enhanced air tightness. The UK is fully committed to achieving its carbon targets under the climate Change Act 2008. However, there is a caveat that comes wit...
Energy Procedia, 2016
There is growing concern in Western Europe that higher insulation and air tightness of residential buildings may lead to increased overheating risk during the summer. This risks undoing the energy savings as it may lead to the introduction of active cooling systems in buildings that so far have been cooled by natural means. This paper discusses temperature monitoring from houses in the Southwest of the UK that were built to low-energy standards (Code for Sustainable Homes Level 5). Results were analyzed using both established static overheating criteria and an adaptive thermal comfort standard. Findings suggest that these houses can be considered uncomfortably warm during summer and that they are at risk of overheating.