Development of an England-wide indoor overheating and air pollution model using artificial neural networks

With the UK climate projected to warm in future decades, there is an increased research focus on the risks of indoor overheating. Energy-efficient building adaptations may modify a buildings risk of overheating and the infiltration of air pollution from outdoor sources. This paper presents the development of a national model of indoor overheating and air pollution, capable of modelling the existing and future building stocks, along with changes to the climate, outdoor air pollution levels, and occupant behaviour. The model presented is based on a large number of EnergyPlus simulations run in parallel. A metamodelling approach is used to create a model that estimates the indoor overheating and air pollution risks for the English housing stock. The performance of neural networks (NNs) is compared to a support vector regression (SVR) algorithm when forming the metamodel. NNs are shown to give almost a 50% better overall performance than SVR.     

Assessing impacts of summertime overheating: some adaptation strategies

The UK is predicted to experience warmer summers in the future, but the domestic building stock in England was not designed to cope with this change. The Standard Assessment Procedure (SAP) 2009 is used to assess the current state of the English building stock in terms of its vulnerability to overheating. The English Housing Survey 2009 provided data for 16 150 dwellings which are weighted to represent the housing stock. SAP predicts 82% of dwellings are currently at ‘slight’ risk of overheating and 41% at medium to high risk. If summer temperatures become 1.4°C warmer, then 99% of properties are predicted to have a medium to high risk of overheating. Several potential adaptations to the housing stock were considered to reduce overheating. Although ventilation strategies had the largest positive effect, the use of solar shading and shutters which allow secure ventilation could reduce vulnerability to overheating in the current climate. In a warmer climate, although some dwellings would still be at slight risk, the results suggest that solar shading strategies could reduce the percentage of those at medium to high risk to 6%. Future energy efficiency programmes will need to include adaptation measures to prevent overheating.     

Overheating in vulnerable and non-vulnerable households

ABSTRACT

As the 2003 European heatwave demonstrated, overheating in homes can cause wide-scale fatalities. With temperatures and heatwave frequency predicted to increase due to climate change, such events can be expected to become more common. Thus, investigating the risk of overheating in buildings is key to understanding the scale of the problem and in designing solutions. Most work on this topic has been theoretical and based on lightweight dwellings that might be expected to overheat. By contrast, this study collects temperature and air quality data over two years for vulnerable and non-vulnerable UK homes where overheating would not be expected to be common. Overheating was found to occur, particularly and disproportionately in households with vulnerable occupants. As the summers in question were not extreme and contained no prolonged heatwaves, this is a significant and worrying finding. The vulnerable homes were also found to have worse indoor air quality. This suggests that some of the problem might be solved by enhancing indoor ventilation. The collected thermal comfort survey data were also validated against the European adaptive model. Results suggest that the model underestimates discomfort in warm conditions, having implications for both vulnerable and non-vulnerable homes.     

An investigation of naturally ventilated teaching spaces with windcathers in secondary school where site is constrained by noise and air pollution

Built environment consumes the bulk of the UK’s fossil fuel. Schools account for 15% of the public sector’s carbon emissions. Energy efficient building design can play a vital role in achieving the national carbon emission reduction target of 80% by 2050. Natural and mixed mode ventilation is at the forefront of suggested energy efficient strategies for reducing carbon emissions from schools while maintaining good indoor air quality and thermal comfort. However, it is challenging to naturally ventilate many urban school buildings through side openings because of high noise and particulate air pollution. An alternative strategy, such as multi floor operation of windcatchers was assessed in this research as a sole source of fresh air in teaching spaces. Dynamic thermal simulation (DTS) and computational fluid dynamics (CFD) simulations assessed the performance of the adopted natural ventilation (NV) strategy in meeting the approved requirements for fresh air, indoor air quality (IAQ) and summertime overheating. Simulation results show that it is challenging to meet approved guidelines on air quality and thermal comfort, only when windcatchers are employed for ventilation purpose. However, fan assisted ventilation in conjunction with windcatchers provided satisfactory results. Detailed performance assessments using CFD seem desirable to validate DTS based findings.     

A questionnaire survey on sleeping thermal environment and bedroom air conditioning in high-rise residences in Hong Kong

This paper reports on the results of a questionnaire survey on sleeping thermal environment and bedroom air conditioning in high-rise residential buildings in Hong Kong. The survey aimed at investigating the current situation of sleeping thermal environment and bedroom air conditioning, in order to gather relevant background information to develop strategies for bedroom air conditioning in the subtropics. It focused on the use patterns and types of bedroom air conditioning systems used, human factors such as the use of bedding and sleepwear during sleep, preference for indoor air temperature settings in bedrooms, ventilation control at nighttime with room air conditioner (RAC) turned on, etc. The results of the survey showed that most of the respondents would prefer a relatively low indoor air temperature at below 24 °C. Most of the respondents might however not be satisfied with the indoor air quality (IAQ) in bedrooms in Hong Kong. On the other hand, 68% of the respondents did not use any ventilation control intentionally during their sleep with their RACs turned on. A lack of knowledge of the ventilation control devices provided on window type room air conditioners (WRACs) indicated an urgent need for user education.     

Zur Aussagekraft von Simulationsergebnissen auf Basis der Testreferenzjahre (TRY) über die Häufigkeit sommerlicher Überhitzung

Frequency of overheating during the summer – How meaningful are simulation results based on test reference years? Thermal comfort during the summer is becoming an increasingly important quality characteristic of modern office buildings. With attention increasingly also focusing on sustainability considerations, designs for such buildings are often based on passive ventilation without air‐conditioning or mechanical ventilation. The design and assessment of such energy‐saving indoor climate concepts is based on peak room temperatures and the frequency of overheating during the summer, usually involving (zonal) thermal simulation software. The calculation of overheating frequencies requires meteorological data for a whole year, in Germany usually in the form of original test reference years (TRYs) provided by Deutscher Wetterdienst (DWD), Germany's National Meteorological Service. However, these TRYs were developed for other purposes and tend to represent hot spells during the summer inadequately. In addition, TRYs do not take into account urban heat islands or the effects of climate change observed since the 1990 (with increasing tendency). Frequencies of high room temperatures during the summer determined using the original TRYs are therefore unrealistically low and unsuitable as a basis for decisions relating to climate concepts. For more realistic overheating frequency calculations it is advisable to use TRYs incorporating extreme summers and perhaps weather data for future years, which will shortly be made available by meteorologists.     

Inhabitant actions and summer overheating risk in London dwellings

ABSTRACT

An indoor overheating assessment study of 101 London dwellings during summer 2009 is presented. The study included building surveys, indoor dry bulb temperature monitoring and a questionnaire survey on occupant behaviour, including the operation of passive and active ventilation, cooling and shading systems. A theoretical London housing stock comprising 3456 combinations of building geometry, orientations, urban patterns, fabric retrofit and external weather was simulated using the EnergyPlus thermal modelling software. A statistical meta-model of EnergyPlus was then built by regressing the independent variables (simulation input) against the dependent variables (overheating risk). The monitoring and questionnaire data were analysed to explore the relationship between self-reported behaviour and overheating, and to test the meta-model. The monitoring data indicated that London homes and, in particular, bedrooms are already at risk of overheating during hot spells under the current climate. Around 70% of respondents tended to open only one or no windows at night mainly due to security reasons. An improvement in the coefficient of determination (R²) values between measured temperature and meta-model predictions was obtained only for those dwellings where occupants reported actions that were in line with the modelling assumptions, thus highlighting the importance of occupant behaviour for overheating.     

夏热冬冷地区住宅建筑新风系统全年运行工况分析

根据夏热冬冷地区的空调期、除湿期和采暖期的划分方法,提出了住宅建筑新风系统全年运行的转换条件,以及新风热湿处理工况要求。并针对该地区气候潮湿、除湿期时间长的特点,认为节能住宅采用温湿度同时监控的独立新风系统,有利于改善室内热环境质量和室内空气质量。     

日较差对居住建筑夜间通风室内热环境的影响

为了研究不同日较差情况下,夜间通风对室内热环境的影响,采用Energyplus软件对西安地区某公寓室内空气温度、平均辐射温度进行了模拟研究。结果表明,与无夜间通风相比,夜间通风时室内最高气温、最高平均辐射温度分别降低了0.32℃、0.34℃。室内空气温度、平均辐射温度随日较差的增大而降低,且机械通风时段比渗透通风时段降低显著。当日较差为4℃、6℃、8℃、10℃、12℃时,室内处于热舒适时段的比例分别为0,16.11%,28.06%,32.01%和34.86%。     

Meta-analysis of indoor temperatures in new-build housing

ABSTRACT

Despite growing concerns about overheating, a lack of evidence exists on the scale of the problem, particularly in contemporary UK housing. This paper presents the results of a meta-analysis of indoor temperatures in selected low-energy housing. Temperature data recorded at five-minute intervals in 60 dwellings across 19 demonstration projects (2012–14) were collated and analysed to investigate the prevalence of overheating. Findings evidence high summertime temperatures, with 27% of living rooms exceeding 28°C during August. Based on the Chartered Institution of Building Services Engineers (CIBSE) threshold of 5% annual occupied hours > 25°C, 57% of bedrooms and 75% of living rooms were classified as having overheated. Overall, 30% of living rooms exceeded the adaptive comfort threshold of > 3% occupied hours ΔT?≥?1?K. The results suggest a fundamental relationship between ventilation and indoor temperatures. The higher minimum and average summertime temperatures observed in mechanical ventilation with heat recovery (MVHR) homes (p?<?0.05) and lower temperature range (p?<?0.001) suggest the need for greater attention to adequate summertime ventilation provision in airtight homes. The results demonstrate a high prevalence of overheating in exemplary housing, indicating the need for greater efforts to ensure the effective implementation of strategies to minimize overheating and improve ventilation in low-energy homes.     

Application of adaptive comfort behaviors in Chilean social housing standards under the influence of climate change

Currently, energy performance indicators for buildings are associated with the primary energy source consumption, CO₂ emissions or net energy distribution, which together set the building’s energy efficiency. The evaluation is frequently based on setpoint temperatures and hours of operation. However, these fixed parameters are not suitable for social housing simulation as their performance tends to be in free running, excluding extremely cold or warm conditions. Therefore, a more successful assessment for the efficiency of these buildings is the users’ capability to live within adaptive comfort ranges without air conditioning systems. The aim of this research is to analyze new Chilean standards for sustainable social housing in the context of climate change using the adaptive comfort approach addressed in EN 15251:2007. Using EnergyPlus simulation software, 16 parametric series are analyzed for current conditions and validated against on-site measurements. Meanwhile, a prediction for the climate in 2050 has also been taken into account. The case study is the most widespread low cost dwelling model. The study demonstrates that the period of time within thermal comfort conditions varies substantially if analysis is done using the adaptive comfort standard or the Sustainable Construction Code (CCS) for Chilean housing. Considering climate change, the percentage of time fluctuates from ?19.00% to 24.30%. Concluding that the adaptive comfort model has a greater capacity to positively assess indoor temperatures for social housing in Central-Southern Chile. This research also establishes that it is possible to provide homes where standards are improved within comfort conditions without using artificial means, 99.67% of the time currently and 88.89% in the future.     

以西安地区为例谈高校教室夏季室内热环境

针对夏季过热的室内热环境,以西安地区为例,结合当地的气候特点、人民的生活习惯以及高校教室的使用情况等,建议采取与本地地区气候特点相适应的"被动式"措施来改善夏季室内热环境.论述了自然通风和结合采光的遮阳设施在改善教室室内热环境中的应用,同时采取其他综合措施如创造适宜的微气候、半地下空间的利用、植物和水等方面来改善教室内的热环境.     

Mapping indoor overheating and air pollution risk modification across Great Britain:A modelling study

Housing has long been thought to play a significant role in population exposure to environmental hazards such as high temperatures and air pollution.However,there is sparse data describing how housing may modify heat and air pollution exposure such that housing's role in poor health and mortality from these hazards may be estimated.This paper describes the development of individual-address level indoor overheating and air pollution risk modifiers for Great Britain,for use alongside historical weather,outdoor air pollution,population socio-economic data,and mortality data in a large-scale epidemiological investigation.A geographically-referenced housing stock database was developed using the Homes Energy Efficiency Database(HEED)and the English Housing Survey(EHS).Simulations of unique combinations of building,fabric,occupation,and environment were run using a modelling framework developed for Energy Plus8.0,estimating indoor temperature metrics,indoor/outdoor ratio of pollution from outdoor sources,and indoor air pollution from multiple indoor sources.Results were compiled,matched back to individual properties in HEED,and mapped using Geographical Information Systems(GIS).Results indicate urban areas had higher numbers of buildings prone to overheating,reduced levels indoor air pollution from outdoor sources,and higher air pollution from indoor sources relative to rural areas,driven largely by variations in building types.The results provide the first national-scale quantitative estimate of heat and indoor air pollution modification by dwellings,aggregated at levels suitable for inclusion in health analysis.     

Perceived and Measured Indoor Climate with Dilution versus Displacement Ventilation: an Intervention Study in a Sewing Plant

Abstract Mechanical ventilation of workrooms was formerly based mainly on the dilution principle. In recent years, however, 50% of new investments in industrial ventilation in Scandinavia have been spent on displacement ventilation. Very little data exist from industrial settings on the relative performance of displacement ventilation versus dilution ventilation as regards air quality and thermal comfort. The present study collected data on the indoor climate in a sewing plant before and after the ventilation was changed from dilution to displacement. The indoor climate was evaluated by hygienic measurements of air pollution, temperature, air velocity, etc., and 40 employees were interviewed about perceived thermal comfort, air quality, and irritative symptoms. Changing the ventilation from dilution to displacement induced a slightly higher air change in the occupied zone of the plant and entailed higher temperature gradients. In spite of these findings, complaints of draught decreased significantly, and temperature was perceived to be more pleasant after the change. The air was perceived as less heavy and less dry, especially when humidification was added to the supply air. The improvements in the workers’ reports on the environment could not be attributed to placebo effects. Generally, the hygienic measurements were improved or unchanged after the change in ventilation system. Thus, displacement ventilation improved environmental conditions in this study. When adding humidification, this improvement was further sustained.     

Evaluation of simplified ventilation system with direct air supply through the facade in a school in a cold climate

Many educational buildings in industrialised countries have poor indoor climate, according to today’s knowledge about the impact of indoor climate on well-being and productivity. Budget restrictions and practical limitations such as lack of space for central air handling units and ventilation ducts, have motivated the application of simplified ventilation systems in some schools, such as taking unconditioned supply air directly from the facade. One such school was recently evaluated in Norway.On cold days, thermal comfort in the classroom deteriorated due to cold downdraught from the supply outlet. In addition, moist and fertile conditions for microbiological growth were observed in the air supply ductwork. On the other hand the same pupils are more satisfied with the school and have less sick building syndrome (SBS) symptoms during winter than summer. An improved control strategy with a temperature-compensated CO₂ set-point for controlling the airflow is suggested. This could improve thermal comfort and reduce energy use without compromising perceived air quality (PAQ) during cold weather. Furthermore it could improve indoor air quality (IAQ) during warm weather with only a slight increase of energy use. Further evaluation of an improved solution is needed before such a ventilation concept can be recommended in cold climates.     

低温送风系统的研究进展

总结了近年来与冰蓄冷相结合的低温送风空调系统的研究成果及进展,认为低温送风系统的研究主要集中在经济性评价和室内气流组织及热舒适性评价两个大的方面.低温送风系统的经济性评价主要取决于室内参数和送风温度的设定及末端送风方式的选择,分析了省能器循环的减少对低温送风系统全年经济性的影响.低温送风的通风及舒适性主要取决于射流结构是否合理及描述室内空气品质和热舒适性的各项指标是否达到标准,总结了在低温送风系统通风及舒适性方面的主要研究方法及研究成果.最后提出了该技术未来的研究方向.     

Will future low-carbon schools in the UK have an overheating problem?

Meeting thermal comfort and internal air quality standards for schools can be difficult for buildings that, traditionally in the UK, have not used mechanical ventilation and air-conditioning. With a trend towards increased internal gains, and climate change predicted to cause a significant rise in temperatures, this issue becomes more problematic. Considering this within the context of low-carbon buildings creates an added hurdle—can low-carbon schools be produced that will provide a comfortable teaching environment in the future? Through a series of simulations on template school buildings, this study highlights the effect that future small power and lighting energy use could have on reducing the overheating of school teaching areas. The effect of a warming climate is also estimated, and the impact that has on the internal temperatures of a school quantified. Introducing external shading and increasing ventilation in classrooms can reduce overheating significantly but, for many cases, the risk that the school building cannot cope with the overheating problem might still remain.     

Romancing the high-rise in Singapore

Since the 1960s, Singapore has continually built high-rise buildings to house its growing population. While many other developing cities are faced with a housing shortage, the greater proportion of the Singapore resident population is living in and owning accommodation in high-rise buildings. Drawing on interviews conducted with public housing families in their homes, this paper seeks to discuss and provide a perspective of the Singapore residents’ attitude to high-rise living. Although the discussion is focused on the Singapore resident perspective, high-rise living experience is not unique to Singapore. If international building and urbanization trends are any indication, more and more urban residents will have the opportunity to live in high-rise housing. A widening number of cities, including London, are building 50-story housing as the latest answer to their country’s housing shortages. Given the extensive high-rise living in Singapore, the findings of this paper stand to offer important implications to cities considering high-rise housing.     

Experimental study of temperature and airflow distribution inside an urban street canyon during hot summer weather conditions—Part I: Air and surface temperatures

This paper describes the measurements and analysis of an experimental campaign performed in an urban street canyon in Athens, Greece. A number of field and indoor experimental procedures were organized during summer 2002 aiming at the investigation of the impact of urban environment on the potential of natural and hybrid ventilation. The present study is focused on the experimental investigation of thermal characteristics of a typical street canyon, oriented in ESE–WNW direction, under hot weather conditions. The temporal and spatial distribution of air and surface temperatures is examined. Emphasis was given on the vertical distribution of air and surface temperatures and the air temperature profile in the centre of canyon under different weather conditions. The measured surface temperature differences across the street reached almost 30 °C and this favored the overheating of lower air levels. Buoyancy generated mainly from asphalt-street heating resulted in the development of the predominant recirculation inside the street canyon.     

Der sommerliche Wärmeschutz eines sanierten Wohngebäudes aus den 1950er Jahren unter Berücksichtigung des Nutzerverhaltens

Sommer heat insulation of a reinstated residential building of the 1950s considering the user‵s behaviour. A verification of the summer heat insulation according to the new issue of DIN 4108‐2 from July 2003 will be required in the future due to the expected amendment of the Energy Savings Regulation that will take effect probably in the autumn of 2004. The effects on the construction requirements and on the indoor climate can be shown using an example of a multiple family dwelling built in the 1950's. Problems with additional thermal heat requirements will be considered as well as the daylight conditions in the living space. The ventilation conditions and the resulting periods of overheating for various occupancies will be discussed using a thermal building simulation with ESP‐r.