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.     

Statistical techniques to emulate dynamic building simulations for overheating analyses in future probabilistic climates

As projections of climate change become more detailed and sophisticated, analysing the effects of these projections on, for example, building performance will become more complex. This study, as part of the Low Carbon Futures project, proposes a method for integrating the latest UK Climate Projections 2009, which are probabilistic in nature, into dynamic building simulation calculations. This methodology offers the possibility that, in an analysis of overheating in buildings, it will be viable for a building designer to assess future thermal comfort of a building in a probabilistic way, with various climate scenarios informing a risk analysis of whether that building will become unsuitable as a working/living environment. To reduce the computational requirements of such an analysis, a series of statistical manipulations and approximations are proposed that serve to reduce substantially the amount of computation that would otherwise be necessary when using such climate projections. The resulting tool, which in essence captures the behaviour of complex simulation models using linear filtering techniques and regression, is successfully validated against results obtained from building simulation software results for a domestic building case-study, including versions of the building with specific adaptation scenarios applied that might offset the predicted overheating.     

Analysis of probabilistic climate projections: heat wave,overheating and adaptation

Climate change could substantially impact on the performance of buildings in providing thermal comfort to occupants. The recently launched UK climate projections (UKCP09) suggest that all areas of the UK will become warmer in the future with the possibility of more frequent and severe extreme events, such as heat waves. This study, as part of the low carbon futures (LCF) project, explores the consequent risk of overheating and the vulnerability of a building to extreme events. A simple statistical model proposed by the LCF project elsewhere has been employed to emulate the outputs of the dynamic building simulator (ESP-r), which if directly used with the numerous replicated climates available from a probabilistic climate database could be practically challenging. For complex probabilistic climate datasets, we demonstrate the efficiency of the statistical tool in performing a systematic analysis of various aspects of heat waves including: frequency of extreme heat events in changing climate; its impact on overheating issues and effects of specific adaptation techniques applied to offset predicted overheating. We consider a domestic building as a virtual case study. Results are presented relative to a baseline climate (1961–1990) for three future timelines (2030s, 2050s and 2080s) and three emission scenarios (Low, Medium and High).     

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.     

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.     

Urban social housing resilience to excess summer heat

The potential levels of exposure to indoor overheating in an urban environment are assessed for vulnerable social housing residents. Particular focus is given to the synergistic effects between summertime ventilation behaviour, indoor temperature and air pollutant concentration in relation to energy retrofit and climate change. Three different types of social housing are investigated (1900s’ low-rise, 1950s’ mid-rise and 1960s’ high-rise). The case study dwellings are located in Central London and occupied by vulnerable individuals (elderly and/or people suffering from ill-health or mobility impairment). Indoor temperature monitoring suggests that occupants are already exposed to some degree of overheating; the highest levels of overheating occur in 1960s’ high-rise tower blocks. The thermal and airflow performance simulation of a mid-floor flat in the 1960s’ block under the current and projected future climate indicates that improved natural ventilation strategies may reduce overheating risk to a certain extent, with night cooling and shading being slightly more effective than all-day rapid ventilation. However, their potential may be limited in future due to high external temperatures and the undesired ingress of outdoor pollutants. This highlights the need for the development of combined strategies aiming to achieve both indoor thermal comfort and air quality.     

Climate change future proofing of buildings—Generation and assessment of building simulation weather files

Simulation packages for predicting building performance in terms of energy and comfort are becoming increasingly important in the planning process. However, current industry standard weather files for building simulation are not suited to the assessment of the potential impacts of a changing climate, in particular summer overheating risks. In addition, no bespoke climate change weather files are readily available that can be loaded directly into environmental simulation software. This paper describes the integration of future UK climate scenarios into the widely used Typical Meteorological Year (TMY2) and EnergyPlus/ESP-r Weather (EPW) file formats and demonstrates the importance of climate change analysis through a case study example. The ‘morphing’ methodology published by the Chartered Institution of Building Services Engineers (CIBSE) is utilised as a baseline for transforming current CIBSE Test Reference Years (TRY) and Design Summer Years (DSY) into climate change weather years. A tool is presented that allows generation of TMY2/EPW files from this ‘morphed’ data and addresses the requirements related to solar irradiation, temperature, humidity and daylighting beyond the parameters provided by CIBSE weather years. Simulations of a case study building highlight the potential impact of climate change on future summer overheating hours inside naturally ventilated buildings.     

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.     

Impact of passive climate adaptation measures and building orientation on the energy demand of a detached lightweight semi-portable building

The building energy demand for heating and cooling is changing due to climate change. The adoption of climate change adaptation measures at the building scale aims at limiting heating and cooling demands. In previous studies on adaptation measures little attention has been paid to lightweight semi-portable buildings, which are increasingly used to temporarily house the growing number of small households (1–2 persons) in peripheral and derelict areas. In this paper the impact of passive climate adaptation measures and building orientation on heating and cooling demands is assessed for a detached, lightweight, semi-portable residential building by means of building energy simulations (BES), considering two climate scenarios for the Netherlands: current climate and a future climate (2050). The results show that the most efficient adaptation measure consists in a combination of exterior solar shading and an increase of thermal resistance of the building envelope, which reduces the annual heating and cooling demand–averaged over eight building orientations – by 11% for the current climate and 15% for the future climate. The impact of building orientation varies according to the climate scenario. Compared to the average over the eight orientations considered, the annual cooling demand for a single orientation varies between about ?31% and +22% and between about ?24% and +18% for the current and future climate, respectively. For the case without adaptation measures, optimizing the building orientation leads to annual total energy savings of about 4% for the current and 3% for the future climate.     

Summer thermal comfort: compliance assessment and overheating prevention in new apartment buildings in Estonia

This study analyses which building parameters contribute the most to overheating in dwellings and which properties will make a room ‘critical’, to be chosen for compliance assessment procedure through temperature simulation, as required in Estonia for new residential buildings. Indoor temperature measurements, conducted in 18 apartments from 16 apartment buildings, show clear evidence of overheating. Compliance assessment of 25 new buildings were conducted using IDA-ICE software. The analysed sample consisted of typical multi-storeyed buildings with mainly massive concrete structures. From the simulated buildings, 68% did not meet the requirements, showing that this relatively new building code requirement was not fully established in practice. Results of the analysis indicate that the requirement in apartment buildings is achievable without cooling, if passive measures are properly applied. Recommendations are given to designers, as well as policy-makers, to improve the situation in the residential building sector.     

Internal surface condensation risk in façades of Spanish social dwellings

ABSTRACT

The poor maintenance of social dwellings causes the possible building deficiencies to be significantly increased, especially when most of these dwellings have been built before any thermal standard and without considering the effect of climate change. Façades are one of the building elements which are most degraded by the contact with the exterior, and surface condensation is the most common cause. This study applies the calculation of surface condensation from ISO 13788 to a representative case of social dwelling in Spain for all climate zones, both in the current and 2050 scenarios. Risks of corrosion, mould formation, and surface condensation were studied in nine different points of the façade, which were validated by in-situ measurements. The results determined that there was a greater risk of condensation or mould depending on the climate zone, and thermal resistance significantly influenced data variation in future scenarios. The results also showed that an adequate ventilation generally decreased risks, removing the risk of mould and surface condensation by 2050. To predict the results obtained, a model based on artificial neural networks was generated, and it could also be used to estimate risks in the future.     

Uncertainty and sensitivity analysis of building performance using probabilistic climate projections: A UK case study

This study explores the uncertainties and sensitivities in the prediction of the thermal performance of buildings under climate change. This type of analysis is key to the assessment of the adaptability and resilience of buildings to changing climate conditions. The paper presents a comprehensive overview of the key methodological steps needed for a probabilistic prediction of building performance in the long term future (50 to 80 years). The approach propagates uncertainties in climate change predictions as well as the uncertainties related to interventions in building fabric and systems.A case study focussing on an air-conditioned university building at the campus of the authors is presented in order to demonstrate the methodology. This employs the most recent probabilistic climate change projections for the United Kingdom (UKCP09 dataset) and takes into account facility management uncertainties when exploring uncertainties in the prediction of heating energy, cooling energy, and carbon emissions.     

基于生态系统的适应在气候变化适应性城市多尺度合作雨洪管理中的实践——以哥本哈根为例

气候变化已成为城市可持续发展的关键挑战。面对该问题,越来越多的学者和从业者关注了基于生态系统的适应（EbA）概念,将其作为管理区域生态系统服务、提高生态系统服务适应能力的高效并且可持续的手段予以推广。然而,目前鲜有研究关注EbA措施在气候变化适应性城市建设中在多尺度上与各利益相关者的合作规划实践。通过定性方法弥补EbA在城市多尺度气候适应计划实践这一领域应用研究的缺失,以欧洲著名的气候变化适应性城市以及欧洲绿色首都哥本哈根市为研究对象,分析了EbA如何纳入当地气候变化适应计划并在多个尺度上予以实施。回顾了EbA发展与其在欧洲的应用现状,分析了哥本哈根市气候变化适应政策以及EbA在市域、社区、单体建筑3个尺度的合作应用,并且通过分析哥本哈根市第一个气候弹性社区的案例,阐释哥本哈根市如何通过政府、企业、公民等多方利益相关者的合作规划将EbA措施应用于当地气候变化适应性城市建设。最后,总结了哥本哈根市多尺度气候变化适应合作规划中的EbA实践经验：1）项目前的深入数据准备和分析;2）EbA措施与城市空间景观设计的紧密结合;3）多个利益相关方协调,促进公众参与。加深了对EbA提升城市生态系统服务建设适应气候变化的城市的理解,并在面对气候变化挑战问题上,为包括中国城市在内的其他城市提供了启示与借鉴。     

Exposure duration in overheating assessments: a retrofit modelling study

ABSTRACT

A new indicator of overheating risk is introduced that more comprehensively represents heat stress and the way thermal environment is experienced. This indicator is compared with the industry standard overheating assessment approach (CIBSE TM52). This is demonstrated using an energy retrofit simulation case study of a typical London, UK terraced dwelling under different climate scenarios. Overheating was evaluated first according to TM52, then via an assessment of continuously overheated intervals (COIs) that account for the duration where adaptive limits are continuously exceeded. Results for the case study show that, first, extent of overheating can vary greatly based on climate uncertainties. Second, insulation retrofit only contributes to substantial overheating when the space lacks proper ventilation or protection from solar radiation. Nevertheless, overheating cannot be avoided completely under future climate scenarios even with appropriate passive cooling. More importantly, the results show that overheated hours tend to occur consecutively. This implies that violations of TM52 criterion 1 (which currently applies only at the seasonal scale) can occur at the monthly/weekly resolutions. This ‘buried’ information can be revealed via the COI approach to more comprehensively capture how an overheating situation unfolds in a manner more relevant to heat stress and occupants’ thermal experience.     

Stochastic analysis of building thermal processes

A methodology is presented for investigating the uncertainty properties of the building thermal processes caused by the random behaviour of the meteorological processes and the casual gains. A detailed building thermal model is used with a stochastic weather model and a random casual gain model. The probability distribution of the zone temperature of the building is calculated directly from these models. The overheating risk has been analysed as an example. The probability distribution of the periods when the zone temperature is higher than the demand temperature is calculated. The result shows all the possible situations rather than only a sample as would be obtained by running a normal simulation using given weather data. The influence of different building components on the overheating risk has been studied. The result shows that the most likely component for overheating risk in a residential building in Beijing is the window size. The thermal mass of the internal walls and the placing of windows have little effect on overheating risk.     

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 integrated adaptive model for overheating risk prediction

Based on the results from a field survey campaign, this article describes three new developments which have been integrated to provide a comprehensive basis for the evaluation of overheating risk in offices. Firstly, a set of logistic regression equations have been derived to predict the probability of office occupants' adaptation of personal and environmental characteristics. Secondly, empirical adaptive increments (offsets in comfort temperature) have been derived for each of these modes of adaptation. Thirdly, these adaptive increments are used to derive adapted degree-days of overheating stimuli for input to a new model to predict overheating risk. Based on the analogy between the charging and discharging of humans' tolerance to overheating stimuli and that of charge in an electrical capacitor, this analytical model uses empirical coefficients to tune its (dis)charging time constants to a given population and situation. This article introduces these developments and how they may be coupled to building simulation programs to predict the risk that proposed design solutions will overheat. Scope for further development, as well as possible alternatives to the presented approach, are also discussed.     

传统民居的建造技术——以湖南传统民居建筑为例

湖南属典型的山地、丘陵地形,气候温和湿润.该文从传统民居的结构、构造与材料工艺等方面研究了湖南民居的建造技术,指出湖南传统民居的建造技术是与其所处的地理环境、气候条件以及当地的历史文化传统、生活习俗和审美观念等因素相关的.建筑技术结合建筑装饰,特色鲜明,技术较高,体现了中国传统民居建筑的许多特点.     

Overheating in care settings: magnitude,causes, preparedness and remedies

ABSTRACT

Research in UK and elsewhere has highlighted that older people are particularly vulnerable to negative health effects of overheating. This paper examines the magnitude, causes, preparedness and remedies for addressing the risk of summertime overheating in four case study residential care and extra-care settings across the UK, spanning different building types, construction and age. An interdisciplinary approach is adopted, drawing from building science and social science methods, including temperature monitoring, building surveys, and interviews with design and management teams. The findings suggest that overheating is a current and prevalent risk in the case study schemes, yet currently little awareness or preparedness exists to implement suitable and long-term adaptation strategies (e.g., external shading). There was a perception from designers to managers, that cold represents a bigger threat to older occupants’ health than excessive heat. A lack of effective heat management was found across the case studies that included unwanted heat gains from the heating system, confusion in terms of responsibilities to manage indoor temperatures, and conflicts between window opening and occupant safety. Given that care settings should provide protection against risks from cold and hot weather, design, management and care practices need to become better focused towards this goal.     

Energy savings in Danish residential building stock

A large potential for energy savings exists in the Danish residential building stock due to the fact that 75% of the buildings were constructed before 1979 when the first important demands for energy performance of building were introduced. It is also a fact that many buildings in Denmark face comprehensive renovations in the coming years and in connection with this renovation process energy-saving measures can be implemented relatively inexpensive and cost effective. This opportunity should be used to insure the buildings in the future as far as energy consumption is concerned. This paper gives a short account of the technical energy-saving possibilities that are present in existing dwellings and presents a financial methodology used for assessing energy-saving measures. In order to estimate the total savings potential detailed calculations have been performed in a case with two typical buildings representing the residential building stock and based on these calculations an assessment of the energy-saving potential is performed. A profitable savings potential of energy used for space heating of about 80% is identified over 45 years (until 2050) within the residential building stock if the energy performances are upgraded when buildings are renovated.