Sukumar Natarajan

Dwelling temperatures and comfort during the August 2003 heat wave

More frequent hot summers in the UK under climate change could lead to increased discomfort in dwellings, but there is little published field data on internal summer temperatures. Temperatures were measured in four dwellings around south Manchester and five dwellings in London during the August 2003 heat wave. Resultant statistics and various comfort metrics indicated a high level of discomfort in most dwellings, particularly in London. Daily internal temperatures were shown to correlate strongly with a time-decaying function of daily outside temperatures. Day and night temperatures were shown to relate to the type of structure. It is concluded that if heat waves become more common, this would lead to increased discomfort, with implications for health, mortality and housing design. Practical application: The results presented in this paper show what actually happens to a sample of dwelling temperatures during a severe UK heat wave, and the consequences for comfort. Little has been published on this previously. The correlations between time-averaged outside temperatures, and internal temperatures, provide a method for predicting dwelling temperatures in the future in a warming climate, without the need for detailed simulation and including real occupancy effects such as window opening, which are difficult to simulate reliably. Since there were many excess deaths during the August 2003 heat wave, health is an important concern. Work by others on this issue has shown that mortality rate is correlated with a three-day moving average of outside temperature above a threshold. This moving average correlates closely with the type of time-averaged outside temperature used in the paper. It seems quite possible that a 3-day moving average is a good predictor of excess mortality because it is also a good predictor of internal building temperatures, due to the mediation of thermal mass. This provides an alternative, or additional, explanation to that which explains the mortality as the cumulative result of high external temperatures acting on the human body over a few days, without considering the effects of buildings.

Climate change and future energy consumption in UK housing stock

This paper examines the likely effects on gas and electricity consumption and carbon emissions from heating and cooling systems in existing dwellings up to 2080, assuming a widespread uptake of cooling systems. This area of research is highly sensitive to the myriad of possible inputs and thus holds a wide range of predicted outcomes. However, general trends have been found, showing significant sensitivity to ventilation rate, U-values, occupant behaviour and location. Heating demand will still be dominant over cooling demand in UK dwellings by the 2080s, based on an UKCIP02 A1F1 weather scenario. A national worst case scenario for the 2050s, shows a 10 megatonne CO2 emissions saving on present levels largely due to a 20% reduction in gas consumption. Practical applications: The balance of heating and cooling demand causes more modest changes in CO 2 than first anticipated. Despite first perceptions of future energy use in housing and climate change, heating appears to remain the major load rather than cooling, even into the 2080s. These predictions of future CO 2 emissions will be useful to those in the building industry planning appropriate proportionate climate adaptation and climate mitigation measures. Also, the prediction of changes to future energy demands from the housing sector will be of interest to energy providers considering future demands for heating and cooling and may feed into larger bottom-up energy models.

A Review of Current and Future Weather Data for Building Simulation

This article provides the first comprehensive assessment of methods for the creation of weather variables for use in building simulation. We undertake a critical analysis of the fundamental issues and limitations of each methodology and discusses new challenges, such as how to deal with uncertainty, the urban heat island, climate change and extreme events. Proposals for the next generation of weather files for building simulation are made based on this analysis. A seven-point list of requirements for weather files is introduced and the state-of-the-art compared to this via a mapping exercise. It is found that there are various issues with all current and suggested approaches, but the two areas most requiring attention are the production of weather files for the urban landscape and files specifically designed to test buildings against the criteria of morbidity, mortality and building services system failure. Practical application: Robust weather files are key to the design of sustainable, healthy and comfortable buildings. This article provides the first comprehensive assessment of their technical requirements to ensure buildings perform well in both current and future climates.

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.

Designing sensor sets for capturing energy events in buildings

We study the problem of designing sensor sets for capturing energy events in buildings. In addition to direct energy sensing methods, e.g. electricity and gas, it is often desirable to monitor energy use and occupant activity through other sensors such as temperature and motion. However, practical constraints such as cost and deployment requirements can limit the choice, quantity and quality of sensors that can be distributed within each building, especially for large-scale deployments. In this paper, we present an approach to select a set of sensors for capturing energy events, using a measure of each candidate sensors ability to predict energy events within a building. We use constrained optimisation -- specifically, a bounded knapsack problem (BKP) -- to choose the best sensors for the set given each sensors predictive value and specified cost constraints. We present the results from a field study of 4 UK homes with temperature, light, motion, humidity, sound and CO2 sensors, showing how valuable yet expensive sensors are often not chosen in the optimal set.

An agent-based infrastructure for energy profile capture and management

Accurately monitoring changing energy usage patterns in households is a first requirement for more efficient and eco-friendly energy management. Such data is essential to the establishment of the Smart Grid, but at this stage, domestic data collection devices are still in development and monitoring-enabled domestic appliances are rare, so that any experimental software framework must be flexible and adaptable both in respect of sensor sources and developer and user requirements. These considerations have been the drivers behind the distributed agent-based platform this paper proposes. It provides: (i) a generic sensor interface that can be specialised for new devices as required, while insulating the rest of the platform from such changes, (ii) persistent unstructured (RDF) data storage, permitting both semantic annotation and semantic-based queries, independent of data sources, and (iii) a flexible, dynamic browser interface, that allows for remote configuration of the sensor platform and accessibility via a wide range of devices. Two small case studies show the utility of the approach.

Refugee housing through cyclic design

ABSTRACT There are more than six million refugees living in camps globally, primarily in places with severe climates. While camps are planned to be temporary, they can be in use for decades. This ‘planned temporariness’, despite their potential longevity, together with the pressures of rapidly emerging situations, means the construction and monitoring of demonstrators is not a primary concern for their developers. This lack of iterative design improvement results in shelters with thermal environments far from ideal and a risk of increased morbidity. Here we propose a cyclical process for improving such shelters involving the thermal monitoring of pre-existing shelters to construct validated baseline simulation models of similar shelters in other areas of emerging crisis. These models can then be evolved and improved within an optimization cycle before mass-construction and field testing. Here we demonstrate the method for the case of Azraq camp in Jordan. Starting from an analysis of field survey data which exposes a high incidence of heat-stress experienced in the shelters, a series of architectural strategies are applied to the design, resulting in significant reductions in overheating. This work suggests that the proposed cyclical approach can lead to significant improvement in conditions currently experienced in refugee camp shelters.

COincident Probabilistic climate change weather data for a Sustainable built Environment (COPSE)

Datasets for the EPSRC funded COPSE project This repository contains the datasets associated with the outputs from the University of Bath.