The energy and thermal performance of UK modular residential buildings

This research concerns the in-use performance of light-gauge steel modular construction used for residential purposes. The aim was to investigate ways to reduce the in-use energy consumption of new buildings, while ensuring thermal comfort. Data were collected from two case study buildings in the UK, one in Loughborough and the other in London, using a variety of methods including building measurement, building monitoring, inspections, and a detailed review of the construction documentation. The case study buildings were monitored using EnOcean enabled wireless sensor networks and standalone temperature sensors. Monitoring data included electricity consumption in individual rooms, often by end use, space heating use, internal temperature and relative humidity, and external temperature. Building measurements included blower door tests to measure fabric air leakage rates, infrared thermal imaging to identify fabric defects and weaknesses, and ventilation system flowrate measurements. Inspections and the review of documentation allowed problems with design, manufacture and construction to be identified. A particular concern for thermally lightweight construction is the risk of overheating, therefore overheating analyses were undertaken. The research identified weaknesses in the design, construction and operation of the case study buildings resulting in increased energy use and poor thermal comfort, particularly overheating. The modular construction studied requires specific design changes to improve the fabric and building services, in order to reduce energy use. There are also specific recommendations for quality control on site to ensure critical stages are correctly completed, such as installing rigid insulation. There are also more general recommendations for how a company operates because this can influence performance; there ought to be greater attention to holistic design and greater collaboration with suppliers and contractors to determine robust solutions. Overheating was a problem in the London case study, and more research is required to understand the scale of the problem. Avoidance of overheating must be a focus in the design of new buildings. The findings suggest that once the problems with the design and quality control on site are rectified, offsite modular construction can be used to consistently and reliably provide low energy homes

Performance of medium-rise, thermally lightweight apartment buildings during a heat wave

There is growing evidence that medium rise, thermally lightweight, well-insulated, naturally ventilated, single apartment blocks are at risk of overheating especially when sited in the SE of England. This paper reports the thermal comfort and heat stress conditions recorded in 15 apartments located in North London on the outer fringes of the urban heat island. The apartments were built using off site, light gauge steel prefabrication methods. Bedrooms on floors one and two and on floors seven to eleven were monitored for 22 days during July and August 2013, a period that included a heat wave, which precipitated a level 3 heat wave alert. The risk of overheating was assessed using the static criteria in CIBSE Guide A and the three CIBSE TM52 adaptive thermal comfort criteria. Heat stress levels in one room were assessed using the Humidex and Heat Index metrics. The bedrooms on floors one and two did not overheat whereas all the apartments on the upper floors failed both the static and the adaptive criteria producing conditions that would lead to heat stress. The results strongly suggest that the design, ventilation and servicing strategy, combined with the inherent fragility of thermally lightweight and well insulated construction, is inappropriate in some areas of the UK and may even be dangerous in hot summers. The findings have significance for construction companies, landlords and social housing providers and those concerned with construction guidelines and the building regulations