Overheating Position Statement
Summary of issue
Ever increasing winter energy efficiency measures and external temperatures as a result of intense urbanisation and climate change will increase the risk of overheating in buildings especially in homes that primarily depend on passive measures to achieve year round internal comfort.
Overheating can be defined as “that state of mind that expresses dissatisfaction with the environment caused by prolonged high temperatures”.
High indoor temperatures affect occupant thermal comfort, health and wellbeing, and productivity.
Environmental factors affecting thermal comfort include air temperature, radiant temperature, air speed and humidity; personal factors include age, gender, state of health, clothing and activity levels. Because of these multiple influences it is difficult to establish a definition of thermal comfort that applies to everyone (an environment which is comfortable for someone who is physically inactive may be too hot for someone engaged in sustained physical activity).
In heating dominated climates, such as that of the UK, winter morbidity and mortality are likely to remain a primary concern in the future. Nonetheless, heat-related deaths are expected to rise as a result of climate change induced increases in the frequency and severity of heatwave events, similar to the European heatwave of 2003.
Productivity could be affected by daytime high temperatures in the work environment or indirectly through sleep deprivation during night-time.
- Apartment blocks with communal heating systems and heat loss into the communal areas can also contribute to overheating.
CIBSE believes that occupant comfort, health and wellbeing should be a priority in the design of buildings and recommends a holistic approach to performance analysis where internal thermal comfort is investigated throughout the year.
CIBSE has adopted the adaptive thermal model to define thermal comfort and design overheating criteria (TM52). The adaptive thermal comfort model is based on the principle that an individual’s thermal expectations and preferences are determined by their experience of recent (outdoor) temperatures and a range of contextual factors, such as their access to environmental controls. The adaptive thermal comfort model allows for the natural adaptation of human physiology to extended periods of hot events. By using the adaptive thermal comfort model, contrary to the use of static comfort temperatures, the periods of discomfort, and so the potential energy demand for active cooling, are not overestimated.
- TM52 Limits of Thermal Comfort: Avoiding Overheating
- KS16: How to Manage Overheating in Buildings
- Guide A: Environmental Design
- Guide F: Energy Efficiency
- Guide G: Public health engineering
- AM10 Natural Ventilation in Non-Domestic Buildings
- AM13 Mixed Mode Ventilation
- TM37 Design for Improved Solar Shading Control
- TM40 Health Issues in Building Services
- Keeping Cool in a Heatwave 1: Top Tips for Facilities Managers
- Keeping Cool in a Heatwave 2: Top Tips for Building Users
- Zero Carbon Hub: Overheating in homes review (to be published in March 2015)
- NHBC Foundation, 2012. Understanding overheating- Where to start - NF 44. An introduction for house builders and designers
- DCLG, 2012. Investigation into overheating in homes, Literature review. London, UK: Department for Communities and Local Government (DCLG).
- BSI (2007) BS EN 15251: 2007: Indoor environmental input parameters for design and assessment of energy performance of buildings addressing indoor air quality, thermal environment, lighting and acoustics (London: British Standards Institution)
- ASHRAE, 2013. ANSI/ASHRAE Standard 55-2013 - Thermal environmental conditions for human occupancy. Atlanta, USA: American National Standards Institute (ANSI), American Society of Heating, Refrigerating and Air-conditioning Engineers (ASHRAE).
- HSE Detailed guidance on workplace temperature and thermal comfort
- HSE Workplace health, safety and welfare. Workplace (Health, Safety and Welfare) Regulations 1992. Approved Code of Practice and guidance
- Building performance evaluation of dwellings: A case study of the Seager Distillery development - Michael Lim, AECOM and Steve Harper, Galliard Homes
Anastasia Mylona, Head of Research
firstname.lastname@example.org, 020 8772 3690
Date produced: 16 February 2015