CIBSE Top Tips Information Sheet 8: Temperature in Indoor Workplaces (Thermal Comfort)
This information sheet is intended to help property operators and designers to understand the requirements of temperature in the workplace and what they can do to ensure the workplace provides a healthy, comfortable and productive working environment in an energy efficient manner. By following the information provided, building operators, designers and employers will be able to demonstrate compliance with Regulation 7, Temperature in indoor workplaces, in The Workplace (Health, Safety and Welfare) Regulations 1992. Where there may be concern or areas of high risk then it is recommended that professional advice is sought.
- Top Tips
- Why buildings provide thermal comfort
- What do I do if the top tips are not enough?
- Design and installation considerations
- Maintenance, examination and testing of mechanical systems
- The cost of not providing thermal comfort appropriately
- Further Reading
Reduce Thermal Gain
- Reduce heat gains (internal, external or solar)
- Improve ventilation
- Switch lights off when not needed
- Use low-energy lights
- Switch off any unnecessary equipment
- Provide air-cooling plant
- Air movement is an important control measure.
Adapt fabric or internal space
- Allow occupant measures to reduce individual discomfort
- Keep direct sunlight off the individual workspace or occupied area, this can help it feel more comfortable
- Insulate hot plant or pipes
- Provide shading to windows
- Locate workstations away from places subject to radiant heat
- Thermometers should be available at suitable locations in every part of the workplace to allow people to measure temperatures.
Training and Information
- Provide information telling people what sort of conditions to expect so that they can dress and behave appropriately
- Train building operations staff to ensure that design intent is achieved over the life of the building.
- Wear more lightweight clothing in warm weather
- Drink fluids to keep cool in hot weather
- Allow flexible working hours and vary work tasks.
During working hours the temperature must be comfortable for the majority of the occupants in all indoor workplaces. There is no law for minimum or maximum working temperatures e.g. when it’s too cold or too hot to work. However, HSE guidance suggests a minimum of 16ºC or 13ºC if employees are doing physical work. There is no HSE guidance for a maximum temperature limit. However, there are operative temperature ranges for different types of rooms in workplaces given in CIBSE guidance (see CIBSE Guide A).
Overheating is a key problem for building design. Overheating happens in a building either through bad design, poor management or inadequate services. Overheating within a building occurs when the actual indoor temperature for any given day is hot enough to make the majority of people feel uncomfortable.
As ‘warm blooded’ mammals, human beings require a near steady internal body temperature in order to remain healthy and active. The metabolic heat being released in the body, and its flow to the environment, are regulated to keep the internal organs, and in particular the brain, at a temperature of around 37ºC. This is a dynamic process because the indoor environment changes and the occupants move around, either indoors, or between indoors and outdoors. The body needs a mechanism for keeping the temperature of our internal organs more or less constant despite these changes. A lot of the time the internal temperature is controlled with little or no conscious intervention.
There are six primary factors that directly affect thermal comfort that can be grouped in two categories: personal factors - because they are characteristics of the occupants - and environmental factors - which are conditions of the thermal environment. The former are metabolic rate and clothing level, the latter are air temperature, mean radiant temperature, air speed and humidity. Even if all these factors may vary with time, standards usually refer to a steady state to study thermal comfort, just allowing limited temperature variations. Psychological parameters such as individual expectations also affect thermal comfort.
Why buildings provide thermal comfort
The indoor environment should be designed and controlled so that occupants are comfortable and that their health is not adversely affected. There are individual differences in perception and subjective evaluation, often resulting in some dissatisfaction within the building population, which may be reduced by introducing some possibility of individual adjustment. This dissatisfaction may be with a specific aspect of the environment or may be general and non-specific. The aim of design should be to minimise this dissatisfaction as far as is reasonably practicable. Overheating can also affect productivity. In addition there is a risk of heat stress that could lead to health problems for the building occupants.
Some user populations such as the young, elderly or infirm may require different comfort conditions such as warmer internal temperatures.
A building can be said to have performed its task if occupants are not ‘conscious’ of its temperature. The building environmental factors or conditions of the thermal environment, air temperature, mean radiant temperature, air speed and humidity, are all likely to be influenced by the building structure and engineering services. In well-designed buildings with modern standards of thermal insulation and air leakage, discomfort arising from draughts is much reduced because downdraughts from cold surfaces are much reduced. Solar energy absorbed at the outside surfaces of walls, windows and roofs is partly transmitted to the interior of the building and needs to be reduced at the design stage. Wind around the building can affect the temperature of the interior of the building and has to be consider in the design. Further information is available in CIBSE Guide A.
What do I do if the top tips are not enough?
Indoor operative temperatures over 28°C for long periods will result in increased dissatisfaction and reduced productivity. In the first instance consider:
- Relaxation of formal office dress to encourage individual adaptation to conditions
- Individual control over the thermal environment where practicable, such as by opening windows, using blinds or moving out of sunny areas
- Flexible working so people can work at more comfortable times
- Availability of hot or cold drinks
- Increased air movement e.g. the cooling effect of local fans can be equivalent to reducing the operative temperature by around 2°C.
If these measures do not work, then seek an expert in the field of thermal comfort as it can be a complex process to resolve the problem.
Design and installation considerations
- Use building orientation and envelope design to minimize the thermal load of the buildin
- Use office equipment and lighting systems that reduce internal loads
- Consider air intakes. Clean outdoor air is preferable or appropriate filtration is required to clean outdoor air of poor quality
- Minimize source pollution through material selections
- Design of an effective ventilation supply and distribution system
- Design of an effective thermal control scheme
- Selection of efficient equipment and proper controls to implement the ventilation and thermal control design
- Commission the design, installation and operation of the systems.
Maintenance, examination and testing of mechanical systems
Provision of a reasonable indoor workplace temperature is a legal requirement. It is likely that mechanical and electrical engineering services will play an important part in this provision. Such plant and equipment needs to be examined, tested and maintained in accordance with the manufacturer’s guidance and recorded in the maintenance log. In the absence of such guidance, the B&ES Standard Maintenance Specification provides information on maintenance and testing. CIBSE Guide M Maintenance Engineering and Management (2014) provides information on good practice.
The cost of not providing thermal comfort appropriately
Provision of a reasonable indoor workplace temperature is a legal requirement. When people are dissatisfied with their thermal environment, not only is it a potential health hazard, it also impacts on their ability to function effectively and their satisfaction at work.
B&ES (2012) SFG20: Standard Maintenance Specification for Building Services (Penrith: B&ES). See http://www.sfg20.co.uk
CIBSE (2014) Guide M: Maintenance Engineering and Management (London: CIBSE). See http://www.cibse.org/knowledge/cibse-guide/cibse-guide-m-maintenance-engineering-management
CIBSE (2015) Guide A: Environmental Design (London: CIBSE). See http://www.cibse.org/Knowledge/CIBSE-Guide/CIBSE-Guide-A-Environmental-Design-NEW-2015
TSO (1992) Workplace (Health, Safety and Welfare) Regulations 1992 No. 3004 (London: TSO). See http://www.legislation.gov.uk/uksi/1992/3004/contents/made
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)
CIBSE (2000) AM13: Mixed Mode Ventilation (London: CIBSE). See http://www.cibse.org/knowledge/cibse-am/am13-mixed-mode-ventilation
CIBSE (2005) AM10: Natural Ventilation in Non-Domestic Buildings. See http://www.cibse.org/knowledge/cibse-am/am10-natural-ventilation-in-non-domestic-buildings
CIBSE (2006) TM37: Design for Improved Solar Shading Control (London: CIBSE). See http://www.cibse.org/knowledge/cibse-tm/tm37-design-for-improved-solar-shading-control
CIBSE (2006) TM40: Health Issues in Building Services (London: CIBSE). See http://www.cibse.org/knowledge/cibse-tm/tm40-health-issues-in-building-services
CIBSE (2010) Keeping Cool in a Heatwave 1: Top Tips for Facilities Managers (CIBSE Heat
Wave Briefing 1) (London: CIBSE). Free to all users. See http://www.cibse.org/knowledge/cibse-other-publications/keeping-cool-in-a-heatwave-1-top-tips-for-faciliti
CIBSE (2010) Keeping Cool in a Heatwave 2: Top Tips for Building Users (CIBSE Heat
Wave Briefing 2) (London: CIBSE). Free to all users. See http://www.cibse.org/knowledge/cibse-other-publications/keeping-cool-in-a-heatwave-2-top-tips-for-building
CIBSE (2010) KS16: How to Manage Overheating in Buildings (London: CIBSE). See http://www.cibse.org/knowledge/cibse-ks/ks16-how-to-manage-overheating-in-buildings
CIBSE (2012) Guide F: Energy Efficiency in Buildings (London: CIBSE). See http://www.cibse.org/knowledge/cibse-guide/cibse-guide-f-energy-efficiency-in-buildings
CIBSE (2013) TM52: The Limits of Thermal Comfort: Avoiding Overheating in European Buildings (London: CIBSE). Free to all users. See http://www.cibse.org/knowledge/cibse-tm/tm52-limits-of-thermal-comfort-avoiding-overheatin
HSE (2007) INDG244 (rev2) Workplace Health, Safety and Welfare. A Short Guide for Managers (London: HSE). See http://www.hse.gov.uk/pUbns/indg244.pdf
HSE (2013) L24 Workplace (Health, Safety and Welfare) Regulations 1992. Approved Code of Practice and Guidance (London: HSE). See http://www.hse.gov.uk/pubns/priced/l24.pdf
HSE Website: Thermal Comfort. Detailed guidance on workplace temperature and thermal comfort is available on HSE’s website. See www.hse.gov.uk/temperature/thermal.
© CIBSE 2015