CTT8 CIBSE Top Tips 8: Temperature in Indoor Workplaces (Thermal Comfort)

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Further CIBSE Top Tips

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.

Contents

Top Tips
Introduction
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
References
Further Reading

Top Tips

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.

Occupant Behaviour

Wear more lightweight clothing in warm weather
Drink fluids to keep cool in hot weather
Allow flexible working hours and vary work tasks.

Introduction

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.

References

B&ES (2012) SFG20: Standard Maintenance Specification for Building Services (Penrith: B&ES). See www.sfg20.co.uk

CIBSE (2014) Guide M: Maintenance Engineering and Management (London: CIBSE). See www.cibse.org/knowledge/cibse-guide/cibse-guide-m-maintenance-engineering-management

CIBSE (2015) Guide A: Environmental Design (London: CIBSE). See 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 www.legislation.gov.uk/uksi/1992/3004/contents/made