Safety, Health & Environment Section
FM SHE 031
Air Conditioning Policy
&
Guidance on Thermal Comfort
October 2013
Version 2.0
Document review due: October 2014
Please Note :This is a controlled document, please ensure you are using the most recent
version available at:
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e_on_Thermal_Comfort.docx
Thermal Comfort
Introduction
Thermal comfort is defined in British Standard BS EN ISO 7730 as: ‘that condition of
mind which expresses satisfaction with the thermal environment.’
The term ‘thermal comfort’ describes a person’s psychological state of mind and is
usually referred to in terms of whether someone is feeling too hot or too cold.
Thermal comfort is difficult to define as a range of environmental and personal
factors must be taken into consideration when deciding what will make people feel
‘comfortable’.
The Health & Safety Executive (HSE) (2005) has stated that the “best that you can
realistically hope to achieve is a thermal environment that satisfies the majority of
people in the workplace, or put more simply, ‘reasonable comfort’. The HSE
considers 80% of occupants as a reasonable limit for the minimum number of people
who should be thermally comfortable in an environment”.
Inadequate thermal comfort can cause psychological issues in relation to
staff/student morale, complaints and productivity.
Health and Safety Legislation
The ‘Workplace (Health, Safety and Welfare) Regulations (as amended) 1992’ set
down specific requirements for most aspects of the working environment. Regulation
7 deals specifically with the temperature in indoor workplaces and states that “during
working hours, the temperature in all workplaces inside buildings shall be
reasonable”. However, there is no maximum temperature stated in the Regulations
or associated Approved Code of Practice.
The Health & Safety Executive’s (HSE) guidance document, HSG194, ‘Thermal
Comfort in the Workplace’ states that 'an acceptable zone of thermal comfort for most
people in the UK lies roughly between 13°C (56°F) and 30°C (86°F), with acceptable
temperatures for more strenuous work activities concentrated towards the bottom
end of the range, and more sedentary activities towards the higher end’. The Trades
Union Congress (2002) has called for these guidelines to be made compulsory.
Additionally, the Chartered Institute of Building Services Engineers (CIBSE) in
Section 1 (Environmental criteria for design) Guide A: Environmental Design,
suggests that for offices the temperature range for comfort should be 21-23º C in
winter and 22-24º C in summer. The latter range applies to air conditioned buildings.
Higher temperatures may be acceptable in non-air conditioned buildings (no figures
are quoted however). The World Health Organisation (WHO) also recommends a
similar maximum working temperature of 24º C.
Additional Factors: The Person
It must be recognised that personal temperature preferences vary greatly among
individuals and there is no single temperature that can satisfy everyone. However,
when considering the implications of high temperatures in the workplace it must also
be born in mind that some people may be more vulnerable to the effects of heat than
others, for example pregnant workers. The HSE’s Guide for New and Expectant
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Mothers at Work states, “Pregnant women tolerate heat less well and may more
readily faint or be more liable to heat stress”.
Additional Factors: Humidity and Ventilation
In addition to temperature, relative humidity (moisture content of the air) and
ventilation (air movement and changes) will influence people's comfort within the
workplace. Low humidity can result in a dry atmosphere, which can lead to itchy
eyes and a dry throat whereas high humidity can make the body's natural reaction of
cooling down (sweating) more difficult.
The Chartered Institute of Building Services Engineers in their Guide Volume A Design Data (1997) recommend that building humidity levels should be between 4070%.
A general lack of ventilation can result in workrooms becoming stuffy and air
becoming stagnant. Ventilation can be achieved naturally by opening windows or,
where this is not practical, by mechanical means. The HSE and CIBSE recommend
offices should have an outdoor air supply rate of 8 litres/second per person.
Mitigation Measures
The HSE (2005) has stated that “engineering controls should be the first choice to
reduce or eliminate the hazard”. Although the initial cost of engineering controls
maybe high, it has been found that the implementation cost is often offset by the
resulting improvements. The latter often include levels of production with a decrease
in downtime and reduced absenteeism due to improved levels of motivation.
It is important to stress that any practical solution to controlling thermal comfort is
likely to require a combination of different options alongside consultation between
employers, employees and their representatives.
The HSE (2005) states that where the temperature in a workroom would otherwise
be uncomfortably high, for example because of hot processes or the design of the
building, all reasonable steps should be taken to achieve a reasonably comfortable
temperature, for example by:
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placing insulating materials around hot plant and pipes;
providing air-cooling or air conditioning plant;
providing fans, e.g. desk, pedestal or ceiling-mounted fans;
ensuring that windows can be opened;
shading employees from direct sunlight with blinds or by using reflective film
on windows to reduce the heating effects of the sun;
ensuring equipment such as PC monitors, printers, photocopiers, etc. are not
left on overnight as these can generate significant amounts of heat;
locating workstations away from direct sunlight or other situations or objects
that that radiate heat (e.g. plant, machinery);
consider keeping a spare jumper in the office for those occasional ‘off days’
when you may feel chilly;
providing additional facilities, e.g. cold water dispensers (water is preferable
to caffeine or carbonated drinks);
introducing formal systems of work to limit exposure, e.g. flexible working
patterns, job rotation, workstation rotation etc;
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allowing sufficient breaks to enable employees to get cold drinks or cool
down;
moving away from a formal dress code in warm conditions – but you must
ensure that personal protective equipment is provided and used if required.
The University, so far as reasonably practicable, will endeavour to ensure
employee’s thermal comfort whilst at work. Nevertheless it should be recognised that
there are times beyond the University’s control for instance during summer ‘heatwaves’, causing high internal temperatures, where this may be difficult to achieve for
all members of staff. During such times we would ask staff to assist the University
and follow as many of the mitigation measures given above as possible.
Air Conditioning Policy
Air conditioned buildings use far more energy than naturally ventilated buildings as
additional energy is required for the refrigeration of air and to power the pumps/fans
which circulate cooled air throughout the building. The process of cooling air within
buildings therefore has a significant impact on the environment and is expensive in
terms of capital investment and ongoing running costs. The University of Central
Lancashire is committed to reducing its carbon footprint under agreed carbon
management plans. Therefore it has adopted a policy of not installing air conditioning
systems where suitable levels of fresh air, odour removal and reasonable thermal
comfort can be achieved by means of natural ventilation. Air conditioning or active
cooling will only be considered as a last resort and requests for such installations will
be judged on their merits. The criteria used for considering all requests for cooling is
as follows:
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Workplaces where the temperature in the non-heating season exceeds either
30oC or is 3oC above the ambient outdoor temperature (whichever is the
higher value) for more than 72 working hours per year in agreement with the
relevant Manager of the area and where all other options have been
exploited;
Where processes or operations necessitate cooling or close temperature
control;
Active cooling is to be limited to those situations where there is a clear case
for the control of temperature and/or humidity or where acceptable conditions
cannot be achieved by passive thermal control or by limiting the heat
generation from activities in the workplace;
Where Schools or Services are prepared to pay for the life-cycle cost of
installation, running, maintenance and decommissioning of an air conditioning
system.
All requests will be considered by the Director of Facilities Management. The use of
portable air conditioning systems is not permitted within University premises unless
specifically authorised by the Director of Facilities Management. The use of desk-top
/ pedestal electric fans is acceptable.
Any heating or temperature problems should be reported to the FM Helpdesk on
extension 2888 for the Maintenance and Development Section of Facilities
Management to investigate and remedy the problem.
Facilities Management
October 2013
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References
Health & Safety Executive. (2005). Thermal Comfort Home Page.
http://www.hse.gov.uk/temperature/thermal/index.htm
Health & Safety Executive. (1992). Workplace health, safety and welfare. Workplace
(Health, Safety and Welfare) Regulations 1992. Approved Code of Practice L24.
http://www.hse.gov.uk/pubns/books/l24.htm
Health & Safety Executive. (2003). Heat stress in the workplace. What you need to
know as an employer. http://www.hse.gov.uk/pubns/geis1.pdf
Health & Safety Executive. (2002). http://www.hse.gov.uk/mothers/
Chartered Institute of Building Services Engineers. CIBSE Guide A: Environmental
design (Environmental criteria for design).
Chartered Institute of Building Services Engineers. CIBSE Guide Volume A: Design
Data.
Chartered Institute of Building Services Engineers. CIBSE Guides A: Environmental
design and Guide B2: Ventilation and air conditioning.
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