Most Health & Safety requirements in relation to the workplace are covered in 'The Workplace (Health, Safety and Welfare) Regulations 1992.
In particular, Regulation 7 of these Regulations deals with the temperature in the indoor workplace and it states;
This should be without the need for specialist clothing. The temperature in workrooms should normally be at least 16 degrees Celsius unless much of the work involves severe physical effort in which case it should be at least 13 degrees Celsius.
Keep warm this winter.
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