Although a maximum temperature is not specified, a workplace must be “adequately thermally insulated” and the “excessive effects of sunlight on temperature shall be avoided”. The WHO world health organisation says that in temperate climates the optimum indoor temperature is between 18°C and 24°C, and reps can use these figures to negotiate better standards than those laid down by law. Other factors such as draughts and humidity must also be considered when aiming for a comfortable temperature.