Clothes drying on a radiator

Specific average moisture generation rates.

A  person could perspire and exhale 40 g of water vapour per hour when sleeping, 70 g/h when seated and 90 g/h when standing or doing housework. 

Theoretically, if the occupants didn’t leave the dwelling, slept for seven hours, sat for ten hours and stood or did housework   for seven hours each could generate 1.6 Kg of moisture purely due to metabolic moisture generation.

Theoretically, therefore, three occupants could produce 4.8 kg and six occupants (potentially in the same size of dwelling ) could produce 9.6 kg, regardless of whatever appliances they use, how often they shower or where they dry their clothes. It is clear the level of occupancy and the duration to which occupants are present each day can be key drivers of moisture content.

Weight of water vapour (i.e. moisture) released by various domestic activities:

Cooking with gas cooker: 3,000 g/day

Cooking with electricity: 2 000 g/day

Dishwashing: 400 g/day

Washing clothes: 500 g/day

Drying clothes indoors: 1,500 g/day

15-minute shower: 600 g (Note: no doubt modern power showers generate more produce much more)

Clearly drying clothes can be but one major contributor to indoor humidity, especially in homes with multiple occupancies