How do I prevent excess moisture entering my home?
Project type
A dry home is key for inhabitants’ health and wellbeing.
A damp home is the perfect breeding ground for nasty organisms and can increase the number of allergy triggers like dust mites, mould and mildew. It will also rot wood in the structure of your home and ruin your furniture and floor coverings.
Efficient heating and adequate ventilation are essential to help prevent excess moisture.
What you need to do
Install an extractor fan in bathrooms, utility rooms and kitchens and close the door while the fan is on. Extractor fans should be able to extract 60 litres per second or 30 litres per second if it’s adjacent to the hob. The air has to be extracted externally.
If the space where you provide an extractor fan also contains an open flued heating appliance then a Competent Person must carry out a spillage test to make sure the flue can still work effectively.
Ventilate by opening the trickle vents in windows (building regulations requirements for new and replacement windows), open a window.
Internal wall insulation is the most efficient way to insulate but if this isn’t possible, then external insulation can be used to achieve at least the minimum U-value required by the building regulations. (U-value is the rate of transfer of heat through a structure and the better insulated the structure is, the lower the U-value.)
Install a PIV (positive input ventilation) system – this supplies fresh air from a unit installed in the loft or on a wall if you have an apartment.
Install an HRV (heat recovery system) or MVHR (mechanical ventilation with heat recovery) – this extracts heat from stale air and returns it to the fresh air that it circulates round your home.
Use a dehumidifier as a temporary measure if the moisture is simply left over from the construction of your extension.
Further information
Approved Document C (England) - Site preparation and resistance to contaminants and moisture
Approved Document C (Wales) - Site preparation and resistance to contaminants and moisture
