Draughtproofing the windows and external doors of UK dwellings can be an effective and relatively inexpensive means of comfort and reducing heat loss by natural ventilation. In most situations, draughtproofing is unlikely tocause any deterioration in the quality of indoor air. There are however a number of simple checks which should be made prior to installation to ensure that the ventilation requirements of the dwelling and its occupants are satisfied. These are summarised in this digest in the form of simple checklists, covering condensation, combustion appliances and other domestic appliances. The digest also presents the results of measurements of air leakage through windows and doors in a sample of typical UK dwellings.