New Building regulations Part L1A "Conservation of fuel and power in new dwellings" stipulates increased insulation and requirements for pressure testing of dwellings. This has made Part F "Means of Ventilation" more important to implement. Part F stipulates the reason why ventilation is necessary (General guidance 0.7 p 6):

1. Provision of outside air for breathing.
2. Dilution and removal of airborne pollutants, including odours.
3. Control of excess humidity (arising from water vapour in the indoor air).
4. Provision of air for fuel-burning appliances.

Part F also stipulates a minimum ventilation rate of 0.3 l per sqm. It also gives guidance to the type of ventilation approved:

1. Background Ventilators.
2. Passive stack ventilation.
3. Continuous mechanical extract.
4. Continuous mechanical supply and extract with heat recovery.