My wife and I are self builders currently building our new house in East Yorkshire. We will be installing UPVC type windows and doors. Unfortunately, the trickle ventilators that provide passive ventilation in the windows are quite ugly inside and out we do not wish to deploy them. We have investigated the use of Positive Input Ventilation (PIV) as an alternative and found a company that sells such a system. The system is approved and meets the Building Regulation Part F, which deals with ventilation requirements of newly built houses. However, the company that provides the system advises that it will only work correctly with buildings that have an air permeability above the value of 3. The actual value is determined at the completion of the build when an air leakage test is carried out. Our house has an air permeability design objective of 5. However, there appears to be a ‘catch 22’ situation in that by the time we establish the air permeability rating, we have already installed the windows without trickle ventilation. The trickle ventilation is added at the manufacturing stage. Actually, this is just the same as wooden windows and adding them later is simply not a practical proposition.

What could we do to adjust the situation if we install UPVC windows without passive ventilation only to find later that the air leakage test shows air permeability to be under 3. It would also be interesting to know what percentage of self build houses achieve an air permeability of less than 3 and also what is the typical value.