Ventilation in buildings is a vital part of a healthy environment, managing the relative humidity and the risks that come from having too high Rh*, condensation and in the worst cases, mould growth.
The legislation assumes that replacing windows will eliminate some natural air infiltration and potentially, having a detrimental effect on the indoor air quality and the natural ventilation, leading to increased Rh*.
Background ventilation can be done by several methods, trickle vents in windows, air bricks or mechanical ventilation.
Therefore, it is a legal requirement where technically feasible to fit background ventilation where required, most commonly in the window through the means of trickle ventilators. The size of the trickle vent will depend on the property, whether or not the extractor fans in the wet rooms are intermittent or continuous, the heating provisions and the size of the window itself.
* Rh – Relative Humidity
