Black Mould Problems

At a relative humidity level of 70% in a dwelling, we know that we will expect to be on the threshold of a condensation problem. As temperatures fall, relative humidity rises and this cooling vapour laden air migrates to the dwelling's cold exterior walls, releasing its moisture.

As this process continues on a daily cycle, the 'dumped' moisture eventually creates the familiar pattern of streaming windows, unsightly black mould on walls and the inevitable unpleasant, musty, damp atmosphere which often transfers itself to fabrics and clothing.

So what is the best way to alter this vicious circle? Certainly, the air needs to be changed. But how? By air from the outside? Indeed, many people just suggest opening windows or the fitting of extraction fans in individual rooms.

But, at best, these are only partial solutions. Positive ventilation will provide a whole house solution to indoor air quality. Normally located in the loft, a positive ventilation unit pulls in fresh air from the outside and filters it before delivering it, gently and almost imperceptibly, into the dwelling. The stale, damp air is forced out of the building through natural leakage and replaced by clean, fresh, dry air. Over a period of hours, the replacement of old air for new, dilutes the relative humidity levels and reduces condensation and its associated problems.