creztor

Thanks, Andrew_C. What I'm a bit confused about is if in winter when RH is say often above 90 outside and houses are getting condensation and mould, this must mean the average RH inside the house is extremely high, like 90 to almost 100. As these piv units are meant to be left on 24/7, then it would mean RH inside the house is always this high, otherwise why would you replace low RH air inside your house with air from the loft which has a higher level of RH? I guess that what's confuses me. We get some condensation in winter here but I've never tracked RH in the loft or house. I'm doing that this winter.

Curious about the humidity where these piv units are being used. My understanding is that air in the loft where these units are being used is lower than that found around the rest of the house. By blowing this loft air in which has a lower level of humidity this then slowly forces out the air in the house hence lowering humidity levels. Is this right? If so then is it common for houses that use piv units to have high humidity levels in the house, much higher than air in the loft? An example of this is I just checked the humidity levels online for London. It's apparently 83% with a min of 1 and max of 8. So, I assume these houses with condensation and mould problems have humidity levels much higher than what it is outside? I ask because I live in Tasmania, Australia. Our winters seem to be like some places in the UK. Outside humidity is usually very high, not uncommon for 90 or higher and the days are just damp, wet and cold. However, house humidity levels inside would be lower or at worst the same as outside. Is this not the case for people who use piv units?