Fitting an Envirovent unit just prior to the winter season has effectively eliminated the problems we have seen with condensation on metal window frames in the house, and has stopped a mould growth problem which had recently started to appear. Prior to our Envirovent unit, the relative humidity upstairs was typically around 70% - now it runs in the 45 - 55% range. Even though our loft space is little more than a crawl-way, the fitter was able to complete the work in an afternoon, with no mess or upheaval evident. Our unit has now been running for about six months, and hasn't missed a beat.