Very good product. The surveyor explained what it did clearly. Installation was quick and neat, and they left the place clean. It makes a massive difference - much much less condensation in our house. It even reduced humidity in the extension, even though the surveyor had said that because it wasn't in the main body of the house, he couldn't guarantee it would make any difference there. We have a humidity meter in the kitchen. Before we had envirovent installed, the humidity was usually around 66%. It's now around 44%. Also, the surveyor had said we might have to wait about two weeks to notice a difference. Well we noticed a difference the evening of the day it was installed. The air in the house seemed fresher already. I've not noticed an increase in our electricity or gas bill. Finally it's very quiet. All in all it's a cheap product considering the benefits.