Don't cover your boil kettle! Sure, that will slow down evaporation but that causes flavor issues with the beer (as boiling is what boils off the DMS precursors).
I have a big fan and an open door when I brew, blowing over the boil kettle and out the full length door, and I brew in a ground floor room. Even so, after a couple of years of this I'm having some ceiling tiles looking a little, er, bulgy. I like in a fairly dry climate, although we will get up to 60% humidity in the summer. In the winter, the moisture is probably welcome in my house as the hygrometer says around 30% humidity in my house in the winter months.
A range hood is a great idea, but if not a range hood then there needs some way for the moisture to escape.