We are looking at alternatives to leaving windows open for swamp cooler exhaust.

I found up-dux but 70-bucks for 10-bucks worth of simple parts does not cut it when we need two of them.

I have ordered two metal registers and thinking of cutting holes in the ceiling.
http://www.amazon.com/Speedi-Grille-...peed i-Grille

Using some fly screen between the register and the ceiling to keep the spiders and bugs out and we should have an OK exhaust. Yes? No?

I can't see the need for the flap on the up-dux, so here's the question.

Do I need a flap?

If there is a compelling reason I can make some vent boxes with flaps to go into the ceiling, however, I am thinking that just the register then some magnetic plastic sheet to cover the register in Winter would work just as well. All for under 20-bucks for two vents and covers.

I can spare the 2-minutes of my time twice a year to install/remove magnetic flaps.

Helpful thoughts?

Dave