Just a quick question... why can't you seal the windows? Don't know if you have a Fred's store around you or not, but any value place, even Wally world, should have black-pull-down (vinyl) blinds for a window. Not venetian blinds, but a solid piece of 1 or 2 mm thick black vinyl that you pull down by hand and it covers well. It took one blind per window and it blocks every photon from my 400 HPS... yeah... 400... i'm on a budget (note Fred's.... lol). I used thumbtacks and scotch tape to "leak-proof" the edges.

That's not the Gospel, but it sure worked for me. If you're running/plan to run say 1000+ watts, let ME know if it works with that much light!

Good luck on the grow, bro!