DIY cat enclosure

Hi
We want to build Buddy an enclosure before temperatures climb into the 20 + c's
Has anyone built their own? We're looking to construct 6' high x 4' wide, mesh with sloping roof, and a large coony box at one end, where the back 'wall' folds back, to enable me to clean it out. Something like that. I'm not the draughtsman in the family. Guess you can tell that:shy: Does anyone have wire mesh across the windows? Am trying to think of ways to get fresh air circulating. Until he's got an outside place of his own, Buddy have to be content with walking with me with harness and lead. What did you do for your maine coons to combat the higher temperatures last year?
Cuddy