We used four windows that are the same size and two that are a bit skinnier for the roof.
Here is Matt lining the up to be perfectly square. I grew impatient with his attention to detail but in the end it was appreciated because the 4th window we added to the base was the door and it swings closed easily on it's hinges. We added a small latch with a simple hook and loop.
Here is the finished project. You can see the the roof is still open, which is fine for ventilation in our area which is plant hardiness zone 8. If you are in a harsher zone, a bit of clear plastic stretched over these triagle shaped gaps would be great. Find your zone here
I planted these spinach and basil seeds 3 weeks ago, which is very early for basil here. They are happy and growing is their little glass house!
Some things to watch for when using old windows is often the paint can flake off and contaminate edible plants. I scraped off the inside of these windows and continue to keep on eye on the surface as moisture and temp created more peeling. I haven't had a problem with it but use common sense, which I know you will.
More fun ideas for re-purposing items this spring can be found on Pinterest.com but here are some of my favorites and hopefully, soon to be in my house!