I have a diy greenhouse built out of cinder block and glass panels & 2 x 4s built up against South Wall of house as 4th Wall of greenhouse. I need to rebuild hole new roof. My question is. What is best material to use? I want to put in a. Couple of vents. Measurements are 12 x 14. Any advice? Thanks

My first choice would be to use twin walled polycarbonate panels. Since your greenhouse has a wood frame, they would be easy to install. You can get them in 2 x 4 panels and put in your own vents. Twin walled polycarbonate would also help to diffuse the sunlight hitting your plants.

If you can't get them locally, Greenhouse Megastore has them starting at $16 a panel. They also sell the fasteners and sealing tape.

I need to replace all the roof 2 x 4s I used treated lumber last time but they still rotted. Could I use the metal 2 x 4s? Thanks

Yes. You will need glazing caps and bars. See the Recommended Accessories on this page: http://www.greenhousemegastore...