Mack

I have been looking at greenhouse builds on various sites and many use plastic sheeting whch is too fine for me since I have 2 young boys who would love to poke holes in it. Glass for the same reason is out. The plastic panels are durable and if one gets damaged it can be replaced so the plastic corrigation was a compremise in my case. Some people seem to be conserned about uv and ir rayes getting into the greenhouse. It does effect the yield of Tomatoes for example but not significantly but that's not a big concern for me since my greenhouse is small.

However, your information has answered my question. A second layer would improve the isulative properties and possibly block some of the harmfull rays. Since the GH is woden framed and with the perspex attached to the outside, I would be able to tack some light plastic sheeting inside. I think based on what you have said that would improve things considerably.

Thank's for the great information Mack1.