I had been getting condensation from my plastic seedling dome dripping at the edges so I put a cookie sheet under the seedling tray. I found after doing this that my heat mat could not get up to temperature. I figured the cookie sheet was acting like a nice heat sink so I put a piece of rigid polyurethane insulation between the heat mat and the cookie sheet. Problem solved, within a couple hours the temp had shot up almost six degrees and my seeds should be happy now.
-Alden
-Alden