I have a 10x20 GH that I built using a Costco shelter frame covered with 7 mil GH plastic film. I have planting beds raised to about hip high. I have used it to grow tomatoes for the last 2 years. I am now interested in growing some winter vegetables. I have buried Heat tape in the beds 1 pass in each bed. but have no other aux heat at this time. I am on the Olympic peninsula in Washington state. and winters tend to be mild but there is not a lot of sun. I saw a reference to installing a double roof in a poly GH on a previous thread. It would help if I had a diagram. Also Aux. Lighting might help. any suggestions??.
George
George