One factor that influences heat loss from a greenhouse is the amount of glazed area. In a 30Â° wide hoophouse, the glazed area from the ground to bench height is about 15% of the total surface area. Insulating this area with an inch or two of polyurethane or polystyrene can reduce total heat loss over 10%. Use a closed cell insulation board and not beadboard as this absorbs moisture reducing its insulating value.
For more energy saving tips see: Greenhouse Energy Conservation Checklist