What is the best, most cost-effective insulation to use for a flat roof? What is the best, most cost-effective insulation to use for a flat roof?
A flat roof, like any other roof, needs insulation installed to prevent heat loss from the house and cold air penetration. Before installing the roof decking on your flat roof, place fiberglass insulation in the areas between the rafters. Unroll and cut to fit. This type of insulation is available everywhere and is resistant to water, fire and mildew. If the roof is already in place, the best insulation material is the blown it type. You can apply it either from the outside or inside of the house by drilling holes and blowing it in.