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Types of Roof Insulation
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The following table lists the types of insulation that are used in low-slope roofing (or found in existing roofs). These insulation materials usually take the form of 4’ x 4’ or 4’ x 8’ rigid boards. They are normally secured with adhesives or fastener systems, but they may be loose-laid in ballasted roof systems, which depend on the weight of the ballast to hold the entire system in place.
These types of insulation are used in above-deck insulation applications, which means that they are installed over the roof deck, and are considered a part of the roof system or roof assembly. Steep-slope or pitched roof systems will almost never include insulation; in steep-slope construction, the insulation will be installed below the roof or above the ceiling.
This is the hole where a roof core sample was taken on an old built-up roof. You can see a layer of expanded polystyrene and gypsum board in the first roof system (at the bottom), and a layer of yellow rigid board fiberglass insulation in the second roof application (above).