Easy to edit specification for design professionals to specify rigid roof insulation, built up asphalt roofing membrane, and related flashings.
Built up asphalt roofing is composed of multiple plies of roofing felt that are applied using hot asphalt, with gravel surfacing or aluminum roof coating applied to provide physical protection and prevent ultraviolet degradation.
This type of roofing is often installed over a cover board to provide protection against hail and foot traffic and for enhanced fire protection.
The ability of a roof to withstand high winds and resulting wind uplift is directly affected by the roof systems construction and attachment. Organizations such as Factory Mutual (FM) and Underwriters Laboratories (UL) rate roof systems for wind resistance. While FM is an insurer and therefore places requirements on more than just the insulation attachment, their ratings can be used as a guide for the roofing system.
Roof insulation is available in many forms, the most common of which are included in this section.
The R-value of any insulation that uses a blowing agent, in this case polyisocyanurate and extruded polystyrene, decreases after the insulation is manufactured. Consequently, the R-value for this type of insulation is rated by LTTR – Long Term Thermal Resistance, typically measured 5 years after manufacture.
For assistance in selecting and detailing built-up asphalt roofing refer to the National Roofing Contractors Association (NRCA) Roofing Manual: Membrane Roof Systems, available from NRCA at www.nrca.net.