Roof Insulation

Many of the insulation products described in the following are available in tapered configurations.
Cellular glass is a rigid insulation composed of heat-fused closed glass cells.
Cellulosic fibers are generally used as loose-fill insulation. They are made of recycled paper.
Glass-fiber batts or blankets (the only difference being the length of the product) are composed of glass fibers and a binding agent. The batts may be finished on one side with a kraft paper or aluminum-foil facer, or they may be left unfaced.
Glass-fiber board is a rigid insulation composed of glass fibers and a binding agent and is faced on the top surface with kraft paper.
Mineral-wool batts are similar to glass-fiber batts, except that they are composed of mineral fibers (produced from molten rock). Mineral-wool batts have high resistance to heat. Typically, they are used for fire-safing; for example, curtain walls or sealing at fire wall or floor penetrations, or steel fireproofing. Mineral batts are typically not used for roofing, except for insulating seismic joints or expansion joints, where enhanced fire resistance is desired.
Mineral-wool board is a rigid insulation similar to glass fiber boards except that it is composed of mineral fibers (produced from molten rock). These boards are available faced or unfaced with aluminum foil.
Perlite rigid insulation is composed of expanded perlite, cellulose, and a binding agent.
Phenolic resin has been formed into a rigid, plastic-foam insulation. It is no longer produced in the United States. It should be noted that phenolic insulation has shown a high potential for causing steel deck corrosion, and in some instances, the structural integrity of the roof deck has been impaired. Deck repair or replacement should be anticipated where phenolic insulation over a steel deck exists.
Polyisocyanurate may be used as rigid, plastic-foam insulation. It resembles, and has essentially replaced, polyurethane board insulation because of better fire resistance. Polyisocyanurate boards have been produced with a variety of facers.
Glass-fiber and organic/ inorganic are now the most common. The boards are also available as composites, which are factory produced by foaming the insulation to perlite, wood sheathing, or other types of substrates. Currently, the foam is produced by an HCFC (hydrochlorofluorocarbon) blowing agent, which initially is the gas that fills the cells. Over considerable time, oxygen and nitrogen diffuse into the cells, and the HCFC diffuses out, thereby decreasing the thermal resistance. This phenomenon is known as thermal aging or thermal drift. Polyisocyanurate insulation has the highest R-value (thermal resistance) per inch thickness of any insulation currently produced in the United States.
Due to government regulations, the HCFC blowing agents currently used in the manufacture of polyisocyanurate foam insulation are scheduled to be phased-out by the end of 2002. It remains to be seen what type(s) of blowing agents will be used in the next generation of this type of insulation.
Polystyrene made into a rigid plastic foam has two distinctly different forms.
Molded expanded polystyrene (EPS) has air-filled cells and hence is not subject to thermal aging. EPS is available with a variety of densities, and its R-value is a function of the density. Extruded polystyrene is blown with HCFC; thus it has a higher R-value than EPS. Extended polystyrene insulation is very resistant to water and water vapor and is available in very high compressive strengths. Accordingly,  it is the only type of insulation recommended for use in protected membrane roofs (PMR) or plaza decks (Art. 12.15).

Radiant barrier system (RBS) utilizes aluminum foil product with a lowemittance (high-reflectance) surface. An RBS is intended to reduce radiant heat transfer between a hot roof deck and cooler floor below (or vice versa).
Reflective insulation system (RIS) employs double-sided aluminum foil product, which is used in combination with bulk insulation, or in lieu of bulk insulation.
The system incorporates an enclosed air space that may contribute significantly to the thermal resistance.
Spray-applied polyurethane foam (SPF), in addition to providing thermal insulation, also functions as the roofing system (Art. 12.4.6).
Wood fiberboard is a rigid insulation manufactured from wood or cane fibers and binders.


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