RCABC - CONSUMER GUIDE TO ROOFING
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Sometimes expensive, and
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Limited availability.
Glass Fibreboard (Fibreglass) Glass fibreboard roof insulations are composed of fine glass fibres compressed into rigid insulation boards. These boards are most commonly available top-surfaced with a glass fibre-reinforced asphalt and kraft paper. This provides a suitable surface for directly mopped bituminous membranes and for some flexible membrane roof systems. In addition, boards made of glass fibres bound in a resinous binder are available either top-surfaced for bituminous roofing, or plain for use under ballasted membrane systems. Glass fibreboard roof insulation may provide the following properties and advantages: •
Compatible with asphalt,
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Compatible with most roof system components,
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Resistant to thermal conductivity,
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Resistant to fire,
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Resistant to the effects of moisture,
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Resistant to cell deterioration (durable),
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Resistant to petroleum solvents,
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Resistant to impact (if top-surfaced),
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Resistant to thermal cycling (dimensionally stable),
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Unaffected by asphalt application temperatures (no fibreboard overlay required),
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Stable K-value (the thermal conductivity does not change with aging),
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Conforms to minor deck irregularities, and/or
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Retains roofing nails (first layer in a two-layer application only).
The possible disadvantages or precautions involved in the use of glass fibreboard insulation include: •
The kraft paper facing may change dimensionally if allowed to absorb moisture (protect from weather prior to application), and/or
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Heavy equipment may compress the insulation and cause delamination of the membrane.
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Glass fibreboard roof insulation should meet or exceed CAN/CGSB-51.31-M84.
Extruded Expanded Polystyrene Foam Molten polystyrene and a blowing agent HCFC (142B) are mixed, under pressure, in an extruder. As this solution is extruded through an orifice into ambient temperature and controlled conditions, the blowing agent vapourizes causing the polystyrene to expand approximately 30 times its original size. The continuous extrusion process produces boards with a surface "skin" and closed cell structure and, for this reason, has been used extensively for protected membrane roof assemblies. The rigid insulation boards are expanded to a specific thickness during manufacture and have an approximate density of 32 kg/cu. m (2 lb/cu.ft.). Extruded expanded polystyrene foam roof insulation is combustible and, when used on steel decks or over a roof that is subject to fire exposure from below, a fire-rated underlayment or thermal barrier
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