Insulation Joints and Overlays

1 General

Insulation overlays are used to separate the roof membrane from the primary insulation, usually for one of two reasons:

• to prevent the insulation from affecting the performance of the roof membrane
• to prevent the roof membrane and / or the method of application from affecting the insulation

The insulation can affect the performance of the roof membrane in the following ways:

• the insulation may be incompatible with the membrane, resulting in a loss of physical properties
• different coefficients of thermal expansion may result in membrane splits / cracks.

The roof membrane and / or the method of application can affect the insulation in the following ways:

• the insulation may not be capable of withstanding asphalt application temperatures and may “burn-out”
• some insulations will not accommodate direct torch-applied membranes
• insulations that are too “soft” may result in delamination or damage to the membrane or insulation when exposed to heavy loads or traffic
• the solvents and adhesives used for flexible membranes may adversely affect the insulation.

NOTE: All hot asphalt-adhered asphaltic membranes (built-up roofing, modified bitumen, etc.) require an insulation overlay over heat sensitive insulations and heat insensitive foamed insulation. RGC Guarantee Standards for heat sensitive insulations require a two-layer overlay board for a five (5) or ten (10) year Guarantee. RGC requires the use of a two-layer overlay board over heat sensitive insulations in all cases, and also requires a single-layer overlay board application over heat insensitive insulations for all hot asphalt-adhered membranes. For single-ply, non-asphaltic membrane roofing systems, the membrane manufacturer should be consulted for proprietary options.

1.1 Insulation Joint Tape

Where the RoofStar Guarantee Standards or the roof system specifications call for taping fibreboard or insulation joints, consult the list of Accepted Materials: Insulation Joint Tape section of this Manual.

1.2 Asphalt and Paraffin-Impregnated / Coated Fibreboard Roof Insulation and Insulation Overlay Board

Under construction

1.3 Proprietary Overlay Boards

Under construction

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2 Materials

To view materials accepted for use in the RoofStar Guarantee Program, see Accepted Materials: Insulation Overlay Board.

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