Insulation Joints and Overlays
Insulation Joints and Overlays
Contents
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 insulation materials will not accommodate direct torch-applied membranes
- insulation materials 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. RoofStar Guarantee Standards for heat sensitive insulation materials require a two-layer overlay board for a five (5) or ten (10) year Guarantee. The RoofStar Guarantee Program requires the use of a two-layer overlay board over heat sensitive insulation in all cases, and also requires a single-layer overlay board application over heat insensitive insulation for all hot asphalt-adhered membranes. For single-ply, non-asphaltic membrane roofing systems, the membrane manufacturer should be consulted for proprietary options.
2 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.
3 Asphalt and Paraffin-Impregnated / Coated Fibreboard Roof Insulation and Insulation Overlay Board
Under construction
4 Proprietary Overlay Boards
Under construction
5 Materials
To view materials accepted for use in the RoofStar Guarantee Program, see Accepted Materials: Insulation Overlay Board.