Rigid Insulation Roof Assembly

Polyiso is an easy cost effective sustainable and energy efficient construction material.

Rigid insulation roof assembly. There s a reason polyiso rigid foam insulation is used in more than 70 of commercial roof construction as well as in many residential builds. Code specifies the minimum r value of the rigid foam layer. If all of the insulation is on the top of the roof sheathing this is pretty much a no brainer. There must be an air control layer air barrier under the rigid insulation boards.

Owens corning foamular xps insulation is a closed cell moisture resistant rigid foam board ideal for many roofi ng applications including single ply protected roof membrane assemblies prma tapered vegetative roofs plaza decks architectural metal roofi ng and recover roofi ng. Or sprayed polyurethane foam spf. Lightweight insulating concrete lwic. The air control layer can be a fully adhered membrane on the roof deck or the air control layer.

In this case the rigid foam can be thinner than when it s used alone. Dual purpose structural deck and insulating planks. Rigid foam also can be installed above the roof sheathing in tandem with air permeable insulation between the rafters. Gba blogs are filled with discussions of wall assemblies insulation vapor air barriers but i haven t found much on roof assemblies particularly cathedral types.

Assuming rafter construction is it best to build them like walls rigid insulation outside breathe to inside or is it best to seal the rafters on the inside with taped rigid foam and let the assembly breath to the outside. All of the rigid insulation board products work. Every one of them foil faced isocyanurate paper faced isocyanurate extruded polystyrene expanded polystyrene mineral wool aka stone wool rigid fiberglass.