Rigid Insulation Roof Assembly

The insulation used in low slope roof assemblies typically falls into one of the four categories.

Rigid insulation roof assembly.

All atlas acfoam polyiso insulation boards are qualitymark certified providing consumers an easy way to identify premium products that meet or exceed building codes for the best in roof performance. The air control layer can be a fully adhered membrane on the roof deck or the air control layer. 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. Lightweight insulating concrete lwic.

All of the rigid insulation board products work. 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. Every one of them foil faced isocyanurate paper faced isocyanurate extruded polystyrene expanded polystyrene mineral wool aka stone wool rigid fiberglass. If all of the insulation is on the top of the roof sheathing this is pretty much a no brainer.

Code specifies the minimum r value of the rigid foam layer. Or sprayed polyurethane foam spf. 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. Polyiso is an easy cost effective sustainable and energy efficient construction material.

Rigid foam also can be installed above the roof sheathing in tandem with air permeable insulation between the rafters. Dual purpose structural deck and insulating planks. There must be an air control layer air barrier under the rigid insulation boards.