Foam Board Roof Decking

After installing several layers of rigid foam above the roof sheathing these workers installed plywood above the rigid foam.

Foam board roof decking.

Rigid foam board is just above the roof deck or an exterior insulation option. The plywood was fastened through the rigid foam to the rafters with long screws. This type of insulated roof assembly limits thermal bridging through rafters. The snugness of the foam itself should be sufficient to hold the strips.

Bare foam board one sided sheathing board or double sided which is also reference as structural insulated panels. Insulated foam sheets are also used as an insulated sheathing underlayment for exterior siding. 1 4 dens deck roof board. 1 4 spans flute widths up to 2 5 8 flexural strengths parallel lbs.

Polyiso consists of a uniform closed cell polyisocyanurate foam core and provides one of the highest r values per inch of any rigid insulation. Johns manville polyiso foam sheathing insulation boards provide a continuous layer of insulation to reduce thermal bridging and improve energy efficiency. Apply continuous air control membrane to existing roof sheathing or implement continuous air control at roof sheathing. It typically has 3 variations.

Position the foam board between the rafters and push it upward until it fits snugly against the underside of the roof deck. Remove existing roofing and non adhered underlayment to expose roof sheathing. The panels provide a continuous energy efficient surface. This construction approach was first used in the 1970s and it has been implemented much more widely since it was first included in the international code council s icc model building code in 2007 irc section 806 4.

R values 28 tested in accordance with astm c518 spannings. This eliminates thermal bridging which is the energy lost through wall studs. The studs conduct more heat than the insulation between them. Unvented roofs with spray foam applied to the underside of the roof deck have been used since the mid 1990s.

Open cell spray polyurethane foam or closed cell spray polyurethane foam ccspf insulation can be sprayed along the underside of the roof sheathing to provide a conditioned and insulated attic space that can be durable and efficient in all climate zones see figure 1.