Foam Board Roof Decking

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.

Foam board roof decking. The studs conduct more heat than the insulation between them. Position the foam board between the rafters and push it upward until it fits snugly against the underside of the roof deck. Bare foam board one sided sheathing board or double sided which is also reference as structural insulated panels. Apply continuous air control membrane to existing roof sheathing or implement continuous air control at roof sheathing.

1 4 spans flute widths up to 2 5 8 flexural strengths parallel lbs. The later is used in new construction as the interior board serves as an inner wall. Insulated foam sheets are also used as an insulated sheathing underlayment for exterior siding. This eliminates thermal bridging which is the energy lost through wall studs.

Polyiso consists of a uniform closed cell polyisocyanurate foam core and provides one of the highest r values per inch of any rigid insulation. The snugness of the foam itself should be sufficient to hold the strips. Remove existing roofing and non adhered underlayment to expose roof sheathing. Most unvented attics incorporate spray polyurethane foam spf on the underside of the roof deck and attic walls.

1 4 dens deck roof board. Unvented roofs with spray foam applied to the underside of the roof deck have been used since the mid 1990s. R values 28 tested in accordance with astm c518 spannings. Install rigid insulation board in multiple layers with joints offset vertically and horizontally between adjacent layers.

It typically has 3 variations. Johns manville polyiso foam sheathing insulation boards provide a continuous layer of insulation to reduce thermal bridging and improve energy efficiency. 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. The panels provide a continuous energy efficient surface.

The plywood was fastened through the rigid foam to the rafters with long screws.