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.

1 4 dens deck roof board. R values 28 tested in accordance with astm c518 spannings. Most unvented attics incorporate spray polyurethane foam spf on the underside of the roof deck and attic walls. The snugness of the foam itself should be sufficient to hold the strips.

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. 1 4 spans flute widths up to 2 5 8 flexural strengths parallel lbs. After installing several layers of rigid foam above the roof sheathing these workers installed plywood above the rigid foam.

Polyiso consists of a uniform closed cell polyisocyanurate foam core and provides one of the highest r values per inch of any rigid insulation. It typically has 3 variations. Unvented roofs with spray foam applied to the underside of the roof deck have been used since the mid 1990s. Install rigid insulation board in multiple layers with joints offset vertically and horizontally between adjacent layers.

Remove existing roofing and non adhered underlayment to expose roof sheathing. Bare foam board one sided sheathing board or double sided which is also reference as structural insulated panels. This eliminates thermal bridging which is the energy lost through wall studs. Johns manville polyiso foam sheathing insulation boards provide a continuous layer of insulation to reduce thermal bridging and improve energy efficiency.

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 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. This type of insulated roof assembly limits thermal bridging through rafters.

Apply continuous air control membrane to existing roof sheathing or implement continuous air control at roof sheathing.