Foam Board Roof Decking

Johns manville polyiso foam sheathing insulation boards provide a continuous layer of insulation to reduce thermal bridging and improve energy efficiency.

Foam board roof decking.

Remove existing roofing and non adhered underlayment to expose roof sheathing. Polyiso consists of a uniform closed cell polyisocyanurate foam core and provides one of the highest r values per inch of any rigid insulation. Bare foam board one sided sheathing board or double sided which is also reference as structural insulated panels. 1 4 spans flute widths up to 2 5 8 flexural strengths parallel lbs.

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. 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 later is used in new construction as the interior board serves as an inner wall.

The panels provide a continuous energy efficient surface. Position the foam board between the rafters and push it upward until it fits snugly against the underside of the roof deck. This type of insulated roof assembly limits thermal bridging through rafters. 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. Apply continuous air control membrane to existing roof sheathing or implement continuous air control at roof sheathing. R values 28 tested in accordance with astm c518 spannings. The snugness of the foam itself should be sufficient to hold the strips.

Install rigid insulation board in multiple layers with joints offset vertically and horizontally between adjacent layers. It typically has 3 variations. Rigid foam board is just above the roof deck or an exterior insulation option. 1 4 dens deck roof board.

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