Rigid Insulation Under Roof Deck

Install nailbase for cladding.

Rigid insulation under roof deck.

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. Rigid insulation layers exterior to existing roof sheathing must provide sufficient thermal insulation r value to control condensation risk see climate specific guidance. For standard steel deck construction this approach has many advantages such as. The dew point is typically within the insulation layer lowering condensation risks.

For most of us in the low slope roofing industry it s considered to be absolutely standard to have insulation placed above the roof deck. The r value is a measurement of the heat loss and heat gain. Additionally densdeck has been shown to withstand de lamination deterioration warping and jobsite damage more effectively than other roofing membrane substrates such as paper faced gypsum board fiber board and perlite insulation. The unique construction of densdeck provides excellent flute spanning that stiffens and provides increased foot traffic resistance to the roof deck.

When installing rigid insulation in an attic to be finished as a living space you must provide a route by which hot air. Rigid foam installation after the roof deck is ready the rigid foam insulation is installed. Install roofing underlayment flashing and cladding as per best practices. Most unvented attics incorporate spray polyurethane foam spf on the underside of the roof deck and attic walls.

Nailbase must be vented in high snow load areas.