Roof Deck Insulation Foam

The amount of closed cell spray foam or rigid insulation is somewhere between 20 to 50 of the r value of the overall cavity insulation depending on your climate zone.

Roof deck insulation foam.

Spray foam insulation applied on the underside of the roof deck in cold climate commercial buildings allows for a significant reduction in condensation potential particularly compared to interior air permeable batt systems. The ratio of insulation above the roof deck or air permeable insulation below the roof deck is a matter of climate and interior conditions. The later is used in new construction as the interior board serves as an inner wall. It s not coming from above the roof and it s not some new moisture source resulting from the spray foam.

Applying closed cell spray insulation to the underside of a roof deck at the sheathing to truss connection can double or triple the strength of the assembly boosting the roof sheathing s resistance to wind uplift in a hurricane. Lstiburek takes blame for bad language. Moisture generated indoors or that infiltrates into the home is responsible for the bulk of the moisture in an attic insulated with spray foam on the underside of the roof sheathing. Most unvented attics incorporate spray polyurethane foam spf on the underside of the roof deck and attic walls.

It typically has 3 variations. Shown to withstand delamination deterioration warping and jobsite damage more effectively than other roofing membrane substrates such as paper faced gypsum board fiber board and perlite insulation. As air impermeable insulation spray foam insulation can be used in such applications. Unvented attics that are insulated on the underside of the roof deck with blown spray foam.

But foam also traps moisture in the roof in case of a leak. Generally more insulation is needed for condensation control in colder climates. With enough closed cell spray foam under the deck or enough rigid above the deck interior moist air can t condense if the there is no condensation you don t need drying thus no need to vent. And vented or unvented attics that are insulated above the roof deck with rigid foam.

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. An excellent fire barrier densdeck roof boards feature a noncombustible core and inorganic surface that offer greater fire protection than other conventional commercial roofing products when applied over combustible roof decks and steel decks. High efficiency attic insulation helps provide added thermal protection lessens wasted energy and increases enhanced comfort and quiet. Also the higher the indoor humidity the more insulation is needed to avoid condensation.

Rigid foam board is just above the roof deck or an exterior insulation option.