Insulation Under Metal Roof Deck

The dew point is typically within the insulation layer lowering condensation risks.

Insulation under metal roof deck.

The code in most climate zones requires a minimum r value of air impermeable insulation on or under the roof deck. Underlayment must also act as a secondary weather barrier in case the roof fails. In addition to installing the foam board on the underside of the roof deck you can attach it to the bottom edges of the rafters in the same manner you would hang drywall. Traditionally metal roofs have used standard 30 pound felt paper underlayment.

We ll add a vapor barrier so the moist air does not flow up through the insulation and condense on the roof. One possible failure mode is that open cell foam was used without a vapor retarder coating. 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. 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.

For standard steel deck construction this approach has many advantages such as. The most common material used for an insulating metal roof is fiberglass batts or glass mineral wool. Fiberglass batts or glass mineral wool metal roof insulation. 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 foam can be used on either the outside or the inside of the sheathing. 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. You can then install. Avoids nails or screws which could penetrate the metal roof and cause leaks.

Use rigid foam insulation to cover wider spans of roof sheathing between joists. Both materials make a great physical barrier between the interior building and the metal roof. The batts are located side to side on the rafter of the roof. Cut each sheet to the desired size using a utility knife then fasten it in place using staples or adhesive.

Traditionally we ve insulated the roof panel to try and keep the temperature on the panel from reaching the dew point. Most unvented attics incorporate spray polyurethane foam spf on the underside of the roof deck and attic walls. But a preinstalled membrane may be even more effective at removing condensation. Insulating with spray foam insulation.

Benefits of densdeck roof board include.