Unvented Attic Metal Roof

An unvented assembly can perform well but it s important to get the details right to avoid sheathing rot.

Unvented attic metal roof. Both vented and unvented attic roof designs can be used in all hygro thermal regions. This is the recommendation of all three local insulation installers. In the process of construction. Unvented roofs have a number of advantages.

Currently have a standing seam metal room installed over synthetic felt over osb. Ventilation becomes more difficult the more complicated a roof s construction is. Unvented attics do not experience such problems. Unvented roofs vented roof.

However the designs need to be climate sensitive. Unvented roof assemblies such as conditioned attics and unvented cathedral ceilings are becoming common in north american construction. However as the future owner i m beginning maybe a bit too. Air permeable insulation such as fiberglass batts dense packed cellulose or blown in fiberglass can t be used alone for an unvented assembly since these types of insulation can allow moist indoor air to reach the cold roof sheathing leading to condensation or moisture accumulation.

Control of ice dams moisture accumulation and heat gain can be successfully addressed by both vented and unvented attic or roof design. Removing moisture from roof cavities structural members sheathing and insulation. No insulation installed yet. Metal cladding manufacturers warranties may be unaffected by whether a roof is vented or unvented as is the case for bossier city la based mcelroy metal s warranty.

There will be ducting and other hvac equipment in the attic. Unvented metal roof assemblies are common on warehouses factories and shopping malls. In vented attics in cold climates warm air can leak from the living space and condense on the underside of the roof sheathing while humid air can easily leak from the outdoors and condense on cold metal surfaces of ductwork and air conditioning equipment typically located in the attic. The plan is to spray open cell foam under the roof deck.

As a result unvented roofs have become popular in homes with feature dense roofs think multiple skylights dormers and other aesthetic flourishes. Most unvented attics incorporate spray polyurethane foam spf on the underside of the roof deck and attic walls. 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. There are traditionally four main reasons for venting a roof.

Controlling ice damming by keeping the roof cold.