Iecc Unvented Roof

Unvented roof construction let s review the basic code requirement for roofs.

Iecc unvented roof.

Attics or roofs can be designed and constructed to be either vented or unvented in any hygro thermal zone map 1. These assemblies are created by eliminating ventilation openings and moving the thermal moisture and air control boundaries to the plane of the 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. Code establishing a baseline for energy efficiency by setting performance standards for the building envelope defined as the boundary that separates heated cooled air from unconditioned outside air mechanical systems lighting systems and service water heating systems in homes and commercial businesses.

The model building codes allow both vented and unvented roof assemblies. Most unvented attics incorporate spray polyurethane foam spf on the underside of the roof deck and attic walls. Based on the 2012 iecc as amended by montana in 2014 11. While the vast majority of roof designs are vented a growing number of homes are being constructed with unvented attics or unvented cathedral ceilings.

Additionally there are requirements related to the arrangement of the insulation so as to prevent moisture condensation in the roof assembly. Unvented roof assemblies such as conditioned attics and unvented cathedral ceilings are becoming common in north american construction. In ceiling assemblies with attic spaces r 402 2 1 states that r 38 is satisfactory wherever the full height of uncompressed r 38 insulation extends over the top plate at the eaves. Although not expressly defined the authors interpretations are that this provision applies to both steep slope and low slope roof assemblies.

The 2012 international energy conservation code iecc requires r 49 for ceilings. Ibc section 1203 3 outlines the only circumstances when a roof may have an unvented attic or enclosed rafter truss assembly. The choice of venting or not venting is a design and construction choice not a requirement determined by the physics or by the building code. The building codes have included requirements for ventilating attics for some time.