Irc Faq Conditioned Attics

If wood shingles or shakes are used a inch air gap must be left above the roof sheathing but below the shingles or shakes and roofing felt.

Irc faq conditioned attics.

The 2009 and 2015 irc verbiage is similar and still applicable. Unventilated attics can help to mitigate energy loss through leaky ducts or ceiling fittings. Design specifications of air supplied to the conditioned attic. They come with their own set of drawbacks according to your own estimates this fundamental design flaw is costing you 1 000 a year.

The irc has permitted unvented conditioned attics since 2006 with certain requirements. 2 air permeable insulation only irc r806 5 5 2 attic while the irc refers to this assembly as air permeable insulation only it also involves installation of rigid board insulation above the roof sheathing. A passageway for conveying water vapor from an unvented attic to the. This guide describes ways to meet the roof venting requirements as per building code while converting the attic into living space by moving the.

Habitable attics require a vertical access and emergency escape and rescue opening. See the irc or the guide unvented attic insulation for details. Attics that meet the size and ceiling height criteria of the habitable attic definition in chapter 2 are considered habitable. For example if an r 80 unvented cathedralized attic is to be constructed in a cold climate a minimum of r 40 50 should be air impermeable insulation installed and layered according to section r806 5 of the 2012 irc figure 4.

High performance housing faq 2009 irc conditioned attics this information sheet has been prepared by building science corporation for the department of energy s building america program a private public partnership that develops energy solutions for new and existing homes. The acceptance of unvented conditioned attics continues to grow among builders and building officials. Code requirements vary across the country. 2015 irc section r202 definitions vapor diffusion port.

Air permeable insulation is typically fiberglass cellulose or low density. The roof deck in an unvented attic must be exceptionally airtight. Section r806 5 unvented attic and unvented enclosed rafter assemblies. However if moisture is able to enter the unvented attic space it may lead to roofing panel issues.

The energy savings touted by unvented attics can be as high as 20. The irc also prohibits a vapor retarder on the attic floor of conditioned attics so that any moisture that may build up in the attic can dissipate into the house.