Irc Faq Conditioned Attics

The acceptance of unvented conditioned attics continues to grow among builders and building officials.

Irc faq conditioned attics.

The irc has permitted unvented conditioned attics since 2006 with certain requirements. 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. 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. Habitable attics require a vertical access and emergency escape and rescue opening.

This guide describes ways to meet the roof venting requirements as per building code while converting the attic into living space by moving the. The energy savings touted by unvented attics can be as high as 20. 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. 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.

Air permeable insulation is typically fiberglass cellulose or low density. But conditioned attics are not unalloyed blessings. 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. 2015 irc section r202 definitions vapor diffusion port.

They come with their own set of drawbacks according to your own estimates this fundamental design flaw is costing you 1 000 a year. See the irc or the guide unvented attic insulation for details. Unventilated attics can help to mitigate energy loss through leaky ducts or ceiling fittings. Design specifications of air supplied to the conditioned attic.

For you the investment in insulation to create a conditioned attic isn t worth it because the payback period is 7 years. Section r806 5 unvented attic and unvented enclosed rafter assemblies. This is applicable to finished and unfinished spaces. A passageway for conveying water vapor from an unvented attic to the.

However if moisture is able to enter the unvented attic space it may lead to roofing panel issues. The roof deck in an unvented attic must be exceptionally airtight.