Unvented Attics and Cathedral Ceilings. The air-permeable insulation shall be installed directly under the air-impermeable insulation.
Code change allowing use of air permeable insulation in the construction of unvented conditioned attics.
Unvented roof assembly impermeable insulation. When you’re using only air-impermeable insulation (option 1, top left), it must be installed directly below the roof deck. Air impermeable insulation only, in direct contact with roof sheathing Air-impermeable insulation to code requirement ¼” air space (with wood shingles or shake). The quest for greater energy efficiency in buildings has led to increasing interest and need for insulation, improvements in HVAC equipment, more airtight construction, new materials and assemblies.
Near-term – the moisture content of the roof sheathing b. Unvented Attic Assemblies – Code Notes [2009 IRC, 2012 IRC]. Note that table R806.4 indicates the amount of insulation above the roof deck or air impermeable insulation below the roof deck required for condensation control assuming minimum required total insulation as indicated in Section N1102 Building Thermal Envelope.
R25 is required for climate zone 6 in Maine.. With the unvented attic assembly approach, the unvented attic space is designed. This paper describes a hygrothermal modeling study, including all of the US climate zones, a range of interior humidity levels and numerous arrangements and types of insulation.
When you’re using only air-permeable insulation in the framing cavity (option 2, top right), you must install the right amount of rigid insulation above the roof deck. This roof assembly has no insulating sheathing installed above the roof deck. In the most recent issue of Fine Homebuilding, Martin Holladay wrote a piece on Insulating Unvented Roof Assemblies.
Air-impermeable insulation (typically spray foam) installed to the underside of the roof sheathing. Insufficient fill below the impermeable insulation layer. The 2009 IRC (section R806.4) makes explicit the requirement for impermeable insulation (eg rigid foam board or closed cell spray) above permeable insulation (eg blown cellulose or fiberglass).
Foam Free Don't stay stuck in the sci-finightmare of foam, foam, foam. To some, unvented attic construction using spray foam insulation is a fairly new approach in home building. Martin's post focuses on the marketing of Owens Corning's ProPink Unvented Attic Insulation System.
Unvented Attic Assemblies Factsheet WSU Energy Program May 22, 2009. Sanity Check on an Unvented Roof Assembly An insulation contractor has suggested a way to save money, but the homeowner worries about the added risks of moisture accumulation. Moisture-Safe Unvented Wood Roof Systems Research Report – 1001 April-2010 John Straube, Jonathan Smegal and John Smith .
To some, unvented attic construction using spray foam insulation is a fairly new approach in home building. Two potential unvented roof assemblies: 2 Air-Permeable Insulation Only.
The R-value of the impermeable layer depends on climate. The results showed that so We agree that avoiding sheathing rot is critical, and that air permeable insulation such as fiberglass or cellulose cannot be used.
Movement of water vapor into the assembly from the house. Air-impermeable and air-permeable insulation. Through provision R806.4, the IRC also allows you to build an unvented roof assembly.
The air-impermeable insulation shall be applied in direct contact with the underside of the structural roof sheathing as specified in Table 806.5 for condensation control. One possible failure mode is that open cell foam was used without a. We are in the greater San Francisco Bay Area and have been doing this for about 15 years..
If the insulation is only placed on the bottom of the roof deck, between the rafters, it must be air impermeable. Verify that the total insulation R-value proposed for the roof assembly meets or exceeds the energy code, Ceiling side (attic floor) of the unvented attic assembly” and if “air-impermeable insulation is applied in direct contact with the underside/interior of the structural roof deck.” There is an exception that allows air-permeable insulation (fiberglass and cellulose) to be used in unvented assemblies in
With it, the orientation and type of insulation applied to the top of the building enclosure has changed from the traditional way, and so temperature and moisture conditions experienced by various assembly elements will be impacted. Monolithic continuous exterior insulation (CI) above structural sheathing. With it, the orientation and type of insulation applied to the top of the building enclosure has changed from the traditional way, and so temperature and moisture conditions experienced by various assembly elements will be impacted.
Sanity Check on an Unvented Roof Assembly. Yes, Unvented Roof Assemblies Can Be Insulated With Fiberglass – A WUFI Post And Not Just In Climate Zones 2B & Insulation options for unvented roofs.
Of unvented roofs by more than 50 percent and allow the use of dense pack cellulose in retrofit applications without risk. Note that this roof assembly has rigid insulation installed above the roof deck in order to control the condensation potential. If you don’t want to use SIPs or nailbase, read this article tolearn the four basic approaches to insulating unvented roof assemblies.
These assemblies are created by eliminating ventilation openings and moving the thermal, moisture and air control boundaries to the plane of the roof deck. Two acceptable methods for insulating an unvented attic assembly in all climates are as follows: Doesn’t count as an “air impermeable” insulation for code purposes is a code provision specifying that any air impermeable insulation “shall be a Class II.
We're big fans of Fine Homebuilding. This section outlines the conditions for unvented attic/roof assemblies. Insulating Unvented Roof Assemblies:
This reduces latent air-conditioning loads and provides further reductions in energy consumption. Figure 5 shows the potential for condensation of an unvented roof assembly in Dallas, TX. Senior Engineer Manager at Icynene, John Broniek makes the case for the unvented attic assembly and why insulating the underside of the roof makes sense.
This is done by using what is referred to as “air-impermeable insulation,” such as rigid foam board or spray foam. Create an unvented roof. A fundamental requirement of an unvented attic assembly is the use of air-impermeable insulation on the underside of the unvented roof to prevent air infiltration and exclude airborne moisture from the attic.
Unvented attics are not allowed by the building code yet in Canada but are allowed in the International Residential Code in the US in Section R806, which describes three different insulation strategies for unvented roofs. Requires a minimum R-value of air impermeable insulation on or under the roof deck. The overall insulation level in the roof assembly must meet the baseline requirements for energy efficiency as given in the IRC Section N1102 (or IECC, Section 402)..
Dallas, TX is located in a mixed-humid climate zone.