U.S. Department of Energy U.S. Department of Energy Energy Efficiency and Renewable Energy

Insulated Corners

Please Register or Login to Provide Feedback.

All corners insulated ≥ R-6 to edge

Scope


Reduced Thermal Bridging

 

All corners insulated ≥ R-6 to edge*

  1. Utilize recessed corners or an equivalent framing technique that uses no more than three studs per corner to allow access to insulate the cavity to ≥ R-6.
  2. If the corner is conventionally framed, drill a hole and fill the cavity with insulation.


* All items of 4.4.5a-4.4.5e must be installed to comply with 4.4.5 and ENERGY STAR.


Notes:


Up to 10% of the total exterior wall surface area is exempted from the reduced thermal bridging requirements to accommodate intentional designed details (e.g., architectural details such as thermal fins, wing walls, or masonry fireplaces; structural details, such as steel columns). It shall be apparent to the Rater that the exempted areas are intentional designed details or the exempted area shall be documented in a plan provided by the builder, architect, designer, or engineer. The rater need not evaluate the necessity of the designed detail to qualify the home.

Mass walls utilized as the thermal mass component of a passive solar design (e.g., a Trombe wall) are exempt from this item. To be eligible for this exemption, the passive solar design shall be comprised of the following five components: an aperture or collector, an absorber, thermal mass, a distribution system, and a control system. For more information see the Energy Savers Website.

Mass walls that are not part of a passive solar design (e.g., CMU block or log home enclosure) shall either utilize the strategies outlined in Item 4.4 (of the ENERGY STAR Thermal Enclosure System Rater Checklist). Or, the pathway in the assembly with the least thermal resistance, as determined using a method consistent with the 2009 ASHRAE Handbook of Fundamentals, shall provide ≥ 50% of the applicable assembly resistance, defined as the reciprocal of the mass wall equivalent U-factor in the 2009 IECC – Table 402.1.3. Documentation identifying the pathway with the least thermal resistance and its resistance value shall be collected by the rater and any Builder Verified or Rater Verified box under Item 4.4 (of the ENERGY STAR Thermal Enclosure System Rater Checklist) shall be checked.

All exterior corners shall be constructed to allow access for the installation of > R-6 insulation that extends to the exterior wall sheathing. Examples of compliance options include standard-density insulation with alternative framing techniques, such as using three studs per corner, or high-density insulation (e.g., spray foam) with standard framing techniques.

Description


Exterior wall corners are typically framed with three studs. The third stud generally only provides a nailing edge for interior gypsum board and its typical placement blocks off the wall cavity, preventing insulation from being installed. If the third stud can be eliminated, there is more room inside the wall for insulation. Drywall clips, a 1x nailing strip, or a recycled plastic nailing strip can be used to create a two-stud corner that still provides a surface on which to hang the drywall. Using drywall clips also reduces opportunities for drywall cracking and nail popping, frequent causes of builder callbacks.

 

The designer should include the corner detail on building plans. It should be installed by the framer. If two-stud corners are used, they can be insulated by the insulation contractor. This task should be included in the contract for the appropriate trade, depending on the workflow at a specific job site. ENERGY STAR Version 3.0 requires that all exterior corners shall be constructed to allow access for the installation of ≥ R-6 insulation that extends to the exterior wall sheathing. See the “compliance” tab for 2009 IECC-specified wall insulation levels.

 

How-To Insulate Corners

Construct exterior corners to allow access for the installation of > R-6 insulation that extends to the exterior wall sheathing in one of the following ways:

  1. Construct a two-stud corner using a nailing strip or drywall clips, which allows the wall cavity at the corner to be insulated in sequence with the rest of the installation at full wall thickness.
  • When drywall clips are used, they should be installed above the level of the interior trim so trim nails will not interfere.
  • If installing trim, the noncoped trim piece should be installed first, against the drywall that bears on the clip, so that the coped trim piece can be nailed to the stud.
  • If rigid foam is used as the sheathing instead of OSB or another solid nailable sheathing, install a wood nailer strip behind the sheathing if necessary for attaching exterior trim or siding at the corner on the side that does not have a stud.

 

Two-stud corner using drywall clips; detail shows nail placement for exterior trim

 

Figure 1 - This side view shows drywall clips installed on studs at a two-stud corner (the second stud is not visible behind the first corner stud). The plan view in the detail shows the placement of nails for fastening exterior corner trim.  Reference

 

 

Conventional three-stud corners leave a cavity that must be insulated by the framers—not good

Figure 2 - Conventional three-stud corners leave a cavity that must be insulated by the framers—not good  Reference

 

 

The improved three-stud corner allows insulation to be installed later, in sequence

Figure 3 - The improved three-stud corner allows insulation to be installed later, in sequence  Reference

 

 

Two-stud corners with drywall clips use the least wood and give the best thermal performance

Figure 4 - Two-stud corners with drywall clips use the least wood and give the best thermal performance  Reference



Ensuring Success


The quality of the insulation installation should be visually inspected by the site supervisor before the drywall is installed. It may be possible to detect heat loss at the corners of exterior walls with an infrared camera, if a sufficient temperature difference exists between the outside and the conditioned space of the house.



Climate


No climate specific information applies.



Right and Wrong Images



Presentations

None Available



Videos

None Available




CAD Images




Compliance


ENERGY STAR Version 3, (Rev. 6)

Thermal Enclosure Checklist, Reduced Thermal Bridging. All corners insulated ≥ R-6 to edge. All exterior corners shall be constructed to allow access for the installation of ≥ R-6 insulation that extends to the exterior wall sheathing. Examples of compliance options include standard-density insulation with alternative framing techniques, such as using three studs per corner, or high-density insulation (e.g., spray foam) with standard framing technique.

DOE Challenge Home

Exhibit 1: Mandatory Requirements. Certified under ENERGY STAR Qualified Homes Version 3. Ceiling, wall, floor, and slab insulation shall meet or exceed 2012 IECC levels and achieve Grade 1 installation, per RESNET standards.

2009 IECC

Table 402.4.2 Air Barrier and Insulation Inspection Component Criteria, Walls: Corners, headers, narrow framing cavities, and rim joists are insulated.* Table 402.4.2, Air barrier and thermal barrier: Exterior wall insulation is installed in substantial contact and continuous alignment with the air barrier. Air permeable insulation is not used as a sealing material.*

 

2009 IRC

Table N1102.4.2 Air Barrier and Insulation Inspection Component Criteria, Walls: Corners, headers, narrow framing cavities, and rim joists are insulated.* Table N1102.4.2, Air barrier and thermal barrier: Exterior wall insulation is installed in substantial contact and continuous alignment with the air barrier. Air permeable insulation is not used as a sealing material.

2012 IECC

Table R402.4.1.1 Air Barrier and Insulation Installation, Walls: Corners, headers, and rim joists making up the thermal envelope are insulated.* Table R402.4.1.1, Air barrier and thermal barrier: A continuous air barrier is installed in the building envelope including rim joists and exposed edges of insulation. Breaks or joints in the air barrier are sealed. Air permeable insulation is not used as a sealing material.*

 

2012 IRC

Table N1102.4.1.1 Air Barrier and Insulation Installation, Walls: Corners, headers, and rim joists making up the thermal envelope are insulated.* Table N1102.4.1.1, Air barrier and thermal barrier: A continuous air barrier is installed in the building envelope including rim joists and exposed edges of insulation. Breaks or joints in the air barrier are sealed. Air permeable insulation is not used as a sealing material.*



*Due to copyright restrictions, exact code text is not provided.  For specific code text, refer to the applicable code.            



Case Studies

  1. David Weekley Homes: Eagle Springs & Waterhaven, Houston, TX

    PNNL. 2012. Building America Case Study: David Weekley Homes, Eagle Springs & Waterhaven, Houston, TX. PNNL-SA-87333, prepared by the Pacific Northwest National Laboratory for the U.S. Department of Energy Building America Program.

    Link to Document
  2. Insight Homes: Deep Creek, Seaford, Delaware

    PNNL. 2012. Building America Case Study: Insight Homes: Deep Creek, Seaford, DE. PNNL- SA-87330, Prepared by the Pacific Northwest National Laboratory for the U.S. Department of Energy Building America Program.

    Link to Document

References

  1. 2009 IECC—International Energy Conservation Code

    2009 IECC, International Energy Conservation Code. International Code Council, Washington, D.C.

  2. 2009 IRC—International Residential Code for One and Two Family Dwellings

    2009 IRC, International Residential Code for One and Two Family Dwellings. 2009. Fifth Printing. International Code Council, Washington, D.C. 

  3. 2012 IECC—International Energy Conservation Code

    2012 IECC, International Energy Conservation Code.  International Code Council, Washington, D.C.

  4. 2012 IRC—International Residential Code for One and Two Family Dwellings

    2012 IRC, International Residential Code for One and Two Family Dwellings. 2012. Second Printing. International Code Council, Washington, D.C.

  5. Advanced Wall Framing

    U.S. Department of Energy (DOE). 2002. Advanced Wall Framing. DOE/GO-102000-0770. Prepared by National Association of Home Builders Research Center, Southface Energy Institute, and Oak Ridge National Laboratory Building Technology Center and the National Renewable Energy Laboratory for the U.S. Department of Energy.

  6. Building America Best Practices Series Volume 12: 40% Whole-House Energy Savings in the Cold and Very Cold Climates

    Baechler MC, TL Gilbride, MG Hefty, PC Cole, and PM Love.  2011.  Building America Best Practices Series Volume 12: 40% Whole-House Energy Savings in the Cold and Very Cold Climates. PNNL-20139. Prepared by Pacific Northwest National Laboratory for the U.S. Department of Energy, Building America Program.

  7. Building Science Insights: Advanced Framing

    Lstiburek, J. 2010. Building Science Insights: Advanced Framing. BSI-030. Building Science Corporation.

  8. DOE Challenge Home National Program Requirements

    DOE. 2012. DOE Challenge Home National Program Requirements (Rev. 02). Office of Energy Efficiency and Renewable Energy, U.S. Department of Energy, Washington, D.C.

  9. ENERGY STAR Qualified Homes, Version 3 (Rev. 06) Inspection Checklist for National Program Requirements

    EPA. 2012. ENERGY STAR Qualified Homes, Version 3 (Rev. 06) Inspection Checklist for National Program Requirements. U.S. Environmental Protection Agency, Washington, D.C.

  10. Thermal Enclosure System Rater Checklist Guidebook

    EPA. 2011. Thermal Enclosure System Rater Checklist Guidebook. U.S. Environmental Protection Agency, Washington, D.C.



Mobile Field Kit

The Building America Field Kit allows you to save items to your profile for review or use on-site.