Walls Adjoining Porch Roof

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Climate

ENERGY STAR Version 3, (Rev. 07)

Thermal Enclosure Checklist, Fully-Aligned Air Barriers. A complete air barrier shall be provided that is fully aligned with the insulation at exterior surface of walls in all climate zones; and also at interior surface of walls for Climate Zones 4-8. 

DOE Challenge Home

Exhibit 2: DOE Challenge Home Target Home. Infiltration (ACH50):  Zones 1-2: 3; Zones 3-4: 2.5; Zones 5-7: 2; Zone 8: 1.5. Envelope leakage shall be determined by an approved verifier using a RESNET-approved testing protocol.

climate zone map

International Energy Conservation Code (IECC) Climate Regions

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Description

In two-story homes with covered porches, builders may sometimes forget to sheathe the wall area that will be hidden when the porch ceiling is installed, because the porch is framed before the wall sheathing is installed. If there is no exterior sheathing, blown insulation cannot be installed. Even if batt insulation is installed, if there is no exterior sheathing that is caulked in place to serve as an air barrier, the insulation is subject to wind washing from outside air, especially if the porch ceiling is vented or is not air tight.

In two-story homes, the air barrier separating the wall insulation from the porch attic is sometimes missing

Figure 1 - In two-story homes with first-story porches, the air barrier separating the wall insulation from the exterior air is sometimes missing because it is hidden from view by the porch ceiling  Reference

In one-story homes with vented attics where the ceiling plane of the living space is level with the ceiling plane of the porch, the wall plane between the house attic and the porch attic does not need to be insulated and air sealed. In this case, the ceiling plane of the living space should be air sealed, especially along the top plate of the walls.

In one-story homes with unvented attics, the wall plane between the porch and the house should have a solid, sealed air barrier on the exterior side of the wall cavity and the wall cavity should be filled with insulation that is fully aligned to this air barrier.

The exterior sheathing that is hidden by the porch roof and ceiling can be rigid foam, OSB, plywood, or another rigid sheathing product, and it may be installed by framers or insulators. This task should be included in the contract for the appropriate trade depending on the workflow at the specific job site. Air barrier effectiveness is measured at the whole-house level. High-performance branding programs and the 2009 and 2012 IECC require that builders meet specified infiltration rates at the whole-house level. See the “compliance” tab for these specified infiltration rates. 

Collage showing air leak in existing porch wall with no air barrier and how air barrier was installed

Figure 2 - Building America researchers were called to investigate high heating bills at an apartment complex in Connecticut. (1) Infrared camera imagery revealed high heat loss on a second-story wall above a location where (2) a porch extended from the first-story exterior wall. (3) Researchers opened up the perforated vinyl porch ceiling to find (4) there was no air barrier covering the batt insulation. Air could flow through the insulation robbing it of its heating value. (5) An air barrier of rigid foam board was put in place with spray foam.  Reference

 How to Install a Fully Aligned Air Barrier in a Porch Wall

  1. Install the exterior wall sheathing to extend to or beyond the porch roof rafters or install sheathing from the house attic side after porch roof framing is installed.

Install the exterior wall sheathing to extend to or beyond the porch roof rafters

 Reference

- or -

  1. If the drywall is already installed on the interior side of the wall, install insulation in the wall cavity. Make sure the insulation fully aligns with (is completely touching) the sheathing on the interior side.

Insulate the porch-attic wall making sure the insulation fully aligns with the inside wall sheathing

 Reference

  2.  Apply a thick bead of caulk to the framing that will be covered.

Apply caulk to wall framing

Reference

  3.  Cut wall sheathing (e.g., rigid foam insulation, OSB, or plywood) to cover the insulation on the exterior side of the wall cavity.

  4.  Nail or screw the sheathing in place over the caulk.

Install rigid insulation or another wall sheathing product

 Reference

  5.  If there are seams in the sheathing, seal them with caulk or tape.

  6.  Install a porch ceiling or cover the wall sheathing with exterior siding.

Ensuring Success

A visual inspection should be made by the site supervisor to determine that the wall cavity separating the house from the porch attic is filled with insulation that is in full contact with the interior drywall and that the wall cavity is completely covered with rigid sheathing that is air sealed at all edges to form a continuous air barrier along the exterior wall of the house. Blower door testing, conducted in conjunction with inspection with an infrared camera, may also be useful in detecting air leakage or lack of insulation alignment at the porch wall.

Scope

Wall adjoining porch roof

Fully Aligned Air Barriers

  1. Install a rigid air barrier or other supporting material to separate the porch attic from the conditioned space.
  2. Seal all seams, gaps, and holes of the air barrier with caulk or foam before building wrap installation.

ENERGY STAR Notes:

ENERGY STAR highly recommends using a rigid air barrier, but it is not a requirement.

An air barrier is defined as any durable solid material that blocks air flow between conditioned space and unconditioned space, including necessary sealing to block excessive air flow at edges and seams and adequate support to resist positive and negative pressures without displacement or damage. ENERGY STAR recommends, but does not require, rigid air barriers. Open-cell or closed-cell foam shall have a finished thickness >= 5.5 inches or 1.5 inches, respectively, to qualify as an air barrier unless the manufacturer indicates otherwise. If flexible air barriers such as house wrap are used, they shall be fully sealed at all seams and edges and supported using fasteners with caps or heads >= 1 inch in diameter unless otherwise indicated by the manufacturer. Flexible air barriers shall not be made of kraft paper, paper-based products, or other materials that are easily torn. If polyethylene is used, its thickness shall be >= 6 mil.

ENERGY STAR highly recommends, but does not require, inclusion of an interior air barrier at band joists in Climate Zone 4 through 8.

All insulated vertical surfaces are considered walls (e.g., above and below grade exterior walls, knee walls) and must meet the air barrier requirements for walls, with the exception of adiabatic walls in multifamily dwellings. All insulated ceiling surfaces, regardless of slope (e.g., cathedral ceilings, tray ceilings, conditioned attic roof decks, flat ceilings, sloped ceilings), must meet the requirements for ceilings.

Training

Right and Wrong Images

Presentations

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Videos

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Compliance

ENERGY STAR Version 3, (Rev. 07) 

Thermal Enclosure Checklist, Fully-Aligned Air Barriers. A complete air barrier shall be provided that is fully aligned with the insulation at exterior surface of walls in all climate zones; and also at interior surface of walls for Climate Zones 4-8. All insulated vertical surfaces are considered walls (e.g., above and below grade exterior walls, knee walls) and must meet the air barrier requirements for walls, with the exception of adiabatic walls in multifamily dwellings.

DOE Challenge Home

Exhibit 2: DOE Challenge Home Target Home. Certified under ENERGY STAR Qualified Homes Version 3. Infiltration (ACH50): Zones 1-2: 3; Zones 3-4: 2.5; Zones 5-7: 2; Zone 8: 1.5. Envelope leakage shall be determined by an approved verifier using a RESNET-approved testing protocol. Building envelope assemblies, including exterior walls and unvented attic assemblies (where used), shall comply with the relevant vapor retarder provisions of the 2012 International Residential Code.

ASTM E1677-11

Standard Specification for Air Barrier (AB) Material or System for Low-Rise Framed Building Walls. This specification covers minimum performances and specification criteria for an air barrier material or system for framed, opaque walls of low-rise buildings. The provisions are intended to allow the user to design the wall performance criteria and increase air barrier specifications for a particular climate location, function, or design.

2009 IECC

Table 402.4.2 Air Barrier and Insulation Inspection Component Criteria, 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, 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

Exterior insulation for framed walls is in substantial contact and continuous alignment with the air barrier.* Table R402.4.1.1 Air Barrier and Insulation Installation, 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

Exterior insulation for framed walls is in substantial contact and continuous alignment with the air barrier.* Table N1102.4.1.1 Air Barrier and Insulation Installation, 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.

More Info.

Case Studies

None Available

References and Resources*

  1. Author(s): Baechler, Gilbride, Hefty, Cole, Williamson, Love
    Organization(s): PNNL, ORNL
    Publication Date: April 2010

    Report identifying the steps to take, with the help of a qualified home performance contractor, to seal unwanted air leaks while ensuring healthy levels of ventilation and avoiding sources of indoor air pollution.

  2. Author(s): DOE
    Organization(s): DOE
    Publication Date: June 2013

    Standard requirements for DOE's Challenge Home national program certification.

  3. Author(s): EPA
    Organization(s): EPA
    Publication Date: June 2013

    Standard document containing the rater checklists and national program requirements for ENERGY STAR Certified Homes, Version 3 (Rev. 7).

  4. Author(s): Moriarta
    Organization(s): Home Energy Magazine
    Publication Date: July 2008

    Journal article describing energy and cost savings potential from air sealing multifamily town homes.

  5. Author(s): EPA
    Organization(s): EPA
    Publication Date: October 2011

    Guide describing details that serve as a visual reference for each of the line items in the Thermal Enclosure System Rater Checklist.

  6. Author(s): Kohta
    Organization(s): BSC
    Publication Date: January 2003

    Document summarizing the various papers on unvented conditioned cathedralized attics found on BSC's website.

Last Updated: 08/15/2013

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