Dropped Ceiling/Soffit Below Unconditioned Attic

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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 interior or exterior surface of ceilings in Climate Zones 1-3; at interior surface of ceilings in Climate Zone 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

Soffits (dropped ceilings) found over kitchen cabinets or sometimes running along hallways or room ceilings as duct or piping chases are often culprits for air leakage. The space above the soffit should be covered with an air barrier material to stop conditioned air from escaping through the soffit and into the attic and to stop unconditioned air from a ventilated attic from coming through the open soffit into the home through air leaks in the soffit. If the soffit is along an exterior wall and there is no air barrier material covering the wall insulation, this unconditioned air can flow through the wall cavity robbing the insulation of its insulating ability. These air barriers are often overlooked due to a sequencing issue. The framer builds the soffit before the drywaller can get to the wall behind it, and when the drywaller installs gypsum board, the soffit is left open from above to install ducts or recessed can lights. An air barrier material like rigid foam, gypsum board, OSB or plywood should be installed over the top of the soffit framing, level with the rest of the ceiling drywall, and the edges of the material should be sealed with caulk. Then attic insulation can be installed above it to a level equivalent with that of the rest of the attic when the rest of the attic is insulated. If the soffit runs along an exterior wall, drywall or some other rigid air barrier material should be installed on the exterior wall, and air sealed to the top plate, before the soffit framing is installed.

These materials may be installed by insulators, framers, or drywallers. This task should be included in the contract for the appropriate trade depending on the workflow at the specific job site.

How to Air Seal a Soffit or Dropped Ceiling

 

For Ducts in an Interior Hallway

  1. Install the hallway framing for the sides of the soffit but not the bottom of the soffit.
  2. Install the air barrier for the ceiling and side walls of the soffit on the inside of the framing. Air barrier material may be gypsum board, OSB, plywood, or rigid foam. Caulk and fasten the air barrier to the framing. Caulk, mud, and tape to seal the seams between the top and sides of the soffit. 
  3. Install ducts. Install framing for the bottom of the soffit. Caulk and fasten ceiling drywall for the bottom of the soffit. 
  4. Install drywall on the hallway walls when the rest of the house is drywalled. Caulk, mud, and tape to airseal seams at the lower corners of the soffit to the hallway walls.

Dropped hallway ceiling duct chase with drywalled soffit

Figure 1 - Dropped hallway ceiling duct chase with drywalled soffit Reference

Dropped hallway ceiling with drywall

Figure 2 - Dropped hallway ceiling with drywall Reference

For Soffits on an Exterior Wall

  1. Install cavity insulation in the exterior wall up to the top plate. Run a continuous bead of caulk along the top plate and install the drywall or other air barrier material on the wall and ceiling behind where the soffit will go. Caulk the seam where the wall and ceiling air barrier meet.
  2. Install framing for the soffit. Seal to the ceiling and wall air barrier material with a continuous bead of caulk.
  3. Install the drywall or other facing for the soffit. Seal to the soffit framing with a continuous bead of caulk. Install drywall on the remaining walls and ceiling. Caulk, mud and tape to seal the seams where these surfaces meet the soffit drywall. Install trim and cabinets if cabinets are being mounted under the soffit. 
  4. In the attic, install insulation over the soffit as you would over the rest of the attic floor.

Installing a soffit in an exterior wall

Figure 3 - Installing a soffit in an exterior wall Reference

For Soffits with Recessed Can Lights

  1. If on an exterior wall, cover the exterior wall behind the soffit with an air barrier material first. Attach the air barrier with a continuous bead of caulk along the top plate and fasteners.
  2. Install framing for the soffit. 
  3. Attach drywall to the side(s) and bottom of the soffit with a bead of caulk and fasteners. Caulk, mud, and tape the drywall at the seams to air seal it.
  4. Install can lights.
  5. Cut air barrier material to fit between joist bays on the attic side of the ceiling. Notch for wiring if necessary. Fasten the air barrier material in place over the soffit with caulk. Caulk edges and caulk around wiring. Cover with attic insulation.

Installing air barrier above a soffit

Figure 4 - Installing air barrier above a soffit Reference

Ensuring Success

Blower door testing, conducted as part of whole-house energy performance testing, may help indicate whether air leakage at soffits has been successfully sealed. High-performance branding programs and the 2009 IECC require that builders meet specified infiltration rates at the whole-house level. See the “compliance” tab for these specified infiltration rates. An infrared camera may also be helpful in detecting air leakage at the soffit, if a sufficient temperature difference exists between the attic and the conditioned space of the house to see the leakage.

Scope

Dropped ceiling/soffit below unconditioned attic

Fully Aligned Air Barriers

  1. Install a continuous rigid air barrier or other supporting material to cap the dropped ceiling and soffits.
  2. Seal all seams, gaps, and holes of the air barrier with caulk or foam before installation of attic insulation.

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.

All insulated vertical surfaces are considered walls (e.g., exterior walls, knee walls) and must meet the air barrier requirements for walls. 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

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Presentations

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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 interior or exterior surface of ceilings in Climate Zones 1-3; at interior surface of ceilings in Climate Zone 4-8. Also, include barrier at interior edge of attic eave in all climate zones using a wind baffle that extends to the full height of the insulation. Include a baffle in every bay or a tabbed baffle in each bay with a soffit vent that will also prevent wind washing of insulation in adjacent bays. 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.

DOE Challenge Home

Exhibit 2: DOE Challenge Home Target Home. Certified under ENERGY STAR Qualified Homes Version 3. Insulation levels shall meet or exceed the 2012 IECC (Table R402.1.1) and achieve Grade 1 installation, per RESNET standards. 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. Steel-frame ceilings, walls, and floors shall meet the insulation requirements of the 2012 IECC – Table 402.2.6. For ceilings with attic spaces, R-30 shall satisfy the requirement for R-38 and R-38 shall satisfy the requirement for R-49 wherever the full height of uncompressed insulation at the lower R-value extends over the wall top plate at the eaves. This exemption shall not apply if the alternative equivalent U-factor or total UA calculations are used.

ABAA 07261

Self-Adhered Sheet Air Barrier. 2006. Air Barrier Association of America, Walpole, MA. This specification for self-adhered sheet air barriers is developed by a professional association, the Air Barrier Association of America, to provide guidance to the design professional.

ABAA 07262

Fluid-Applied Air and Vapor Barrier. 2012. Air Barrier Association of America, Walpole, MA. This specification for air barriers that are fluid-applied and also act as vapor barriers is developed by a professional association, the Air Barrier Association of America, to provide guidance to the design professional.

ABAA 07263

Closed Cell, Medium-Density Spray Polyurethane Foam Air Barrier. 2011. Air Barrier Association of America, Walpole, MA. This specification for closed cell, medium-density spray polyurethane foam air barriers is developed by a professional association, the Air Barrier Association of America, to provide guidance to the design professional.

ABAA 07265

Fluid-Applied Vapor Permeable Air Barrier. 2012. Air Barrier Association of America, Walpole, MA. This specification for fluid-applied vapor permeable air barriers is developed by a professional association, the Air Barrier Association of America, to provide guidance to the design professional.

2009 IECC

Table 402.4.2 Air Barrier and Insulation Inspection Component Criteria,  Ceiling/attic: Air barrier in any dropped ceiling/soffit is substantially aligned with insulation and any gaps are sealed.* Table 402.4.2, Air barrier and thermal barrier: Air permeable insulation is not used as a sealing material.*

2009 IRC

Table N1102.4.2 Air Barrier and Insulation Inspection Component Criteria,  Ceiling/attic: Air barrier in any dropped ceiling/soffit is substantially aligned with insulation and any gaps are sealed.* Table N1102.4.2, Air barrier and thermal barrier: Air permeable insulation is not used as a sealing material.*

2012 IECC

Table R402.4.1.1 Air Barrier and Insulation Installation, Ceiling/attic: Air barrier in any dropped ceiling/soffit is substantially aligned with insulation and any gaps are sealed.* 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

N1102.4.1.1 Air Barrier and Insulation Installation, Ceiling/attic: Air barrier in any dropped ceiling/soffit is substantially aligned with insulation and any gaps are sealed.* 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.

More Info.

Case Studies

  1. Author(s): PNNL
    Organization(s): PNNL
    Publication Date: April 2012

    Case study about design and testing 10 high-performance homes in Farmington, Connecticut.

References and Resources*

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

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

  2. 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).

  3. Author(s): Lstiburek
    Organization(s): BSC
    Publication Date: January 2010

    Fact sheet providing detailed information about air sealing attics.

  4. 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.

Last Updated: 08/15/2013

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