Dropped Ceiling/Soffit Below Unconditioned Attic

Scope

Install an air barrier over dropped ceilings or soffits
Install an air barrier over dropped ceilings or soffits

Install a continuous rigid air barrier or other supporting material to cap dropped ceilings or soffits.

  • Rigid air barrier material could include rigid foam insulation, drywall, plywood, or OSB, among others.
  • Install the air barrier flush with the surrounding ceiling.
  • Seal all seams, gaps, and holes in the air barrier with caulk or foam before installation of attic insulation.
  • Ensure that the air barrier is continuous and in full contact with the insulation.
  • If the dropped soffit runs along an exterior wall, ensure that an air barrier is installed on the interior side of the exterior wall insulation before installing the air barrier over the soffit.

See the Compliance Tab for related codes and standards requirements, and criteria to meet national programs such as DOE’s Zero Energy Ready Home program, ENERGY STAR Certified Homes, and Indoor airPLUS.

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 use screws or nails to secure in place.
  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. Some building codes and high-performance home labeling programs require that builders meet specified infiltration rates at the whole-house level. See the “Compliance” tab for specified infiltration rates for several codes and program. 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.

Climate

ENERGY STAR Certified Homes 
ENERGY STAR Certified Homes (Ver. 3/3.1 Ver 08) 
National Program Requirements. Exhibit 1. Design the ENERGY STAR reference design home to meet the following infiltration limits: 6 air changes per hour at 50 Pascals (ACH50) in IECC Climate Zones 1 and 2, 5 ACH50 in CZ 3 and 4, 4 ACH50 in CZ 5, 6, and 7, or 3 ACH50 in CZ 8. Rater Field Checklist, 2. Fully-Aligned Air Barriers. A complete air barrier is provided that is fully aligned with the interior or exterior horizontal surface of ceiling insulation in Climate Zones 1-3; at interior horizontal surface of ceiling insulation in Climate Zones 4-8. Also, at exterior vertical surface of ceiling insulation in all climate zones.

DOE Zero Energy Ready Home

DOE Zero Energy Ready Home (Rev 05) Exhibit 2:  Infiltration: Climate Zones 1-2: 3 ACH 50; Zones 3-4: 2.5 ACH50; Zones 5-7: 2 ACH50; Zone 8: 1.5 ACH50. 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

Training

Right and Wrong Images

Presentations

None Available

Videos

  1. Dropped Ceiling/Soffit Below Unconditioned Attic
    Publication Date: July, 2015
    Courtesy Of: NYSERDA

    Video describing how to air seal attics.

CAD Images

Compliance

ENERGY STAR Certified Homes

ENERGY STAR Version 3/3.1 (Rev. 08) National Program Requirements. Exhibit 1. Design the ENERGY STAR reference design home to meet the following infiltration limits:
IECC Climate Zones 1 and 2 - 6 air changes per hour at 50 Pascals (ACH50)
CZ 3 and 4 - 5 ACH50
CZ 5, 6, and 7 - 4 ACH50
CZ 8 - 3 ACH50

Rater Field Checklist, Thermal Enclosure System: 

2. Fully-Aligned Air Barriers.5 At each insulated location below, a complete air barrier is provided that is fully aligned as follows: 

Ceilings: At interior or exterior horizontal surface of ceiling insulation in Climate Zones 1-3; at interior horizontal surface of ceiling insulation in Climate Zones 4-8. Also, at exterior vertical surface of ceiling insulation in all climate zones (e.g., using a wind baffle that extends to the full height of the insulation in every bay or a tabbed baffle in each bay with a soffit vent that prevents wind washing in adjacent bays).6

2.1 Dropped ceilings/soffits below unconditioned attics, and all other ceilings.

Footnotes:

(5) For purposes of this Checklist, 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. EPA recommends, but does not require, rigid air barriers. Open-cell or closed-cell foam shall have a finished thickness ≥ 5.5 in. or 1.5 in., 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 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.

(6) 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.

ENERGY STAR Revision 08 requirements are required for homes permitted starting 07/01/2016.

DOE Zero Energy Ready Home

Per the DOE Zero Energy Ready Home National Program Requirements (Rev. 05), Exhibit 1: Mandatory Requirements, homes must be certified under ENERGY STAR  Qualified Homes Version 3 or 3.1. 
Exhibit 2. Design the DOE Zero Energy Ready Home Target Home to meet the following infiltration limits:
IECC Climate Zones 1, 2: 3 air changes per hour at 50 Pascals (ACH50)
CZ 3, 4: 2.5 ACH50
CZ 5, 6, 7:  2 ACH50
CZ 8: 1.5 ACH50

 Envelope leakage shall be determined by an approved verifier using a RESNET-approved testing protocol. Insulation levels shall meet the 2012 (or 2015) IECC and achieve Grade 1 installation per RESNET standards.

(14) Insulation levels in a home shall meet or exceed the component insulation requirements in the 2012 International Energy Conservation Code (IECC) - Table R402.1.1. The following exceptions apply:

a. Steel-frame ceilings, walls, and floors shall meet the insulation requirements of the 2012 IECC – Table 402.2.6.

b. 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 calculations in d) are used;

c. For ceilings without attic spaces, R-30 shall satisfy the requirement for any required value above R-30 if the design of the roof / ceiling assembly does not provide sufficient space for the required insulation value. This exemption shall be limited to 500 sq. ft. or 20% of the total insulated ceiling area, whichever is less. This exemption shall not apply if the alternative calculations in d) are used;

d. An alternative equivalent U-factor or total UA calculation may also be used to demonstrate compliance, as follows: An assembly with a U-factor equal or less than specified in 2012 IECC Table 402.1.3 complies. A total building thermal envelope UA that is less than or equal to the total UA resulting from the U-factors in Table 402.1.3 also complies. The insulation levels of fenestration, ceilings, walls, floors, and slabs can be traded off using the UA approach under both the Prescriptive and the Performance Path. Also, note that while ceiling and slab insulation can be included in trade-off calculations, Items 4.1 through 4.3 of the ENERGY STAR for Homes Ver 3 (Rev 07) Thermal Enclosure System Rater Checklist [Items 3.1-3.3 or the ENERGY STAR Ver 3 Rev 08 Rater Field Checklist] shall be met regardless of the UA tradeoffs calculated. The UA calculation shall be done using a method consistent with the ASHRAE Handbook of Fundamentals and shall include the thermal bridging effects of framing materials. The calculation for a steel-frame envelope assembly shall use the ASHRAE zone method or a method providing equivalent results, and not a series-parallel path calculation method.

(15) In states where the residential provisions of the 2012 International Energy Conservation Code (IECC) have been adopted, qualifying homes must instead meet the envelope insulation requirements of the 2015 IECC, effective 12 months after the effective date of the 2012 IECC in that state. The exact date at which time a state will migrate to 2015 IECC envelope compliance may vary based on the timing of RESNET rating software updates, but will not be any sooner than 12 months following the effective date of the 2012 IECC in that state.

Note that sub-items A through D of the previous end note all still apply for 2015 IECC envelope compliance.

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 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.

2009 IECC

Table R402.1.1 Insulation and Fenestration Requirements – meet or exceed the insulation levels listed in this table.

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.*

Section R402.4.2 Air sealing and insulation is demonstrated by testing or visual inspection. Testing.  The building should be tested for air leakage should have an air leakage rate of ≤ 7 at rough-in.

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 R402.1.1 Insulation and Fenestration Requirements – meet or exceed the insulation levels listed in this table.

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.*

Section R402.4.1.2 Testing.  The building should be tested for air leakage and should have an air leakage rate of ≤ 5 in CZ 1 and 2 or ≤ 3 in CZ 3-8.

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.*

2015 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. General requirements: A continuous air barrier is installed in the building envelope; breaks and joints in the air barrier are sealed. Air-permeable insulation is not used as an air-sealing material.*

2015 IECC

Table R402.1.2 Insulation and Fenestration Requirements – meet or exceed the insulation levels listed in this table.

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. General requirements: A continuous air barrier is installed in the building envelope; breaks and joints in the air barrier are sealed. Air-permeable insulation is not used as an air-sealing material.*

Section R402.4.1.2 Testing.  The building should be tested for air leakage in accordance with ASTM E 779 or E 1827 and should have an air leakage rate of ≤ 5 in CZ 1 and 2 or ≤ 3 in CZ 3-8.

*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: May, 2015

    Standard requirements for DOE's Zero Energy Ready Home national program certification.

  2. Author(s): EPA
    Organization(s): EPA
    Publication Date: September, 2015

    Document outlining the program requirements for ENERGY STAR Certified Homes, Version 3 (Rev. 08).

  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.

Contributors to this Guide

The following Building America Teams contributed to the content in this Guide.

Building Science-to-Sales Translator

Fully Aligned Air Barriers =
Whole-House Draft Barrier

Technical Description: 

A whole-house draft barrier is a continuously connected layer of solid or air-tight materials that block air leaks. This barrier can also function as part of a water barrier, thermal barrier, and vapor barrier, if the location and materials are compatible. For example, rigid foam insulation can provide a combined function. Rigid foam sheets can be used to block air flow when seams are sealed with tape, caulks or adhesives, or liquid applied sealants. An example of an interior air barrier may be the drywall on the home’s walls and ceilings, when the seams are taped and mudded, and caulk, spray foam, or gaskets are used to seal around wiring, plumbing, and other penetrations. Insulation should be in full contact with the air barrier layer.

Alternate Terms

Air Contaminant Barrier
Energy Saving Air Barrier
Advanced Air Barrier Technology
Professionally-Installed Draft Barrier
Moisture Control Air Barrier
Whole-House Draft Barrier
Sales Message
Whole-house draft barriers block air flow that can undermine the thermal protection with a complete high-performance insulation system. What this means to you is less wasted energy along with enhanced comfort, quiet, and durability. Wouldn’t you agree it would be a shame to only get a partial return on your investment in advanced insulation?
Last Updated: 04/01/2016

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