Air Sealing Recessed Light Fixtures Below Unconditioned Space

Scope Images
Air seal around recessed can light fixtures installed through ceilings to keep conditioned air from leaking into unconditioned space.
Air seal around recessed can light fixtures installed through ceilings to keep conditioned air from leaking into unconditioned space.
Scope

Air seal around recessed can light fixtures installed through ceilings to keep conditioned air from leaking into unconditioned space.

  • Using a saw, cleanly cut a hole that is no more than 1 inch larger in diameter than the diameter of the can.
  • Install ICAT-labeled recessed lighting fixtures.
  • Seal around the can with caulk before installing trim or install a trim kit with a gasket.

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

Recessed “can” ceiling fixtures, or downlights, are the most popular home lighting fixture in the United States. However, recessed can fixtures can be energy intensive in three ways—if they are not approved for insulation contact and are installed in an insulated ceiling, insulation has to be kept at least 3 inches from the fixture all the way around, leaving about 1 square foot of uninsulated ceiling space. Second, many homeowners and contractors install incandescent bulbs or R-lamps in the fixtures; they use four times the electricity of fluorescents and six times the electricity of LEDs, as well as generating heat that adds to air-conditioning loads. Third, if the cans are not airtight, they allow conditioned air to escape from the living area into unconditioned spaces such as the attic. Leaky recessed cans are like a hole in the ceiling, only worse. A non-airtight recessed can with an incandescent bulb can draw 3 to 5 times as much air as a hole the same size, thanks to the “stack effect.” When the light inside the can is turned on, the heat it generates turns the can fixture into a chimney, pulling air from the house up into the attic (McCullough and Gordon 2002).

 

Non-ICAT-rated recessed lights waste energy

Figure 1 - Typical non-airtight recessed can light fixtures waste energy in several ways

 

Recessed downlights that are installed in insulated ceilings are now required by code to be rated for insulation contact (IC) so that insulation can be placed over them. The housing of the fixture should also be rated airtight to prevent conditioned air from escaping into the ceiling cavity or attic, and unconditioned air from infiltrating the conditioned space. The fixture should bear a label showing it meets the ASTM E 283 requirement of ≤ 2.0 cfm of air movement from the conditioned space to the ceiling cavity when tested at 75 Pa, and the housing should be caulked or gasketed where it meets the ceiling (Lstiburek 2009). Some brands of can lights designated ICAT may leak air; check the fixtures you intend to use to see whether they appear to be well designed to be air-tight. See the guide Insulating and Air Sealing Existing Non-ICAT Recessed Lights for more information.

If recessed lights are installed in insulated cathedral ceilings, there must be at least R-10 of insulation above the can in IECC climate zones 4 and higher to minimize condensation potential. Extra caution should be taken to ensure the recessed can is airtight in unventilated cathedral ceilings. Leaky light fixtures can allow moisture-laden indoor air to enter the roof assembly. If the moisture encounters cold roof sheathing, it can condense, leading to moisture accumulation and rot (Holladay 2011).

Some building scientists recommend against putting recessed can lights in cathedral ceilings (see for example Holladay 2011) and some recommend against putting recessed can lights in any insulated ceiling (for example, Bailes 2011). Other alternatives are to install the recessed cans in an air-sealed dropped soffit or to limit use of recessed cans to only ceilings of rooms that have conditioned space above them such as a second floor. Another option is to avoid recessed can fixtures all together and use surface-mounted or pendant fixtures instead. LED surface-mounted kits that look similar to recessed can lights are now available.

How to Air Seal Recessed Can Lights in Insulated Ceilings

  1. Choose fixtures that are labeled ICAT, meaning they are approved for insulation contact and are airtight as determined by the ASTM E 283 air leakage test.
  2. Install according to the manufacturer’s instructions. Before installing the decorative trim, caulk the housing to the ceiling, or install the fixture using a manufacturer-supplied gasket. 
Use ICAT-rated recessed lights and caulk the housing to the ceiling
Figure 2 - Look for recessed lighting fixtures that are ICAT-rated with sealed cans. Install the manufacturer-supplied gasket or caulk around the fixture housing before installing the decorative trim 

 

Ensuring Success

Inspect and verify that recessed can light fixtures installed in ceilings below unconditioned space are rated insulation-contact, air-tight (ICAT). Blower door testing, which is conducted as part of the whole-house energy performance test-out, may help indicate whether the recessed can lights are sufficiently air sealed. An infrared camera used in conjunction with the blower door testing may assist in detecting leakage. Experienced contractors can also detect air leakage with a smoke stick or by hand.

Climate

ENERGY STAR Certified Homes, Version 3/3.1 (Rev. 09)

National Rater Field Checklist

Thermal Enclosure System.
4. Air Sealing (Unless otherwise noted below, “sealed” indicates the use of caulk, foam, or equivalent material). 
4.2 Recessed lighting fixtures adjacent to unconditioned space ICAT labeled and gasketed. Also, if in insulated ceiling without attic above, exterior surface of fixture insulated to ≥ R-10 in CZ 4-8.

The map in Figure 1 shows the climate zones for states that have adopted energy codes equivalent to the International Energy Conservation Code (IECC) 2009, 12, 15, and 18. The map in Figure 2 shows the climate zones for states that have adopted energy codes equivalent to the IECC 2021. Climate zone-specific requirements specified in the IECC are shown in the Compliance Tab of this guide. 

IECC Climate Regions

Figure 1. Climate Zone Map from IECC 2009, 12, 15, and 18. (Source: 2012 IECC). 

Climate Zone Map from IECC 2021.
Figure 2. Climate Zone Map from IECC 2021. (Source: 2021 IECC)

 

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Compliance

The Compliance tab contains both program and code information. Code language is excerpted and summarized below. For exact code language, refer to the applicable code, which may require purchase from the publisher. While we continually update our database, links may have changed since posting. Please contact our webmaster if you find broken links.

ENERGY STAR Certified Homes, Version 3/3.1 (Rev. 09)

National Rater Field Checklist

Thermal Enclosure System.
4. Air Sealing (Unless otherwise noted below, “sealed” indicates the use of caulk, foam, or equivalent material). 
4.2 Recessed lighting fixtures adjacent to unconditioned space ICAT labeled and gasketed. Also, if in insulated ceiling without attic above, exterior surface of fixture insulated to ≥ R-10 in CZ 4-8.

Please see the ENERGY STAR Certified Homes Implementation Timeline for the program version and revision currently applicable in in your state.

DOE Zero Energy Ready Home (Revision 07)

Exhibit 1 Mandatory Requirements.
Exhibit 1, Item 1) Certified under the ENERGY STAR Qualified Homes Program or the ENERGY STAR Multifamily New Construction Program.

2009 International Energy Conservation Code (IECC)

Section 402.4.5 Recessed lighting. Recessed lights in the building thermal envelope are 1) type IC rated and ASTM E283 labeled and 2) sealed with a gasket or caulk between the housing and the interior wall or ceiling covering.

2012, 2015, and 2018 IECC

Table R402.4.1.1 Air Barrier and Insulation Installation, Recessed lighting: Recessed light fixtures installed in the building thermal envelope are airtight, IC rated, and sealed to the drywall with gasket or caulk. “Air tight” is defined as not more than 2.0 cfm when tested in accordance with ASTM E 283 at a 75 Pascal pressure differential.

Retrofit: 

2009, 2012, 2015, 2018, and 2021 IECC

Section R101.4.3 (Section R501.1.1 in 2015, 2018, and 2021 IECC). Additions, alterations, renovations, or repairs shall conform to the provisions of this code, without requiring the unaltered portions of the existing building to comply with this code. (See code for additional requirements and exceptions.)

2009 International Residential Code (IRC)

Section N1102.4.5 Recessed lighting. Recessed lights in the building thermal envelope are 1) type IC rated and ASTM E283 labeled and 2) sealed with a gasket or caulk between the housing and the interior wall or ceiling covering.

2012, 2015, and 2018 IRC

Table N1102.4.1.1 Air Barrier and Insulation Installation, Recessed lighting: Recessed light fixtures installed in the building thermal envelope are airtight, IC rated, and sealed to the drywall with gasket or caulk. “Air tight” is defined as not more than 2.0 cfm when tested in accordance with ASTM E 283 at a 75 Pascal pressure differential.

2009, 2012, 20152018, and 2021 IRC

E4004.8. A recessed luminaire that is not identified for contact with insulation shall have all recessed parts spaces at least 1/2 inch from combustible materials. The support and trim parts can be in contact with combustible materials. A recessed luminaire that is ICAT rated can be in contact with combustible materials.

E4004.9. Thermal insulation shall not be installed above a recessed luminaire or within 3 inches of the recessed luminaires enclosure, wiring, ballast, etc., unless the luminaire is ICAT rated.

Retrofit: 

2009, 2012, 20152018, and 2021 IRC

Section N1101.3 (Section N1107.1.1 in 2015 and 2018, N1109.1 in 2021 IRC). Additions, alterations, renovations, or repairs shall conform to the provisions of this code, without requiring the unaltered portions of the existing building to comply with this code. (See code for additional requirements and exceptions.)

Appendix J regulates the repair, renovation, alteration, and reconstruction of existing buildings and is intended to encourage their continued safe use.

This Retrofit tab provides information that helps installers apply this “new home” guide to improvement projects for existing homes. This tab is organized with headings that mirror the new home tabs, such as “Scope,” “Description,” “Success,” etc. If there is no retrofit-specific information for a section, that heading is not included.

Existing Homes

For information on air sealing recessed can lights in existing homes, see the guide Insulating and Air Sealing Existing Non-ICAT Recessed Lights.

For more information, see the U.S. Department of Energy’s Standard Work Specifications regarding general penetrations

See Compliance Tab. 

More Info.

Access to some references may require purchase from the publisher. While we continually update our database, links may have changed since posting. Please contact our webmaster if you find broken links.

References and Resources*
Author(s)
U.S. Environmental Protection Agency
Organization(s)
EPA
Publication Date
Description
Guide describing details that serve as a visual reference for each of the line items in the Thermal Enclosure System Rater Checklist.
Author(s)
Pacific Northwest National Laboratory
Organization(s)
PNNL
Publication Date
Description
Report providing information about techniques and approaches to improve the efficiency of recessed lighting.
Author(s)
Lstiburek
Organization(s)
Building Science Corporation
Publication Date
Description
Information sheet about air sealing.
Author(s)
Baechler,
Gilbride,
Hefty,
Cole,
Williamson,
Love
Organization(s)
Pacific Northwest National Laboratory,
Oak Ridge National Laboratory
Publication Date
Description
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.
Author(s)
Baechler,
Gilbride,
Hefty,
Cole,
Love
Organization(s)
Pacific Northwest National Laboratory,
Oak Ridge National Laboratory
Publication Date
Description
Guide describing measures that builders in the cold and very cold climates can take to build homes that have whole-house energy savings of 40% over the Building America benchmark with no added overall costs for consumers.
Author(s)
Lstiburek
Organization(s)
Building Science Corporation
Publication Date
Description
Fact sheet providing detailed information about air sealing attics.
Author(s)
U.S. Environmental Protection Agency
Organization(s)
EPA
Publication Date
Description
Website providing the technical specifications and related documents for home builders, subcontractors, architects, and other housing professionals interested in certifying a home to the EPA's Indoor airPLUS program requirements.
Author(s)
Holladay
Organization(s)
Green Building Advisor
Publication Date
Description
Information sheet presenting the correct methods for building an insulated cathedral ceiling.
Author(s)
McCullough,
Gordon
Organization(s)
Pacific Northwest National Laboratory
Publication Date
Description
Report discussing the potential energy savings of new high-efficiency downlights, and the results of product testing to date.
Author(s)
U.S. Department of Energy,
National Renewable Energy Laboratory
Organization(s)
DOE,
NREL
Publication Date
Description
Website providing standard performance specifications for common residential retrofit measures and related health and safety measures.
Author(s)
U.S. Environmental Protection Agency
Organization(s)
EPA
Publication Date
Description
Website providing the technical specifications and related documents for home builders, subcontractors, architects, and other housing professionals interested in certifying a home to the EPA's Indoor airPLUS program requirements.
*For non-dated media, such as websites, the date listed is the date accessed.
Contributors to this Guide

The following authors and organizations contributed to the content in this Guide.

Building Science Measures
Building Science-to-Sales Translator

Tight Air Sealed Home = Comprehensive Draft Protection

Image(s)
Technical Description

Poorly air-sealed homes are less comfortable and cost more to maintain because they provide a pathway for drafts, cold spots, moisture, and insects into the home. Comprehensive draft protection includes a continuous air barrier around the whole house along with caulking and sealing in all holes and cracks. This includes around wiring, plumbing, ducts, and flues; where wall framing meets flooring; around windows; where drywall meets top plates and sill plates; where rim joists meet foundation walls and subfloors; etc. Spray foam insulation can be used at rim joists, floors above unconditioned space, and in attics to insulate and air seal at the same time.

Comprehensive Draft Protection
Sales Message

Comprehensive draft protection minimizes air flow that can undermine a complete high-performance insulation system. What this means for you is less wasted energy along with enhanced comfort, health, quiet, and durability. Wouldn’t you agree it would be a shame to only get a partial return on your investment in advanced insulation?

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