Recessed Light Fixtures Below Unconditioned Space

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Climate

ENERGY STAR Version 3, (Rev. 07)

Thermal Enclosure Checklist, Air Sealing. If in insulated ceiling without attic above, exterior surface of fixture insulated to >= R-10 in CZ 4 and higher to minimize condensation potential.

climate zone map

International Energy Conservation Code (IECC) Climate Regions

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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 in the fixtures that use 4 times the electricity of fluorescents and add 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 Reference

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 (EPA 2010). 

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.

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 Reference

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.

Scope

Recessed lighting fixtures adjacent to unconditioned space ICAT labeled and fully gasketed. Also, if in insulated ceiling without attic above, exterior surface of fixture insulated to ≥ R-10 in CZ 4 and higher to minimize condensation potential

Air Sealing

Recessed lighting fixtures adjacent to unconditioned space ICAT labeled and fully gasketed. Also, if in insulated ceiling without attic above, exterior surface of fixture insulated to >= R-10 in Climate Zone 4 and higher to minimize condensation potential.

  1. Install ICAT labeled recessed lighting fixtures.
  2. Seal all gaps and holes to unconditioned space with caulk or foam.
  3. Install a proper trim kit with a gasket.

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Training

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Compliance

ENERGY STAR Version 3, (Rev. 07)

Thermal Enclosure Checklist, Air Sealing. Penetrations to unconditioned space fully sealed with solid blocking or flashing as needed and gaps sealed with caulk or foam. Recessed lighting fixtures adjacent to unconditioned space ICAT labeled and fully gasketed. Also, if in insulated ceiling without attic above, exterior surface of fixture insulated to >= R-10 in CZ 4 and higher to minimize condensation potential.

DOE Challenge Home

Exhibit 1: Mandatory Requirements. Certified under ENERGY STAR Qualified Homes Version 3.

2009 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.*

2009 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 IECC

Table R402.4.1.1 Air Barrier and Insulation Installation, Recessed lighting: Recessed light fixtures installed in the building thermal envelope are IC rated, airtight labeled at air leakage rate <= 2.0 cfm, and sealed to the drywall with gasket or caulk.* 

2012 IRC

Table N11402.4.1.1 Air Barrier and Insulation Installation, Recessed lighting: Recessed light fixtures installed in the building thermal envelope are IC rated, airtight labeled at air leakage rate <= 2.0 cfm, and sealed to the drywall with gasket or caulk.* 

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

More Info.

Case Studies

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References and Resources*

  1. Author(s): Baechler, Gilbride, Hefty, Cole, Love
    Organization(s): PNNL, ORNL
    Publication Date: February 2011

    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.

  2. 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.

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

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

  4. 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).

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

    Fact sheet providing detailed information about air sealing attics.

  6. Author(s): McCullough, Gordon
    Organization(s): PNNL
    Publication Date: January 2002

    Report discussing the potential energy savings of new high-efficiency downlights, and the results of product testing to date.

  7. Author(s): Holladay
    Organization(s): Green Building Advisor
    Publication Date: November 2011

    Information sheet presenting the correct methods for building an insulated cathedral ceiling.

  8. Author(s): PNNL
    Organization(s): PNNL
    Publication Date: January 2011

    Report providing information about techniques and approaches to improve the efficiency of recessed lighting.

  9. Author(s): Bailes
    Organization(s): Energy Vanguard
    Publication Date: April 2011

    Information sheet discussing the downside to recessed can lights.

  10. Author(s): Lstiburek
    Organization(s): BSC
    Publication Date: May 2009

    Information sheet about air sealing.

  11. Author(s): EPA
    Organization(s): EPA
    Publication Date: February 2013

    Website providing technical guidance to help home builders and their subcontractors, architects, and other housing professionals understand the intent and implementation of the specification requirements of the IAQ labeling program.

  12. 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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