Air Sealing Light Tubes

    Scope Images
    Image
    Light tubes adjacent to unconditioned space include lens separating unconditioned and conditioned space and are fully gasketed
    Scope

    Air seal around light tubes to minimize leakage to and from unconditioned attic space.

    • Seal all gaps around the light tube at the ceiling plane with caulk and/or spray foam.
    • Seal and flash around the light tube at the roof plane.
    • Select a light tube kit that includes a lens and a gasket..
    • Cover the tube with R-8 or greater duct insulation that includes a vapor barrier.

    See the Compliance Tab for related codes and standards requirements.

    Description

    A light tube (also known as a solar tube or tubular skylight) is a tube that brings light from the roof to a room inside the house. One end of the tube has a clear dome that is mounted on the roof to allow in sunlight from any angle. The sunlight is directed down the tube, which is lined with highly reflective material that carries the sunlight to a diffuser mounted at the ceiling. The diffuser distributes the light inside the room. Light tubes can save energy by replacing electric lights for daytime light in rooms that do not have windows. Energy savings can be lost however if the tube is not air sealed and insulated.

    How to Air Seal a Light Tube

    1. Locate a spot centered between ceiling joists. Cut the ceiling hole no larger than necessary and use a saw that will provide a clean smooth cut, which will be easier to seal.
    2. Following the manufacturer’s instructions, cut a hole in the roofing to the appropriate size. Apply a bead of caulk to the underside of the flashing collar that will be installed on the roof. Use a shingle ripper or reciprocating saw to loosen the roof shingles above the hole where the tube will be installed. Slip the flashing base under the loosened shingles above the hole. Screw the flashing into place. Cover the screw heads with caulk. 
    3. Assemble the tube and use metal tape or mastic to seal any seams in the tube. Install the light tube according to the manufacturer’s instructions, installing any gaskets or seals supplied by the manufacturer. Ensure that a manufacturer-supplied gasket or caulk is applied around the base of the tube in the bottom tube assembly between the flange and the drywall.
    4. From the attic side, caulk or spray foam where the tube meets the drywall.
    5. Cover the tube with R-8 or greater duct insulation that includes a vapor barrier. Use mastic, metal tape (not duct tape), or fasteners to seal the insulation to the light tube.
    Air seal and insulate light tube.
    Figure 1. Light tubes can represent a significant amount of surface area that is exposed to unconditioned attics. The metal tube needs to be air sealed at both ends and along all seams and it should be insulated (Source: Courtesy of PNNL). 

     

    Ensuring Success

    Visually inspect and verify that the light tube is sealed at the ceiling deck and roof deck and is covered with insulation and an air barrier. Blower door testing and use of an infrared camera may help indicate whether a light tube is sufficiently air tight.

    Climate

    No climate specific information applies.

    Right and Wrong Images
    Image
    The solar tube installed in the ceiling of this bathroom brings natural light into an interior room that doesn’t have window access.
    The solar tube installed in the ceiling of this bathroom brings natural light into an interior room that doesn’t have window access.
    Image
    Right – Airtight boxes are installed for LED can lights.
    Right – Airtight boxes are installed for LED can lights.
    Image
    A solar tube provides more natural light while maintaining privacy for this bathroom.
    A solar tube provides more natural light while maintaining privacy for this bathroom.
    Image
    Right – A solar tube brings natural light into this large walk-in closet.
    Right – A solar tube brings natural light into this large walk-in closet.
    Videos

    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 Single-Family New Homes, Version 3/3.1 (Rev. 11)

    National Rater Field Checklist

    Thermal Enclosure System.
    4. Air Sealing (Unless otherwise noted below, “sealed” indicates the use of caulk, foam, or equivalent material). 
    4.1 Ducts, flues, shafts, plumbing, piping, wiring, exhaust fans, & other penetrations to unconditioned space sealed, with blocking / flashing as needed. (Light tubes are not specifically mentioned in the ENERGY STAR Version 3/3.1, Rev. 11 specifications.)

    Please see the ENERGY STAR Single-Family New 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 402.4.1. The building thermal envelope shall be durably sealed to limit infiltration...including joints, seams, and penetrations. 

    2012, 2015, 2018, and 2021 IECC

    Table R402.4.1.1 Air Barrier and Insulation Installation, Shafts/penetrations: Duct shafts, utility penetrations, and flue shafts opening to exterior or unconditioned space are air sealed.

    Retrofit:  2009, 2012, 2015, 2018,  and 2021 IECC

    Section R101.4.3 (in 2009 and 2012). 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.)

    Chapter 5 (in 2015, 2018, 2021). The provisions of this chapter shall control the alteration, repair, addition, and change of occupancy of existing buildings and structures.

     

    2009 International Residential Code (IRC)

    Section N1102.4.1 Building thermal envelope. Joints (including rim joist junctions), attic access openings, penetrations, and all other such openings in the building envelope that are sources of air leakage are sealed with caulk, gasketed, weather-stripped or otherwise sealed with an air barrier material, suitable film or solid material.

    2012, 20152018, and 2021 IRC

    Table N1102.4.1.1 Shafts, Penetrations: Air Barrier and Insulation Installation, Shafts/penetrations: Duct shafts, utility penetrations, and flue shafts opening to exterior or unconditioned space are air sealed. General Requirements: 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.

    Retrofit:  2009, 2012, 2015, 2018,  and 2021 IRC

    Section R102.7.1 Additions, alterations, or repairs. 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 the requirements of this code, unless otherwise stated. (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.

     

    American Architectural Manufacturers Association (AAMA)/ Window and Door Manufacturers Association (WDMA)/CSA 101/I.S.2/A440-08 North American Fenestration Standard/Specification for windows, doors, and sky lights (NAFS)

    North American Fenestration Standard/Specification for Windows, Doors, and Skylights.  Available from AAMA.  This is a voluntary standard/specification that covers requirements for the following components for new construction and retrofits: single and dual windows, single and dual side-hinged door systems, sliding doors, tubular daylighting devices, and unit skylights.

    Existing Homes

    SCOPE

    In existing homes, air seal and insulate around a new or existing light tube (also known as a solar tube) to minimize air leakage to and from unconditioned attic spaces.  

    • If adding a new light tube, see the Description tab.
    • Inspect any existing light tubes for water damage and air leaks. Repair or replace any damaged materials. Add air sealing and/or insulation as needed. 
    • See the Scope and Description tab for additional instructions.

    For more information on conditions that may be encountered when working in existing attics, see the Pre-Retrofit Assessment of Attics, Ceilings, and Roofs. Also see the U.S. Department of Energy’s Standard Work Specifications (SWS) guidance on air sealing skylights and shafts.

    DESCRIPTION

    1. Inspect any existing light tubes for water damage and air leaks. Repair or replace any damaged materials. Add air sealing and/or insulation as needed, as needed.
    2. See the Description tab for additional installation information.

    COMPLIANCE

    Alterations

    2009 IECC and 2009 IRC, 2012 IECC and 2012 IRC 

    2012 IECC, Section R101.4.3 / 2012 IRC N1101.3 and 2009 IECC 101.4.3 / 2009 IRC N1101.4.3 Alterations – General.  Alterations to an existing building or portion of a building should comply with the provisions of the code as they relate to new construction without requiring unaltered portion(s) of the existing building to comply with this code.

    2015 IECC and 2015 IRC, 2018 IECC and 2018 IRC

    2015 IECC/2015 IRC, Section R501.1.1/N1107.1.1 Existing Buildings – General.  Alterations to an existing building or portion of a building should comply with Sections R502/N1108, R503/N1109, or R504/N1110.  Unaltered portions of the existing building are not required to comply.

    R503.1/N1109.1 Alterations. General.  Alterations to any building or structure should comply with the requirements of the code for new construction.  Alterations should not negatively impact conformance of a building or structure to the provisions of this code; that is, code conformance should be the same as existed for the building or structure prior to the alteration.  Alterations should not create an unsafe or hazardous condition or overload existing building systems.  Alterations should be such that the altered building or structure uses no more energy than the existing building or structure prior to the alteration.

    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)
    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.
    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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