Air seal the rough opening around doors and windows prior to installing trim to minimize air leakage.
- Fill the rough opening around windows and exterior doors with caulk, canned spray foam, or foam backer rod. If spray foam, use a low-expansion foam designated for doors and windows.
- Do not rely on fibrous insulation alone to block airflow; it will not air seal.
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 Single-Family New Homes, and Indoor airPLUS.
Window and door rough openings are essentially big holes in the building envelope, and while these holes get filled with window and door units, the gaps between the units and the framing rough openings can be major sites for uncontrolled air leakage in a home (DOE 2000). However, by sealing these rough opening gaps, this air leakage can be significantly reduced. A study conducted at Oak Ridge National Laboratory’s Buildings Technology Center on window air sealing showed that windows with 3/4-inch rough-in gaps had an equivalent leakage area of 28.2 cm2/ m2. When the gap was sealed from the interior side of the wall, the equivalent leakage area was cut to 0.5 cm2/m2 (Baechler et al. 2010).
Sealing the gaps between window and door units and the framing rough openings requires care and precision. Unlike other parts of the air barrier on exterior walls, which have layers of redundancy, the seal around a window and door unit stands on its own: usually only a single closure separates the indoor air from the outdoors (BSC 2009).
Window and Door Sealing Materials
Too often, an attempt to seal around a window or door unit is made by stuffing the gap with fiberglass insulation. However, fiberglass is not an air barrier; air can readily seep through the insulation fibers. Instead, the gap should be filled with one or more of the following materials (DOE 2000):
- Backer rod comes in both open- and closed-cell varieties. Only closed-cell products (usually made of polyethylene foam) should be used for sealing window and door rough openings, as open-cell foams can absorb and hold moisture. Closed-cell backer rod is typically stocked at hardware stores in 1/4 to 1-1/2-inch-diameters, and sold by the foot from a reel. Larger diameter backer rod (up to 4 inches) is also available in 6- or 7-foot lengths. Always use backer rod that is wider than the gap, so it can be pressed firmly into the gap and create a tight seal.
- Caulk can be used to seal smaller gaps less than 1/2 inch wide. Caulk has the advantage of providing a more positive seal in irregular gaps, and when applied carefully, can create a tight seal around the shims used to install window and door units. For best results, use a silicone or polyurethane sealant that will shrink less than acrylic products when fully cured (Jackson 1997).
- Nonexpanding foam can be used to quickly and effectively seal the gap between the wall framing and window or door unit. It is important to use a nonexpanding product specially formulated for use as a window or door sealant. Ordinary expanding foam can swell with enough force to distort the jambs, and cause problems with operating the windows and doors. Use of ordinary expanding foam will often void window and door warranties.
Air Sealing Window and Door Rough Openings
Air sealing window and door rough openings is typically done by the insulation contractor, but in some cases it may be done by the window and door installer or by the finish carpenter prior to installing window and door trim.
With the window or door unit permanently installed in the rough opening, air seal the opening as follows:
- Trim back the shims securing the window or door unit to the wall framing. If possible, try to cut these back behind the interior face of the wall and jambs, so that sealant can be applied over the shims for a tighter seal.
- Apply the sealant toward the interior edge of the window or door unit. Using this approach, the gap to the exterior can drain freely and will be pressure equalized with the exterior, which limits the potential for an air pressure difference to force water into the joint (BSC 2009).
- With backer rod: Press the backer rod into the gap between the wall framing and the window or door unit. Use a flat bar to push it in. Apply even pressure; don't force it in, or the tool will tear the backer rod. Push the backer rod to an even depth. If caulk will be applied over it, take care to create an even surface that will provide a uniform substrate for the caulk.
- With caulk: If the gap is less than 1/2 inch wide, apply caulk over the backer rod for a tighter seal. Caulk should always be applied against backer rod, not just squeezed into the gap. Tool the bead against the backer rod. This will create an hour-glass shape (see Figure 3 below), which allows the sealant to expand and contract over time without cracking. Without the backer rod, the bead of caulk would be too thick and would be prone to cracking when it cures, and it would be resistant to flexing with movements in the building materials of the wall system as they change dimension with seasonal changes in temperature and humidity.
- With nonexpanding foam, wear gloves when applying spray foam; the foam has an especially aggressive bond that will adhere to skin. Insert the spray nozzle about half an inch into the gap between the wall framing and the window or door unit. Keep the spray nozzle moving at a steady speed while applying the foam: Too slow and the foam will fill too much of the cavity; too fast will result in gaps in the bead.
- With all types of sealant materials, pay close attention near the shims that hold the unit in the rough opening. It is important that the sealant fit tightly around these obstacles in the sealant path.
Visually inspect the seals between the window rough openings and the window and door units prior to installing interior finish materials. The seal from caulk or nonexpanding foam should be uniform without any visible gaps.
Blower Door Testing with Smoke Pencil Diagnostics
Blower door testing, conducted as part of whole-house energy performance testing, may help indicate whether windows have been successfully sealed. With the blower door pressurizing the house, use a smoke pencil to check for air around windows. A smoke trail moving away from the smoke pencil into the wall around the window or door unit indicates a leak that should be sealed.
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.
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.
National Rater Field Checklist
Thermal Enclosure System.
4. Air Sealing (Unless otherwise noted below, “sealed” indicates the use of caulk, foam, or equivalent material).
4.6 Rough opening around windows & exterior doors sealed.29
Footnote 29) In Climate Zones 1 through 3, a continuous stucco cladding system sealed to windows and doors is permitted to be used in lieu of sealing rough openings with caulk or foam.
Please see the ENERGY STAR Single-Family New Homes Implementation Timeline for the program version and revision currently applicable in in your state.
Exhibit 1 Mandatory Requirements.
Exhibit 1, Item 1) Certified under the ENERGY STAR Qualified Homes Program or the ENERGY STAR Multifamily New Construction Program.
Section R402.4 specifies that the home should be constructed to limit air leakage. Section 402.4.1 indicates specific areas to be caulked, gasketed, or sealed, including all joints, seams, and penetrations. Section 402.4.2 specifies that air leakage should be tested with an extensive visual inspection or with a blower door test with a maximum air leakage of <7 ACH 50.
Table 402.4.2 Air Barrier and Insulation Inspection Component Criteria, Windows and doors: Seal space between window/door jambs and framing.
Section R402.4 specifies that the home should be constructed to limit air leakage and should be blower door tested to confirm air leakage is <5 ACH 50 in Climate Zones 1-2 (Climate Zones 0-2 in 2021 IECC) and <3 in Climate Zones 3-8. Table R402.4.1.1 specifies the installation of a continuous air barrier and notes specific air barrier details.
Table R402.4.1.1 Air Barrier and Insulation Installation, Windows, skylights and doors: Seal space between window/door jambs and framing and skylights and framing.
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.
Table N1102.4.2 Air Barrier and Insulation Inspection, Windows and doors: Seal space between window/door jambs and framing.
Table N1184.108.40.206 Air Barrier and Insulation Installation, Windows, skylights and doors: Seal space between window/door jambs and framing and skylights and framing.
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.
Door Gasketing and Edge Seal Systems. Available from ANSI. This standard sets performance and installation of gasketing systems applied to doors and/or frames. It includes definitions, general information, and tests.
Standard Practice for Installation of Exterior Windows, Doors and Skylights. Available from ASTM. The standard covers fenestration product installation from pre-installation through post-installation procedures in new and existing construction.
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.
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.