What is air sealing?

What this means for your home project

1. Look at accessible caulk and weatherstripping for poor application or deterioration; list areas needing attention. Source: U.S. Department of Energy, read 2026-11-05.
2. Request a written scope distinguishing caulk at fixed joints from weatherstripping at moving doors and windows. Source: Vermont Department of Public Service, read 2026-11-05.
3. Ask for the proposed airtightness target based on the initial test, so the written scope states the intended result. Source: U.S. Department of Energy, read 2026-11-05.
4. Request the list of needed repairs before air sealing begins; use it to identify work that must come first. Source: U.S. Department of Energy, read 2026-11-05.
5. Discuss old recessed lights with a professional before sealing them; establish how their heat-venting space will be preserved. Source: ENERGY STAR, read 2026-11-05.

How is air sealing done?

Use Vermont’s materials guidance to distinguish the treatments proposed for different joints in your air sealing scope (read 2026-11-05). “Air sealing uses a variety of materials, including caulk, spray foam, metal flashing, weatherstripping, and rigid foam.” (source) “Caulk is generally used for cracks and openings between stationary building components, such as around door and window frames, while weatherstripping is typically used to seal components that move, such as doors and operable windows.” (source)

What is the difference between air sealing and insulation?

Use DOE’s checklist and Vermont’s guidance to keep the two jobs distinct when comparing proposed work (read 2026-11-05). “Fibrous insulation is not an air barrier and shall not be used for air sealing.” (source) “For example, air sealing doesn’t eliminate the need for proper insulation to reduce heat flow through the building envelope.” (source)

How do I air seal before insulation?

Use Vermont’s recommended sequence to decide which work belongs first in your combined sealing and insulation scope (read 2026-11-05). “The recommended strategy is to reduce air leakage as much as possible, add insulation and provide controlled ventilation, as needed.” (source) “Adding insulation without sealing air leaks first can significantly reduce the insulation’s effectiveness in saving energy.” (source)

How do I test the air tightness of a house?

Use DOE’s equipment guidance and Vermont’s comparison advice to decide what testing to include in the written scope (read 2026-11-05). “Make sure the assessor uses a calibrated blower door, which is connected to a pressure gauge called a manometer that measures the pressure difference between two locations as the fan is running.” (source) “Blower doors that don’t use such measurement can spot air leaks in the home, but not the amount of air leakage.” (source) “This is one reason why a blower door test is typically done before starting and after finishing home energy improvements, as it is often the best way to show a comparison.” (source)

How long does air sealing take?

Use ENERGY STAR’s scoped estimate and DOE’s pre-work checklist to discuss scheduling for an accessible attic project (read 2026-11-05). “Attic air sealing and adding insulation are do-it-yourself projects if your attic is accessible and not too difficult to move around in.” (source) “The projects recommended in this guide can usually be completed in a day or two and will provide benefits for years to come.” (source) “A list of all needed repairs shall be provided to the homeowner before air sealing work begins so remediation can be fully addressed as necessary.” (source)

Can a house be too tight?

DOE’s 2019 checklist uses ASHRAE 62.2-2013 when checking ventilation; ask how adequate ventilation will be maintained after sealing (read 2026-11-05). “The home shall be inspected for the presence of a whole-house ventilation system.” (source) “If the home has no whole-house ventilation system, or if the existing system does not meet the target ventilation rate, recommendation shall be made to the homeowner to either install a new system or repair the existing system to meet the target ventilation rate.” (source) “After air sealing, a combustion safety test shall be performed if any natural-draft combustion equipment (e.g., water heater, furnace) exists in the home to ensure there is no back-drafting or spillage of combustion gases.” (source)

How should I air seal recessed lights?

Use ENERGY STAR’s light-specific cautions to discuss a safe sealing scope before work around existing recessed fixtures (read 2026-11-05). “Recessed lights can be sealed, but it is difficult and can create a hazard if not done properly with non-combustible materials.” (source) “Since any old-style lights need adequate air space around them to vent the heat they create, it’s best to consult with a professional before sealing them.” (source) “Caution: Keep all insulation 3 inches from “can” lights, except those rated IC (insulation contact).” (source)

Sources

• Air Sealing — Vermont Department of Public Service; read 2026-11-05.
• Consumer Guide to Air Sealing the Home — U.S. Department of Energy; published 2021-08; read 2026-11-05.
• Consumer Guide to Home Energy Assessments — U.S. Department of Energy; published 2021-08; read 2026-11-05.
• A Do-It-Yourself Guide to Sealing and Insulating with ENERGY STAR — ENERGY STAR; published 2016; read 2026-11-05.
• Home Improvement Expert Checklist: Home Air Sealing — U.S. Department of Energy; published 2019-03; read 2026-11-05.