Air Sealing Contractors: What to Look for When Hiring

Choosing an air sealing contractor affects your home’s comfort, indoor air quality, and energy use for years. Done well, air sealing targets gaps, penetrations, and thermal bypasses that drive heat loss and moisture problems. Done poorly, it can trap humidity, ignore safety requirements for combustion appliances, or miss hidden roof leaks. Below is a clear framework to evaluate companies in your area, including how spray foam insulation fits into the picture, what credentials matter, and what typical services cost.

Understanding air sealing companies and their services

Reputable air sealing companies begin with diagnostics, not caulk. Expect a home energy audit that may include blower door testing to quantify leakage and infrared imaging to locate it. Core tasks typically include sealing attic penetrations (wires, plumbing stacks, top plates), weatherstripping attic hatches, foam or mastic around duct joints, and sealing rim joists in basements. In many projects, spray foam insulation is used strategically as both insulation and an air barrier around complex gaps, while other locations may rely on sealants, tapes, and rigid materials. Quality contractors document before-and-after leakage numbers and provide photos of sealed areas.

Selecting an attic air sealing contractor

The attic is the most common source of uncontrolled air movement. When selecting an attic air sealing contractor, ask how they handle recessed lights, bath fan housings, flue and chimney clearances, and attic ventilation. Confirm they will install fire-rated barriers where required and preserve safe clearances around heat sources. For older homes, verify they will baffle eaves before adding insulation so soffits remain ventilated. A solid scope of work should prioritize sealing first, then insulating; for example, sealing top plates and chases before installing cellulose, fiberglass, or spray-applied materials. Make sure the crew protects indoor spaces and cleans thoroughly after the job.

Importance of roof leak detection in air sealing

Air sealing reduces unintended airflow, which can change how moisture moves through your home. If the roof leaks, sealing the attic floor may trap water vapor, worsen mold risk, and degrade new insulation. Ask for a basic roof and attic moisture check as part of the bid—stains on sheathing, damp insulation, or active drips should be addressed before sealing. Contractors should also evaluate bath and kitchen exhaust routing to the exterior to prevent humid air from venting into the attic. Addressing roof integrity first protects your air sealing investment and helps maintain a durable building enclosure.

Evaluating contractor qualifications and credentials

Look for credentials that indicate building science competency. Many strong contractors hold Building Performance Institute (BPI) certifications or work with RESNET professionals for testing. Request proof of general liability and workers’ compensation insurance, and verify any state or local licensing for insulation or weatherization work. Ask for blower door results in writing, product data sheets for sealants and spray foams, and clear ventilation strategies when tightening a home. If you have gas appliances, confirm they will perform combustion safety checks. Finally, review a sample report from a recent project and check references from homes similar to yours in climate and construction.

Cost considerations and service comparisons

Costs vary by home size, climate, and scope. Whole-home air sealing commonly ranges from modest, targeted work to comprehensive projects that include diagnostics, attic and rim joist sealing, duct sealing, and follow-up testing. Materials may include sealants, tapes, rigid foam, and in some cases closed- or open-cell spray products for durable, code-compliant air barriers in complex areas. Use written, line-item proposals so you can compare what is and isn’t included.

Prices, rates, or cost estimates mentioned in this article are based on the latest available information but may change over time. Independent research is advised before making financial decisions.

These figures are estimates and can vary by region, access, and complexity. For example, the cost of a spray-applied air barrier depends on thickness, area, and preparation, while attic air sealing is influenced by the number of penetrations, presence of can lights, and whether ventilation upgrades are needed. Always compare at least two written bids with similar scopes and confirm post-work testing is included.

A brief word on materials: spray-applied products can deliver both insulation and air sealing in one step, especially around irregular penetrations, while mastics, gaskets, and caulks excel at small gaps and duct joints. A qualified contractor will combine methods based on location and building code requirements rather than defaulting to a single product.

Wrap-up: Choosing an air sealing contractor comes down to diagnostics-first thinking, roof and moisture awareness, proven credentials, and transparent pricing. With a careful review of scope and results—including blower door numbers—you can hire with confidence and achieve durable comfort and efficiency gains for your home in your area.