Who seals leaking ductwork in a crawl space or attic?

In most Virginia homes, the person who seals leaking ductwork in a crawl space or attic is a licensed HVAC contractor. Virginia Cooperative Extension recommends having a licensed heating and air conditioning contractor repair duct leaks,^[1] and most heating and cooling contractors repair ductwork as well.^[2] Home energy auditors and the state's weatherization providers find and fix duct leaks too. Here is who does what, and how to choose.

A licensed HVAC contractor

This is the default choice, and in Virginia it is also the licensed one. Under the Code of Virginia, no individual may do or offer to do HVAC work for the public for pay unless licensed as a tradesman or working under the supervision of a tradesman licensed in that specialty.^[6][7] The Board for Contractors' HVAC classification covers the installation, alteration, repair and maintenance of heating, ventilating and cooling systems.^[8]

Two other kinds of business often get asked, and their licences are narrower. The residential building contractor classification does not provide for HVAC work,^[8] and the insulation and weather stripping specialty "does not include the insulation of mechanical equipment and ancillary lines and piping".^[9] If a builder or insulation crew offers to seal your ducts, ask what HVAC licence covers it.

Check any business on DPOR's License Lookup^[12] before you sign, and look for the HVAC classification on the licence.

Home energy auditors and raters

Auditors are the people to call when you suspect leaks but don't know where they are. Some utilities and home energy raters offer energy audits and diagnostic tools such as blower door, duct blaster and pressure pan tests to detect leaks a homeowner can't easily see.^[1] ENERGY STAR suggests looking for NATE or BPI certified contractors, and notes that a local utility may have pre-screened contractors and service discounts for its customers.^[3] An auditor who finds the leaks may also seal them, or may hand you a report to take to an HVAC contractor; ask which before you book.

Weatherization programs

If your household qualifies, the work may cost nothing. Virginia's Weatherization Assistance Program lists repairing drafty duct systems among its typical services, delivered by a network of local nonprofit providers; you apply to the provider where the home is located.^[10] Dominion Energy's Income and Age Qualifying Energy Savings Program includes duct sealing at no cost for qualifying customers in its Virginia service territory, with the assessments and installations done by local weatherization service providers.^[11] Dominion tells customers to ask to see the provider's weatherization service provider identification before letting anyone in.^[11]

What a crawl space job needs

Crawl spaces are cramped, often damp and full of the system's return ducts. Sealing the return leaks is the more critical part, because they can cause back-drafting of atmospherically vented equipment in the crawlspace.^[4] Sagging flex is part of the job too: flexible duct strapped at 3-foot intervals stops sagging and delivers more air.^[4] And in older houses, look at the wrap before anyone disturbs it. Old crawl spaces may have asbestos-based insulation wraps on ductwork and pipes, and a certified asbestos abatement firm has to inspect them if found.^[4] For the moisture side of a crawl space, see how to lower humidity in a crawl space.

What an attic job needs

Attic ducts sit in the hottest air in the house in summer and the coldest in winter. Ducts that run through an unconditioned attic, basement, garage or crawl space lose energy when they are poorly insulated.^[1] Ducts in unheated attics, basements and crawl spaces should be insulated and tightly sealed, and the duct leakage should be tested by a professional before and after sealing.^[5] Attic work usually means moving through deep insulation in summer heat, so the job can take longer than its size suggests.

Questions to ask before you hire

• What is your DPOR licence number, and does it carry the HVAC classification?
• Will you inspect the whole system, returns included, and not just the run I pointed out?
• What will you seal with? Mastic, metal tape or an aerosol-based sealant are the right materials, and any sealant should carry the UL 181 rating for that type of duct.^[2][1] Virginia Cooperative Extension's test is simple: "If you see the contractor bringing in duct tape, hire someone else."^[1]
• Will you insulate the ducts in unconditioned areas such as attics, crawlspaces and garages to R-6 or higher?^[2]
• Will you test leakage before and after, and give me the numbers?
• If you have gas or oil-burning appliances: will you run a combustion safety test after the ducts are sealed?^[2]
• Who handles the permit, if the job needs one?

When to call a licensed pro

Call one when rooms upstairs or at the far end of the house never get comfortable, when you see a duct lying on the crawl space floor or a flex run flattened in the attic, when ducts sweat or drip in summer, or when you have a gas furnace or water heater and suspect the returns leak. For what the visit involves, see what repairing damaged ductwork involves; for the price, how much duct repair costs in Virginia.

Finding one

Loclis lists DPOR-licensed HVAC businesses with their licence number and class. Find HVAC businesses in Blacksburg or another town, see duct repairs, or browse more HVAC repair answers.

To have your crawl space or attic ducts looked at, describe the job once and licensed local HVAC businesses quote it.