Air Sealing near you

DOE's Building America measure guideline separates leakage into two modes, and the distinction matters because they are sealed with different materials. Large bypasses in the air barrier need sheet goods: the guideline describes using plywood or extruded foam sheathing, attached with mechanical fasteners and then sealed with caulk or expanding foam around the edges. Small holes, cracks and seams between building materials are sealed with expanding foam or caulk, with backer rod used to support the sealant in seams larger than five-sixteenths of an inch.

The guideline is also clear about scale and about why older houses are the candidates. It notes that homes built before current building codes may have high levels of air leakage and inadequate insulation, that air leakage can account for a high percentage of heating and cooling bills in an especially leaky house, and that homes built before 1980 often have little or no wall insulation. It also makes the point that walls can represent most of the building envelope area, which is why wall-to-adjacent-space junctions deserve attention rather than just the obvious openings.

Finding the small ones is a diagnostic job rather than a visual one. The guideline says large air leakage pathways can be identified through visual inspection, while smaller ones are located using a blower door together with a smoke pencil or infrared thermography, and adds that the contribution from small cracks and holes can be significant and should not be discounted.

Air leakage is quantified as air changes per hour at a test pressure of 50 pascals, abbreviated ACH50, and measured by depressurizing the house with a calibrated fan. DOE's guideline explains the method: the fan pulls air out of the house at a specific pressure, outside air then flows in through all unsealed cracks and openings, and the calibrated airflow through the fan is a measure of the total air leakage from the home. For measuring infiltration rates the house should be depressurized to 50 pascals below the outside reference pressure.

DOE's summary of the 2021 IECC residential provisions gives the compliance targets: a maximum air leakage rate of 5 air changes per hour in climate zones 1 and 2 and 3 air changes per hour in climate zones 3 through 8, both at a test pressure of 50 pascals, together with field verification of the air barrier items listed in the code's table. The same summary notes the 2021 edition sets a 5.0 ACH50 trade-off limit on tested air leakage for any climate zone in the performance path.

None of that is a legal requirement for an existing house being retrofitted, and you should be suspicious of anyone who says otherwise. Its value is as a reference point. A pre-work number tells you how leaky the house is compared with what new construction has to achieve in your zone, and the post-work number tells you what you bought. DOE's guideline is explicit that a record of the pre-work measurement can then be compared with tests following air sealing upgrades.

Tightening a house changes how its combustion appliances breathe, and this is the one part of air sealing that can hurt somebody. DOE's guideline states the rule without hedging: any combustion venting problems identified during combustion appliance zone testing must be addressed before air sealing begins. Its safety checklist opens with professionally testing all combustion appliances and remediating as required, using a BPI or RESNET certified inspector, having the professional discuss the results and ongoing care with the homeowner, and, where they are absent, including carbon monoxide detectors in the improvement's scope of work.

The guideline points to BPI standards for how combustion safety inspections should be carried out, and its diagnostic list includes draft pressure testing with a combustion analyzer alongside the blower door and duct pressurization tests. If a quote for air sealing does not mention combustion appliances at all in a house with a gas furnace, gas water heater or any vented fuel-burning appliance, that is a gap worth raising before work starts.

Moisture is the other systemic risk. The guideline notes that retrofit upgrades reduce air infiltration and heat loss across the envelope, which also reduces natural air exchange and the ability of wall assemblies to dry after bulk moisture gets in. That is an argument for fixing leaks and flashing problems as part of the same project rather than sealing over them.

Door and window work is real and worth doing, but it is a different service and a different scale. Weatherstripping seals moving joints that are opened and closed thousands of times a year and wears out as a consumable. Air sealing addresses fixed openings that were never intended to exist, most of them concealed inside the building assembly, and once sealed they stay sealed.

The practical difference is how the work is found. You can see a draughty door. You cannot see a chase around a plumbing stack, an open stud bay behind a dropped soffit, or a wall cavity connected to a return air plenum, and the DOE guideline specifically warns that wall cavities open to ducts or plenums have to be identified by inspecting the HVAC system and then sealed and separated.

The two also differ in what has to happen afterwards. Replacing a door sweep has no consequences for the rest of the house. Reducing whole-house leakage enough to matter can change combustion appliance behavior and the house's ventilation rate, which is why the blower door appears at both ends of a proper air sealing job and not at either end of a weatherstripping one.

A leaky house ventilates itself badly and expensively. A tight house does not ventilate itself at all, which is why the ventilation decision belongs inside the air sealing project rather than after it. DOE's guideline frames it as a system interaction: air sealing a home may necessitate the installation of mechanical ventilation based on the blower door test results, to ensure occupant health and indoor air quality.

It also explains why deliberate ventilation beats accidental ventilation. Mechanical ventilation is preferable to relying on infiltration to provide fresh air, because the source and pathway of the ventilation air can be controlled, which reduces contamination and the potential for durability problems. Air coming in through a crawlspace or an attached garage is not fresh air in any useful sense.

The guideline points to ASHRAE Standard 62.2 as the controlled ventilation standard for new and existing homes, advises that additional controlled mechanical ventilation be installed where post-retrofit infiltration levels call for it, and tells contractors to develop a climate-appropriate strategy for bringing in outdoor air where the upgrade warrants it. Ask whether your contractor has assessed this and what the answer was, rather than discovering it through condensation on the windows in February.

Air sealing prices are driven by access and diagnosis more than by materials. What moves a quote is the size and age of the house, how reachable the leakage areas are, whether blower door testing is done before and after, whether duct sealing and duct testing are included, whether combustion safety testing is in scope, how much of the work is in a crawlspace or a low-clearance attic, whether hazardous material testing is needed, and whether mechanical ventilation is being added as part of the same project.

Insist that the before and after blower door numbers appear in the paperwork. Without them you have bought an unverifiable service, and DOE's own guideline treats the comparison between the pre-work measurement and the post-retrofit test as the way the result is established. Ask separately whether combustion appliances will be tested and by whom.

LokalMatch is the introduction, not the inspection. Post the job once and contractors covering your area see it; interested ones contact you. Homeowners use the service free and pros pay for the requests. LokalMatch does not perform air sealing, does not set or negotiate prices and does not vet, rank or recommend any contractor, so credentials, insurance and the written scope stay yours to check.