Air sealing is the work of closing the hidden gaps and cracks that let heated and cooled air escape a house — around plumbing stacks, wiring, recessed lights, the attic hatch, and the rim joist above the foundation. It is a different job from insulation. Insulation slows heat moving through a surface; air sealing closes the actual holes air travels through. A home needs both, and sealing should come first.
That is why a house can have a foot of attic insulation and still feel drafty. The Home Insulators has air-sealed homes across Westchester and Rockland County, NY, and Bergen County, NJ, since 2015. Call 914-825-6824 for a free energy audit.
Why isn’t insulation alone enough?
Insulation and air sealing solve two different problems, and a home needs both. Insulation slows conductive heat transfer — that's what an R-value measures. But insulation does very little to stop air movement. Fiberglass batt, for example, is a filter, not a barrier; air passes right through it. Air sealing closes the actual holes air travels through.
The driving force behind most of that leakage is the stack effect. In winter, warm air rises and pushes out through gaps high in the house — the attic in particular — which pulls cold outdoor air in low, through the basement and crawlspace. Your home is essentially breathing out the top and inhaling at the bottom all season long, and your furnace works overtime to keep up. In summer the pattern reverses, loading your air conditioning with hot, humid outside air.
Where does a house leak air the most?
The leaks that matter most are rarely the ones you can feel at a window. During a professional assessment — often using a blower-door test to depressurize the house and reveal leakage — the usual culprits are:
- Attic bypasses: gaps around plumbing stacks, wiring, chimney chases, and top plates where walls meet the attic floor
- Recessed can lights that open directly into the attic
- The attic access hatch or pull-down stairs, frequently uninsulated and unsealed
- The rim (band) joist around the basement or crawlspace perimeter — one of the largest single leakage areas in most homes
- Sill plates where the wood framing sits on the foundation
- Penetrations for dryer vents, cable, electrical, and HVAC lines
- Window and door frames, plus tired weatherstripping
What materials are used for air sealing?
Effective weatherization matches the right material to the size of each gap: caulk for fine cracks, one-part expanding foam for gaps up to a few inches, weatherstripping for doors and operable windows, and rigid board or spray foam for larger openings like rim joists.
This is where spray foam earns its reputation, because it air-seals and insulates in a single step. Closed-cell spray foam runs roughly R-6 to R-7 per inch — the products we install are rated at R-6.9 to R-7.1 per inch — and doubles as an air and vapor barrier, making it ideal for rim joists and other leak-prone areas. Open-cell spray foam is about R-3.9 to R-4.2 per inch, more breathable and lower in cost, and still a strong air barrier. For comparison, standard fiberglass batt delivers about R-3 to R-4 per inch and, on its own, no meaningful air sealing at all. That's why best practice is always to air-seal first, then insulate over a tight surface.
What should I expect, and can a house be sealed too tight?
Air sealing is one of the least disruptive upgrades we perform. Most of the work happens in the attic and basement, there's no demolition, and a typical home is completed in a day or less. The payoff is immediate and lasting: fewer drafts, more even temperatures from room to room, less strain on your heating and cooling equipment, and quieter, less dusty indoor air.
There is one trade-off worth understanding. A well-sealed house is a good thing, but a home can be made tight enough that it needs deliberate fresh-air ventilation, and any fuel-burning furnace, water heater, or fireplace must be checked to confirm it still vents safely. A qualified contractor accounts for this as part of the job — it's a reason to seal the right way, not a reason to skip it.
Common questions about air sealing
What is air sealing?
Air sealing closes the gaps and cracks that let conditioned air leak out of a house and outdoor air leak in. It is a different job from insulation: insulation slows conductive heat transfer, which is what an R-value measures, while air sealing closes the actual holes air travels through.
Why isn't insulation alone enough?
Insulation does very little to stop air movement. Fiberglass batt, for example, is a filter, not a barrier — air passes right through it. Without sealing, a house keeps leaking no matter how much insulation is added on top.
What is the stack effect?
In winter, warm air rises and pushes out through gaps high in the house, especially the attic, which pulls cold outdoor air in low through the basement and crawlspace. The home is effectively breathing out the top and inhaling at the bottom all season, and the furnace works overtime to keep up. In summer the pattern reverses, loading the air conditioning with hot, humid outside air.
Where does a house leak air the most?
The leaks that matter are rarely the ones you feel at a window. The usual culprits are attic bypasses around plumbing stacks, wiring, chimney chases and top plates; recessed can lights that open into the attic; the attic hatch or pull-down stairs; the rim joist around the basement perimeter, which is one of the largest single leakage areas in most homes; sill plates; penetrations for dryer vents, cable, electrical and HVAC; and window and door frames with tired weatherstripping.
What is a blower door test?
It is a professional assessment that depressurizes the house to reveal where air is leaking, so the work targets the real leaks rather than the obvious ones.
What materials are used for air sealing?
The material is matched to the size of the gap: caulk for fine cracks, one-part expanding foam for gaps up to a few inches, weatherstripping for doors and operable windows, and rigid board or spray foam for larger openings like rim joists. Closed-cell spray foam runs roughly R-6 to R-7 per inch — the products we install are rated at R-6.9 to R-7.1 — and doubles as an air and vapor barrier. Open-cell is about R-3.9 to R-4.2 per inch, more breathable and lower in cost, and still a strong air barrier.
Should air sealing be done before insulation?
Yes. Best practice is always to air-seal first, then insulate over a tight surface. Insulating over an unsealed surface is the most common reason a job underperforms.
How long does air sealing take?
Most of the work happens in the attic and basement, there is no demolition, and a typical home is completed in a day or less. It is one of the least disruptive upgrades we perform.
Can a house be sealed too tight?
Yes, and it is worth understanding. A home can be made tight enough that it needs deliberate fresh-air ventilation, and any fuel-burning furnace, water heater, or fireplace must be checked to confirm it still vents safely. A qualified contractor accounts for this as part of the job — it is a reason to seal the right way, not a reason to skip it.
How much can air sealing save on energy bills?
Towns where we install air sealing
Westchester County, NY — Armonk, Bedford, Briarcliff Manor, Bronxville, Chappaqua, Cortlandt, Eastchester, Greenburgh, Harrison, Hartsdale, Irvington, Larchmont, Lewisboro, Mamaroneck, Mount Kisco, Mount Pleasant, Mount Vernon, New Castle, New Rochelle, North Castle, North Salem, Ossining, Peekskill, Pelham, Port Chester, Pound Ridge, Purchase, Rye, Scarsdale, Somers, Tarrytown, Tuckahoe, Valhalla, Westchester County, White Plains, Yonkers, Yorktown.
Rockland County, NY — Clarkstown, Haverstraw, Nanuet, Nyack, Pearl River, Ramapo, Rockland County.
Bergen County, NJ — Closter, Cresskill, Englewood, Fort Lee, Hackensack, Leonia, Mahwah, Montvale, New Hillsdale, Norwood, Palisades Park, Paramus, Ramsey, Ridgefield, Rutherford.
We also work across Fairfield County, Connecticut, and the wider Hudson Valley. If your town is not on the list, call 914-825-6824 — we very likely still cover it.
Air sealing is often the single most cost-effective step toward a comfortable, efficient home. Many of our customers see 20% or more off their monthly bills. A free energy audit pinpoints exactly where the house is losing air.
Do you serve my area?
We work across Connecticut, the Hudson Valley, and all of New Jersey, with most projects in Westchester, Rockland, and Bergen County. Call 914-825-6824 to check your address.
Air sealing is often the single most cost-effective step toward a comfortable, efficient home, and it's a natural companion to the insulation work we've done across Westchester and Rockland County, NY, and Bergen County, NJ, since 2015. A free energy audit will pinpoint exactly where your home is losing air and show you the savings — many of our customers see 20% or more off their monthly bills. Call The Home Insulators at 914-825-6824 to schedule yours.