Attic air sealing with closed-cell foam
Warm air escapes a house through gaps at the top: around lights, pipes, wiring, chimneys and the top plates of walls. Closed-cell foam sprayed at those gaps, or across the underside of the roof deck, seals and insulates in one pass. Which boundary to seal depends on the house, its ventilation and what's in the attic.
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Why the attic is where air gets out
Warm air rises and pushes out through any gap in the ceiling below the attic: around light fixtures, plumbing stacks, wiring holes, chimneys and the top plates of walls. As it leaves, cold air gets pulled in somewhere lower, and that's the draft you feel at outlets and baseboards in January. Loose insulation laid on top slows heat loss but doesn't stop air moving through it.
A house Nick worked on, about 5 years old and 2,500 square feet, tested at 15 air changes per hour at 50 pascals, mostly through the attic. The walls and crawl space were closed in with drywall and flooring, but the attic was still accessible. Empire sealed the attic, and the retest came in at 5. Every house is different, but the attic is usually the first place to look.
Two ways to seal an attic
Sealing at the attic floor keeps the attic outside the house: the gaps in the ceiling get sealed and a vented attic stays vented. Spraying the underside of the roof deck brings the attic inside the insulated boundary, which can make sense when ducts or equipment live up there, but it needs a coordinated ventilation and moisture-control plan.
Filling every visible cavity isn't a design rule. Nick looks at the house, talks through what you want and what your budget allows, and recommends the boundary that fits.
Why closed-cell
Closed-cell foam is dense and bonds to wood, so it seals gaps rather than just covering them, and it resists moisture. It's Empire's main product: Nick sprays 2-lb closed-cell and HFO closed-cell and only uses open-cell for a specific project. Actual R-value and thickness come from the product's documentation.
Foam doesn't replace attic ventilation where the design needs it, and sealing alone won't promise an end to ice dams. Results also depend on the rest of the house and how it's heated.
Working in a lived-in house
Attic air sealing is usually a retrofit in a home people live in, so prep matters: plastic, floor protection where needed and ventilation during and after spraying. Occupants stay out of the work area during spraying and the product's re-occupancy period, so ask for the product-specific return instructions before you schedule. If you plan to sell in a year or two, Nick will tell you foam may not pay you back.
Related questions
Can you seal the attic without opening walls or ceilings?
Usually, if the attic is accessible. On the house described above, the walls and crawl space were closed in with drywall and flooring, so Empire worked from the attic, where most of the leakage was. What can be reached decides what can be sealed, and Nick will tell you what's practical once he has seen it.
What is a blower door test?
It depressurizes the house to 50 pascals and measures how many times the air inside changes in an hour, which shows how leaky the house is and helps find where the air gets out. On the house above it pointed straight at the attic, and a retest after sealing showed the difference.
Will air sealing the attic stop ice dams?
It can help by keeping warm house air out of the attic, but foam alone doesn't promise an end to ice dams. Roof ventilation, snow, sun and how the roof was built all play a part. Nick will tell you what sealing can and can't do for your roof before you commit.
Can the foam stay exposed in the attic?
Some attic and crawl space applications allow an ignition barrier or a specifically tested assembly instead of a full thermal barrier such as drywall. What applies depends on the product, the assembly, how the attic is used and local code. Ask about it at the estimate so the plan covers it.
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Services
- Closed-Cell Spray FoamMore insulation per inch than open-cell foam, with greater resistance to water vapor. Useful where cavity depth is limited or moisture control matters.
- Shop & Garage InsulationReduce heat loss and drafts in a shop or garage you plan to heat. Foam type and coverage depend on the building and how you use it.
- Pole Barn InsulationInsulate pole barn walls and roofs to reduce heat loss and help manage condensation. The plan should account for ventilation and how the space will be used.
- Crawl Space InsulationSeal air leaks at crawl space walls and rim joists to help with drafts and cold floors. Drainage and ground moisture need their own plan.
- Attic InsulationReduce heat loss through the top of your home. Roof-deck and attic-floor insulation are different approaches; the right choice depends on ventilation and moisture control.
- New Construction InsulationInsulate accessible walls and roof cavities before finishes go in. Plan the foam type, thickness and installation stage with your builder.
- Commercial InsulationInsulation for workspaces, warehouses and other commercial buildings. Plan access, ventilation and time out of the work area before installation.
- Metal Building InsulationClosed-cell foam can help manage condensation on metal panels and reduce heat loss. Surface condition, ventilation and building use guide the installation plan.
- Retrofit InsulationAdding spray foam to existing homes and buildings during remodels, re-roofs or when walls and ceilings are open.
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