Spray Foam Insulation
The foam is only as good as the installer
Spray foam is two chemicals mixed at the gun, on your house, in whatever weather it is that day. Done right it's the best-performing insulation you can buy. Done wrong it shrinks, smells, or traps moisture. This page covers cost, open vs. closed cell, safety, mold, savings, and the install conditions that decide which one you get.
Free inspections • Spokane & Coeur d'Alene • We'll tell you if foam is the wrong choice for your house
Why the installer matters more than the brand
Fiberglass forgives a bad day. Spray foam doesn't.
A batt is a finished product when it leaves the factory. Spray foam is manufactured in your attic, by the person holding the gun, in a 30-second window. The chemistry has to be the right temperature, mixed at the right ratio, applied to a surface that is warm and dry enough, in passes thin enough to cure. Miss one and you get foam that pulls away from the studs, stays soft and smelly, or seals moisture into the wood.
Every spray foam horror story you've read online comes down to one of the variables below. None of them are about the foam. All of them are about the install.
A and B, 1 to 1, every pass
Off-ratio foam is the number one cause of odor and soft spots. We check pressures and pull a test shot before the first pass on every job, not just the first job of the week.
Chemical, air and surface
Drums warm, hose heated, and the wood itself above the product minimum. Cold sheathing is the usual reason foam shrinks and pulls away from the framing a month later.
Dry wood, no condensation
We meter the wood and read the dew point. Spraying onto damp framing or a surface sweating at the dew point traps water behind the foam. That's how foam gets blamed for rot it didn't cause.
Thin lifts, with cooling time
Closed-cell goes on in passes of about two inches with time to cool between. Too thick in one shot scorches inside, and that's the foam that smells for months.
Air moving during, 24 hours after
Negative-pressure ventilation while we spray, and the house stays empty for the manufacturer's re-occupancy time. The chemistry isn't the risk once it's cured. The shortcut is.
Thermal or ignition barrier
Foam is combustible. Living space needs half-inch drywall over it. Attics and crawl spaces need an ignition barrier or an intumescent coating. If a bid doesn't mention this, it's not a complete bid.
Five questions to ask anyone bidding spray foam
- What's the substrate temperature minimum for the product you're using, and how will you measure it on my job?
- How thick is each pass, and how long do you wait between passes?
- What ratio and pressure are you running, and do you do a test shot?
- How long do we stay out of the house, and how are you ventilating during the spray?
- What thermal or ignition barrier is in the bid?
If the answer to any of these is a pause, you have your answer. Ask us the same five.
The install window
The conditions that decide whether foam cures right
These are the variables we check and log on every spray foam job. Exact numbers vary by product, so we work from the manufacturer's technical data sheet for the foam we're spraying that day, not a rule of thumb.
| Variable | Typical window | What happens outside it | How we check |
|---|---|---|---|
| Substrate (wood) temperature | Above about 50°F for most foams; winter formulas go lower | Poor adhesion, shrinkage, foam pulls off the studs weeks later | Infrared thermometer on the actual surface, not the air |
| Ambient air temperature | Product-specific; roughly 40°F to 100°F | Slow or uneven cure, inconsistent yield | Thermometer at the spray area |
| Substrate moisture | Wood under about 18% moisture content, no visible wetness | Moisture sealed behind the foam, blistering, long-term rot risk | Pin moisture meter on framing and sheathing |
| Relative humidity and dew point | Surface at least 5°F above the dew point; RH generally under 85% | Condensation on the surface during spray, weak bond, voids | Hygrometer, dew-point calculation before starting |
| Chemical (drum) temperature | Roughly 70°F to 90°F, per data sheet | Off-ratio mixing, poor cell structure, odor | Drum heaters and thermometers, checked before spraying |
| Hose heat and pressure | Heated hose; gun pressure in the range the product calls for, A and B balanced | Off-ratio foam: soft, sticky, or crumbly, and it smells | Proportioner gauges logged, test shot before the first pass |
| Mix ratio | 1:1 by volume, within a couple percent | The classic "bad foam" job: odor that never leaves | Pressure balance and visual test shot, every job |
| Pass (lift) thickness | Closed-cell about 2 inches per pass with cooling time; open-cell thicker passes allowed | Exothermic scorching inside the foam, odor, cracking | Depth gauge; timed passes |
| Ventilation during spray | Mechanical exhaust pulling air out of the work zone | Fumes migrate into living space | Negative-air fan ducted outside; occupants out |
| Re-occupancy | Typically 24 hours after the last pass, per manufacturer | Exposure to uncured chemistry | We give you the time in writing before the job |
| Surface prep | Clean, dry, free of oil, dust, loose material and old insulation | Foam bonds to the dust, not the wood | Old insulation removed, surfaces brushed or blown off |
Two Spokane-specific notes: winter jobs are routine, but they're planned around substrate temperature and may need a heated space or a winter-grade foam. And a crawl space with standing water gets drainage fixed first. Foam does not go over a wet problem.
Open-cell vs. closed-cell
Two different products that happen to come out of the same gun
Closed-cell is dense, about R-6.5 to R-7 per inch, adds rigidity to framing, and acts as a vapor retarder at two inches. Open-cell is soft, about R-3.6 to R-3.8 per inch, costs less, quiets a room, and lets an assembly dry. The wrong one in the wrong place is a real problem. The right one is the best insulation money buys.
R-value per inch of thickness
Depth matters in walls and rafter bays where you can't go deeper. In an open attic floor, blown cellulose at R-60 is often the better buy.
Where each one belongs
| Location | Our usual pick | Why |
|---|---|---|
| Crawl space walls and rim joist | Closed-cell | Moisture resistance, air seal, no vapor barrier needed at 2 in. |
| Rim and band joists | Closed-cell | The leakiest few feet of most homes; foam seals and insulates in one step |
| Roof deck, conditioned attic | Closed-cell, or hybrid | Vapor control in our climate; hybrid with open-cell or cellulose keeps cost down |
| Interior and sound walls | Open-cell | Sound absorption, lower cost, lets the wall dry |
| Open attic floor | Usually not foam | Air seal the plane, then blown cellulose to R-60. Better dollars per R |
| Metal buildings and shops | Closed-cell | Stops condensation on the steel, adds rigidity |
The cost question
Why spray foam costs more, and when it earns it
Installed spray foam typically runs two to four times the price of fiberglass or blown cellulose for the same square footage. Most of that is real: the chemistry costs more per inch, it takes a $100,000-plus rig to apply, and the crew has to be trained to manage every variable in the table above. You're not paying for insulation. You're paying for an air barrier, a vapor retarder, and insulation installed in one pass, by people who can't afford to get it wrong.
Typical installed cost per square foot
Open-cell at about 5.5 in. (a 2×6 wall). Closed-cell at 2 in. and 3 in. Blown cellulose at attic R-49 to R-60. Fiberglass batts at R-19 to R-21. Removal, prep, and ignition barrier are separate line items on any honest bid.
Where a spray foam dollar goes
Material is the largest share and it's priced per board foot, so depth drives cost. Equipment covers the proportioner, heated hose, generator, compressor, and the truck they live in. Safety covers supplied-air respirators, suits, ventilation, and the insurance to spray a combustible product in your home.
Crawl spaces and rim joists
Damp, leaky, hard to insulate any other way. Closed-cell solves moisture, air, and R-value at once. This is where most of our foam goes.
Conditioned attics and vaulted roofs
When the ductwork is in the attic or there's no room for depth, foaming the roof deck brings the whole system inside the envelope. Also the fix for chronic ice dams.
Open attic floors
If you can walk across it and add depth, air sealing plus blown cellulose to R-60 gets you most of the result for a fraction of the price. We'll say so.
Existing closed walls
Injection foam exists, but it's a different product with different tradeoffs. Dense-pack cellulose is usually the better retrofit for a finished wall.
The ten questions homeowners actually ask
Straight answers, in the order people search them
1. How much does spray foam insulation cost per square foot?
In our market, open-cell in a 2×6 wall usually lands around $2.50 to $4.00 per square foot installed, and closed-cell around $2.50 to $3.50 at two inches, $3.50 to $5.50 at three. Fiberglass batts run about $1.00 to $1.75 and blown cellulose attics about $1.50 to $2.75 at R-60. Foam is priced per board foot (one square foot, one inch thick), so depth is the biggest lever on the bill. Expect separate lines for removal, prep, and the ignition barrier.
2. Is spray foam worth the extra money?
In a crawl space, rim joist, roof deck, or metal building: yes, because nothing else does the air seal, the vapor control, and the R-value in one product. On an open attic floor: usually no, because blown cellulose over a sealed attic plane gets you most of the benefit for far less. The honest answer depends on where it's going, and a good installer will tell you when the answer is no.
3. What's the difference between open-cell and closed-cell?
Closed-cell is dense (about 2 lb per cubic foot), R-6.5 to R-7 per inch, water-resistant, a vapor retarder at two inches, and it stiffens the framing. Open-cell is light (about 0.5 lb), R-3.6 to R-3.8 per inch, absorbs sound, costs less, and lets moisture pass so an assembly can dry. Closed-cell for moisture and structure; open-cell for interior walls and budget-sensitive depth.
4. How long does spray foam last?
Properly installed, the life of the building. It doesn't settle like blown insulation or sag like batts. The failures you hear about, shrinking, pulling away from studs, cracking, trace back to cold substrate, off-ratio chemistry, or passes sprayed too thick. Those happen in the first weeks, not decades later, and they're install failures, not aging.
5. Is spray foam safe for my family and pets?
Cured foam is inert, the same way cured epoxy is. The risk window is during and shortly after spraying, which is why the house is empty, the work zone is under negative-pressure ventilation, and the crew is in supplied-air respirators. Plan on being out, pets included, for the manufacturer's re-occupancy time, typically 24 hours after the last pass. Lingering odor months later is a sign the foam was sprayed off-ratio or too thick.
6. Can spray foam cause moisture problems or mold?
Closed-cell is one of the best moisture tools in a crawl space, because it stops vapor from reaching the cold framing. It can also trap moisture if it's sprayed over wet wood or over a bulk-water problem nobody fixed. The order matters: drainage and grading, then remediation if there's existing mold, then dry framing verified with a meter, then foam. Foam sprayed over a problem seals the problem in.
7. How much can spray foam reduce my energy bills?
Air leakage is roughly a quarter to 40% of a typical home's heating and cooling load, and spray foam is the only insulation that closes it while it insulates. In Spokane winters, a foamed crawl space or roof deck in a leaky older home commonly cuts heating use 15% to 25%; a tight newer home sees less. Summer gains are smaller here but real in a conditioned attic with ductwork. We'll run your numbers against your Avista usage before you decide.
8. Can spray foam be installed in an existing home?
Yes, in the places you can reach: crawl spaces, rim joists, attic roof decks, knee walls, garages, and shops. Finished walls are the exception; closed walls are usually better served by dense-pack cellulose than by opening them up for foam. Existing insulation has to come out first so the foam bonds to the wood and we can see what we're sealing.
9. Is spray foam better than fiberglass or blown-in cellulose?
Per inch and per air leak, yes. Per dollar, it depends on the location. Cellulose at R-60 on an open attic floor is hard to beat on cost. Fiberglass batts are the cheapest and the most forgiving to install, and the most often installed badly. Foam wins where depth is limited, moisture is present, or air sealing is the main problem, which describes most crawl spaces and roof decks in this area.
10. Does spray foam increase the value of my home?
Lower utility bills, a dry crawl space, and no ice dams are things inspectors and buyers notice, and a documented install with product data and depth measurements is something you can hand over at sale. We give you that documentation. We can't promise an appraisal number, and anyone who does is guessing.
Why homeowners call us first
Straight answers, since 2012
"We'll tell you when foam is the wrong answer. Then we'll tell you what the right one is."
Spray foam is one tool in the truck, next to cellulose, batts, air sealing, baffles, and a mold remediation crew. That's the point. We don't need every job to be a foam job, so the recommendation is the one that fits your house.
Good foam isn't a brand.
It's the person holding the gun.
Free inspections • Spokane & Coeur d'Alene • 509-879-0495 Copied
