Spray Foam in Winter: What Changes in Western PA

Short answer

Yes, closed-cell spray foam can be installed in a Western PA winter, using the winter-grade versions most manufacturers make for cold conditions. What decides the job is not the outdoor temperature but the surface being sprayed: it has to be above the product's minimum, free of frost and moisture, and at least 5 degrees above the dew point. The chemicals have to be kept warm, and the space usually has to be heated before, during and after.

Key points

Winter-grade closed-cell foams are rated for cold work. One maker lists substrate and air above 15°F for its winter grade; another lists 20°F for normal surfaces and 30°F on steel and concrete.
Frost, ice, snow and condensation on the surface are what ruin winter jobs. Foam sprayed on a wet or frosty surface does not bond.
The chemicals have to be warm before they are processed. One manufacturer asks for drums close to 70°F, and says material under 50°F may be hard to pump.
Never warm the building with an unvented propane or kerosene heater before spraying. Those heaters add water vapor to the air.
Some jobs are better left for spring: frosted steel that can't be warmed, sheathing soaked by snowmelt, a building that can't be heated while the foam cures.

Can spray foam be installed in winter?

Yes. Manufacturers make closed-cell foams in summer and winter versions because the reaction gives off heat and a cold surface pulls that heat away. The winter grade is formulated to react and rise on a cold surface.

Two examples from current manufacturer documents:

	HFO closed-cell, maker A (winter grade)	HFO closed-cell, maker B (fast grades)
Lowest substrate and air temperature	Above 15°F	Air from 20°F; substrate 20°F, or 30°F on heat sinks such as concrete and metal
Dew point	Substrate at least 5 degrees above the dew point	No spraying with the air within 5 degrees of the dew point
Moisture	Free of dew or frost; wood at 19% moisture content or less	Check for condensation, frost, ice or snow before and during spraying; wood over 18% needs extra preparation
Chemical storage	A-side 50 to 100°F, resin 50 to 70°F	Drums 50 to 80°F, brought close to 70°F before processing

Maker A is Huntsman (HEATLOK HFO High Lift); maker B is BASF (WALLTITE HFO). Other foams have their own limits on their data sheets, so the product's sheet is the rule on any given job.

Erie's normal January runs from an average low of 21°F to an average high of 35°F. Outdoor air in that range is inside what winter grades are made for. The surface temperature is what decides the job, and steel and concrete are the hard cases because they soak heat out of the foam.

What changes on a winter job

The chemicals are kept warm

Both sides of the foam come in drums and have storage ranges. One manufacturer says material colder than 50°F "may be difficult to pump" and asks for it to be brought close to 70°F before processing. On a winter job the drums ride and sit in a heated space, and the proportioner's heaters and the heated hose bring the two sides up to the processing temperature on the data sheet before they meet at the gun. Spray Foam 101 shows how that equipment fits together, and shelf life and drum storage covers the storage side.

The surface is measured, not guessed

An infrared thermometer reads the substrate, and a hygrometer gives the air's temperature and humidity, which give the dew point. Take a shop that has been heated to 50°F at 60% relative humidity: its dew point is about 37°F, so the surface needs to be at least 42°F to meet the 5-degree rule, even if the foam itself is rated for colder.

Steel and concrete come up last

Metal roof panels and concrete walls stay cold long after the air in the building has warmed. In a pole barn, the steel can still carry frost from the night at mid-morning. The space gets heated long enough for those surfaces to come above the limit, and any frost or condensation on them is gone before spraying starts.

The foam goes on in measured passes

Cold surfaces make thermal shock more likely. One manufacturer's guidelines say rapid cooling "may lead to disbondment before the foam fully cures," that cold can leave a "powdery surface," and that a thin first pass and "picture framing" the edges "help prevent curling and shrinkage." Pass thickness and the wait between passes come from the data sheet. Pulling away from the framing, cracks, and a rippled or shrunken surface are the signs of foam that went on too cold; how to spot bad spray foam and off-ratio spray foam show what they look like.

Three temperatures decide a winter spray job: chemicals near 70°F before processing, a substrate above the product's minimum, and a surface at least 5 degrees above the dew point.

What you do as the owner

Heat the space ahead of time and keep it on through the job and the cure. Ask your installer what temperature and how far ahead, for the product they will use.
Use the right heat. Electric heaters, the building's furnace, or a vented or indirect-fired heater. Not an unvented propane or kerosene heater: those fill the air with water vapor that condenses on the cold surfaces you are about to spray.
Keep the building dry. Close it up before a storm, shovel snow away from open doors, and don't park wet vehicles inside the day before.
Check the wood. Framing that took snow or rain needs to be at or below 18 to 19% moisture content. A pin-type meter settles it.
Plan for ventilation and time away. A closed-up winter house still needs fresh air during and after spraying; see how long to stay out after spray foam.

When to wait for spring

Winter work is routine when the building can be heated and kept dry. Wait when:

The building can't be heated, and the steel or concrete won't come above the product's minimum.
The sheathing or framing is wet from snowmelt or a roof leak and won't dry before the job.
There is active frost or ice on the surfaces and no way to remove it.
The roof leaks. Fix it first in any season; see does spray foam trap moisture.
On new construction, the building isn't closed in yet. Spray foam in new construction covers where the foam fits in the schedule.

Want a number for your own project? Price My Project or call (814) 208-3478.

FAQ

How cold is too cold to spray foam?

It depends on the product and the surface, not the weather report. The two closed-cell winter grades above go down to 15°F and 20°F for normal surfaces, but frost, moisture and the 5-degree dew point rule usually stop a job before the temperature limit does.

Do I need to keep the heat on after spraying?

Yes, for as long as the manufacturer's guidance and your installer say. One manufacturer's guidelines say to keep the space warm enough "to allow for the complete curing" of the foam.

Can you spray foam a pole barn in January?

Yes, if the steel can be warmed above the product's minimum and is free of frost when it is sprayed. Steel is a heat sink, so one manufacturer sets a higher minimum for metal than for wood. See why your pole barn roof drips.