Spray Foam Insulation: Closed Cell and Open Cell

Spray foam is applied as a liquid and expands in place, filling the cracks, gaps and irregular cavities that cut sheet and batt insulation cannot reach. Once cured it forms a continuous layer that both insulates and air-seals. That combination is what makes it behave differently from traditional insulation in a real building: most materials slow heat conducting through them, while foam also stops air moving through the assembly. It is installed by trained applicators using specialised equipment, because the two components have to be mixed and applied under controlled conditions.

Neither is better in general — they suit different assemblies. Closed cell is dense and rigid, delivers roughly R-6 to R-6.5 per inch, and resists moisture movement, so it is normally used in basements, crawl spaces, rim joists and anywhere in contact with concrete or exposed to damp. Open cell is lighter, delivers roughly R-3.5 to R-3.8 per inch, stays vapour-permeable so an assembly can dry inward, and absorbs sound noticeably better. Where cavity depth is limited, closed cell is usually the practical answer. Where depth is not the constraint, open cell often makes more sense per dollar.

As a general industry range, closed cell foam is around R-6 to R-6.5 per inch and open cell around R-3.5 to R-3.8 per inch. The figure that matters for your project is the total, which is thickness multiplied by that rate, so the depth applied is what determines the result. That is why we measure thickness during application rather than estimating it, and why the target depth is stated in the written quote. We will not promise a specific whole-assembly performance figure for your building without knowing the assembly.

Very often, yes. Foam plastic insulation is combustible, and requirements generally call for it to be separated from an occupied space by an approved covering rather than left bare. Drywall is the usual solution and frequently the cheapest. Where drywall is impractical, a sprayed covering achieves the separation without framing and boarding every surface. Whether a covering is required in your particular space, and what is acceptable there, comes from your project documents and the requirements applicable to the building. Our fireproofing page covers this in detail.

Sometimes, but it is often the wrong move. Spray foam needs to bond to a clean, sound substrate, and applying it over compressed, damp or contaminated insulation traps whatever is underneath rather than fixing it. In attics especially, removing the old material first is frequently the better outcome, because it also gives proper access to the ceiling plane for air sealing. We assess this on site rather than assuming, and we will tell you when removal is genuinely worth the additional cost and when it is not.

The foam cures within minutes, but the area needs to be ventilated and unoccupied for a period after application. We will not publish a single figure here, because the correct interval depends on the specific product and the space, and giving you a number that turns out to be wrong would be worse than giving you none. We confirm it for your job before work begins, so you can plan around it. Occupants and pets need to be out of the work area during application and for that ventilation period.

Air sealing is the main thing spray foam does that batt insulation does not, so it addresses drafts caused by air leaking through the assembly being sealed. It cannot fix drafts coming from somewhere else. A leaking window frame, an unsealed exterior door or an open chimney damper will still leak after the attic or the rim joist has been foamed. That is why the assessment looks at where the air is actually moving rather than assuming the answer, and occasionally why we recommend a smaller job than the one you called about.

Yes, and a good deal of our work happens through the cold months, which is when people notice the problem. Conditions do matter: the substrate temperature and the ambient conditions during application affect how the product behaves, and every product has a range stated by its manufacturer. Working within that range is part of installing it properly. In practice this affects scheduling and preparation more than it affects whether the job can be done, and we will tell you if conditions mean a job should wait.

Correctly specified, it usually solves them, because the moisture that damages assemblies most often arrives as humid air leaking through gaps rather than as bulk water. Incorrectly specified, it can create them, which is why the choice between closed and open cell is not cosmetic. Closed cell resists moisture movement; open cell stays permeable so an assembly can dry inward. Making a wall airtight without thinking about which direction it needs to dry is how problems get created. That is a judgement call, and it is the main thing we are assessing.

It is the wrong choice more often than a spray foam company is usually willing to say. Regular framed cavities with good access are frequently served just as well by batts at lower cost. An assembly that needs to dry in a particular direction may be better with a permeable material. Some substrates are unsuitable without preparation. And on many houses the money is better spent on air sealing a few specific locations than on foaming a whole building. We would rather tell you that at the assessment than after the invoice.

A hybrid assembly. A thin layer of closed cell foam is applied against the sheathing to air-seal the cavity and control moisture, then fibreglass batt fills the remaining depth to add R-value at lower cost per inch. It captures most of the air-sealing benefit of full-depth foam while keeping material cost down, which frequently makes it the best value on a wall. Whether it suits a particular assembly depends on the cavity depth available and how the wall needs to dry, so it is assessed rather than applied by default.

Cured foam is not a consumable in the way loose fill can be. It does not settle, slump or compress the way materials resting under their own weight eventually do, and it stays bonded to the substrate it was applied to. What can change is the assembly around it — a roof leak, a renovation that cuts through it, or services run through it later. We will not attach a specific number of years to it, because that would be a warranty claim rather than a description, and we do not make warranty claims on this site.

Closed cell foam is rigid and adds stiffness to the assembly it is bonded to, which is one reason it is used on steel and post-frame agricultural buildings. That is a real property of the material, but it should not be read as a structural upgrade to your building. Any structural question about a building belongs with an engineer, not with an insulation contractor, and we do not offer engineering services. If your project depends on a structural determination, get that answer from someone qualified to give it.

Yes. Commercial work covers mechanical rooms, service voids, exposed structure and warehouse envelopes, often to a specification issued with the project. Agricultural buildings are genuinely different work: large uninterrupted spans, steel or post-frame construction rather than stud framing, condensation control under a metal roof, and sometimes a need for a surface that tolerates washdown. Closed cell foam suits many of these buildings because it adheres directly to steel and there is frequently nothing to hold a batt in place.

We work across the Simcoe County area from our base in Barrie, covering Innisfil, Orillia, Midland, Alliston, Bradford, Collingwood and Wasaga Beach along with the surrounding townships, and the lakes immediately north of the county for cottage and waterfront work. Staying close enough to attend quickly, and to come back if something needs a second look, is part of doing the work properly. If you are unsure whether your address is covered, call and ask.