Does Two Component ‘Kit’ Foam Insulate?

Polyurethane spray foam can be applied with 3 entirely different delivery systems and for simplicity sake lets call them “can” foam, “kit” foam and “bulk” foam. All spray foam systems are not equal as far as insulation R-value and air-sealing for energy performance goes and some systems can be a liability to the uninitiated.

In particular, kit foam can be a liability for the professional contractor and DIYer if not trained in proper application techniques, is unaware of the products limitations and isn’t wearing appropriate PPE. The liabilities include the potential for “kit” foam to go off ratio, if not careful the system can make a mess, disposal issues and the installer can become sensitized to MDI – a chemical that can’t be easily filtered out.

A Primer on Systems for Spray Applied Foam

“Can” foam is a one component system sold by all hardware stores that squirts out much like a grocery store can of whipped cream. Installed at room temperature and used to air seal a gap, this spray foam is particularly useful for sealing the gap between windows and rough opening or other deep gaps that won’t move much.  Its not used as an insulation. May take several minutes to cure if temperature and humidity levels optimal. Aerosol can can’t be recycled.

Two-component “Kit” foam is a two part (A – Isocyanate/ MDI and B – Polyol) spray foam applied at room temperature. The two pre-charged canisters that range in size from paint spray can to propane-sized BBQ cylinders which are joined by a set of hoses and mixed at the nozzle tip and sprayed into a gap to form an air seal in a gap that hopefully won’t move much. As the tanks empty, the pressure drops in the tank cylinders. Its common for one of the tanks to deplete before the other and for the foam to go off-ratio near the end – not a desirable quality in spray foam. It should cure to the touch within 5 seconds if the chemical ratio, temperature, pressure and ambient humidity levels are optimal. Local dumps won’t accept the tanks with chemical or pressure in them.

Bulk spray foam is a two part (45 Gallon drums of A – Isocyanate and B – Polyol) spray foam applied at a greater range of temperatures by a $50-$100,000 truck or trailer system, hopefully by a licensed professional who wears proper PPE and knows the foam and “manufacturing system” intimately. The temperature and pressure are controlled precisely to ensure consistent quality spray foam. This spray foam has a high R-value and is used as both a sealant and insulation. Should cure to the touch within 5 seconds if the chemical ratio, temperature, pressure and ambient humidity are optimal. An attentive sprayer knows almost immediately if the spray foam goes off ratio and will stop the application to figure out what’s happening, though its always nice to let the newly sprayed foam set a few days to check for shrinkage before dry-walling over. Once empty, barrels are cleaned and can be recycled.

I’ve used “kit” foam from a few manufacturers and the spray foam usually looks good for two thirds of the tank set. When the tanks are full and warm, kit foam is wonderful for sealing attic penetrations quickly and effectively. If a clog in the nozzle doesn’t slow one of the components down to throw off the chemical flow in either line, typically the last third to quarter of chemical in the tanks become a liability with the dying pressure. About the dregs, if you’re in the habit of spraying out everything, come back to your job a few days later and test the foam with a blower door.

The people most vulnerable to using ‘kit’ spray foam are renovators. Renovators who have crews who may not know a lot about insulation and very little about the dangers of using a pressurised two component spray foam system that will produce noxious chemicals during application. It should be noted that the MSDS’ are published for each liquid component under pressure in the tank, but that once these two chemical mix to form a new set of chemical compounds no MSDS exists for the newly ‘manufactured’ foam, so don’t expect the MSDS to provide any accurate safety guidance on the mixed reagents.

Just Pay for Bulk Foam!

I’ve had the misfortune of having to return to client’s homes to re-do foam that shrunk in a rim-joist or to clean up a foam system that leaked or exploded in the client’s home. It’s practically impossible to clean up without ruining finishes and its expensive to go back and redo work. Our advice to renovators is that kit foam is a fast, expensive effective air sealant but should not be used as insulation. For field insulation with a high R-value dig in your heels and get the client to commit to using a different insulating strategy or invest in bulk spray foam instead.

“Kit” foam available from a Toronto building supplier. No mention on its packaging that it shoudl be used for wall or attic insulation. Unfortunately, whom ever set up this display was careless about the brand’s image.  Note the reflective wet-looking drip of what was likely uncured spray foam drooling down the back of the stud cavity (photo below shows closeup).

A close up of the “kit” spray foam display above of a foam bead applied to the back of the stud bay which  shows a dark reddish crusty resin covered by a newer white fluffy coat of spray foam. The reddish resin is the result of an improper application of the foam. It can stay in liquid form for several days – it has no beneficial insulative or air sealing properties.

More ‘kit” foam from another Toronto supplier. Dow’s Froth-Pak states clearly on their packaging that the foam is intended as a sealant and it does an excellent job at air sealing bigger gaps that can foam just won’t cover effectively.

This ceiling detail shows what can happen when “kit” foam goes wrong. The applicator sprayed quite a bit of foam even though the foam wasn’t setting up quickly. He did what most of us do, “Maybe if I keep spraying it’ll right itself and start curing up!” The home owners had a mess to clean up in their kitchen as finished surfaces weren’t protected with drop sheets from the over-spray. Note the same deep reddish colour pooling on the 6mil poly.

This rim joist was spray foamed with a thick coat of “kit” foam that looked alright, but within hours, the foam’s edges pulled away from the floor joists revealing the leaky joints. This job had to be redone, an expensive proposition.

The floor rim joist was sprayed with “kit” spray foam and had to be redone as the off-ratio foam massive shrank revealing all the leaky edges .