Spray Foam – still great, not perfect.
April 5, 2015


Last week we attended a seminar from Building Science Corporation, on the latest science and stories from the world of spray foam.  This is a material that has seen a lot of ups and downs since its introduction to the Canadian market in the 1970’s.  Still suffering under the stigma of UFFI and concerns about indoor air quality (not helped at all by the RetroFoam debacle of six years ago), spray foam has alternately delighted and scared people for a long time.

I’d like to make a few statements, dispel a few rumours, and share some of the condensed wisdom from Dr. John Straube’s presentation last week.  If you are a building science professional or nerd at all, you should definitely go watch John in action.  He can get you weeping with laughter over a flashing detail.  I kid you not.   So when it comes to foam, of the spray-in-place type:

1/ UFFI is almost certainly not dangerous, any more.  The stigma associated with this product which is perpetuated by the real estate industry is purely anecdotal, not scientific.  All the bad stuff is long, long gone, evaporated into the atmosphere.  What you are left with is typically a reasonably well insulated and air sealed wall.  Which is significantly better than an uninsulated one, especially after you’ve blown the bank on removing the UFFI.

2/  Spray foam is amazing for cathedral ceilings, flat roofs, and unvented roofs in general.  That doesn’t mean it’s infallible.  It is still vapour permeable, and roofs can still rot if humidity is high (i.e. in restaurants, gyms, pools, Ripley’s Aquarium…).  Moisture always gets in, and it always needs somewhere to go.

3/  Open cell spray foam, like Icynene, is generally much healthier for your lungs, the people spraying it, and the environment in general.  The downside is that it is not an effective vapour retarder, and has a lower R-Value per inch.  We use it a lot, but typically in 12″ thick double stud walls, and we still add a vapour retarder (6 mil poly) on the interior.

4/  Closed cell spray foam is much higher performing, but has gotten a bad rap due to the atmosphere destroying properties of the blowing agents traditionally used in the process of spraying it into buildings.  If you’ve got to use it (like in the perfect application, the aforementioned unvented roof assembly), shop for foams with low GHG potential, and make sure that the literature addresses the blowing agents as well as the foam itself.  Once it’s in and cured, if it’s applied properly and not too fast or thick, it is perfectly healthy in 99% of cases.  If you’ve heard of it wrecking people’s health due to VOC off gassing, there’s a very high likelihood it was installed incorrectly, i.e. too thick.  2″ at a time, 4″ per day max, folks.

5/  I’m intrigued by the hybrid spray-foam-plus-batt insulation strategy for unvented roofs suggested by Dr. Straube in his presentation.  It’s high performance, not dangerous if you get the ratios right, and of course not permitted by code.  Don’t be suprised if I suggest this method for your project in upcoming months, and prepare yourself for a protracted battle (er, I mean education process) with your local building department to get it approved.

Want more?  Joe Listuburek of BSC has some wise words on the topic.