The context:  I am from a northern climate municipal electric/natural gas utility.  We provide rebates to customers for various energy efficiency projects, including adding insulation to existing homes.


The issue:  We've had a few issues with the application of injection foam (spray foam applied directly into closed wall cavities of existing homes).  I've attached a few pictures from a customer that removed their drywall about 3 weeks after the insulation was installed (because the area still felt very cold to him, for obvious reasons). The last picture is a "test" cavity one of our engineers rigged up, to mimic some of his existing wall cavities (he removed the drywall covering this portion after 1 week's time).  We have some IR images that I didn't attach here, but reveal similar results.

Inspections of several other homes revealed similar results as well.  This is typically very expensive insulation in my service territory.  


My questions:

1) Does anyone else know if there are any utilities that have banned injection foam insulation projects from their rebate programs for sidewall or basement/foundation insulation?  

2) Does anyone recommend any basic ground rules for utility rebate programs that do fund injection foam insulation projects?  One basic rule we have at this time is to not fund residential injection foam of concrete block basements (i.e., funding the injection of this foam insulation into hollow cores of cement block walls in a residential basements).


Other utilities in my area do not seem to have policies or opinions about this issue, but do allow this type of insulation in their rebate programs.

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Ed - I agree with you on the interpretations of the IR photos.  Please see my post from 5/27, specifically the comment to David & Curtis re verification and IR interpretations.


As far as verification - shy of pulling down the drywall, I'm not sure a foolproof procedure for verifying closed-cavity insulation exists - regardless of whether it is injected foam or dense packed fibers.  Blower door and IR imaging can certainly give us clues about what is going on inside the walls.


I’d also like to point out that I'm not grouping all "foams" into one category.  I've seen low-density, high-expanding spray polyurethane foam injected into closed wall cavities.  That material comes out of the gun at 120 to 140 degrees F, which makes it very easy to see with an IR camera during installation, regardless of outdoor temps.  At the very least, this would help eliminate missing partial cavities due to framing / blocking and/or other obstructions in the cavities.  It seems like SPF has been around as long or longer than the UF foams and I’ve never been to, or heard of, a home that had total product failure.  If someone is aware of this, please share.


As for other closed-cavity insulation, cellulose has been the insulation of choice for many government sponsored weatherization programs.  Many of those programs do pre- and post-improvement testing to measure air infiltration.  In addition, many of these programs keep records of consumption.  So even if immediate verification is difficult, at least there is long-term consumption data for review.


To your comment re the auditors - there are good auditors and bad auditors, just like good installers of products and bad installers of products.  I think we can both agree that some verification is better than no verification - especially when ratepayer dollars are at stake.


In the end, I just want customers to make informed energy-related decisions.  In our marketplace, I don't hear the dense pack cellulose guys advertising that people can save 50% on their "heating & cooling bill" - a fictitious item created by marketers to make their claims sound even better than what they're actually stating - but I do hear those ads coming from the injected foam folks.  If they're going to advertise it, I'd like them to be able to prove it, especially when people are paying premium dollars for it.  So far, I haven't seen any "pudding."

Great pictures, thanks!  


Exactly what I would expect to see from an expanding foam inside an invisible cavity.  This, blown out walls, or both. 


AirKrete or dense pack cellulose are the only cavity solutions I've seen that work.  If someone has other solutions I'd love to see them!



My experience w/ injected foam is even if it is installed well and fills all cavities, it still has the problem of shrinkage. I went through a training a year ago at a foam mfg. I took a form with a plexiglass cover w/ me and had it injected. The form had a recpt. box attached to it. The box filled up w/ foam. Within 3 wks.  the foam had shrunk away from the framing on all six sides. The shrinkage was most severe on the top and bottom ( 1/2"-3/4" ) and approx. 3/8"-1/2"  on the sides. The other problem w/ injected foam is the strength of the wall and blow out.

I would not recommend injected foam under any conditions. Some may say it is useful for CMU cavitie fill, but it does not solve the thermal bridging problem of block.

Here is your fix.

Require infrared testing of each job wanting govt money as rebates.

What type of foam is this? All the foam pros in the Bay Area tell me they are scared to death of putting foam in walls as they want to avoid drywall blowout?

I'd love to know how they do this w/o ruining any drywall. Is it open cell or closed cell?


The materials discussed on this blog post have generally, but not all, been open cell. 

To my knowledge, one customer in town did actually have a blown-out wall that occurred a few hours after installation (there are about 70-90 in my service territory that have received some type of injection foam within the last 12 months - either UF powder resin foams or phenolic foams - only this one customer had a problem to my knowledge, which the installer fixed at their own cost).  However, I wouldn't be able to answer for them regarding installation specifics, unfortunately.


Regarding IR testing, we've debated this at our utility and agree it is a valuable tool for this issue - thanks to you and others who have responded to this.  The implementation is where it gets sticky. 






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