Injecting Foam Into Existing Walls
walta100
| Posted in General Questions on
A company called “USA insulation” has been running a lot of ads in my TV market.
They show foam being injected into existing walls. I had not heard about that technique since the early 1980s when they stopped due to off gassing.
They claim R 5.1 per inch sounds to high for open cell foam and to low for closed cell.
I am sure it is not the cheapest way to buy an R of insulation.
Anyone have any thoughts or experience?
Walta
GBA Detail Library
A collection of one thousand construction details organized by climate and house part
Search and download construction details
Replies
I had some foam injection done on about 20 feet of exterior walls which were later fully demo’d, giving me a chance for some analysis. Here are some comments.
1. The injected foam (injected at the top of walls) had great coverage in the plaster/lathe wall cavities.. It was less dense than the closed cell we normally use which correlates with your R value comments.
2. It was a royal mess during demo of the wall as it was adhered to everything in the wall.
3. No mould was found in the wall system, approx 7 years after installation, zone 7A with shiplap exterior sheathing, tar paper and brick.
4. Typical thermal bridge issues still existed at studs etc as expected, with larger issues at the base of stud cavities/fir stops where plaster was sitting (from lathe application). These were quite noticeable in FLIR IMAGES of the wall taken at low temps.
I would imagine that the foam was more effective than other areas (vs blown in cellulose) with respect to air movement. The final wall (after a full reno) was a lot better performing with offset studs, full clean up of plaster and 4” of closed cell applied to the open wall. FLiR showed the thermal bridging had been addressed, and wall temps were about 19 to 20C with outside temps in the -20C range.
It's hard to imagine this is successful given how difficult spray foam is to get done right under the best situation (totally open) and then it works under the worst situation (into drywalled bays). Just seems highly suspect.
I did it once on a renovation, way back in the late 1990s, long after the UFFI problems but before spray foam had fully hit the mainstream. It went poorly enough that I have not considered doing it again. All of the drywall was blown off the walls so we had to strip it all and start over. We found a lot of significant voids as well. The spray foam company gave us a discount but wouldn't help us fix it. Hand-sawing two rooms' worth of closed-cell foam flush was not fun.
I made a thread a week or two ago about my daycare doing sprayfoam in the basement. It was this company doing the work. She also had her walls injected with foam, I haven't heard if she had any issues or positive feedback. This was the company that said it was perfectly safe for toddlers to be in the building while doing spray foam as long as they weren't in the basement. On the day of installation they changed their tune to say "maybe a second floor bedroom would be better, if anyone has asthma, they will likely have a reaction."