Taping EPS foam
user-5644012
| Posted in General Questions on
I am currently putting two layers of EPS foam on the outside of our 120 year old farm house. I wanted to tape and stagger each layer but can’t find a tape that will actually stick to the tiny beads of the EPS foam. I have resorted to caulking the seams. Any suggestions?
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Replies
Ryan,
There are many types of EPS. The denser types have a smooth surface, like XPS, without small visible beads that crumble easily. It sounds like you bought the cheap stuff -- a type of EPS that is hard to tape.
You can try a high-quality tape like Siga Wigluv. I've never tried to tape cheap EPS with Wigluv, so I don't know how it will work, but it's worth a try. The alternative solution is to use caulk and canned spray foam.
Ryan. Where are you located, and what is your overall wall stackup? You may not have enough exterior foam. If that's the case, you may need another layer (or layers) and could overlay the EPS with easier-to-tape XPS or polyiso.
Siga and Pro Clima both offer solvent-free primer that I think would work in your situation. Neither one states compatibility with EPS, as they are designed for fibrous material, so you should check with the suppliers.
https://sigatapes.com/product/dockskin-2-2-lb/
https://foursevenfive.com/product/tescon-primer-rp/
Siga Wigluv explicitly lists EPS (but says nothing about "cheap").
Thanks for the great advice; I'll look into these products. We are in climate zone 6A (northern Michigan). We have 4 actual inches of blown in cellulose in the wall cavity and are adding house wrap and 3 inches of EPS foam to the outside of the house in two staggered layers. We added 6 inches to the roof. We elected to use the EPS because of the increased permeability to the outside. I don't think it was the cheap stuff -- or at least my wallet doesn't feel that way. It looks like a solid sheet and doesn't easily break but you can definitely see the beads when you cut it apart. Thanks again for the help!
I heard this from my local Siga rep:
"All of the Siga tapes will stick to EPS without primer.
As long as the tape will not have long term UV exposure."
And from my Pro Clima rep:
"You'll definitely need to use PRIMER RP on any foam. You could use it with an all-around tape like TESCON VANA, or try our new COMPEGO tape that adheres especially well to low energy materials like poly and many foams, with a plastic carrier film that's vapor retarding."
A quick test with 3M 8067 indicates that it works very well on fairly smooth, unfaced EPS.
I have done a slew of tests of various high performance PSA tapes (see my company website: https://building-wright.com/blog/) and you should consider/try Huber's ZIP tape. I agree with others above, that your EPS may be particularly challenging but worth buying a couple or so different tapes and seeing which works.