Foil-faced polyiso left exposed longterm - impact to R-Value?
A client's deep energy retrofit got started but stopped about 16 months ago, right after the foil-faced polyiso was installed but before the siding was installed. All polyiso joints and almost all edges were taped and sealed. The tape looks great (pretty amazing after two very hard zone 5 winters).
So what to do about the polyiso? The R-Value has decreased, but by how much? Has the overall durability of the product been compromised? The Dow techline says that exposure up to 45 days is ok, but then the R-Value will change due to water and sun. Depending on location on the house, the reduction will vary. No idea if it will be decreased by 10% or 75%. This is what I am trying to determine.
I see the options as follows:
1. Remove and replace all polyiso ($$$, but clearly the bullet-proof solution)
2. Keep existing, if can determine if r-value of existing install is acceptable (even if compromised) by testing or rule of thumb. Can this be determined without testing samples?
Anything else to be considered? Thanks.
Posted Jun 25, 2014 1:45 PM ET
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