We’re installing two inches of polyiso over the sheathing, then 3/8 strip of ripped down TREX, then Hardipanel. My three questions:
1. I know they say housewrap over foam is useless, but wouldn’t it add another layer of protection against water penetrating joints in the foam–in the event that the tape over those joints failed?
2. Our local foam supplier (Japanese company) insists special high-performance screws are mandatory in fastening the strips to sheathing through two inches of foam, due to shear stresses and the like. The special screws he sells are extremely expensive ($200 for 2500 s.f house). Any suggestions?
3. Similarly, the tape he supplies for the joints between panels is incredibly expensive ($1500 for a 2500 s.f. house). What is a good and affordable tape for use with polyiso?
Replies
I would be a redundant safety to use the housewrap over, but given the cost of the tape, I might almost be inclined to use housewrap instead of tape.
The screws - he is right. Don't spare the expense on that item. The panel is heavy and you have two inches of no support.
Welcome to the
Taunton University of Knowledge FHB Campus at Breaktime.
where ...
Excellence is its own reward!
I intend to use the special screws, unless I can find a
cheaper generic version.As for the tape they use, it looks like duct tape, only green
and maybe thicker. Don't see why it should cost so much.What do you use for taping foam seams? How about Gorilla tape?
I had the best luck with real furnace tape...the foil stuff with the release paper.Gorilla , and regular duct tape work, but that foil tape burnished on with a gloved hand was my pick.A medium to large guy named Alan, not an ambiguous female....
NOT that there is anything wrong with that.
Something like the stuff on this page:http://amconservationgroup.com/catalog.aspx?catid=169
yes, number 1 or 2 is what I used. Mine was only 2-3" wide, but wider would be better for outside corners.I used foam board adhesive (pl3000?) for the horizontal seams instead of tape, because I feared if the tape ever did come loose it would be a funnel for water into the building, but your mileage may vary.A medium to large guy named Alan, not an ambiguous female....
NOT that there is anything wrong with that.
What they push for it here is a foil peel and stick kind of stuff
Welcome to the Taunton University of Knowledge FHB Campus at Breaktime. where ... Excellence is its own reward!
My choices would be- aluminum tape
typar tape (in a pinch:)
Duct tape, last resort!
In my opinion duct tape dries's out and crumbles, unsticks's over time.
Ps- Just bought some Gorilla tape for the snow machine seat( patching :) not to impressed.
Northeastvt
OK, I don't see the aluminum tape as being particularly
expensive. (looks like closer to $500 in tape rather than
the above $1500)Do you have any brand that you prefer? Is
a width such as 4" or 6" preferable?
I have been using(only thing available in this area) Nashua tape. http://www.covcorp.com.
I't is two inches wide. If it sticks and stay's there, not sure why wider would be better, ok wider would be better but this all I have access to;)
Dennis
I think Dow has tape for sealing the seams in polyiso. I think it was a transparent blue with blue lettering on it. If it is designed for foam, by dow I think I would trust it.
I also use the peal and stick tin tape or Tyvek tape, duct tape wont last.
Garett
PS I also like the idea of pl at the joints, would silicone work also?
Thanks, that is precisely the answer I was fishing for. No doubt I can even get that product here locally. STYROFOAM All-Purpose TapeHere's what their promo says about the effectiveness of extra width:"The wider width of the tape also means that the product has 33 percent more bond strength, which enables it to adhere better to housewrap or insulated sheathing than other products."
Gee, that leads me to the Dow Weathermate housewrap, flashing and sill pan, all designed for foam application. That looks perfect.Now, if they just had molded corners for polyiso.
I used polyiso (super tuff-R).Silicone will eat away at XPS, and EPS, or so I was told, so I used the PL for foam.Afterwards I tried some silicone on the polyiso, and saw no ill effects, so I suppose I could have used silicone all along. ?A medium to large guy named Alan, not an ambiguous female....
NOT that there is anything wrong with that.