[Greenbuilding] Insulation fasteners

[John Salmen]

Sounds like you have two components; the foam and the nailers. The best
fastener for the foam is actually adhesive (I typically specify enerbond or
some equivalent foam adhesive). Nails really only hold it in place while the
adhesive sets so nails/staples/screws can be used for the foam to foam bond.
The foam can be 'structural' in that it will have some compressive
resistance (stiffening the nailer that you attach) and can also provide some
predictable shear resistance (if foam panels are glued and stiffened with
nailers in some pattern).

The nailers need a mechanical attachment right through to the stud framing
and I specify a structural screw like Headloc or GRK (and yes they are
expensive). Nail penetration into the stud should be min 1-1/4 and most
codes require 1-1/2".

It gets difficult with sheathing assemblies over foam as most codes still
require a siding nail sufficiently long to penetrate into a stud an 1-1/2 -
not going to happen. Rainscreen battens are typically only 1/2" and if over
foam and providing siding support don't provide much wood for nailing. Some
siding manufacturers have reduced nailing depth for products (hardie
requires only about 1/2" depth into strapping). Codes are defaulting to
manuf. as siding is increasingly decorative and sacrificial.

So code nail depth requirement is based on smooth nails going into wood and
the resistance provided for withdrawal. Screws and ring shank nails provide
more resistance and battens provide more opportunity for nailing (more than
1 in 16 or 24"). So I think the ideal is to focus on providing good long
screw attachment for the battens (1-1/2" into stud), don't worry about
nailing the foam and then find a good ring fastener for the siding and
increase the spacing to 12 or 14. 

-----Original Message-----
From: Greenbuilding [mailto:greenbuilding-bounces at lists.bioenergylists.org]
On Behalf Of bill.allen at verizon.net
Sent: November-14-12 5:07 AM
To: Green Building
Subject: [Greenbuilding] Insulation fasteners

Hi,
I am in the process of putting rigid insulation on an out building.  I am
installing 2 layers of 2" styrofoam. I found 3" "nails" (very thin with
plastic washers to hold the foam) but am having trouble finding fasteners
for the next layer....I'm figuring 6" (2x2"foam+1"sheathing + 1" in the
stud).
Any suggestions would be greatly appreciated. Regular nails that big are WAY
too expensive.
I will also need a fastener (maybe a screw?) for the next layer...the
occasional nailer that will hold the siding. What do people use?
Thanks,
Bill

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