Posted By jdebree on 24 Feb 2012 04:10 PM

That's a great article, but, believe it or not, they never mention how to fasten the siding to the furring strips! They also point out that the testing in no way means the fastening is adequate for wind or seismic loads. I'm going to go with ring siding nails, and call it good. I doubt the inspector will object, although I am going to ask before I do the actual installation. The manufacturer of the screws calls for at least twice as many fasteners as the article does. Seriously, I doubt a few extra screws would make a measurable difference in heat transfer, unless you're building a house in a test lab. I'd rather have more screws on a stormy night than save a couple dollars cents a year in heating costs.

Screws 24" on center can have more mechanical retentive strength for the furring than ring shank nails 4" o.c. and less than half the thermal bridging. If you want to shrink that to 16 o.c. for the screws knock yourself out, but nailing the furring through the foam would be a step backward both structurally & thermally.

This is pretty standard stuff these days:

http://www.greenbuildingadvisor.com...athed-wall

Scroll down to the discussion about fastening the siding to the furring- Hardie accepts a 7/16 minimum penetration into wood for their lap siding.  Ring shank nails are clearly better here, but short enough to just penetrate the furring, not the foam.

I'm definitely using screws to attach the furring. It's the siding attachment that's been hard to come by. As I said, I'll use ring siding nails to attach the siding to the furring. Unfortunately, the shortest nail I can use in my siding nailer is 1-1/2", which will go through the furring and into the foam.

Thanks for that article Dana. That should suffice for anyone that has stick framing and studs to attach the furring to. Has anyone run across a similar discussion concerning fastening to only sheathing, as in a SIP situation? That seems to be more problematic and I have not seen any articles with a strong recommendation on that front.

Dont use treated wood. It is corrosive to the metal and what would be the affect on other materials. Untreated lumber will stay dry and will be just fine. I would get epoxy coated fasteners that penetrate the structral lumber to the depth recommended.

Posted By jdebree on 28 Feb 2012 06:11 PM
I'm definitely using screws to attach the furring. It's the siding attachment that's been hard to come by. As I said, I'll use ring siding nails to attach the siding to the furring. Unfortunately, the shortest nail I can use in my siding nailer is 1-1/2", which will go through the furring and into the foam.

While it's still more labor, it doesn't take a lot of practice to get it to where you can sink 1"  or 1-1/4" in a single tap.  Going with thicker foam so that there's 3/4" of foam beyond the nail points provides at least some thermal break.