timberframe cabin wall insulation
I have just about finished framing a timberframe cabin in ontario, canada. It is 8 x 16 ft with a sleeping loft. A wood stove will provide heat during winter weekend stays. Pine boards will cover the framing from outside, followed by styrofoam insulation,air space and white cedar siding. I’m not much concerned about the r-value of such wall since the stove will easily heat such small space.
I’m concerned about humidity resulting from the frequent heat-cool cycles and the ability of the wall to either avoid the condensation or to dry out. Carpenter ants are plentiful in the area. Do ants nest in styrofoam? I know they love the old wallboard sheeting under the siding of my other cabin.
The advice I have received on the use of vapour barrier and house wrap ranges from “do not use any” to “use all you can”.
Any thoughts?
Andrew
Replies
Andrew,
Do you know what a SIP is? It's a panel made with two sheets of plywood or OSB and foam inbetween. You nail or screw the panel to the outside of your timberframe.
There are no studs in such a panel nor do you need them.. there should be plenty of information on SIP's on the web..
Why the air space?
Ants love foam. Ants love air spaces. Borate treated foam is available, which while about as toxic as table salt to you and me, wreaks havoc on the digestive tracts of invertabrates such as ants and politicians.
Or, as Frenchy suggests, SIPs.
Andy
"Never try to teach a pig to sing. It wastes your time and annoys the pig." Robert A. Heinlein
"Get off your dead #### and on your dying feet." Mom
andy.
Why the air space?
The posts are on 4ft centers so strapping nailed over the foam will provide nailing surface for the exterior siding. The strapping will create an air space. This will allow any wind driven rain to drain out , and the inner face of siding to dry out. Dry wall cavity,no nesting material= no ants.
So what are your thoughts on vapour barrier/ house wrap?
Andrew
House wrap or tarpaper for sure as a secondary weather barrier. Vapor barrier optional given the occasional use of the cabin. I wouldn't do it if it were my own place.
I didn't realize the air gap was intended as a rain screen. That's a great technique, although it complicates flashing doors and windows.Andy
"Never try to teach a pig to sing. It wastes your time and annoys the pig." Robert A. Heinlein
"Get off your dead #### and on your dying feet." Mom
When we were considering building a cabin on our land in Northern Maine last summer, we visited a company that offers post and beam cabin kits. Their wall system is very similar to yours - tongue and groove boards over the frame, vertical strapping, foil-faced foam board, and exterior siding. They actually pre-assemble the interior tongue and groove boards with the strapping into 4' wide sections - the panel seams are hidden by the 4' post spacing of their frames. Any electrical wiring is run through the space between the strapping after the panels are mounted, but before the insulation and exterior siding is added. They have some pictures on their web site at: http://www.backwoodspostandbeam.com.
I remember them stressing how important it is to use foil-faced insulation board in the northern Maine climate.
Bob