Posted By Redsa on 22 Nov 2021 03:53 PM

In the planning stage of building a small summer camp. The walls will be constructed of 2 2x6 (sideways) sandwiched between 2 3/8" Plywood.

We are thinking of grooving the 2x6's as way to reduce Thermal Bridging.

Would the grooves make 'any' deference even if we were unable to insert some spry-foam?

Thanks.

P.S. unable to post image.

if this is a summer camp what is the great effort to reduce thermal bridging for?
Location?

Why walls with two 2x6's sideways?

Sandwiching 2x6's between plywood DOES NOT reduce thermal bridging.
You still have the thermal bridge. It's just THICKER. But it's still a solid wood connection.

Figure 1 or 1.25 (some say 1.41, I prefer pessimism) per inch.

2x6's are 1.5" x 5.5"
Sndwiching 2 together gives you 3".
2 sheets of 3/8" plywood will give you 3/4"
So you're looking at R3.75 or R4.6.
Even using crappy insulation, the heat will just bleed right through the "studs" AND the plywood.

If you're serious about reducing/eliminating thermal bridging, go for continuous insulation around the outside of the structure, underneath whatever sheathing you're going to use on the building.
You COULD do double-wall construction with offset studs. But that's probably more expensive than just wrapping the building in insulation.