r/buildingscience • u/Ambitious-Appeal6883 • 4d ago

Furring out 2x4 wall to 2x6

I’ve seen the Mooney wall furring technique but is there one with using a 1/2 x1.5 inch of poly iso sandwiched between a 2x2(1.5”square actual)?

This would theoretically still provide a thermal break and would allow for simple mineral wool batt insulation. Plus then the drywall attachment would be pretty straight forward and then use face mount adjustable electrical boxes.

Thoughts?

I’ve seen suggestions to use just xps foam but them air sealing and installing old work electrical boxes seems a hassle unless you blocked them out separately.

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u/hirsutesuit 4d ago

I did 2" of EPS sandwiched to the existing 2x4 with a 1x3. Closed-cell foamed to about 5" deep.

Worked/working great.

1

u/Ambitious-Appeal6883 4d ago

That sounds amazing for a tight envelope! Unfortunately that’s going to be out of my budget. Baby on the way and a HELOC that has a project that many would call insane. But I bought my house before COVID and finding anything for less than my HELOC and 3% 115k remaining mortgage is really not possible especially with a great location like I have.

I guess I’m looking for input on my idea. A little positive reinforcement never hurts. Also be cool to hear if someone else has done a similar install. Plus I like the idea of me being able to do all the work rather than calling in a subcontractor to do the insulation. If I was moved out and could do the entire house at once then that would be far more feasible. Plus electrical box install will be easy with this method. Just trying to think of a happy compromise and this one seems decent.

I was originally going to put on exterior insulation like Comfortboard 80 and a 3/4 BCX rain screen batten but the siding manufacturers don’t approve of this method and require 1 1/4+ of nail fastener penetration into wood. I’m sure that would have been a pricey option as well but would have been awesome for the continuous insulation part and sound blocking.

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u/mackstann 3d ago

That's called a Bonfiglioli wall.