Exterior walls

jbillups

What if any down falls to building exterior walls with 2x6 oppose to 2x4 and, whats the highest R factor insulation I can install.

woodworkbykirk

the only downfall of using 2x6 walls is that you will lose 2" of space from the thickness of the material. its stronger, wont twist and warp as easily as 2x4

for insulation r-24 in fibreglass batts, and roughly r-30 if you use 6 lb spray foam

ratherbefishing

Agree with Kirk. Main advantage is more R-value. No big tradeoffs. A minor one may be that some of your "accessories"; doors, windows, trim, etc may be designed for 4" walls. So you may have to special order or adjust. Inside jambs, stools, etc may look a little different from what you are used to.

MNsawyergp

Spray foam is the highest R value per inch...about 5.5. So for a 2 x 6 that would amount to about R30. Very expensive, but very good. Better to spray in 2" and fill the rest with fiberglass.

woodworkbykirk

currently the highest r-value for spray foam is r-7 and the engineers who design the mixtures for it are workign on getting it up to r-10..


spraying in 2" of foam then filling the rest with fibreglass will only get r-22 roughly.. just buy r-24 batts

ddawg16

If you use good lumber....you will also end up with a straighter wall. Look down the walls in your house....notice how wavy they are? 2x6 Will not be as bad....

We are doing a 2-story addition right now....even though the drawings show all the walls ax 2x4 construction, I am doing 2x6 in the main room downstairs....it has a 9' ceiling so the extra strength will make for straighter walls and I can put in more insulation.

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concretemasonry

Just keep in mind that the studs (wood or metal) are "thermal short circuits" and the "R-value" of the wall will never be as god as the advertised value of the insulation. It can be 10% to 45% lower depending on spacing and materials used. More loss through steel studs than wood, but still significant.

The additional use of rigid XPS form is a positive thermal barrier that can minimize the thermal transmission.

Dick

jklingel

A 9'-2x6, braced laterally, will carry 7061 lbs; a 9'-2x4, 1820 lbs. They also cost (up here) about 2.5x as much money. If you want R and thermal break, double stud w/ 2x4 (if they will carry your load) and dense packed cellulose. WAY cheaper than foam, and MUCH better for the environment. Leave the fiberglass batts at the store. Use mineral wool, wool, cellulose, or cotton batts instead, IMO.