Next construction debate 2x4 or 2x6 exterior walls?

[jcc911]

Ok for those who followed along and participated in the siding discussion, thank you, but now am questioning the next topic.

Some builders here use 2x6s and others 2x4s and each say their way is superior in terms of total r value with the assistance of condensed/compressed (?) insulation, foam board, tyvek, etc.
One also said that with 2x6 the max total r value obtained is only 15.7 when entered into some r value calculator.
(Hope I remembered this all correctly it s been quite a bit of information).

Thanks as always. Jeremy

[Porsche-O-Phile]

There's no "one-size-fits-all" answer. You can get very good "R" values with 2x4 framing construction.

You'll get more mileage out of using tight construction methods and holding the builder(s) to good detail construction than fretting over 2x4 versus 2x6.

I haven't calculated it out, but I suspect the cost differential of using 2x6 versus 2x4 construction (assuming there's no other compelling reason to use 2x6 and 2x4 suffices) would more than offset any marginal increase in "R" value via overall envelope performance.

At the end of the day it's more about the detailing than about how thick the insulation is. You can have a lot of insulation, crap detailing and get not-so-great overall envelope performance. By contrast, you can get pretty good "R" values with good/tight detailing and get spectacular envelope performance.

[vash]

would this complicate all the windows and doors?

[vonsmog]

Most heat loss is out the ceiling (heat rises), so attic insulation is more important than wall, as windows have a "R" value of what, 2. So what good is it having walls with a high "R" value next to a bunch of windows. When I built my house 24 years ago we used 2X4 for most walls and 2X6 where plumbing would be in the wall. We have over 60 windows in the house so high "R" value for the walls would be a waste. So we have "R" of 19 for most of the walls.

[kach22i]

Getting condensation or dew point on the outside of the wall sheathing of lieu of inside of it (inside the batt) can do a lot for comfort levels and reducing the risk of mold.

2-layers of staggered 1/2" rigid insulation on the outside of the house (taped and sealed) is the way to go according to a green energy house tour I took a while back.

This was for a 2x4 wall existing house to outperform new 2x6 construction.

This home owner actually found old Iso roof insulation 1" thick (recycled it - saved from dumpster) and was using 2-layers of it.

[Christien]

Originally Posted by vonsmog

Most heat loss is out the ceiling (heat rises), so attic insulation is more important than wall,

I'll second this. We've never had "cold walls", even in the dead of winter (-30C/about the same F), but we had massive heat loss in the house until we reinsulated our attic. Immediate improvement, as in, that very day. Temperature rose at least 5 degrees within an hour or so - it was about 10C out and we had to turn the heat down. The winter was much warmer and the summer much cooler. Wish we did it years ago.

[Shuie]

Originally Posted by vash

would this complicate all the windows and doors?

Ye$$$$.

[wdfifteen]

They are doing some low energy houses in my town this summer. It looks like they are using 2x4 walls with foam sheets on the outside and Drivit finish. They are also putting some reflective corrugated metal siding on portions of the east walls.

[RWebb]

they are all made for one or the other thickness walls - so, yes if already ordered; no if not

one trick I've seen is to use 2x4's and offset them for noise isolation and extra insulation

you can always get better insulation with a single row of 2x6 than with a single row of 2x4, assuming the same materials are used in each - people get high insulation with 2x4s by using higher R value insulation, but you can use that with 2x6s too

you will want to seal the eff out of the house - there are special sealing materials used here for the most thermally efficient houses - a neighbor can heat his new house with the body warmth of 4 people for most of the year

highly sealed houses need special moisture control

[RWebb]

Originally Posted by wdfifteen

They are doing some low energy houses in my town this summer. It looks like they are using 2x4 walls with foam sheets on the outside and Drivit finish. They are also putting some reflective corrugated metal siding on portions of the east walls.

this is trick b/c then you avoid the heat flow thru the wood studs themselves - foam insulates the wood itself

it is all about the heating or cooling costs vs. the cost to construct

if you really want a high efficiency house, then get rid of all windows (!)

or pay $$$$$$$$$$$$$ for a high R window from Germany - another neighbor did that; makes no sense to me

[jcc911]

Getting condensation or dew point on the outside of the wall sheathing of lieu of inside of it (inside the batt) can do a lot for comfort levels and reducing the risk of mold.



2-layers of staggered 1/2" rigid insulation on the outside of the house (taped and sealed) is the way to go according to a green energy house tour I took a while back.



This was for a 2x4 wall existing house to outperform new 2x6 construction.



This home owner actually found old Iso roof insulation 1" thick (recycled it - saved from dumpster) and was using 2-layers of it.

And that was the sentiments of the 2x4 builder, that moisture tends to condensate in 2x6 walls as there is more space.

[onewhippedpuppy]

All things being equal, more area to insulate will yield higher R values. It will also provide a more robust home. Does it pass the point of diminishing returns? Very likely.

My father in law the contractor built a foam block house, foam blocks that fit together like Legos and then are filled with rebar reinforced concrete. Ultimately you get a home built of 12" concrete walls, with high efficiency HVAC, blown attic insulation, and Andersen windows their heater bills for the new almost 6000 sq ft house is about 50% what they paid for their old 2500 sq ft place.

[jcc911]

highly sealed houses need special moisture control

Interesting. I had asked about that once too and the builder said a humidity control system was not needed and rarely installed any more because houses today "are more tight."

[scottmandue]

Originally Posted by RWebb

one trick I've seen is to use 2x4's and offset them for noise isolation and extra insulation

^^^If I were going to all the trouble of building a house I would do this.^^^

I will have to check but we just had new windows installed and I don't think wall thickness (2x4 Vs 2x6) was a big deal.

[MotoSook]

2x6 all the way.

Althoug it is true you lose a lot of heat out your roof/attic/ceiling, you can't discount the heat loss through the walls. Going to 2x6 is maybe 15% cost increase for better thermal and sound insulation.

Both our house and the newly built guest house have 2x6 walls and we're glad they are. I'm glad I went with the 2x6 walls. In some counties it is required in order to meet certain efficiency thresholds.

[MotoSook]

Originally Posted by Shuie

Ye$$$$.

Not that much Sherman. I shopped for doors and windows myself and got the best balance between performance and asthetics...got them delivered and my builder installed them. Whne pricing out windows and doors I mentally added up the difference between 2x4 and 2x6 jams...not enough to make me wish I had gone 2x4 walls.

[RWebb]

Originally Posted by jcc911

Interesting. I had asked about that once too and the builder said a humidity control system was not needed and rarely installed any more because houses today "are more tight."

it doesn't have to be an active mechanism - some of the construction techniques they use will do the control too

of course, I mainly see houses built in 100% humid Orygun

but the tight thing he said does not account for moisture from humans & from cooking which both create moisture INSIDE the house

[notfarnow]

Originally Posted by vonsmog

Most heat loss is out the ceiling (heat rises), so attic insulation is more important than wall, as windows have a "R" value of what, 2. So what good is it having walls with a high "R" value next to a bunch of windows.

Some truth, some myth.

Hot AIR rises, but heat radiates 360*. An uninsulated basement is often the biggest area of heat loss, sometimes 30% or more.

[id10t]

Our house is 2x6. We live on a very sharp corner. When someone skips the corner and heads into the yard, we don't hear the accident - the neighbors another 100 yards away (in a house with 2x4 walls) hear the accident.

Hurricanes and massive storms? Don't even hear 'em.

Also, even when our AC was on the fritz, our largest mid-summer massive power bill was just over $200...

Granted, the double layer of insulation in the attic, and the insulation in all of our walls (interior and exterior) may have something to do with it (sure made running CAT5 everywhere a pain) but if I were building new and had the $$ for the price difference I'd go wtih 2x6 again.

[ckelly78z]

In the long run, I don't think you'll regret spending a few extra bucks now on 2x6 construction. The house will be quieter, stronger, more attractive to buyers, and weather resistant (wind, storm damage).