Practicality of 2x8 walls

Out of curiosity (I live in a cold-ish climate, so thicker walls strike me as a good idea)
Does anyone do home construction using 2x8 (or two 2x4s)? I haven't seen anything like this locally, but that doesn't necessarily mean it doesn't exist.
Despite a material cost increase (and larger external footprint required for the same internal square footage), wouldn't the increase in R-value offset the additional cost over time?
Alternately, assuming 2x6 exterior walls, are any homes constructed with additional EPS/XPS insulation on the outside of the wall?
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In a previous post David Bonnell wrote...

Finding single batt insulation to fill a 2X8 space will be difficult. You would need to install two sets of batts.
If energy efficiency is your paramount consideration, then you might want to look at Structural Insulated Panels (SIPS) as your method of construction. Another method gaining favor in some areas is Insulated Concrete Forms (ICF) for the whole house (not just the foundations).
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Bob Morrison, PE, SE
R L Morrison Engineering Co
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Sprayed in place cellulose would be better in any case anyway. Would work perfectly in this case.
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Steve Barker

"Bob Morrison" < snipped-for-privacy@junk.com> wrote in message
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Only when thicker = warmer. Thicker for thicker's sake is a stylistic concern. I'm not saying that's a bad reason...just making a distinction.

I've done it in places where the walls were very tall, but not typically.

Yes, but that's a 'present value of money' question. Maybe Pat has something to say about ROI, etc.

Ever heard of EIFS?
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MichaelB
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Absolutely. Even with 2x6 studs, the studs represent a significant loss of insulating value compared to the cavities. Adding a continuous layer of insulation over the entire structure improves the performance of the whole system. I like Tuff-R, which has the highest R value combined with the lowest cost per sheet (in my area, Northern Ohio).
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Dennis


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I saw one of these hombuilder TV shows and all of the houses were either 2x6 or 2x8 (I forget which) with blown in foam insulation. This was for houses in the DC area.
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Remember that you can get a house too tight. You need a little clean air to breath once in a while because if you don't turn green, the walls might.

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Glenn wrote:

True, but an HRV/ERV is a better solution to this problem than is leakage through the structure.
Matt
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I'm currently working on a project using double 2x4 walls. It is also fairly common to see 2x6 walls skinned with 1" of xps. Practical? Sure. It costs more, but I suppose there will be a savings down the road. With the double 2x4, you wind up with some pretty deep window jambs, but the rest is straightforward. As Bob M. says, batts wouldn't really work, so we are using blown in cellulose, which gets blown behind netting. Of course, you still have heat loss through the windows. We are using the most energy efficient windows out there, but they are still only have a U of .17, which I believe translates into R 6 or so. HRV's are required by code where I live.
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wrote:

You make that sound like a problem... it's a glorious thing! Check out traditional buildings with thick masonry walls and note the beveled or chamfer window reveals, sometimes with interior shutters built in. They soften the harsh line between the bright glass and the dark interior walls. A beautiful problem to have.
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I've been trying to find that stuff (in the KC area) for a solar collector project. Who the heck sells it?
thanks,
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Steve Barker


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Home Depot, and I believe Lowes does also. I'm not sure what temperature it is rated for, might be a factor in a collector.
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Dennis


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On Feb 1, 1:02 pm, snipped-for-privacy@SPAMwowway.com (DT) wrote:

FWIW about that stud loss ... up here code spacing is 2' with a 2x6 ... less studs, less loss.
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bowgus wrote:

Yes, and there are other benefits such as less noise.
Matt
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double wall systems been around a long time also known as envelope systems, double shell systems. Works in conjunction with passive solar designs.
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The R value of a 2x is about .6/inch So an 2 x 8 would be apx 4.8 R.
If you are that concerned and willing to pay a little more. Move to SIPs or ICF. Go to www.futurestone.com for info on ICFs

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2x6 construction is common in colder climates. The pay back on 2x8 construction in years VS $ would not be worth it. You could do 24" framing instead of 16" OC. Depending on the size of the house this could make a large imnpact, and still meet code. Regaurdless of what you do cellulose is the best bet for insulation.
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replying to David Bonnell, Stefan wrote: Although i couldn't tell you what others do, and I'm not proficient in state to state housing code, i can say this all with confidence. I have builded (built) 12 high efficiency houses, 6 in Maine 3 in Minnesota, 1 in Wisconsin, 2 in Missouri. Exterior walls need to be built to the code of the area you are building. Code is by all means a minimum requirement, anything beyond (better) code is good. So start with 2x 10 exterior walls. After framing and siding, before wiring and plumbing, build a second wall inside the exterior wall, running parallel. This interior wall should NOT be structural. Leave a space of 1-3 inches between walls, and at no point should they touch. Plan your exterior size accordingly. Making your basement 10 to 12 inches thick instead of 8 will help immensely. Insulate the excretor wall with the proper sized insulation, and insulate the interrupt wall like wise leaving the couple of inches as a dead air space, which BTW could also be insulated but would only invade the efficiency by a fraction. In doing the roof, follow the same principle, insulated the rafters or trusses, and so the cowling and insulate it also. Plan ahead for your desired ceiling height. I hope this helps you, and if you have questions, i can be emailed through this website.
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replying to David Bonnell, Paul wrote: My parents have this in Vermont. The studs are staggered and you use R-13 (twice)
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