Yes, an old thread, but just as timely now as when started, and in 1976...
I happen to have a degree in Construction as well, with specialization in solar/alternate energy systems (albeit class of '76).
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I agree most heat loss occurs through ceilings, windows, & doors, but IMO that is no reason to cut corners on wall construction.
Tyro
I'm curious about the above. I mean, don't you hit a diminishing returns with the wall insulation? Oh wait - just re-read my comments in post #15 of this thread from 2008!
http://www.early-retirement.org/for...n-2-x4-or-2-x-6-framing-40991.html#post756322
Regarding heat loss through the studs, we were also playing around with 2x4 studs between 2x6 plates, alternating between inside & outside of the wall. I haven't seen/heard of this lately (and didn't find it on a quick search), so I don't know if it caught on or was abandoned...
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Tyro
I like the concept of less bridging (incredible how much there is in the exterior corners), you could even 'snake' electrical through the gaps. But you need 24" spacing to hang drywall (or maybe not - if they go horizontal? Just some multiple of 8 or 10 or 12'? Not sure about code limits on that staggered wall.). But if you need 24", that is effectively a 2x4 every 12" rather than the usual 16", or 2x6 every 24". So it is going to be more material than 2x6 24" OC.
So looking back at my 2008 post, even if this gives ~ 10% better overall wall performance, I'll just guess walls are less than half the loss, you need to determine if ~ 5% fuel savings is worth the cost.
I have a largish home, probably sub-par insulation, in Northern IL with heating and cooling required. And not sighted well - summer sun kills us. Yet, my total utility costs were just under $2000, and only a portion of that is for heat/cooling. Twenty YO furnace (~85-88% eff?), older A/C. In fact, I just looked at my spreadsheet with 2012 annual bills, and if I use the lowest month each for gas & electric in the non heat/cooling season for each as a baseline, it appears only 1/3 was for heat/cooling (we had a mild winter, but a long hot summer - AC was on much more than normal).
So even a generous 10% fuel savings based on half the $2000 rather than the third of it is ~ $100/year. If it costs more than 25x to get that $100 savings, wouldn't the $2,500 plus be better in my retirement account? I doubt a buyer would compensate me for what's in my walls, and could I prove $100 annual savings? I'd rather have the $2,500 (and I suspect it would cost MUCH more to add those features to new construction), and pull an inflation adjusted $100 plus from that.
I'm stingy with the thermostat, dressing for the season goes a long way towards comfort w/o expending energy - and donning a sweater/socks/slippers or going in shorts/t-shirt costs near nothing and is not a sacrifice.
All this needs a good financial scrub - maybe you need to get the house tight enough and efficient enough that you can downsize the furnace and A/C to make the numbers work? But at that point, you need an air exchange unit, and those are not cheap. Passive solar, overhangs, etc can help and maybe not much $ if planned for (I know proper sized/oriented overhangs can make a big difference in my latitude/climate, and look good IMO). But again, even if I spent $1000 on heat/cool, and could cut it in half, that's would need to add less than ~ $13,000 to the construction costs, relative to my current bare minimum construction. Can $13,000 cut a heat/cool bill
in half on a largish house? I think that would be challenging.
-ERD50
