Posted By bobarchitect39 on 22 Jul 2010 10:22 PM
Great thread all. But what about the insulation? What distinguishes "superinsulated" from just normal insulation?

the answer is in your question

Posted By bobarchitect39 on 22 Jul 2010 10:22 PM
Great thread all. But what about the insulation? What distinguishes "superinsulated" from just normal insulation?

TOTAL, clear R value, higher the number the better. After R60 in the attic/ceiling it's a moot point, not much gained going to a higher number. The walls an R40, the real key is to have as little a number for unaided air changes per hour, then you get to pay for it by doing mechanical air changes by an HRV or ERV.

A typical tract home where I live is a 2 x 6 wall, R20 at best and R40 in the attic, this is to code. The stick home I had built in 1987 has R60 in the attic and R40 in the double walls, with a GREAT deal of attention payed to air infiltration/sealing!

Now you have superinsulated and a more economical home to heat and air condtion and it's quieter inside!

Cheers John

I'm sure others will pipe in with there concept of "superinsulated"

Posted By JohnyH on 23 Jul 2010 07:25 AM

"A typical tract home where I live "

True qualifying statement that will vary by geographical areaa
anything above the norm is considered super

After starting to get some more 'concrete' numbers , I am now leaning toward stick framing the walls myself.  Material costs for the wood would be around 15-20k cheaper then the ICF block and concrete...NOT including labor on the ICF.  With the stick frame, I know I can build it has I have many times in the past.  ICF is an unknown and could be very costly if I screw it up.  I do not want to spend another 15k to pay someone either. 
However I think I will still plan on ICF for the basement walls.  By the time you add over excavation, forming, furring the walls and insulating, it will cost higher then an ICF basement and wont be the same insulation value either.
Just to clarify, my stick frame price was not just for 2x6 and batt.  I also included 2" of EPS on the exterior to give me a decent thermal bridge.

OK while you are crunching numbers, consider this.

I built my own house with 2X6 OVE walls, and exterior insulation. I used zip wall sheathing and taped the seams and then glued and cap nailed 1” polyiso over that and taped the seams with zip tape.
I then used 1X3 to provide a ¾” airgap/drainage plane/ airspace with radiant barrier and sided over that. This can work very well. Do the rim joist detail so the zip panel and external insulation covers the rim joist also and is taped to the ICF on the outside. Ideally they should end up in the same plane as the outside of the icf wall so the siding materials can cover over the gap to prevent any water access.

At the ceiling there is very little cost penalty for increasing the insulation. I used a scissor truss with an 8” energy heal. I used 1” isocyanate insulation to make a 1” air gap on the underside of the roof decking where the trusses were the thinnest near the soffits. I did not want to use an unvented attic. On the underside of the trusses I added a 1” layer of isocyanate insulation and taped all seams as well as taping it to the framing members and intersecting walls. Basically I used the ridged insulation as the air sealing detail for the ceiling plane. I then strapped the ceiling perpendicular to the trusses with 1X3 (creating a ¾” airspace) and sheet rocked over that. I then blew in cellulose insulation to r50 so most of the ceiling is ~R56. I spend a lot of time on air sealing details prior to blowing in cellulose. I think this gives a great bang for the buck.

Posted By bobarchitect39 on 22 Jul 2010 10:22 PM
Great thread all. But what about the insulation? What distinguishes "superinsulated" from just normal insulation?

There's no hard definition, but 2x code minimum for clear-wall R values for the location would be a typical starting point.   eg:  If the code minimum for the area is R19 batts or blown in 2x6" 16" o.c. construction, which has a clear wall value of ~R18, a superinsulated house for that area would have R36 clear-wall values.  Slapping an inch or two of foam sheathing on the outside to bring it up to R23-R28 might be good, way better than code, but wouldn't be considered superinsulated by most.  If code minimum for the climate is R13 batts in 16" o.c. 2x4, a 24" o.c. 2x6" framing with blown cellulose and an inch of iso on the outside could be considered minimally superinsulated.

Others definitions of "superinsulated" might be "heating & cooling requirements for the structure is less than 1/4 of a code-minimum house", which would involve tweaking aspects beyond simple rated-R, like pressure verification of the air-tightness of the envelope,  controlling convective R-losses within the insulation at high delta-T,  designing glazing & overhangs/shading for managed solar gain/loss, etc.

Still others consider any clear-wall R value above R30 to be superinsulated, but in my mind it would depend on the climate. R30 walls might be good enough to achieve PassiveHouse spec in some temperate zones in the US when combined with air tightness and a decently insulated foundation/slab relative to local subsoil & seasonal average temps, and well-considered glazing.  But R30 wouldn't be as significant an upgrade in ND, MN or the MI-UP, (but still a significant uptick from code-minimums.)