Will you be having a blower door test done? At what point in the build and what number is the builder shooting for?

I second dekeobee, without blower door goals, thermal bridging and Rvalue upgrades could be wasted resources.

As for the staggered stud walls, Iam guessing you could have gotten better performance more affordably with insulative sheathing.

R19 attic floor? Thats not really legal anywhere. You should have R38 or R49 as the minimum performance level at least. So the house youve described sounds like it could perform much worse than most of the production/track housing currently being built across the country. Hope that last jab was for the honesty you were looking for!

I will have a blower test after its insulated through my local Coop Electric. To be honest, my builders are Amish and they don't do blower tests or have any scores in mind.

You say the R19 isn't enough? Even with the entire ridge line with 8" of sprayfoam? That should equate to around an R49 combined R rating.

Also wanted to add that I actually asked them about putting on some type of insulating foam board sheathing and it would have been more money. I assume it's because they own their own lumber yard, build their own trusses etc that that is the case. It was only about $1700 more but I chose to go with the staggered wall.

honest reply

your concerns with 2x6 with thermal bridging & strength
can easily be addressed.
foam sheathing on exterior of walls will eliminate thermal
bridging, Simpson Strong Ties will add additional strength.
this is what we do here in hurricane alley.

2x6 will allow for R-19. combined with R-7 per inch
foam sheathing, you can meet required R-value for Ill.
fill stud bays with conventional insulation..have drywall
installed with ADA Airtight Drywall Approach and your
wall will be air tight.
use sill seal under sole plates for walls to seal to slab.

I"I've never heard of cold climates using open cell for the
roofline. if you use 7"-8" of closed cell you'll meet R-50.
insulation has to be continuos with no voids & gaps
to perform. splitting the R-value between roofline &
attic floor puts a huge void space between the two &
de rates the R-value.

use hurricane strapping for the roof. we've learned
that unvented attics survive hurricanes, simply because
the uplift of the roof isn't there as with vented attics.
unvented attics cover a multitude of errors, oversized
cuts in sheetrock ceilings, open thermal bypasses...
and the always present recessed lights.
here people put their heating system & ductwork in the attic
stupid move...but it is what it is. foam insulating the roofline
keeps the ducts/equip in semi conditioned space.
and with air barrier & thermal barrier moved to roofline,
the holes/bypasses don't suck attic air into the house.

I hear you loud & clear about the hvac system.
most of my clients start out wanting geothermal...but costs.
most opt for heat pumps or a/c with gas furnaces.
of course I'm in a cooling climate...

wish we'd have had this conversation sooner...4 days
to build is short notice.

google Airtight Drywall Approach & go to www.buildingscience.com & search "perfect wall"

best of luck

Open cell or closed cell work equally well under roof decks, according to Dr. Lstiburek.

But according to this study in Building Science Corp., if the spf is sprayed onto a wet substrate, there is a risk of damage. As well, ocspf should be installed with a low perm Class II vapor barrier. Can you be sure your builder will avoid the first and follow the second?

If you have no plans for the attic--you didn't say where the HVAC is going--I would just pile it high with loose fill cellulose.

And what is the point of insulation on the attic floor? I'm not sure you can add up the R factors on two separate areas to calculate a total value.

Furthermore, Lstiburek points out other consequences of using spf under a roof deck that have not been addressed by Codes (which he helps write) but will be eventually, namely the need for air returns and ignition barriers on the spf.

Also, sheathing 2x6s with 1"-2" of XPS, then dense-packing cellulose or at least, high-density fiberglass batts would be my choice. Just as efficient and doesn't take up floor space.

Asking for second opinions three days before framing is a little late in the day!

Spray Foam Recommendations in Unvented Attics Source: Building Science Corp.

This post was edited by worthy on Fri, Jan 2, 15 at 17:24

I'm sorry if I wasn't clear, the contract is signed I won't be making changes. I just tried to do the best I could bang for buck for my family. I guess I was just wanting opinions on if you felt it would be fairly efficient.

I live in a very rural area and to get truly green contractors you're looking at $170-$200 per sq ft. I'm looking at spending $190,00 for a 3400 sq ft home including HVAC, flooring, cabinets and new appliances for the wife. Basically about $56 per sq ft.

As I stated earlier Graber didn't do cellulose just spray foam.So I added attic trusses and a staircase and added a 16 ÃÂ 68 ft storage room that could be finished out at a later time. It will also house my furnace.

Could I have been my own contractor and gotten more of the products I wanted? Absolutely. I just don't have the time or patience to do that. I farm 1700 acres, have a hardware store and have a 14 month little girl. I just don't have the intelligence to spread myself any thinner.

As for the builder, I checked with 2 people from my town they had built homes for and they were both happy with the workmanship. As for the class I I vapor barrier under the roof I know they are putting down bubble wrap under it. I know it's a vapor barrier but don't know if it's a class I I barrier.

Thank you all for your thoughts. Wish me well in my endeavor.

Open cell spf typically has an R Value of 3.5 per in. So your roof insulation doesn't meet Code outside of the Deep South and is woefully short in any other climate. Southern Illinois is in Climate Zone 4, which requires attic/roof insulation of R49, as per IECC 2012.

If the bubble wrap also includes a reflective foil, the builder may be adding that exaggerated claimed value to reach Code.
I've heard that building inspection in rural areas is spotty at best, so this may pass muster.

Otherwise it sounds fine. And that price is incredibly low--as a builder, my costs on a quality custom home in Toronto would run at least C$150 s.f. Good luck on your build!

This post was edited by worthy on Sat, Jan 3, 15 at 15:05

Why do the amish love that shiny bubble wrap so much anyway?

FEMA has a great plan for a tornado safe room. Cheap and easy with 2X4 and plywood. I will do this with my master bedroom walk in closet too.

bubble wrap does nothing under foam.
big waste of money/labor/expectations.

in hot climates it can act as a radaint
barrier with some benefits, but has
to have a minimum of a 1" air space
on foil side.
in cold climates it does
so little as to be next to worthless.

as is batts on floor of attic with foam
on roofline.

just answering honestly as per your thread title.

The builder has an oxymoronic understanding of the meaning of conditioned attic, i.e., clearly muddled. The insulation goes on the roof, not the floor. Splitting the difference is nonsensical.

Here is a link that might be useful: Principle of an Unvented Attic

This post was edited by worthy on Sat, Jan 3, 15 at 15:13

The bubble wrap is not for insulation values, merely as a vapor barrier.

Actually the builder was going to put in the 8 inches of open cell and I asked for the fiberglass just to give myself a little more insulation over the living area.

By conditioned I mean, I can have water lines up there without fear of freezing lines and you can go up in the attic and store things without excessive cold or heat.

The builder actually through in that request in for no charge because I was going to do away with it because I wasn't sure if it would do any good and save the money and he told me he had thrown it in anyway so I figured go ahead and take the free R19.

Get out of this contract. First off, it's not priced realistically. The change orders and allowances will kill you. Second, it isn't doing what you want. It's poorly thought out and detailed. It wont be what you hope it will be. Not even close.

To repeat:

Southern Illinois is in Climate Zone 4, which requires attic/roof insulation of R49, as per IECC 2012.

There are no local exceptions, according to the Illinois government website linked above. To wit: "for residentialÃÂ buildings, local governments may not adopt or regulate energy conservation standards either less or more stringent than the Illinois Energy Conservation Code."ÃÂ

Since all you're using the attic for is storage, it would be a lot cheaper to just pile on the insulation on the attic floor to Code, R49 and run water pipes in conditioned space. Also, you won't be paying to heat and cool the attic. If however, you also have your HVAC in the attic, continue as planned but ditch the fg on the floor and bring the roof insulation up to Code.

Best of luck!

I'm looking at spending $190,00 for a 3400 sq ft home including HVAC, flooring, cabinets and new appliances for the wife. Basically about $56 per sq ft.
______________________________________

I don't believe that is possible at all. I'd be interested to hear how your pricing ends up when all is said and done.

We are just about done with our build. We did ICF and geothermal. Those were two things my husband did not want to give one. We aren't in the house yet, but so far we've noticed that it is a lot warmer than our current one and we are able to keep the heat set lower.