All the research I did on going green said put your money into insulation as, no matter how you generate a BTU, the longer you hang on to it, the better. So we chose closed cell spray foam insulation. It's waterproof so needs no vapor barrier, it adds structural rigidity and is amazing at sound proofing. It also allows no air infiltration. So you will need a good air recirc system to keep the house fresh.

But, before you use any spray foam insulation, be sure you have all your electrical and wiring (alarm systems, cable, etc.) done exactly as you wish ahead of time because any changes means cutting up your expensive insulation and snaking wires is all but impossible. We also added boxes around our in-wall speakers so they would be protected from the foam.

We found the most efficient route to a high efficiency wall in our renovation was to wrap the exterior with 2" of rigid blue foam and then use blown-in cellulose in the stud bays. Continuous coverage of the outside adds a lot, there is a surprising amount of heat loss via conduction through framing members which can make up 20% of the total wall surface. The addition we built was panelized construction that came with 4" of closed cell foam. We wrapped the outside of that with an additional inch of continuous rigid foam, again as a thermal block for the framing. With a fair amount of attention to sealing the house now seems to be using about 60% less energy for heating and cooling than our previous 15 year old similarly sized house with fiberglass batts in 2x6 conventional wall framing.

asking something like "is your home less drafty" really isn't a good baseline to go off of since most new homes shouldn't feel drafty at all.
However perhaps this: Is a home with "r21 batts (not even close btw) more drafty compared to a home with blown insulation and 2"+ of rigid exterior foam and properly air sealed? Absolutely. IN a heating climate such as MN (zone 6) what you are proposing is code MINIMUM, and infact the r39 in the attic doesn't meet code (I assume you meant r49).
The #1 best thing you can invest your money in your house on a new build is the structure and shell. No other area will provide you payback than shell and window upgrades. Sure, adding the foam to the exterior will cost a few thousand more, but it creates a thermal break in your wall and aids in air sealing. Your home loses more heat through air exchange in a leaky house than higher r values. Insulation can not work if air is moving through it. You need to stop the air first, and then insulate.

In your climate you would be money ahead considering super insulation, but most builders roll their eyes and run and instead push you to build the minimum allowable house by code instead. Why they do not want to upsell you on a better home and product has always confused me.
Spend the time and money air sealing the shell. Get a blower door test done to confirm air tightness. Check with your local utilities and state rebates. You may get big rebates for building a higher efficient home.

I am in Iowa zone 6, similar heating conditions as yourself.
My 3800 sqft house that is highly air sealed on above code insulated cost $60 in electric to air condition during July and natural gas for furnace and water heater averaged $30/month for the year. I could get into the specifics and deep technicalities, but those seem to be the important parts most people want to know. I also was able to qualify for $5500 in rebates which more than paid for the upgrades to qualify for 10% over Energy Star 3.0.

So the best thing you can do and spend your money on:
air seal first. do the reading and research on air sealing. Green Building Advisor is a great website to start with.
Next focus on insulating and thermal breaks. 2" of exterior foam, tyvek house wrap, sheathing, 2x6 framing (go 24" oc if you want to reduce some costs, increase insulation value and reduce thermal bridging), blown fiberglass or cellulose insulation, no vapor barrier, then air tight drywall. Spring for triple pane windows if you can, if not focus on good dual pane windows. Shoot for R60 in the attic space after air sealing the ceiling plane. The upgrade from r49 to 60 is typically minimal. This will give you a high performing, low cost to condition home for life. You can also save some costs on your hvac since you should be able to slightly decrease the size of the equipment needed for your home.
Example, the generic, poorly designed "rule of thumb" hvac contractors will do is anywhere from 500-1000 sqft per ton of heating needed. On my home that would place me at a 4 ton unit. I only have a 2 ton unit and it runs on low speed most of the time.

good luck with your home!

We are doing blown-in cellulose and a 1.5 inch foam "wrap" around the sheathing and we are in a much milder climate than yours. Will still focus on the air sealing as well, though.

Have you already started the build? If not have you looked into an ICF house?

I'm in Iowa. I did ICF for my basement, which has a walkout).

If I could do it all over again, I would have done the entire house in ICF.

Lawpaw-Glad you like the ICF. We are looking at doing it for our basement. Is it really that incredible?

we used full ICF as well, but its a higher r form (r30 average), also live in Iowa. Doing it over, would I use it again? Not real sure. Its high performance for sure, but Next time I would probably go ICF foundation and double stud r40 wall above. However for sound, strength, and air tightness, its a perfect way to go. Certainly would go ICF over any standard framing method, even rigid exterior foam on 2x6 framing.

Offset double 2x4 framing offers better R value with less expense than any other type of home construction method. It gives you a greater thermal break, and you can use standard inexpensive insulation, like a spray in cellulose. For anyone in a cold climate, that should be the first thing they should be researching. It provides lower cost and quicker payback than ICF ever does. ICF isn't cheap. Spray foam isn't cheap. Lumber and cellulose IS cheap. And very very effective.

I had thought about ICFs (my late father was a concrete and excavating contractor so I'm partial to poured concrete), but I was thinking it would be out of my budget. Did you have a plan that you had converted to ICFS, or did you have an ICF plan drawn up?

I really do like my plan, so how would I go about finding out if it would work for ICFs? The builder is drawing up the modified prints now, so if I want to go this route I should decide soon.

spray foam is awesome just remember that closed cell spray foam is about 2x the cost of open cell. I've seen houses that do closed cell in the attic to make the roof more rigid but open cell everywhere else.

we used full ICF as well, but its a higher r form (r30 average), also live in Iowa. Doing it over, would I use it again? Not real sure. Its high performance for sure, but Next time I would probably go ICF foundation and double stud r40 wall above. However for sound, strength, and air tightness, its a perfect way to go. Certainly would go ICF over any standard framing method, even rigid exterior foam on 2x6 framing.

Katmu
there is no reason at all your plan would not work with ICF without any modifications. Obviously the wall thickness would need adjusted and could throw off your interior space sizes unless you increase the footprint slightly. typically 2 story homes have to be more thought out so things can stack to avoid steel, but a range is no problem.
For budgeting to compare to stick frame homes however, assume $11-12 sqft of wall surface to build an ICF shell, and $6-8 for a 2x6 shell with exterior foam.

Do keep in mind the ceiling and attic. Its needs to have the same air sealing as your walls. Easy way to do this is with an attic seal of spray foam. Basically after the ceiling drywall is installed, they simple spray the top plates, plumbing, electrical and mechanical penetrations through the drywall with 1-3" of foam to fill any cracks of voids creating and air tight ceiling plane. then blow in r60 of loose fill of your choice on top of that. I would also recommend foaming the attic baffles to the deck as well to prevent wind washing through the thick insulation. Obviously attic trusses with energy heals (12" min) should be used.

We recently built a house in MN. I spent a lot of time reading about different approaches to sealing and insulating houses. I would have loved to go with the 10-20-40-60 rule, however that wasn't realistic for us due to budget. We ended up with more of a 10-10-21-50 with close attention to air sealing (I know that the walls aren't actually R-21, but that's the stuff we put in there). There is spray foam in certain areas, but otherwise it is rigid foam under/in the basement, batts in the walls, and blown-in fiberglass in the attic.

If I had the extra money, the first thing I would have done was put rigid foam around exterior of the house (under the siding). But unfortunately we had to draw the line somewhere...we didn't go bare bones nor extravagant in any area of the house, just tried to make sure it had "good bones" as people say.

I'd also try to identify the point of diminishing returns...insulation is a good investment, but at some point it's going to be more money than it's worth.

Oh and if you're putting insulation under the basement slab, go buy some pex and rough in radiant heating before they pour the slab :)

Just my .02 cents, good luck!

MNTwins,

What kind of batts did you use in the walls? (R and kind of insulation).

Did anyone use Roxul rather than fiberglass batts?

Thanks,

Carol

OntarioMom -

They were R-21 high density batts...I forget the brand off the top of my head.

this is what is spec'd in our contract:
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we are in michigan.

spray foam should not be used for ductwork.
not a continous depth of foam, not approved
duct sealant or insulation type.

Thanks MNtwins and illnigirl for the insulation info. MNT were you batts pink, green or another colour? That will give me info on the kind.

Carol

OntarioMom -

The batts were yellow and unfaced...I want to say they were Certainteed.

At a minimum, spray foam the rim joists, if budget and/or lack of contractor's experience make better options unavailable.

I sprayfoamed the rim joists (headers) on both floors, in addition to the underside of my balcony which rests over living, heated space. I'm up in North Dakota, so similar weather to you.

It was pretty expensive, so I opted to do Roxul for the remainder. I heard that loose can settle over time, which was a concern on my vaulted ceilings. So I chose Roxul batts everywhere, doubling or tripling them to achieve over R40. My walls are all 2x6 and R24. Roxul product is really nice because unlike fiberglass the squirrels and creatures don't like living in it (problem around here).

Really, the insulation ISN'T what's going to make your house tight. It's the vapour-barrier. My Building Inspector said that as soon as you cut close-cell spray foam, it's no longer closed cell and therefore no longer a vapour barrier. And my spray foamers cut LOTS when they trimmed back the over spray (okay for an attic but doesn't work where you're drywalling).

My place is SO tight that opening a door causes some windows to flex. Yeah. Because every gap and crack is accoustically sealed, vapour barrier is overlapped by 2-stud lengths (and then caulked AND taped), all seams are taped, caulked, openings, like crazy. $400 in caulk and tape alone. But it's tight. And it's warm to be honest. My spray-foamer was still only getting something like R22 in between 2x6 studs so I don't know if I see how you're getting extra insulation by sprayfoaming. It just makes it a hell of a lot easier to get it sealed up and means you're not covered in gooey black tar for weeks on end (ugh).

Awn- I assume you have an HRV? Also did you conduct a blower door test on your home?

btw the information your inspector has on spray foam is incorrect. The thickness of foam determines the permeability of expanding foams (open or closed) and thus would qualify it as an air barrier or vapor barrier (closed cell only) Also its not the vapor barrier that makes a home tight, its the air barrier. Your vapor barrier is critical to detail correctly so you can force drying of your wall depending on your condensing location. Because every 16" you have thermal bridging, you still have condensing within your wall cavity when the vapor drive is to the inside. You want vapor to pass through sometime and dry, not stop it. You want to stop air. This is why building codes are now moving away from sealed plastic interior vapor barriers since the possibly of trapping moisture is higher. An accidental nail hole in the plastic can let a lot of moisture through and get trapped in the plastic. Luckily your Roxul doesn't like to be eaten by mold, so you should be ok. This is why building science is pushing for homes in heating climates to detail the wall assembly to have the condensing plane outside of the wall cavity (through the use of exterior foam sheathing for an example).