Hello, I'm wanting to build a super insulated ranch house with an attached garage and walk out basement. It will have a 2400 sq' basement and main floor and 1200 sq' in the garage, 6000 total. I'm going to try and include my floor plan but I'm not very computer savvy. It will be in central wv (zone 6 I believe) on a hill with good southern exposure and the hill rises behind to block some of the north wind. I'm figuring on a poured basement with rigid foam inside and out glued on after curing. Then 2x4 framing and spray foam. The main floor will be 2x6 framing spray foamed inside with rigid foam outside. I'm going to use an outdoor wood boiler that also burns natural gas because I have more wood than I'll ever be able to burn and free gas off of an oil well on the property. I'll have radiant heat in the garage and basement slabs and under the main floor.  Now the start of my million questions. Is spray foam and rigid a good idea (basement and main/garage) or should I use something different inside?  What kind of waterproofing should I use on the 3 sides of the basement that are buried? With radiant heat in the floors and central air what's my best option for another heat source, radiators or forced air? If I glue foam outside how do I attach stone to the exposed parts of the foundation? Is the glued foam even a good idea? Where should I put the house wrap inside or outside the rigid foam? There will be attic storage over part of the house, should the attic be spray foamed too? How much foam should go under the slabs? I'm going to stop here for now. Thanks in advance for the expertise. I've got another year before I'm going to build, so I'll be spending a lot of time studying and asking questions here. Any advice or questions about this will be welcome and appreciated. Thanks again and merry christmas.

It's great you're studying up- a year will go by quicker than you think!

Have you looked into ICF, at least for the basement? It's essentially the same as you're doing, but all in one process, and the foam is better integrated and attached. Also, you then have fastening strips embedded in your walls for fastening exterior and interior wall finishes. There would be no need for the 2X4 studs and additional insulation, as the ICF is around R-25. I did my own ICF, then paid an experienced crew to pour the concrete.

For the main floor, spray foam gets pretty expensive. It's more effective to 'flash' with foam to seal the structure, and then fill the stud bays with cellulose or the like. Rigid foam on the outside is great for a thermal break over the studs.

As for waterproofing the basement, I used peel and stick membrane over the ICF, then dimpleboard, which protects the underlayment and creates a drainage plane so water doesn't sit against the wall. You need a perimeter drain system at the bottom of the hole to carry water away, and then backfill with gravel to promote drainage. This gets topped with geotextile fabric to keep the topsoil from plugging up the gravel. Attention needs to be paid to grading the ground away from the house to carry surface water away. Lastly, gutters are a good idea to handle all of the bulk water from your roof rather than allowing it to dump right against your basement walls.

As for attic storage, bear in mind that you're going to want a lot of insulation up there- 12" or more. Again, a foam flash is a good way to seal the attic, followed by lots of cellulose blown in. That doesn't make for a good storage place, though, unless you build a second floor over the insulation.

I have looked at icf and at one point was going to use them from the slab to the roof. I talked to a concrete contractor at a home show who said I could pour the walls, glue on foam and frame cheaper. I haven't crunched the numbers but it would be easier to wire and offer more insulation. I'm shooting for r-40 walls. I really like the icfs, the idea of concrete walls really seems good to me, but with 6000 sq' I've got to pay attention to costs. I'm going to use attic trusses with an open area through the middle, I think if I seal it tight I can treat the rest of the space like a regular attic and just put thick cellulose on the floor right. Or should the roof be insulated too? Thank you again for taking interest and talking with me, I greatly appreciate it.

You might look at a poured concrete wall and then an offset stud wall inside of that with the gap filled with cellulose - no foam needed.

Most of WV is in US climate zones 4 or 5- you might have a zone-6 climate if you lived literally on the highest mountaintop in the county though.

Rigid foam is fine for the basement & garage if you're selective about the type.  Polyisocyanurate (iso)  can be used on the interior, but rigid foam in contact with the ground shoule be an expanded or extruded polystyrene (EPS or XPS).  EPS and iso are 100x  "greener" than XPS, since they're blown with relatively benign pentane rather than HFC134a (which has ~1400x the greenhouse gas potency of CO2.)  There are similar issues with most (but not all) closed cell spray polyurethanes, which are most commonly blown with HFC245fa (with ~1000x the greenhouse potency of CO2.)  Open cell foams do not have that issue.

Gluing foam to the exterior of a poured wall is rarely (if ever) done. It's easier and more reliable to use ICF (most of which are made with Type-II EPS)  In a zone-5 climate even a minimalist R20 ICF (2.5" EPS interior, 2.5" EPS exterior) is good enough for a "pretty good house" unless you're looking at Net Zero Energy or PassiveHouse type energy use levels. If you want to finish it out with an interior studwall you can add some cheap R with unfaced batts if you like, but that would only make sense on the foundation walls that are more than half above-grade (common, in walk-out basements.)  An R20 ICF with a batt-insulated 2x4 wall runs about R30 whole-wall, after factoring in the thermal bridging of the studwall framing.

In climate zone 5 with radiant slabs you'd be looking at ~R15 under the slab (3.5-4" of Type-II or Type IX EPS, or 3" of XPS.)  For slabs that aren't being used as heat emitters half-that is enough to keep the floor comfortable and at low-risk of condensation/mold on any finish floor you might add. (2" of EPS, or 1.5" of XPS.)

Spray foam is ideal for air-sealing foundation sills and band joists to the interior side foundation insulation, but unless there is exterior foam sheathing on the band joist as a thermal break it needs to be closed cell, not open cell.  It only takes an inch of closed cell foam (R6)  to air seal, but 2" is better from an insulating point of view.  It's also OK to cut'n'cobble rigid foam in there and use closed cell foam only to seal the edges, but it becomes labor intensive- it's often cheaper to hit it with 2" of cc foam and call it a day.

With ICF construction and a studwall with insulating sheathing over the structural sheathing above it's pretty easy to align the studwall's foam with that of the exterior EPS of the ICF to get a good thermal break over the band joist & foundation sill, in which case it's fine to go ahead with open cell foam rather than closed cell foam as the air seal, and to fatten out the R on the interior side to about the same as your above-grade walls.  Closed cell foam runs about 17-19 cents per square foot per R, whereas open cell runs 10-12cents. Unless you NEED the vapor retardency of the closed cell foam for dew point control (which you won't, if you have a couple inches of foam on the exterior of the band joist), open cell foam is a much better deal, and gives the wood much better drying capacity toward the interior.  A 2x6 studwall with o.c. foam in the stud bays comes in at ~R13-R14 after thermal bridging, but if you add 2.5" of polyiso on the exterior (to align with the ICF's outer foam) it fattens the wall-R up to about R28. If you use 3" iso (to be a bit proud of the ICF's foam) you'd be at R31-R32.  In your climate zone as long as you have at least 2" of insulating foam (any type) outside the structural sheathing on 2x6 framing, you won't need (and shouldn't use) any type of interior-side vapor retarder- latex paint on wallboard would provide adequate vapor retardency to keep the sheathing from loading up with moisture from vapor diffusion But if you use cellulose or fiberglass rather than open cell foam it becomes somewhat important to air-seal the wallboard carefully, since air-transported moisture can run an order of magnitude higher than vapor diffusion when the cavity-fill is as air-permeable as fiber insulation.

The window mounting relative to the sheathing determines where the housewrap goes outside the foam or whether it's place between the foam and structural sheathing.   If the window is set in roughly co-planar with the structural sheathing that's where it's flashing will be, and that's where the housewrap needs to be to form a continuous drain plane. (Don't forget to Z-flash the bottom where the foam hits the ICF's foam though- you don't want your drain-plane to terminate on the concrete at the foundation sill or it'll rot- it needs to be directed toward the exterior.) If the windows are going to be set roughly co-planar with the exterior foam the housewrap and flashing go outside the foam (the no Z-flashing is required at the bottom.) There are many good tips on how to install exterior rigid foam on this blog page, and it's associated links.

Designing your roof trusses with "energy heels", to accommodate up to 20# of insulation would allow you to hit the R60+ range pretty cheaply using blown cellulose, at a fraction of the cost of foam.  Be sure to space the trusses closely enough for the gypsum to handle the dead-weight load of the cellulose, or use 1x strapping screwed or ring-shanked nails to the truss chords at a sufficiently narrow spacing.  Be sure the truss chords are designed for that much dead-loading too.  With cellulose you'd be looking at about 2.2-2.5 lbs per square foot @ R65.  Cellulose will outperform fiberglass blowing wools in attic applications, and has a more stable R value over temperature than polyurethane foam- it's really the right material for the application.

Wood boilers present something of an air-pollution problem that you need to consider if you're building in a sheltered hollow.  They burn cleanly and efficiently when the draft is fully open, but most are controlled with a hard-stop when the thermal storage tanks' aquastat (or the house's thermostat) is satisfied, leading to 10s of minutes of VERY heavy smoke as the flame dies back and the firebox cools.  I'm not sure if any US manufacturers have fully addressed that issue yet.

In a high-R/low loss building in climate zones 4/5, if your central air is a high-efficiency heat pump rather than cooling-only it would deliver pretty good peformance & efficiency down to about +15F.  With ductless air source heat pumps you can do OK down to about +5F before total heat output and efficiency start sliding off a cliff. The Mitsubishi H2i series still has reasonable output capacity at -13F, but it's efficiency is pretty abyssmal at sub-zero temps. But at your average winter temps it's not so bad. With ducted air source heat pumps the seasonal average coefficient of performance (COP) will run about 1.8-2.2, but with ductless you'd be knocking on 3 (or maybe a hair over) in a WV climate. But it's hard to do 6000 square feet with ductless systems unless the floor plans are fairly wide-open and the heat loads are low. The peak heating loads will depend heavily on window sizing & performance if you're going with ~R30 walls and ~R60 attic, R20 foundation wall, R15 slab. 

BTW: To hit R40 walls would take ~5" of iso sheathing on a 2x4 16" o.c. framed studwall, or 4.5" of iso on a 2x6 24" o.c. studwall. It's still below the ~6" threshold at which exterior foam begins to get awkward, with VERY long timber screws on the furring that holds the foam to the studs. Since the windows tend to dominate the wall-losses at anything over R20, it may be more cost-effective and easier to build R30-ish walls and go with higher performance windows. But run the numbers a couple of different ways.

Also, there are several dealers who trade in reclaimed roofing foam, one of which does business nation-wide, and has a distribution center in WV: Insulationdepot.com They won't ship in small quantities, but they'll sell small quantities if you bring your own truck. They usually have quite a selection of EPS and you may have to wait for iso. With roofing iso 2", 2.5", 3", and 3.25" are fairly common thicknesses. With EPS it's usually on 1-inch boundaries. But it takes about 50% more thickness to hit the same R with EPS than it does with iso. (R4/inch rather than R6/inch.) Reclaimed goods tend to run 25-35% the cost of virgin stock, and in a project of any size that adds up to a significant cost savings. (It's cheaper per unit R than virgin stock mid-density fiberglass batts.)

Some people have put EPS in the concrete forms - ie, a poured wall with no need to attach the foam.

Wow this is exactly what I need. Thank you for the great information. So an R30 wall is going to be more practical and match up with an icf wall. If I spray 2" of foam do I fill the rest of the cavity with unfaced batts? The house is going to be about 60 vertical feet from the top of the hill so I don't think I'll have a problem with the boiler smoke. The attic trusses I saw looked like a standard truss with an open box in the middle I guess I could pile the cellulose around and on top then maybe batts on the sides. It's just going to be extra storage so it really doesn't need much I just want to keep the heat in the house. So there isn't much difference between 2x4 & 2x6 wall R value? I'm wanting to use cement siding, with the extra weight how well can it be attached to the house? I have looked at the insulation depot and I'm figuring on making a couple trips up there for truck an trailer loads. Where is the best place for the windows to sit, toward the outside or inside or centered? I can also see I need to study a lot more on the technical (numbers) side of insulation and heating & cooling. My experience is just doing my own remodeling and helping friends and family on small projects. But I want to make a really solid and comfortable house to raise my family and live in till I die. I'm going to have to do a lot of the work myself to be able to afford it so I'll be asking a lot of you all. I'm still trying to get my floor plans on here to give you a better idea of what I'm wanting. If I can't get it today I'll have the wife do it tonight. Thanks again everyone, please keep it coming.

If you spray 2" of closed cell foam in a 2x6 studwall cavity DO fill the rest with batts (or blown).  Without insulation in the wall cavity you would have R2 thermal bridging on the framing, since the sides of the uninsulated part of the studs would be at room temp.  With 2" of closed cell foam you have the nominal amount of space for batts designed for 2x4 framing.  Long vertical voids in a wall cavity are just flues helping flames to spread- even if fire-blocked it's worth filling them (cellulose or rock wool is preferred, but R13 or R15 fiberglass works too.)

But with exterior foam protecting the sheathing from wintertime moisture accumulation you can just fill the cavity completely with 5.5" open cell foam for about the same cost as 2" of closed cell foam, and the sheathing would have better drying capacity (recommended).  You'd only need to use closed cell if you didn't have enough insulation outside the sheathing. At 2.5-3" you'll have huge margin on the interior dew point, but you'd also be reducing the ability to dry toward the exterior.  Open cell foam or fiber are better options than closed cell foam for the cavity fill in this stackup.

If the roof insulation is on the attic floor rather than the roof deck it has to extend at full depth all the way out over the top-plates of the studwall (and exterior foam, if possible) to get the full value out of it.  With a vented attic design you'd have to use chutes to maintain clearance 2" from the roof deck for ventilation air.  Google up some images of "energy heel truss"- you'll see how they make high-R possible.  It's possible to go unvented using insulation above the roof deck, but it's both more expensive and more important to go high-R if you do (the ice-damming potential goes up if you don't take it to at least R60 if unvented.)

Fiber cement siding mounted to 1x furring on the exterior foam works, but you may need to use ring-shank nails or screws (and pay attention to the metal alloy types allowed with fiber cement.)  The furring  is held to the studs with pancake head timber screws (eg. FastenMaster HeadLok)  24" o.c., and need to bite into at least 1.5"  of sheating + stud.  At 2.5-3" of foam you don't have to go any tighter than 24" on the timber screws for fiber cement.  At 6" of foam you's have to tighten it up a bit. See: http://www.greenbuildingadvisor.com...athed-wall

A typical 2x4 wall with fiber or open cell foam cell cavity fill comes in around R9.5-R10 after thermal bridging.  A typical 2x6 with fiber or open cell foam comes in around R13-R14.  The difference is about R3-R4, which is a ~35% uptick in thermal performance by going with 2x6 rather than 2x4.

The windows should be EITHER at the outside of the foam sheathing, OR at the structural sheathing, but definitely NOT somewhere in between, or you'll have issues getting the flashing aligned with the housewrap/drain-plane.  It's primarily an aesthetic decision, not a functional one.

Read all of the hyperlinked pages in that "how to" blog, and keep referring back to it. There are many details to figure out ahead of time to get it right, but they pretty much walk you through it.

Insulation Depot has a warehouse in Williamsport Md. While they advertise trailerload, they'll sell less if you pick it up. Look on Craigslist as well. I found a source near Pittsburgh selling 2x8x2" XPS for $5 ea. We hired a terrific stucco guy from Charles Town WV. Dunno if you are interested.

Typical new construction in my area uses poured wall with exterior foam. The reason for this is unless you are finishing your basement prior to occupancy, raw foam is not allowed exposed in the basement unless you use Dow's Thermax foam. This will be the case with ICF as well.

Most builders don't go the Thermax route since a 1" 4x8 sheet is between $29-$37 here.

It is a real confusing & difficult area. Exterior foam is subject to insect infestation, and other problems over time. I've seen many many houses which were insulated on the exterior years ago and have seen very few where the coating is still viable, so given a 100-200 year house lifetime, It's apparent that it (exterior foam) generally won't last anywhere near that long.

Interior insulation has its own issues as you have mentioned but builders concerned about a long term solution need to put costs in perspective and do the right thing.

I recently saw a house built about 30 years ago, excellent construction except that the builder made some very rosy assumptions about exterior foam, resulting in damages that could run into tens of thousands to repair.

It's apparent that it (exterior foam) generally won't last

I don't think that is the case, as long as it is covered. But perhaps you have more than just vague details.

Sure, a covering works - for a while. All I said is that over time, most of the coverings I have seen have failed, either by insect infestation, or the stucco wearing off. I've also seen galvanized steel, which of course will rust over time. It is an area that almost no one maintains, and is often hidden by plants, so to do something in that location that will need maintenance is unrealistic IMO. What do you cover it with that will last?

If I"m going to use a product like rub-r-wall to water proof the foundation could it be sprayed over the rigid foam also? It should stop bugs and make a good air and water seal for the whole house.

Also what about using two layers of foam with all the joints taped and offset from one layer to the next?

I would like to post a reply and request some addition info from Dana if I may.

I am building a rather large 2 story over a walk out basement and just finished placing 3" XPS in 2x8 sheets with a half sheet at across the top of our 9 FT poured walls. I am in the process now of decidin how to best cover the top few inches so it will not get ruined by the sun.

My question is more along the lines of our above grade foam. I aquired some 1.5 inch Poly ISO for a great price and my plan is to use that over the sheathing with 1x4 furring strips for the vinyl siding. My question is how do I set the floor joists back to ensure that JUST THE SIDING is proud to the basement foam? I want to use painted metal for my protective layer over the basement foam and I will use a drip edge under the vinyl to direct water away from the basement foam as well. Also, do I have enough exterior foam over my sheathing or do I need more? We are literally on the line of the top of climate zone 4 and bottom of 5 where the house is located. My plan is to insulate for climate zone 5 since we are on the line.

The issue I have with exterior metal as a covering for exterior foundation foam as opposed to stucco, is that metal will corrode over time. In thirty years most metal (at least what I have seen) will no longer keep out insects/termites/rodents. If anyone knows of a long lasting (100 yrs) metal that will not corrode underground, let me know.

Bob has a point- either a polymer or cementicious EIFS type finish is the better way to deal with it- something moisture tolerant over the long term.

At 3" of XPS sheathing on a poured concrete wall you meet the IRC 2012 code minimum R for basement walls in zone 5:

http://publicecodes.cyberregs.com/icod/irc/2012/icod_irc_2012_11_sec002.htm

With 1.5" of polyiso (even if derated to R5/inch for a cold climate sheathing application) you're good for dew point control on 2x6/R20 stud framing in zone 5:

http://publicecodes.cyberregs.com/icod/irc/2012/icod_irc_2012_7_sec002_par025.htm

It's perfectly acceptable to cantilever 2x6 sill plates up to 2" off the foundation edge, but you won't be needing to go that far. With half-inch wall sheathing and 1.5" of foam you would only have to hang it off 1" for the polyiso to be co-planar with the basement foam. If you want the 1x furring to be roughly co-planar with the foundation foam you only have to hang it 1/4" out. But you would then have to use some Z-flashing and lap the housewrap carefully to keep the drain-plane continuous, but that's fine.

As always thanks Bob and DANA for your insight.

Question: So hanging the sill plate 1" off the wall would allow for the foams to be even and the furring and siding to be PROUD to the foam. I like the sound of that and I assume I can just utilize the screen that I see folks using to allow airflow up underneath the siding but no bugs or animals. However, is there some concern with the non pressure treated lumber for the furring strips being exposed to that much airflow since they will be proud to the foam? I was thinking the best case scenario would be for JUST the siding to be proud so there was not even the smallest gap for air infiltration? Which is best??