Located in Tennessee about 1.5 hours NE of Chattanooga. The plan is 2020 square feet with an additional 250 square foot bonus room over the garage. About 20 windows and two exterior doors plus the garage door entry. Two porches, one on the south side and one on the north side over looking the creek. 2x6 walls with 2 x 8"  white pine log sidding. There is a crawl space and the roof pitch is 10/12. I need help trying to decide on the best bang for the buck for insulation and windows.

1) if I glue and caulk all studs and osb etc. will it be as air tight as foam or so close I will not notice the difference?

2) If I use foam where and how should I use it to get the most bang for the buck?

3) How can I avoid moisture issues?

4) Could I use radiant barrier osb on the roof if there was a airspace between the aluminum side and where the spray faom started? the air space would run from the eves to the ridge vent. I could use carboard or xps to form the airway that the foam could be applied to. Would that help or just cost more for not much gain?

5) Where can I get an afordable R3 window that will qualify for the tax credit?

Thanks for your help

Wendt,
I am surprised no one has answered your insulation questions yet.
My suggestions will, of course, be biased. But I have done this, with success, on numerous projects.
First, find a qualified open cell spray foam insulation contractor (Icynene, etc.)
Have this product applied to interior of foundation walls and sill and band board areaa, all exterior walls, and underside of roof deck. This creates a sealed foundation and attic areas that are good for our climate. The only vapor barrier you will want to use in on the floor of your crawl space, no walls, no attic area vapor barriers.
Your wood siding definitely needs a drainage plane between logs and house wrap over your sheathing. Preferrably 2x furring strips for that heavy wood, a minimum of 1x furring.
If you are planning on metal roofing, which I would recommend with the log siding, then look at one of the vented underlayments not available.
As to windows, the magic numbers for the rebate program are U value and SHGC value both less than .30.
You should be able to find a cheap vinyl window that meets these numbers for about $200 each. However, these are not the only things you should look for in a good window.
Hope this helps a little.

How thick should the faom be in crawlspace, walls and roof?
about the unvented basement: One person reported that he built a sealed crawlspace, but while he was still building the rest of the house the crawlspace developed mold because of no ventelation. This makes me wonder if there was no electricity which house would develop mold faster a) a traditional 2x6 house with regular insulation and a vented crawl space and attic or b) a totally sealed foam house?

As to the amount of foam.
In the crawlspace, about 2" on the inside of the foundation, stop the foam an inch or so above the crawlspace floor (this gives the termite inspector a place to look during his inspections, otherwise they will want to tear it all down), fill the rimboard/sill plate areas.
For 2x6 walls, fill them up.
In the attic, 6+ ", enough to completely cover the top chords of your trusses, and acheive your required R value.
As to the mold in the sealed crawlspace, the only time I have seen this problem occur, there was no draintile installed in the crawlspace, the outside grading had not been completed, and the house was located on a low spot of the lot, so tons of water was beening introduced into the crawlspace, with no drainage available. When the grading was completed, and draintile installed, the moisture problems and the mold went away. (And no, I did not build the project).

In most of the southeastern US, crawlspace ventilation is more likely to be the CAUSE of crawlspace mold rather than the cure. But for both humidity & radon reasons it's generally a good idea to put down a 10mil vapor retarder on the floor of an unvented crawlspace sealed to the foundation with your foam, and leave the termite-inspection gap at the top of the concrete just below the foundation sill rather than slightly above the floor. Any seams between sheets of poly need to be overlapped by a foot or so, and sealed with duct mastic.

I've also read that using copper flashing as the capillary break between the foundation and the sill would serves as termite inhibitor, if the flashing is slightly proud of the conctrete and folded over with at least 1/2" of vertical exposure. A metal capillary break is at least 10x as effective at stopping water migrating up from the foundation as most foam sill-gaskets (which are rarely good enough stop the air-leak anyway- use ample caulk when you put the sills, and seal that interface when you spray-foam insulate the band joist (to ~R10-R12, which is ~ 1.5-2" of closed cell SPF, or 3-4" of Icynene.)

To seal the seams on the OSB, paint the seams 2" on both sides of the separation with a decent latex primer and tape them with a suitable material like FSK tap or Huber Zip stuff. (Huber sheathing comes pre-primed to help the tape stick.) Wet-spray cellulose wicks moisture away from the wood, and it's borate fire-retardents are toxic to ants & termites, whereas insects can and do tunnel through half-pound density SPF such as Icynene pretty readily.

A 1" flash of closed cell foam on the interior of the sheathing, then filling the rest of the cavities with wet-blown cellulose will give you a higher-R and as least as-good (or better) air-seal as doing the whole shebang with half-pound foam.

Using half pound foam as attic insulation gives you a decent amount of R per lb, but 6" wouldn't even get you to code minimum (you'd need 9" to hit R30) which gets kind of expensive. Rather than a standard soffit & ridge venting scheme, you may want to price out using ventilated insulating-panel iso or EPS products that can put between R8-R25 or so ABOVE the roof deck, and air-seal it with 2-6" of icynene on the interior. (Hunter Panels, Atlas and a few other rigid-board iso manufacturers make both vented & unvented 4'x8' panels with OSB nailer-decks pre-built at the factory. Follow the manufacturers fastener spacing & depth recommendations.) That way the structural roofing & trusses/rafters are well inside the thermal boundary of the structure, where they'll run warmer in winter, with less risk of structural rot or mold. With a large fraction of the insulation on the outside of the trusses/rafter it forms a thermal break over those low-R elements, and it will outperform an all-interior insulation job. R30 might be code-minimum in your neighborhood, but R40+ is usually still cost effective if you're heating with electricity or propane, depending on the cost of that R. And R30 achieved with R20 iso or EPS panell on the exterior + 3" of Icynene under the roof deck will measurably outperform 9" of interior Icynene due to the thermal-breaks over the rafters.

A ventilated R20 iso panel for steep roofs like yours is ~5" thick, unventilated R20 nailer deck panels run ~ 3.5" thick. In EPS, add about an inch. (lower pitched roofs require deepr air-spacing for ventilation.) Doing the extra R20 in a 4x8 section with Icynene would run ~$80-ish installed, so you might do the cost-compare when looking at panelized products, then add the labor of screwing the panels to the roof deck for apples-to-pears, but if it's a simple enough roof design (with a limited number of dormers & valleys) going with panelized goods is often cost-competitive. If you compare the cost of the ventilated-panel systems to building your own ventilation spacing and spraying SPF from the interior it's usually cost-competitive go with the system-goods. Going with a thinner nail-base panel, and staggering seams with an underlayment of thicker non-nail-base goods can also work, and will form a better air barriers. (R20 x 4x8' without nailer deck runs ~$55/sheet in iso, less but thicker in EPS.) On a steep pitched roof like yours it may be possible go with non-vented versions (which are cheaper still), or build your own gap with exterior furring & 7/16" OSB after the panelized goods are down, seams sealed with mastic.

See: http://cambridgebuildersinc.com/ice-dam-management/cold-roof-systems/hunter-panels/

http://www.atlasroofing.com/tabbed.php?section_url=51

http://www.atlasroofing.com/tabbed.php?section_url=58

http://www.achfoam.com/NailbaseRoofInsulation.aspx

http://www.teamindustries.com/downloads/brochure/Foam-Control-Nailbase.pdf

You might find this article on air-sealing sheathing & roof decks useful (especially the bit about the roof overhangs!:

http://www.greenbuildingadvisor.com/blogs/dept/musings/airtight-wall-and-roof-sheathing

A few things...

1.) Never apply open cell foam insulation below grade.  The lowest point on a residential project that open cell foam insulation should ever reach is the basement/crawl space rim joist.  Theoretically, you could apply open cell foam insulation to an interior basement wall for sound deadening, but I think you would be taking on a potential problem. 

I am not saying that closed cell is better than open cell.  What I am saying is that every building product has its place in design - open cell should not be applied below grade.

2.) What open cell product needs to be installed at 9" to reach R-30?  Try demilec Agribalance, R-31 @ 7.0"  and its very affordable.

3.)  Per ICC code you cannot apply an air impermeable insulation medium on roof deck sheathing at a depth lower than 3".  Flash and batt is a very concerning application approach that should be scrutinized over more closely in climate zone above 5.   Many building scientists cannot say with any certainty how these wall and attic flash & batt systems will affect sheathing and framing over the long term.  I would stay away.

Posted By Johnny Boy on 09 Jun 2010 02:16 PM
Never apply open cell foam insulation below grade.  The lowest point on a residential project that open cell foam insulation should ever reach is the basement/crawl space rim joist.  Theoretically, you could apply open cell foam insulation to an interior basement wall for sound deadening, but I think you would be taking on a potential problem. 

I am not saying that closed cell is better than open cell.  What I am saying is that every building product has its place in design - open cell should not be applied below grade.

Also - what open cell product needs to be installed at 9" to reach R-30?  Try demilec Agribalance, R-31 @ 7.0"  and its very affordable.

Actually, the rim joist & sill needs to be insulated with closed-cell, not open cell in places as cold as NH.

But you're at odds with the science about open cell below-grade- it NEEDS to be vapor permeable, which becomes an issue with higher-R using closed cell goods.

By keeping the sub-grade portion of the insulation vapor permeable it allows the foundation to dry toward the interior, reducing the capillary drive upward to rot out the sill, or to create efflorescence & spalling issues on the exterior of the above-grade portion.  With 2lb closed cell on foundation walls you're limited to ~ R12 before it becomes too vapor-impermeable.  With 1.5lb foam that doesn't happen until ~ R18. But with half-pound open cell (and probably with 0.7lb Demilec) you can hit R35 before it's low enough perm to create a problem.

See this. (Read the section titled "Walls".) There are numerous existence proofs of 2lb foam retrofits on foundation walls creating sill rot & concrete spalling issues in New England.

Open cell foam has pretty crappy acoustic attenuation properties too- indeed, even low density blown fiberglass will beat it by a dB or 3 in most assemblies.

But if you go ahead and use EPS concrete forms you can put unfaced batts or open cell on the interior to bring the R-value up, if you like.  Usually it'll be cheaper to just spec an insulated concrete form that's already at the design spec.

ICC prescription notwithstanding, or moisture performance of variable stackups/types of unvented roof deck with with interior-only insulation download this:

http://www.buildingscience.com/documents/reports/RR-1001_Moisture_Safe_Unvented_Roofs.pdf/view?searchterm=rr-1001

Any time you can put some or all of the R on the exterior the warmer & drier the roof deck (or wall sheathing) will be, and the lower the risk of moisture buildup is.

A flash & batt or flash & spray-fiber wall is not just a vertically sloped roof- the ICC prescription for roof decks is moot. Walls will never be covered with snow for weeks/months on end, crippling it's capacity to dry toward the exterior for those periods. The concern that an inch or less of closed cell as an air-barrier would cause a problem down the line seems unfounded. What would be the mechanism by which it creates a problem? Building in a rainscreen gap of at least 3/8" between the siding an drain-plane layer also enhanced drying toward the exterior, and reduces direct wetting of the assembly from wind-driven rain or the high vapor drives of sun on dew or rain-wetted siding. (IMHO rainscreen gaps should be a code requirement in places that see more than 15-20"/year of precipitation. In Canada it's required everywhere.)

...

OK.  I really don't want to argue about this.  You have your thoughts and I have mine.  You have your experiences and I have " ".  You have documented references of failures concerning my application approach and I have..... well, you get the idea.

ALL, sill's and rim joists should be sitting on foundation wall gasket to prevent capillary suction of moisture to the sill which prevents the occurence your talking about.  BTW - I have never heard of sill rot occuring as a result of using CC.  People have been coating interior foundation walls with water proof/vapor barrier paint for decades.  I never heard about any problems from that either.

While all polyurethane is hygrophobic (seeks to get rid of moisture), open cell will take on moisture and hold on to it, if not given an opp. to dry.  Apply drywall, primer and a few coatings of latex paint and taa dahh - you have a vapor retarder and a potential condensing point.  Hence - don't apply OC below grade unless you want rotted out studs... My $0.02.

You people need to get your heads out of the books, get into the field and get your hands dirty.  All your modeling software  cannot account for first hand experience.  I have a deep appreciation for wall and roofing theory; however, so much of the lectures and the reports and the studies have hundreds of variables that make silver bullet conclusions of design impossible to make.  Try to get a firm answer on vapor retarder usage in climate zone 5 from any of the PHD's at BSC and they will have you chasing your tail around.

I hate to say it, but, no one has the answers.  ITS ALL THEORY.  The physics involved with moisture movement and the principles of thermal energy movement are easy to understand - the problem is when you apply these principles in a lab: 1 +1 = 2, in the field, 1 + 1 = ?.  Every house, property, building is different and is presented with their own unique set of circumstances and variables.  There are no silver bullet answers.

I would trust the feedback from local builders in your zipcode over national hired guns.

Johnny Boy,
Interesting comments in your last post.
It is a restatment of a point of view I have heard many times.
The one that comes to mind most easily happened many years ago, a one of my first design/build projects.
One of the biggest builders in the county stopped by for a visit. Walking through the freshly dryed in house, he looked at the T&G OSB subfloor, OSB wall sheathing and roof decking. Shaking his head he said "I heard about this, but I couldn't believe it, your actually using the ply crap. This ain't the way we do things around here. My daddy would be rolling over in his grave."
Those few sentences summed up the attitude that I hear yet once again in your post.
I have been building for over 30 years. The homes I build today are different from the ones I built last year, much less the ones I built last century.
As new materials are incorporated into everyday building, the systems have to change to accommodate their peculiar traits. If not the system fails, and the house falls down.
The 'talking heads' are not always correct, but in todays technology, their batting average is a lot better than the local builders who don't listen to anybody outside their zip code.

I do indeed trust SOME of my local builders (others are pretty clueless), but also my own eyes. ( And I don't live in an ivory tower- my hands get plenty dirty.)

We agree- there are many aspects to where & when problems will occur. Retrofits of closed cell onto houses built before sill gasket was invented are particularly susceptible in my neighborhood, but not exclusively (and some sill gaskets seem to work better than others.) I've yet to see a sill-rot problem created by a below grade application of open cell, I've seen several created by sub-grade application of open cell. I've also never seen below grade open-cell foam become saturated as you describe except in bulk water flooding situations. I'm not saying it doesn't happen, but it's not common around here. This sort of thing is becoming common though:

http://basementsolutions.blogspot.com/2009/11/do-not-spray-foam-your-crawlspace.html

It's still better to insulate the sill & rim joist with closed cell in this neighborhood, which are by definition above-grade, and insulating the above grade portion of the foundation with closed cell shouldn't cause a problem- it's below grade & high-R where the problems seem to begin.

Wood studwalls built against foundations still need both a capillary break & class-II vapor retarder between the wood & the foundation, in which case an inch or closed cell fills the bill (and even 5" of open cell doesn't.) Even 1/4" fan-fold XPS is enough, yet still allows the foundation to dry toward the interior. R20 of closed cell is an iffy proposition anywhere the ground moisture levels are high, which would largely be a function of annual rainfall (we get ~ 65"/year here), and proximity to the local water table. Eave overhang distance can also play a factor in the average moisture content of the foundation, even where the foundation is already well-drained at grade. Using all open cell & steel 2x3 studwalls can also work.

I'm currently working out proposal details on a 110 year old full-gut rehab with a combination of stone (below grade) and red brick (above grade), built with a very porous mortar that can't hold a parge. Currently slabless, we're designing in a sub-slab perimeter drain (with redundant sumps), and 2" of XPS under the slab. We're going with 4" (~R25) closed cell at the rim & band joist as well as the joists & subfloor ~1' in from the foundation along the perimeter. But the foundation we'll insulate with 4" of unfaced EPS rigid board (taped & sealed seams) with a ventilation & drainage gap between the foundation, with a 2x3" steel studwall with either unfaced R8 f.g. or open cell cavity fill :

Ground(exterior) | masonry | ~1" gap | eps | R8 batts/ocSPF & steel studs| gypsum & semi-permeable latex

...for ~ R25 (clear-wall).

The alternative had been an inch of closed cell on the sill band joist & subfloor, and steel studwall and all open-cell for rounding out the rest of the R, but the known bulk-water issues in this particular neighborhood made that less desirable for the very saturation potential that you site. The closed cell structure of EPS combined with it's higher perm perm rating (as well as the ventilation cavity) reduces the moisture content of the foundation, protecting the (very substantial full-dimension 2x10) foundation sill. Closed cell SPF on the interior of this particular foundation would likely doom the sill. We're looking at all closed-cell cavity fill for the rest of the building.

Like you say, there are no silver-bullet absolutes in the biz. Never say never, and never say always. Pay attention to the details and there are usually good/better/best ways to go in any particular situation.