ICFHybrid - yes, less house would be a reasonable choice. My problem is that my house is already framed, sided and shingled so can't do anything about reducing square footage at this point. The interior is just not finished.

Engineer - I totally agree! But the appraisal was based on certain specs (tiled floors, granite countertops, trim pck, solid wood doors and cabinets, etc). We had 2 appraisals, one cost to build, one retail value. Cost to build was higher than what I can sell it for because of comps. My problem is I can't downgrade the pretty too much because then the house will be worth even less which means even less money on the bank to finish it. When geo will take 24K in one swipe off my dwindling budget, it sucks. Not so big house is not an option at this point. I got the big house, I want to finish it.

Joe - Iowa now has a new tax credit of 20% off the 30% fed, plus utility rebates it looks like we're down to $12,500 K on the geo vs. 8K for the ASHP. It was the main reason we considered adding it now since it got so close. But at that time we thought for sure the house would appraise for what it would cost to build from scratch today!

Dana1 - my concern is that insulation I can't upgrade and whatever we end up for HVAC equipment won't get upgraded either. Once the walls are closed I can't go back!

Optimizing for appraisal value and for energy use are conflicting goals. But it might help to put things into two lists - things that can be improved later and things that can't. Resistance heat and window air conditioners are probably disposable.

What's the estimated annual operating cost of the ASHP vs. the GSHP?  

Earlier you made the comment "...even at 10 yrs, still hard to say let's spend $6K more to save $1700 up front."

With geo vs. ASHP you're looking at spending another $4.5K up front to save what?  It's a similar magnitude of investment.

Unless the geo costs $450/year less to run than the ASHP, the 10 year simple-return financial analysis fails, and in another 10 you'd be looking at major component swap-outs looming.  I suspect the operating cost delta is going to be less than that unless you cranked the temp in the basement way up and burn a lot of power with the electric boiler.  It'll probably be at least $150/year savings (which take 30 years to pay out in simple terms), but probably less than $300 (which would be a 15 year payout-simple.)  But that's just a WAG. If it were MY house I'd model the energy use with BeOpt and work backwards from the anticipated COPs of the equipment to come up with a realistic kwh/year delta, converting that to $/year delta.

And I'd do the same for the insulation game:

If the extra $6K in insulation knocks off $1700 off up front (assume it knocks off $0 up front for the ASHP) and say, $150/year off the operating cost, in 10 years it still hasn't broken-even.

But with modest price inflation assumptions it will have paid off in 25 years, and will still be going strong for another 50+, no maintenance required. To get $150/year savings out of $6K in insulation once you're at code min means you have to insulate wisely- R100 attics don't make sense with ~R20 (whole-wall) walls, but R60 probably does in the long term (maybe only R50, if GSHP.)

The thermal performance of the wall was baked into the cake the day the siding went up- whether you go with all dense-packed fiberglass vs. an all closed cell foam fill makes less than a 10% difference in whole-wall R.  Whether you spend a little or spend a lot, there's not much further savings to be made there, so spend a little, keeping the long term in mind. (Were to do it over again, 2" of rigid  iso on the outside and 5.5" of fiberglass in the cavities likely would have come in at lower cost w/higher performance, but with the siding up that ship has long since sailed, time to move on.)

It's now only a matter of how cheaply can you protect the sheathing from wintertime moisture drives, since there isn't sufficient exterior R to provide that function with an all-fiberglass fill.  It would be safest to go with 2" of closed cell and no interior vapor retarder, but you're still in great shape with a sloppy 1"  flash-foam + fiberglass, no interior vapor retarder solution.  At a buck a board-foot putting more cc foam into stud bays than is necessary to protect the sheathing is a lousy investment-  a 1" shot of interior foam buys a lot of resiliance for the assembly that just can't be had with strong interior side vapor retarders. (Which is why the blowing mesh needs to be a high-permeance type, which is most of them.)  It's half the foam, 25-30% more fiberglass (material, not cost)- keep the mid-winter indoors RH at or under 30-35% (not 40%+) and it'll be fine. 

In the attic you can just air-seal the seams & penetrations with foam, not a full coverage flash, then shoot R50 cellulose and defer going higher-R for now. Unlike walls, you CAN go higher later in attics.   If the inspectors require a stronger vapor retarder, use a barrier-latex primer on the ceiling- it's a heluva lot cheaper than a 1" shot of foam, in a location that matters less than in wall assembly.  Low density cellulose WILL settle a bit in 10-15 years in an IA climate, but it'll pretty much stop there.  If you blow in 16-18" now it'll start out at R55-60, settling to 14-15" and ~R50 in 10-15 years.

Yes, to question value of more insulation vs. value of more cash for geo is the same argument. One difference is that the appraisal showed that the comps similar to my house without geo the difference in value in my area is about $5K more for houses with geo vs those without. So with tax credits getting the difference between ASHP and Geo to within 4 grand almost seemed like that investment would pay for itself, IF we had a need to sell the house. Plus geo is all the hype here now. Last two home shows 95% of houses in the parade praised the fact that theirs had geo. And the cheap bills!

The only calculation that I have been able to get comparing my boiler/ASHP vs geo operating cost did show huge difference in operating costs. But looking at the numbers I saw that the electric rate used for the ASHP/boiler was twice that of the one used for geo. Maybe it was a mistake, maybe not. But hard to trust it. The general that used this company was way more than we could afford so we did not continue to talk with them. So I don't know for sure what the difference in operating cost is of one vs. the other for my house.

I've asked the hvac company we want to hire if they will consider us prepaying for the heat loads/cost analysis then credit once we purchase equipment. Have not heard back, so we'll see.

I agree that with siding up, I have no choice but to make the best I can in the interior for insulation. And your comment that insulation will be going strong 50+ years is why I want to get it right now. If I can afford the best insulation stack up, that's what I want to do now.

I know with time I can air seal just as good with foam, but I don't have the time, not when we're getting a loan and having a contractor run the project. If we were still self financed I would not be trying to figure it out since we'd just save the money to pay for what we want. But that's not an option anymore for all sorts of reasons.

Also in the attic, the spray foam is not just for air sealing. I do have concern for the edges of the attic where I can't get 16" of cellulose, specially right over the double top plate. The foam would help max r value in these areas. Plus I would think that even a sloppy flash would cover better than one guy crunched up in the attic foam sealing things. One could cut up blue board and foam glue it for the same effect, but then again, no time to do a good job, no money to hire the labor for it.

My area has not adopted code yet so technically where I live, code is R0 since no one will come out to inspect it. The city nearby has R13, R38 in attic. I've given up trying to get R100 installed now. I'm having a hard time convincing insulators that R50 is needed without them turning around and bidding high since they never done that. And since apparently no one has done flash and fill around here, they are concerned about moisture and mold. Hence my questions here so I can be educated on what's right or not. So I keep looking.

My concern with 1" foam would be getting 1" of foam. With 2" I'll probably get some low spots at 1", which I think is the minimum we'd want to get in the low spots.

But you have given me a lot to think about. I really appreciate your insight and discussion. Thanks!

Posted By Dana1 on 10 Sep 2012 04:54 PM

Posted By joe.ami on 08 Sep 2012 06:29 AM
Why not upgrade insulation and go ASHP?

Into kicking over hornet's nests, are we?

I have come to understand geographical disparities in heating strategies- (you have taught me well obi-wan).

In a new build little is cheaper than shrinking the load (to a point of diminishing returns).   
Folks who have done a thousand manual J loads, come to understand ventilation requirements eventually cancel greater insulation.
KY or Boonetucky, would seem to be a good fit for more insul and less heat/cool plant as they should be relatively balanced between heat/cool......MI not as much.

I'm a geoadvocate- when it's the best technology for the job. I just suggested an electric boiler to a customer the other day.
                                                

My concern with 1" foam would be getting 1" of foam. With 2" I'll probably get some low spots at 1"

I can certainly understand that concern, but on the foam jobs I have seen, the application has been remarkably accurate. You can get (or make) a probe similar to what the foam technicians use to pierce the foam and see if the thickness is correct. It would be like an ice pick with the tip properly blunted so you could feel the sheathing when it touches. If you showed up with one of those on spray day, you could do your own verification and nearly eliminate that concern.

Yes, it does seem that when you are present things are different than when not. But I work full time and don't know if I'll be able to schedule vacation to be there for everything.

I meant to ask this question here, and posted it on my insulation thread.

I can't seem to convince the insulator that works with our general to do a flash n fill because of their concern for moisture trap and mold. So instead he's going to give me a bid for full foam cavity.

I think it's the half lb foam, and other than knowing it has less R/inch than 2lb foam, i don't know much about it. Assuming that came back cheaper than the flash n fill bids I have using 2 separate subs, is a full 2x6 cavity of half pound foam a good option with my stackup (1" iso, OSB on the exterior)?

Thanks.

you should shop your foam installer the same as your geo installer. I have seen many bad insulation jobs as people simply shopped by lowest bidder.

I can't seem to convince the insulator that works with our general to do a flash n fill because of their concern for moisture trap and mold.

Sounds like they aren't too facile with their knowledge of what is appropriate for open cell (half lb) and closed cell (2 lb) foam.

don't know if I'll be able to schedule vacation to be there for everything.

That seems like an argument for the flash coat of foam. That seems like a better path to air sealing than to have to make sure it is done yourself.

Joe - I've been talking to insulators since March. Not many do multiple kinds of insulation. They either do foam, or bib, or cellulose. I don't know how many phone calls it took me to find 1 dense pack cellulose contractor. 1!
The very few that do more than one, will not even consider doing the flash and fill. When someone did call back or replied to inquiry, after I asked what I wanted I would never hear back from them. So after two calls and messages I give up and keep looking. You have no idea how frustrated I am feeling like I'm up a creek! I'm just about ready to give up. I've been to some friend's houses that are under construction and I can tell you their insulation jobs sucked. I went to visit a couple before drywall went up. On one they used a clear plastic and the BIB looked like ice scream scoop balls of fiberglass were loose blown in, and to me that did not look like a dense packed. I could see gaps everywhere. I hoped the plastic was not meant to be some sort of vapor barrier it was so full of holes and rips. The other house the job looked much better, a bit neater job. But that contractor is not comfortable with a hybrid like I asked.

ICF - yes. It has been hard to find someone that understands what I am asking for. It has been that way since we started 4 years ago. ICF, OVE, hydronic radiant, heat loads, you name it. I have to keep searching to find the 1% of contractors that have the right kind of knowledge. And I've paid the premium for some things just because they are a niche, not the norm!

So I'm not really going for the cheapest bid. But before I had the luxury of getting the bid for the job I wanted, saving the money to get it, then buying it. But now with a loan and budget and time constraints, I don't any more. I want someone knowledgeable of what they are doing, but most seem stuck in the "this is the way we do this here" and don't want to consider alternatives. Which I understand. I don't want to tell them how to do their job. I'm trying to find someone that knows what I'm talking about and I can feel confident will do a good job.

Thanks for the discussion.

I should have added to my question about a 2x6 wall full of half pound foam: Would it give me the same or better Rvalue and performance compared to the flash n' fill for my stack-up with the 1" of iso on the exterior? No moisture/mold problems with this scenario? I know I've read that half pound foam will absorb water, like in a leaky roof. So just wondering.

Because if it is the same R value and it would perform just as good as the flash n' fill, then if it is cheaper, I could probably make enough cuts in other places to get it.

Posted By Boontucky-girl on 13 Sep 2012 03:50 PM
I should have added to my question about a 2x6 wall full of half pound foam: Would it give me the same or better Rvalue and performance compared to the flash n' fill for my stack-up with the 1" of iso on the exterior? No moisture/mold problems with this scenario? I know I've read that half pound foam will absorb water, like in a leaky roof. So just wondering.

Because if it is the same R value and it would perform just as good as the flash n' fill, then if it is cheaper, I could probably make enough cuts in other places to get it.

It's pretty close to the same whole-wall R as the flash'n'fill. Assuming R6/inch closed cell foam, R4/inch fiberglass and generic R3.5/inch open cell foam it's not a big hit at all.

At a 25% framing fraction and R6 R-board you're looking at

With bottom of the line R3.2/inch foam you get  R18.2 for a whole wall R.

with R3.5/inch generic oc foam you get  R18.9 for a whole wall R.

or about R19.9 for a 1" flash cc foam + 4.5" dense-pack

or about R20.3 for a 2" cc foam + 3.5" dense-pack

With R3.8/inch foam (Demilec Sealection 500) or R3.7/inch foam (Icynene LD-C-50) the difference between that and a flash'n'fill is less than R1, either one comes in between R19 & R20.

How much would you pay for R1?

Any o.c. foam would require either a vapor retardent paint or a semi-permeable film like MemBrain to bring the vapor retardency on the wintertime interior permeance to about 1 or a bit less to fully protect the sheathing from vapor diffusion loading, but the o.c. foam will end up about as air-tight as a flash'n'fill.

Thanks Dana1. I greatly appreciate your technical expertise. And you do a great job of keeping it simple enough that us simple folks can learn.

I'd be willing to pay for the R1 difference if the quality of the contractor warrants it. But it's a balancing act on how much I can afford vs. the quality I want to get. It seems that with the open cell I can control the paint job, since it will most likely be DIY to save that cost and we can paint. I would have to really trust the vapor barrier install. I wonder if the contractor will tell me I don't need vapor barrier with a full cavity of open cell foam? Any bets? :)

That's what my insulation installer told me, but the building official would not sign off on insulation until a vapor barrier was put up. I have 2 x 6 filled cavity open cell.

ChrisJ

Find a bucket o' paint labeled "VAPOR BARRIER LATEX", or similar, and have it (and it's specs) on-site for the inspector.

eg: http://www.gliddenprofessional.com/gliddenProProducts?other=x&platform=Special_Surface_-_Special_Task&pnameNoTrade=Vapor_Barrier_Primer_Sealer

http://duspec.com/DuSpec2/document/DocumentDisplayController.htm?documentId=934445 (<<0.6 perms at the specified coverage, which is about PERFECT)

or the Ben.Moore version at 0.5 perms:

www.benjaminmoore.com/DownloadBinaryServletTDS?fileName=20120314+260+TDS+US+OKF.pdf&propertyName=multidatasheet%5B0%5D.data_sheet_file_en_US&np=productcatalog_datasheets%2Ftds%2FTDS_0260

If they make you put up some sheet goods, do whatever you can to avoid poly sheeting. MemBrain is good though:

http://www.certainteed.com/products/insulation/mold-prevention/317391

http://www.certainteed.com/resources/3028080.pdf

MemBrain releases water fast if the humidity in the cavity-foam rises, but with dry winter air it's under 1 perm.

With o.c. foam and only R6 sheathing you DO need some interior vapor retarder better than standard latex to be safe during the 25 year extremes, but keep it at a minimalist class-II (<1.0 perms), not class-I (<0.1 perms, like poly).

If the inspector would accept kraft facers on batt insulation, if they know anything at all about the building science of it they should be THRILLED with o.c. foam + v.b. paint or MemBrain.

I'm not in the city limits. The only inspection we got was septic tank, set backs from property line, and electrical. After that... no one's coming to check... except me.

I'll see what they use for barrier, but now I know that if they say none needed, then I need to get some paint if we go open cell route. Still waiting on numbers and answers.