This is a little off topic, but I still wanted to pick people's brains about this, and the ICF Forum seems to be the best place.

I'm doing a ton of research right now trying to decide the best material to be using to create an air-tight, high R-value, soundproof home.   I've looked at SIPs and ICFs so far, and would like to learn a bit about the feasibility of using a spray foam insulation for the walls and roof of this next house I'm building.    I read a great article about a superinsulated house that was built back in NH in the mid '90s that used 11-1/2" of dense-pack cellulose for the walls.    I hear that dry insulation, no matter how well it's packed, does have a tendency to settle over time.   So I'm wondering what the feasibility would be to use spray foam insulation in the same capacity.    OSB SIPs don't seem to be able to do much better than an STC of around a 22 and ICFs have an R-value somewhere in the low to mid 20's, depending on thickness.   From what I've read, the spray foam insulation would give you an STC of at least 50, the house would be complete airtight, and depending how thickly the spray foam was applied, you'd could end up with somewhere between an R-50 and an R-60 for the walls and roof, especially if you build the frame two-layers deep out of staggered 2x6s and in essence built these two walls separately to create one 11-1/2" thick mega-insulated and sound-proof wall.    Sounds too good to be true.    I know it wouldn't be cheap, but I'd still like to hear people's ideas about whether this is a direction worth exploring.    The couple of Net Zero 'passivhaus'(es) that have been built in IL have me wondering whether this same goal could be accomplished with spray foam.

Thoughts?  Questions?  Concerns?  Criticisms?   Bring 'em on!  :)


John

John

One word...cost

Now to elaborate, once you get into double framing cost will kill you on the job, 11 1/2" of Demelac I'm guessing is over $ 6.00 per sq.ft., since 5 1/2" is being billed at $ 3.00 plus here in CA.

ICF has an insulation value of around R-22, add concrete and get the thermal mass and you have R35 and up depending on your geographical location. ICF has a STC rating of 50 for sound transmission.

The R-value really means nothing, it is the way peoples mindsets have gone since the pink panther really promoted R values for years and people think they know what they are talking about when someone says it's an R-20 wall. Same as how Sears sold people on carpet weight in oz's. Suggested advertising that the world bought.

ICF's have been proving themselves time and time again with a quality installation the product is second to none in terms of strength, energy efficiency, etc.

I know the SPF option would not be cheap.   The question is how it ultimately would compare to an ICF home that's able to achieve the same thermal barrier, especially with the cost of concrete and rebar continually being on the rise.

By the way, I do appreciate your comment that one can't measure by R-value alone.    However it was my understanding that ICF's were around an R-24 after being filled with concrete.    I may be completely wrong though.   Any chance you could point me to a objective and unbiased data on the subject? 

I'm still going to price out the spray foam insulation option here in Maine, just for comparison's sake.    My goal is a superinsulated house, not just a well-insulated one.     I'll post the numbers once I've got 'em.

Thanks for your feedback,


John

If your in Maine and need to see unbiased, valuable comparisons you need to seek out Pieter VanderWerk at BuildingWorks, he is in your area. That's the guy with all the right answers who has researched and studied all these myths.

ICF's R value varies between 20 and 24 prior to concrete depending on foam thickness and density

There is a chart somewhere that shows the R-Value, Pieter may have it, he has every conceivable piece of info on ICF's. My area as an example I believe is R-38, I am in Napa, CA which only has 3-4 days a year of 30F temps and maybe 10 that go above 100F, average is around 77F I believe

Chris,

I'll get in touch with VanderWerf tomorrow.   Thanks for mentioning the guy.


John

do a search on google about r-value.

 

here is just a short list of what comes up. r value is important. but air and vapor exchange is much more important.

http://www.rvaluehomes.com/rvalue.htm

http://static.monolithic.com/plan-design/rfairy/index.html

there are many many more. but rather than talk about it. i can show you a house that is silver rated LEED certified.

its about 3500 sqft with a guest house. there avg total electric bill is around $100. that not just heating and cooling that is total. http://www.webuildconcretehomes.com/


there are many more examples. of how r factor is not what you should be looking at.

we have a local doctor who has built so far 2 offices one with standard CMU and the last one with ICF's.
there about 6000 sqft. the ICF office cost them $700 dollars less a month in electric. so the next office coming out of the ground this week im sure you can guess wich method of building they will be using.

just going to ICF's over conventional stick and bricks will give you about 30% savings in electric. if you get better windows and doors and seal up the attic or go with a cement roof. you will see 60-70% savings in electric usage over a conventional built building.

i know your just trying to make an informed choice. but dont try to reinvent the wheel. ICF's have been developed and proven over the last 30 years.

Chris:

Here's Pieter VanderWerf's official response:

There was a really good thread a while ago about R values and one person gave a great explanation about it. A real interesting and informative read, you should track it down, will clear things up for you.
The topic reads "The 'R' Fairy Tail-The Myth of Insulations 'R' value".
When people say ICF has an R value of 50 it is not true, BUT it may PERFORM to an R 50 wall. In this thread that reasoning is explained, hats off to the writer.
When I talk to people about it, I have them think of the weather in the summer. It may be 80F outside but with the humidity it feels like its 100F. So when you go outside what do you prepare yourself for? 80 or 100. Same as ICF's
It is a good read!!!!!

You should post the link.   It would save people from having to dig for it (which few will bother to do.)


John

reminds me something about "give them the fish they eat for a day. teach them to fish they eat for life."

 

 

I am sure that your home page for the site is the same as mine. At the top it has page numbers 1 through 100, just click on the number 5 and there it is.

Here's the link.


John

I agree with the posters above, forget about R-Value and look at the true efficiency of each wall type. That being said, I think that you would have an incredibly efficient spray foam wall at 11 1/2" thick, although it would also be equally expensive. The nice thing about most spray foams is that you don't need 11 1/2" of the stuff to have an efficient wall system. The spray foam company that I use discourages their foam sprayed any thicker than 4" due to the fact that you are just wasting money. In my opinion Its the first 1/2" of foam applied to the wall that does the most for you because that is what seals your house up, and prevents any air movement. If you are concerned about thermal bridges maybe a better wall would be a conventional 2x6 wall sprayed with foam inside and then apply rigid insulation to the exterior to prevent any sort of thermal bridging. With all of that said the other consideration is Thermal Mass, depending on your climate this can also add to the true efficiency of your house.

MDiver:

Great post. You've basically just summed up everything that I've been told over the last 24 hours by 4 or 5 different sources. It's good to have somebody knowledgeable confirm it.

I've decided to go with the original ICF envelope from the footers to the roofline, which would be a total of 25 courses (33'4" of block) to the roof.  And I'm still committed to keeping the open attic loft space under a full 12/12 pitch. But instead of using SIPs on top of the house as I'd originally considered (and settling for the mediocre soundproofing), I'm going with a super-insulated unvented cathedral roof.   I'm having it framed, going with a heavy-duty Glulam ridge beam running the full 42' length of the house, and using 2x10 studs (16" o.c.) for the rafters.  To insulate this, I'm having 5" of closed cell 2 lb foam plus an additional 4 1/2" of 1/2 lb open cell foam sprayed between the 2x10s clear up to the ridge beam.

I'll then have all of this sealed in with drywall on the inside, a sheet of 7/16" OSB on the outside, and 4 1/2" panels of Hunter H-Shield-NB polyiso roof insulation on top of the OSB to avoid any potential thermal bridging (short of the fasteners being used) as well as to further beef up the insulation.   This will be finished off with Click-Lock metal roofing and a layer of Sharkskin Ultra polypropylene underlayment sandwiched in between.   The roof should test to R73, but even more importantly should be virtually soundproof, bombproof, COMPLETELY airtight, thoroughly cross-ventilated and have negligible thermal bridging.   The STC for this new roof should be somewhere between 75 and 80, which would be a HUGE improvement in soundproofing from the STC of 22 or so that I'd have gotten from 12-1/4" SIPs.

This may sound like a bit of an unconventional (albeit pricey) way to go, and a lot more work than just slapping some SIPs together to make a roof, but I elected to build a modest sized house with a small footprint (1,765 sq ft, spread over three floors) so that I could justify pushing the envelope a bit further regarding how the place is built, heated, insulated, finished and furnished.   And I really like that the roof will be even more soundproof than the ICF walls.    This house will be primarily heated by 4 floors of radiant heat (3 plus the basement) and juiced by a propane boiler used in conjunction with an Apricus solar hot water system, so I want to do everything I can within reason to minimize the boiler kicking in and burning propane.    The turbocharged roof and ICF walls should help this considerably.

Do you see any major nightmare I'd be facing with this approach (aside from the cost)?    Let me know.   I want to tweak this until I get it just right.    Any suggestions or feedback would be greatly appreciated.


John

dont vent the attic / roof space at all. just seal it all up. seal the eves/overhangs, underside of roof deck and trusses. the rest sounds great. (does golf clap and does a little dance) good job.

dont forget the good doors and windows. :)

EDIT: i re-read that and see the ventilation is going on the outside under the roofing material even better. very very nice.

lambabdey, I am not sure if you have looked at this possibility or not but have you looked at Nudura's 'ceiling technology' which is available for ceiling insulation? I have used it once before and quite liked it. It is supposed to give comparable to R 70 (there we go again using the "R" rating). Its 2 layers of 4x8 sheets of foam insulation which you attach to the trusses. Check out Nudura's web site for more info. when I have a bit more time I will figure out how to attach pictures and will post the ones I took from my job.

Paul:

Thanks for the response.   I am familiar with the Nudura product, but elected against it because I wanted a solution for extra insulation that would be going onto the outside of the house to stop the thermal bridging between the 2x6s and the metal roofing.   Plus, given that the Nudura product would be on the attic side of the spray foam insulation, it would swallow up that many more inches within the attic of valuable ceiling height.    It's definitely a product that's worth consideration; it's just not right for this particular application.   I appreciate you suggesting it though.

Cheers,


John

I have quite a few sips roof jobs under my belt (including a 3800 sq ft 12/12 house). In my honest opinion if your doing 'open-beam' construction and a fairly simple roof, the bang for the buck factor that you get with the sips roof is hard to pass up. With a competent crew your roof can be up in a few days, it is already insulated, ready for roofing, ready for interior finishes and ready for exterior trim. Just my .02.

I think that the roofing system that you are piecing together will work quite well, I am curious what the difference in price per sq. ft would be in terms of materials and labor with comparing it to sips. - Pete