ICF VS advanced framing and spray foam.
Last Post 12 Jun 2011 07:58 PM by toddm. 44 Replies.
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insuldeckfloridaUser is Offline
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08 Jun 2011 10:37 AM
no argument with you academic types and other experts here on R value, K value, whatever......

BUT: what about sound transmission, floor to floor or external? (airport approach noise in my case) fire? tornado? maybe even hurricanes? termites? insurance? do i dare add re-sale value in 20 years?

for almost 10 years now we live in an icf house with icf concrete floors and roofs (edited/added: plus some interior cmu and loadbearing icf walls) and a few huricanes under our belt....

whenever we visit our neighbors in their 2 story wood framed house house i realize how much i miss the house shaking when someone slams the front door, or the sound of kids trampling upstairs, and oh, that sweet sound of flushing toilets, creaking stairs or squeaking floors...

just my 2 cents of sarcasm....

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jonrUser is Offline
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08 Jun 2011 10:52 AM
BUT: what about sound transmission, floor to floor...fire


Don't forget room to room - those interior walls should be concrete too.
lzerarcUser is Offline
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08 Jun 2011 02:33 PM
and the sound transmitted through doors and windows.  Doors and windows should also be concrete.
insuldeckfloridaUser is Offline
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08 Jun 2011 03:12 PM
2" solid core lumber doors with 1" steel armor plating both sides should do the job...
or hollow core metal doors filled with molten lead....
who needs windows anyway?
:-)))))
Dana1User is Offline
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08 Jun 2011 03:53 PM
Structural & sound transmission aspects are all valid reasons for paying the ICF premium. I like ICF construction (I really do) but the thermal mass dynamic-R aspect of ICF has been over hyped- it's a secondary aspect. When going for truly high-R structures it gets to be pretty expensive (yet still worth it, for some.)

High mass homes perform a lot better when the thermal mass is NOT behind R8+EPS + foam & finish-wall. High-R counts for a lot more than high mass, in both comfort and energy use. At equivalent whole-wall R there is but a marginal (sub-10% energy use) advantage to ICF, that all but disappears if the interiors are designed with a modicum of thermal mass (slab floors, fat wallboard, etc.).

24" o.c. studwall construction doesn't have to be cheap in look & feel, or particularly noisy just because it CAN be in it's lowest-cost implementations. My in-laws built a 2-story w/full basement with dense pack cellulose in the cavities behind metal-lath hard plaster finish walls & fiber-cement clapboards, with gypcrete slab radiant floors (putting thermal mass fully inside the thermal envelope where it belongs.) It looks, feels & performs pretty good, and performs. Sure, it's less hurricane & tornado resistant than ICF, but to hit the same thermal performance (~R25 whole-wall R with the 2" XPS factored in) with ICF would have been a budget buster (and it WAS considered.)

It's been a good half-dozen years or so, the plaster hasn't cracked and the place hasn't fallen down yet, but give it time- I'm sure it'll feel "cheap" when it gets dead-centered by a tornado. ;-) It is at the top of a hill, and the wind-stresses are substantially higher than most in that town- if it were going to have issus they probably would have seen something by now. But you can't hear kids, or traffic outside without the windows open, and the coyotes are only evident when howling in the yard.

Squeaks & creaks in timber framed is usually a fastener problem- screwing rather than nailing critical components like subfloors (and using engineered joists for planar flatness & rigidity) can make a real difference.

Or you could just go with the absolute min-spec joists & subfloors, slam it all together with nail guns with the minimum allowable fasteners for the squeaky-creaky trampoline effect, and go with a vinyl siding over an inch or three of EPS, low density batts & half-inch wallboard and still get decent thermal performance so long as you've air-sealed it, but with a very different feel (and price-point and performance/$.) But you don't have to. Most custom-builds are done much better than that, because the buyers value more than mere thermal performance, even when they DO demand thermal performance.
galoreUser is Offline
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08 Jun 2011 07:27 PM
Why is R25 using EPS with a concrete core a budget buster? I paid $0.25 per 1 inch thick EPS per SF. Type II EPS is rated at R4.5/inch so it takes a bit more than 5 inches of foam to achieve R25. Is $1.25/sf of wall space a budget buster?
jonrUser is Offline
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08 Jun 2011 07:59 PM
Interior mass is only slightly better than middle mass. Factor in thermostat setback and I'll take middle mass (like ICF). All of this varies with climate.

I've heard people complain about concrete floors being harder on the feet - I think they like a little give.

But sure, same price for ICF + concrete floors and I'll take it over traditional stick framing.

insuldeckfloridaUser is Offline
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08 Jun 2011 08:15 PM
agree on the concrete being harder on your feet...
but also cooler in warmer climates, whether raw, stained, tiled or marbeled....
for comfort in colder climates add radiant floor heating (into the mass) or use carpet and good padding...
also workes well with real or laminate wood floors...
in the end you get what you really want and are willing to pay for...
insuldeckfloridaUser is Offline
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08 Jun 2011 08:21 PM
Posted By insuldeckflorida on 08 Jun 2011 08:15 PM
agree on the concrete being harder on your feet, and colder in the cool months...
but also cooler in warmer climates, whether raw, stained, tiled or marbeled....
for walking comfort or colder climates add radiant floor heating (into the mass) or use carpet and good padding...
also workes well with real or laminate wood floors...
in the end you get what you really need or want, and what you are willing to pay for...
all you really do is spend most of your free time in it...


Peter JacksonUser is Offline
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09 Jun 2011 12:29 AM
I'm personally convinced that in central and west Texas that simply keeping the sun off the house with solar sails or trees would probably be as effective as any amount of additional insulation over say r-10. I'm going to prove it one day too =8^]
jonrUser is Offline
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09 Jun 2011 08:07 AM
You have a point - 30% savings on cooling costs is common when shade trees are added.





Dana1User is Offline
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09 Jun 2011 06:46 PM
Posted By galore on 08 Jun 2011 07:27 PM
Why is R25 using EPS with a concrete core a budget buster? I paid $0.25 per 1 inch thick EPS per SF. Type II EPS is rated at R4.5/inch so it takes a bit more than 5 inches of foam to achieve R25. Is $1.25/sf of wall space a budget buster?

Show me Type-II EPS that's rated at 4.5/inch. (Seriously?)

It may approach R4.5/inch or  so for the exterior third of the EPS in a very cold climate, the interior third is only going to average ~R4/inch. 

When it's 100F out that exterior third is going be averaging something like R3.75/inch- even less under sun-baked 115F+ siding. See: 

http://www.transconsteel.com/products/ultraframe/docs/Other_Properties_of_EPS.pdf

(Type-II EPS is ~1.55 lbs/ft nominal density)

And of course ICFs never get dinged, chipped or compressed in installation and experience no separations at the seams, so it really IS a perfect insulating plane with no defects...

Overstating R values by 12-20% I'm not sure what weight to apply to the rest.  I can make all sorts of systems appear to have premium performance if I'm allowed to add 12-20% of fantasy-R. 

Type-II EPS is going to run ~R4 per inch, seasonally averaged, maybe a bit less in TX, and maybe bit more in ND, but it's not R4.5 anywhere south of Fairbanks AK.

The cost delta issues for in my in-laws' place were timber framing vs. concrete (distance from the plant matters), and the cost of mostly-cellulose vs. all-EPS insulation package. YMMV

And R25 whole-wall R wouldn't be considered "high-R" in US Zone 5, but it's above code-min.  At R30-35 it would be, but even that isn't considered "superinsulated" by any means. (R50+, now you're talking, and they DO exist.)  A gut-rehab project on a 115 year old building I'm consulting on right now is going to end up a hair under R30 for whole-wall R (full dimension 2x4 w/spray cellulose, 3.25" iso on the exterior), but that's not very extreme compared to some houses in the area.


jonr: I'll grant that the difference in dynamic R between interior mass vs. ICF isis pretty neglible in fairly temperate climates like Seattle or strongly heating-dominated climate zones 6 or higher.   But in places with high sensible-cooling loads and huge diurnal temperature swings in summer it can be almost twice as effective to have the mass on the interior rather than an ICF.  See:  http://www.ornl.gov/sci/roofs+walls...e5.pdf

galoreUser is Offline
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09 Jun 2011 07:45 PM
So add another inch for $0.25/sf. Still negligible cost wise unless you are building above your means.
Dana1User is Offline
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10 Jun 2011 03:52 PM
An inch of Type-II EPS purchased as is only 25 cents a foot, or ~6 cents/R/foot?

Installed cost of Type-II EPS as sheet goods is about 10cents/R/foot, so a 1" would be more like 40 cents.

Is it somehow much cheaper to install ICF foam than sheet goods?

I can sometimes get used Type-I EPS for about about 3 cents/R/foot ( at which it's at rough parity with spray cellulose). Raw cost to me for virgin Type-II sheet goods is usually more like 7-8cents/R/foot, not 6.

Could it be that this is a 12-20% fantasy price discount that goes along with the magical R-value up-rating?

It's about half the installed cost per R/foot as EPS. At R25 it's not as big a deal as at R50, but it's still not nothing.

I suspect it was the concrete more than the EPS that would have broken the budget on their house (not that I saw all the quotes, which I surely didn't- it wasn't my project.)
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11 Jun 2011 12:18 AM


Jonr said:

"Interior mass is only slightly better than middle mass. "  I agree with this statement -- it is definitely true in the lab.

I've read at least most of the ORNL material on DBMS - Dynamic Benefit for Massive Systems (like the link Dana1 provided).

In digging through this data I found some interesting stuff. 

DBMS charts comparing interior mass and ICF are based on R-17 ICF --- I don't know of any ICF on the market that has this low of an R-value so we can call this a hypothetical ICF at best.   Not such a big deal since the entire study was about isolating the benefit of thermal mass.   But if you read the small print you'll find that in order to extract the benefit of whether or not the mass is better inside or out -- both mass and R-value have to be the same for each of the computer models.   Makes sense, if you vary r-value or mass for any of the systems you really can't isolate the benefit of the thermal mass.

So if you take your typical real life ICF with 2 1/2 inches of foam on each side of the 6" concrete core -- then the interior mass model has to use the same amount of foam and the same amount of mass in order to prove anything.  Therefore,  the interior mass system has to have 5" of foam to the exterior and 6" of concrete to the interior.  I'm sure it did - in the computer model.   Although it would be easy enough to accomplish -- this is a rare wall system in the real world -- I'll call this system a hypothetical competitor.

This report is often misquoted by folks trying to sell that internal mass is better.   You might say that someting like CMU is better if you put 5" of foam on the outside.   But CMU has a small fraction of the heat capacity of solid concrete.   Then when you look at these systems you will usually find that they usually have less than 5" inches of continous insulation (LESS R value) and they don't have anywhere near 6" of heat capacity (LESS MASS). 

I've found that the more I dig into this subject the more I realize that we really just don't know that much about it.    Regards.

galoreUser is Offline
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11 Jun 2011 12:26 AM
The $0.25 per inch per sf is what I paid for Type II EPS for my house. It wasn't a fantasy price discount but the actual amount I was billed by the foam factory.

My wall assembly is actually siding + 1" air gap/drainage plane + 7" EPS Type II + 8" concrete so I didn't purchase ICF blocks but used EPS foam panels inside conventional concrete forms with the goal of having the thermal mass inside and all insulation outside. I thought that the foam was exceptionally cheap so I was a bit puzzled by the statement that it was a budget buster... I would think that ICF forms would track similarly, price-wise.
toddmUser is Offline
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11 Jun 2011 07:52 AM
Ah yes, TexasICF. Insulation is good and more insulation is better. Or is it? Look at Fig 8 at the very end of this paper http://www.ibsadvisorsllc.com/_library/ORNL_Thermal-Mass_Energy_Savings_Potential_in_Residential_Buildings.pdf

If you used Logix blocks to built a house in Phoenix and I slipped 2 inches of EPS in a concrete form and poured 8 inches of interior concrete, which house would perform better? Cost less?

That R17 ICF doesn't exist today is neither here nor there. ORNL did this work in the '80s by comparing test buildings. (One suspects that R17 blocks did exist then.) Then the lab developed a computer model and tested it against the performance of these buildings. Hypothetical? Yes. Wrong? Well, construct your test buildings and prove it.

The fact remains that high mass houses have worked for centuries with zero insulation. It takes the right climate: dry, big extremes in daily temps but a comfortable daily average. I was amused to read that the builders of the Tucson zero energy house say that their approach to thermal mass needs more work. (R14 EPS over CMU filled with concrete.) Surely there are hundreds of adobe houses in Tucson that have worked just fine for decades.

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11 Jun 2011 11:41 AM
 the interior mass system has to have 5" of foam to the exterior and 6" of concrete to the interior... this is a rare wall system in the real world


Good point. And I suspect that most people will cover a poured or CMU interior concrete wall with an air gap + drywall - which makes it "nearly interior" mass. CIC (often thinner concrete sprayed over foam) looks to be pretty good and is capable of values all the way from R5 to R25.

Last but not least, the savings from high mass can also be achieved with active systems - heat pumps or radiators + water storage tanks. Might be cheaper, more even in temperature and save more; definitely if there are off-peak utility rates involved.

Galore - do you have more info on the cost for forms in your design? I wouldn't be surprised if it came out better than ICF. No problems with the foam floating upwards?
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11 Jun 2011 01:16 PM
Posted By galore on 11 Jun 2011 12:26 AM
My wall assembly is actually siding + 1" air gap/drainage plane + 7" EPS Type II + 8" concrete so I didn't purchase ICF blocks but used EPS foam panels inside conventional concrete forms with the goal of having the thermal mass inside and all insulation outside. I thought that the foam was exceptionally cheap so I was a bit puzzled by the statement that it was a budget buster... I would think that ICF forms would track similarly, price-wise.

Do you have metal form ties protruding through your EPS insulation?  If so, doesn't that effectively negate some/much of the insulation value provided by the EPS?

Is your foam continuous on the exterior or are there areas where the concrete flowed to the surface?  How did you attach your siding to the structural wall through 7" of EPS foam?
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11 Jun 2011 03:50 PM
Here is what Certainteed does. One would hope that their R value specs are whole wall.

http://www.certainteed.com/resources/Fnd_ThermaEZE-Brochure_40-96-02B.pdf

Any foam joint can be glued to prevent leaks. T-Roc also looks interesting. Drywall + foam is installed in the forms, so combined with a textured pattern or thin stucco layer on the outside, the wall is almost finished right out of the forms.

http://www.greenstreak.com/subpacks/Stone_Pattern_Flyer.pdf

http://www.specformliners.com/Hack/PDF/SheetsPDF/1205.pdf
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