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Old 10-28-2011, 09:44 PM   #16
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ICF vs. Wood Framed


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a previous poster said that icf's need to be insulated on teh outside, um they are thats the 2 1/2" of foam on the outside of the concrete.... hence I.C.F insulated concrete form...... To add to that, they need to be insulated on the outside TO BE MORE USEFUL in the sense of thermal mass when in a heating dominated environment. As they are usually made (symmetrical), any heat that gets into them will go to the outside faster than the inside, generally, as the outside is generally colder than the inside. The delta T determines the flow rate. Thermal mass is always insulated on the outside in a heating dominated environment.

for energy efficiency, icf's by far outperform wood framing.. case in point last year i built a 4000 sq foot vet clinic which was 90% icf. Again, anecdotes do not replace science. Anyone who cares to read about all this is invited to buildingscience.com, greenbuildingadvisor.com, or to just apply what knowledge you have. ICFs ARE NOT GREAT INSULATION for the money, but can work great if you have a lot of sun heating them and not a bitterly cold environment. A wood frame, double stud wall and dense packed cellulose, for example, can be built to a far higher R value much cheaper than concrete, not to mention the embodied energy required to make concrete and all the petrochemical-foam needed in the ICF and outside it (that is what people usually insulate outside w/).

I've run the price numbers, and anyone else is welcome to run their own, too. We've had this conversation before, and others have found the same thing; ICFs are spendy. If you want "earthquake proof", then git 'er done. But, ICFs are not the material for an inexpensive, high-R structures. Anecdotes of one cat's place are meaningless; there are way too many other variables at play to allow anyone to make any claims about anything. I know a cat who has smoked for 85 yrs; so what does that "prove"? Nothing.
Pls see above after the bullets. I want to make it clear that I am not anti-ICF, but I do like to get the facts straight, at least as far as I can determine.

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Old 10-29-2011, 03:01 AM   #17
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I appreciate all the input. Each building method has its pros and cons. My main concern is strength in regards to earthquakes/high winds, rodent proofing and longevity. As far as R-value goes, ICF just like wood, needs additions in order to get high R-values. Whether it be cellulose or styrofoam backed stucco.

With ICF, can one still install cellulose in the interior walls for added R-values?
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Old 10-29-2011, 09:53 AM   #18
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An R-value only has real application for lightweight construction and the test to determine it is just a quick short term snapshot. The value is convenient for advertising and the use by people for a short term analysis of the materials to determine and approximate wall heat resistance while neglecting the heat capacity and concept of thermal inertia that is frequently used on passive solar homes. The thermal heat storage/inertia is one reason why heavier home always outperform the calculated performance because simplifying assumptions are made in the testing and calculations.

I think the most ridiculous use of R19 fiberglass in a stud wall that can only obtain an R9 or R10 even under ideal conditions and short term test.

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Old 10-29-2011, 09:58 AM   #19
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What did he just say?

Andy.
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Old 10-29-2011, 10:58 AM   #20
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I've looked heavily into ICF construction. The claimed R equivalency is just plain unrealistic, but it would be much more realistic were you are at than were I am at. going hot to cold in a 24 hr period in the desert vs. months straight of below 0 temps for me.

Don't go cheap on the re-bar if you want earthquake protection. since it is earthquake resistance you are looking at, don't skimp on the ceiling/floor joists and their anchors either.

are you going with a concrete roof too? otherwise you'll get creatures going in through the roof on you.

Last edited by forresth; 10-29-2011 at 11:00 AM.
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Old 10-29-2011, 12:30 PM   #21
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With ICF, can one still install cellulose in the interior walls for added R-values?
Jack: I would not insulate inside the concrete, as that puts all the thermal mass on the outside, negating what positive effect that would have thermally, and also violates the "rule" of having the exterior wall 5x more vapor permeable than the inside. Were I insulating ICFs, I'd put more foam on the outside. I would also suggest that you read about this on buildingscience.com and greenbuildingadvisor.com, as those folks have the real experience and knowledge. I get a lot of info from those sites, and though not perfect and sometimes you get slightly different opinions, they sure seem to be the best we have at present. Learning is an evolving process, so ideas change now and then, of course. People once thought that visqueen on interior walls was the Holy Grail for every environment, etc. As much as I hate using foam, I think that is what you'll need. BTW: I'll have 10 to12" under my entire slab and outside any stem wall I will have, so you sometimes have to bite the bullet; there's nothing else to use below grade, so.....
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Old 10-29-2011, 12:41 PM   #22
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What did he just say?

Andy.
Dick is not a fan of R value, and has a point. However, I contend that it is a valid metric, if understood, and beats a guess from a 3rd grader. People in the building science community seem very comfortable with it and the folks that run this spendy software when designing houses seem to get fairly accurate results. Always keep in mind, though, that advertised R value by any industry is suspect. For example, fiberglass batts work as advertised, but what is not advertised is that they can never be installed perfectly and they are not dense enough to prevent internal convective loops, so in reality the R value OF THE WALL is much less, as Dick stated. (This is why the "Pink Panther" companies are selling foam sealing kits with the batts; they are fessing up to their not really being all that great, and need assistance to perform closer to claims.) That said, if you don't air seal well, ANY insulation is not going to "be the best it can be", borrowing from the Army. Foam needs seams caulked and taped; cellulose needs similar air barrier measures, etc.
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Old 10-29-2011, 01:20 PM   #23
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I like to use this analogy regarding R value....

You buy a car with xxx horsepower.....but just because you have that big engine, it does not mean all of the power gets to the wheels.

Same with insulation. The R value is a relative # to give you an idea what you 'should' be able to get in insulation value. But like most things, it is part of a total system. You could have R50 in your walls...but it could be worthless if you have holes in the wall.
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Old 10-29-2011, 09:48 PM   #24
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Dawg:So the blown and injected 454 Chevy engine (running nitro) that I just put in my Subaru wagon won't work well? Damn. I thought I had a hot street rig there.
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Old 10-29-2011, 10:27 PM   #25
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The big Chevy will not turn the same times the "stock" engines that are used in road racing. Brutes are fine as long as the street is smooth and there are no turns. - Not quite as bad as a NSCAR unit that can really only turn left with a bank to help.

Time to go because the Indian Formula 1 race on TV from Delhi starts at 4:00 AM tomorrow. I hate to see cars governed down to about 19,000 rpm, but there is a reason.

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Old 10-30-2011, 11:05 PM   #26
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Were I insulating ICFs, I'd put more foam on the outside. I would also suggest that you read about this on buildingscience.com and greenbuildingadvisor.com, as those folks have the real experience and knowledge. I get a lot of info from those sites, and though not perfect and sometimes you get slightly different opinions, they sure seem to be the best we have at present. .
So what you are saying is to add more insulating value on the exterior wall. The ICF block has 2 1/2" of styrofoam on each side. How would one go about adding more to this? I was going to finish the exterior with stucco. Which out here is usually 1/2" styrofoam, chicken wire and 1/2" stucco.

As far as water barrier goes, it appears that it is a good idea to wrap the home with such a barrier. That is what the one study shows, that ICF blocks homes are not completely "water proof". Which seems weird to me as styrofoam in and of itself is water proof and the ICF blocks lock into place, so water intrusion would seem highly unlikely.

The ICF contractor I talked to said he would use 6" of 3,000 psi concrete, with 1/2" rebar - 16" O.C.. This would give me a wall thickness of 11" as the styrofoam is 2 1/2" thick on each side.

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Old 10-31-2011, 12:16 AM   #27
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First, I am not an expert at anything, let alone ICFs. I have never insulated them more than what they are, but I understand, and it seems logical, that you can screw through your foam into the plastic channels in the ICF, as people do when insulating w/ foam on the outside of stick houses (REMOTE wall, for example). The rub w/ ICFs as far as insulation is what I mentioned above, about the heat going out of them more than into the house. Putting foam on the outside tends to reduce that, but there is no point in doing anything if they already have sufficient R for your area, esp if the sun is being used to warm up the concrete; that is free heat, and concrete and sun do well together (but watch for overheating, of course). I would then goo and/or tape the seams of the added foam. As for a weather resistant barrier, I'd sure use one. All those joints in the blocks will possibly leak by wicking water in, if it gets past the outer layer; accidents happen. When we built below grade w/ ICFs we were advised to use bituthane membrane over the blocks to water proof them. It is a rubbery, sticky membrane that comes in rolls. The ICF provider sells it, and I see something like it used wherever ICFs are below grade. Above grade, I think Tyvek, or the like, would be fine, plus a rain screen, like vertical 1x4s (if that is appropriate w/ stucco).
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Old 10-31-2011, 09:15 AM   #28
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First, I am not an expert at anything, let alone ICFs. I have never insulated them more than what they are, but I understand, and it seems logical, that you can screw through your foam into the plastic channels in the ICF, as people do when insulating w/ foam on the outside of stick houses (REMOTE wall, for example). The rub w/ ICFs as far as insulation is what I mentioned above, about the heat going out of them more than into the house. Putting foam on the outside tends to reduce that, but there is no point in doing anything if they already have sufficient R for your area, esp if the sun is being used to warm up the concrete; that is free heat, and concrete and sun do well together (but watch for overheating, of course). I would then goo and/or tape the seams of the added foam. As for a weather resistant barrier, I'd sure use one. All those joints in the blocks will possibly leak by wicking water in, if it gets past the outer layer; accidents happen. When we built below grade w/ ICFs we were advised to use bituthane membrane over the blocks to water proof them. It is a rubbery, sticky membrane that comes in rolls. The ICF provider sells it, and I see something like it used wherever ICFs are below grade. Above grade, I think Tyvek, or the like, would be fine, plus a rain screen, like vertical 1x4s (if that is appropriate w/ stucco).

Hey J, do me a favor and break up the next paragraph for me would you?

Thank you sir.

Andy.
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Old 10-31-2011, 01:54 PM   #29
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Hey J, do me a favor and break up the next paragraph for me would you?

Thank you sir.

Andy.
Sure. Sorry about that; my etiquette slipped away in my haste.

First, I am not an expert at anything, let alone ICFs. I have never insulated them more than what they are, but I understand, and it seems logical, that you can screw through your foam into the plastic channels in the ICF, as people do when insulating w/ foam on the outside of stick houses (REMOTE wall, for example).

The rub w/ ICFs as far as insulation is what I mentioned above, about the heat going out of them more than into the house. Putting foam on the outside tends to reduce that, but there is no point in doing anything if they already have sufficient R for your area, esp if the sun is being used to warm up the concrete; that is free heat, and concrete and sun do well together (but watch for overheating, of course).

I would then goo and/or tape the seams of the added foam.

As for a weather resistant barrier, I'd sure use one. All those joints in the blocks will possibly leak by wicking water in, if it gets past the outer layer; accidents happen.

When we built below grade w/ ICFs we were advised to use bituthane membrane over the blocks to water proof them. It is a rubbery, sticky membrane that comes in rolls. The ICF provider sells it, and I see something like it used wherever ICFs are below grade. Above grade, I think Tyvek, or the like, would be fine, plus a rain screen, like vertical 1x4s (if that is appropriate w/ stucco).
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Old 11-01-2011, 07:17 AM   #30
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you'll invest a bit more for icf - typically 10%,,, however the amortization of the addl exp is about 18mos of energy savings,,, after that, is always less $$ out of your pocket,,, then add in the addl strength & lack of exterior noise,,, if electrician can't learn to pull wire in 2hrs, get another guy,,, when we applied our stucco coat, the mesh was stapled directly to the icf's exterior surface.

i've built w/wood & icf's & our next home will be icf,,, as dick (concmasonry) posted, are you building for short-term or not ?

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