AAC vs ICF vs Stick vs Cost vs Speed vs Performance
Last Post 05 Feb 2010 06:45 AM by renangle. 8 Replies.
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codetranceUser is Offline
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15 Feb 2007 09:46 AM
Hi all,

I have enjoyed all the interesting, and often 'opinionated' threads here, and thought I'd throw my scenario out there to see what people suggest.

I'm building a home in Northern Virginia that will feature stucco on the exterior and plaster on the interior, so I'm looking for a good wall system.  The exposed portions of a walk out basement will have stone veneer.

Although I know ICFs are the best solution from an R-value perspective, I'm pretty leery of the idea of having the massive amounts of foam in the house, as this may may off-gas and contribute to poor indoor air quality, and would certainly create noxious gasses in the event of a fire.

That said I'm considering:

1) AAC (autoclaved aerated concrete)
2) Rastra (a composite ICF with polystyrene beads supended in concrete)
3) Durisol (a composite ICF with wood fiber suspeded in concrete)
4) 2x6 framing, with wrap and lathe/stucco on the exterior, and blueboard and veneer plaster on the interior

With any of these I'd likely do one of the above mentioned ICFs for the foundation, unless people can recommend the Superior Walls's product. I hear they can leak at the corners though... The house is located in a swale and there will be a lot of water pressure on the basement walls (the prior house's basement flooded quite a bit)

Does anyone have experience with these? What would be the cheapest? what's most durable?  An AAC guy claimed that given my stucco/plaster route, AAC would be cost competitive with Stick, and I like the idea of not having to use stucco over wood, but it's steady state R-value is not terrific, 1.1 to 1.2 per inch.  From an esthetic standpoint I want to have thick walls, (like 1 foot) I want the house to feel like it's really solid  (like traditional stucco over stone), and AAC does have 12 inch thick blocks which would have an R value of 13.2-14.4...

Durisol or Rastra can be done 12 inch thick and would have an R-value of 1.7 per inch - or R 20...

Both AAC and the Composite ICF's benefit from less air infiltration, greater thermal mass and all that dynamic r-value voodoo.

While 2x6 stick can have R-22 batts, there's more air infiltration and thermal bridging.  I could still create the impression of massive thick walls by building out around windows and doors, but using the wall depth for built-ins in other areas. Stick would likely be cheapest though.

Lastly, I'm not totally opposed to EPS ICFs, if it were only used in the basement, as I think any potential fires would be more likely to start on upper levels.  I'm leery of finishing foam with stucco though, and how would I attach a stone veneer on the exterior?

I'm driving myself nuts with the whole cost vs. performance vs. speed vs contractor familiarity equation...

Any ideas?

Thanks,

RC
bonzai95User is Offline
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15 Feb 2007 10:11 AM
First off I'm not a pro at all, just someone doing research.

This is all from technical specs for SIPs, but I'd imagine that ICF's are similar (same material). As far as offgassing goes, there doesn't appear to be any with EPS. EPS doesn't support a flame itself, and the fumes given off are less toxic than cotton.

Can't speak to the rest of your questions, but I hope that helps.

John
Alton C. KeownUser is Offline
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15 Feb 2007 12:02 PM

Codetrance,

Have you considered the Styrofoam T-Mass Technology?  This system places Styrofoam between two layers of concrete.  Electrical wiring can be placed within the inside layer of concrete thus negating the need for a false wall inside the home.

Alton

codetranceUser is Offline
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15 Feb 2007 12:18 PM
Thanks guys. I did read the report by the EPS association which said it was less toxic than cotton. I'm more concerned though, by the quantities of smoke being put out... Styrofoam makes a really dense black smoke, if you've ever burned it, you know what I'm taking about.

I am interested in the T-mass walls, and I contacted Dow- it was recently sold to a company called Composite Technologies Corp. My only concern with T-mass is the same as with the Superior Walls product- what happens at the joints between panels? It just seems to make sense that a monolithic pour would be more waterproof.
APWUser is Offline
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15 Feb 2007 04:05 PM
I built a T- Mass home in 2001, waterproofing was not an issue. I can send more info if interested.
I didn't agree with Dow on their R value specs ( 4" of concrete 2" of foam and 2" of concrete wall )
Alton C. KeownUser is Offline
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15 Feb 2007 04:47 PM
RC,

If I remember correctly, the Styrofoam T-Mass Technology can be accomplished three ways:
1.  Cast and finished in factory - very nice finish
2.  Cast and tilted up on job site - finish depends upon skill of local crew
3.  Placed in continuous forms at the job site - finish not as nice as cast in factory finish but nice enough for a basement since each side can be covered with other materials.  Continuous placement of concrete avoids cold joints in concrete.

Alton
renangleUser is Offline
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04 Feb 2010 05:45 PM
RC,

We'll agree the the EPS is less toxic than cotton, but I am a little curious about your concern regarding the "smoke" put out with the EPS of the ICF walls? Have you been in a house that has caught fire before? What do you plan on doing with the interior walls of the house, build them with something that is also non-combustable? ICF houses are much tighter than most other homes, thus the ability for a fire to really get started is diminmishied due the the required quantities of oxygen to really get it to flare up. I would have to think this would be more the case should it be an electrical fire in the wall, because there would be so little room (between the EPS and the sheetrock) for the fire to go anywhere. Why I would agree that 2 x 6 would be slightly less expensive, if you concern is fire, then you are back at square one. I have seen the "smoke" created by the EPS during work, but it wasn't that bad. Plus it isn't flamable or not that I have experienced. In an ICF house, the fire/smoke would have to get through the sheetrock or plaster before achieving any "smoke" associated with the EPS.

I would think that an ICF house would more than suite your needs and would arguably be the most energy efficient. A 6" ICF wall has a fire rating of about 3 hours (depending on what you read), so if the fire is outside you should be pretty safe inside.

I think that you should choose the material that makes you the most comfortable, but I don't see where the "smoke" that could possiibly be associated by the EPS should be a concern to you.

renangle
arkie6User is Offline
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04 Feb 2010 06:03 PM
Looks like someone dug this thread out of the historical files. Do you guys realize that the guy that started this thread hasn't posted on this forum in nearly 3 years?
renangleUser is Offline
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05 Feb 2010 06:45 AM
arkie6,

Thanks for pointing that out as I missed it. Thank you synergybuilding for wasting my time! Why respond to a 3 year old post?
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