The mistake in that analysis is that the presumption that your wall-R is a dominating factor in the heat load, whereas it is not.  In most homes with R20+ whole-wall values the window losses alone exceed the wall losses, and wall area only accounts for something on the order of 25% of the whole-house heat loss. (And that's why the mass effect in mass-walls in most climates is only a single-digit percentage reduction in fuel use, even if it allows you to undersize the mechanicals by double-digit percentages sometimes.)

Nor is the heating system very likely to be designed EXACTLY to balance at the the outdoor design temp. Most heating systems even if designed precisely to Manual-J with ZERO oversizing would have at least 15% margin,  and usually more like 25%.  If the heating system was designed even 10% above Manual-J (most are more oversized than that) most would be able to dwell for weeks at temps below design temp and still keep up. 

For the sake of argument let's say your outside design temp is -32C, and you treated the walls as a low-mass R50 based on some DBMS figure in your heat loss calc by which you sized the mechanicals (not recommended, but people do- there are better models for sizing mechanicals in high-mass houses), and in the calculation the walls counted for fully 30 percent of the total heat loss (that would be the exceptional case with an R20+ whole-wall house,  but let's just say it is.)  At a steady-state ASTM C518 R of R24 that means the heat loss through the walls is ~2x what you calculated for if you stagnated at -32C for a ~30% increase in the whole house heat load above what was calculated.

If your Manual-J was only a 15% overshoot, and the heating system was only 10% upsized from the Manual-J you might fall a few degrees short after a few days, but you would NOT be freezing.  You're looking at a heating system that's only putting out 1.15  x 1.10=  127% of the  calculated load, and you're stagnating at 130% , so your heating system is only putting out (1.27/1.30=) 97.7% of your calculated heating needs. You want to keep it at +21C, but the system can only maintain 19.8C after days of -32C.  Are you freezing yet? (I didn't think so.)  If a 1.2C undershoot is too much to handle, you could close the shades at night.

And if it actually got up to -26C with a daily average of -29C you'd undershoot by less than a degree with just the thermal mass of a low-mass house, and only briefly at that, but with ICF you'd probably coast through just fine.

With more typical 15%+ oversizing of the mechanicals above you could stagnate at design temp forever and still keep up.  (1.15 x 1.15= 132% of your calculated and your stagnated heat load is at only 130% of the calculated design load- you have a slim margin.)


 


Dana - in this case we know what the maximum energy consumption is. We know that the windows, slab and roof will remain the same if there is frame walls or ICF walls. We want to figure out how long at a delta of 95 to 100 it will take to remove the effect of mass from the icf walls. Once we have that then all required heat is for conductive loss.  
 
52000btus is a pretty low heat loss for 6300 sq.ft. or 58000 cu.ft. I know that I can heat for somewhat less than that for at least 3-4 day at design. You are suggesting that it would take longer than that to eliminate the effect of mass. Well how long? Do we figure out what the specific heat of 5" of concrete is, decide what the average actual temp of the concrete is and then wait for enough hours at a d.t. of 100º to consume that heat? After that it would be straight conductive? I'm sure there is a formula out there but I haven't looked for it yet. Maybe you know one off the top of your head? 
I would like to know if the good performance is all mass or not. For sure low infiltration and low bridging play a part, but is that all? As you know I don't like the insinuation that icf is not really for cold climates. I happen to think it is one of the best building models we have up here ;-) Also happen to think it is one of the most cost effective over the long haul.
 
Btw a recovery to 26 would still only give us a mean average of somewhere around 31. The rise is all solar effect and the sun is pretty lazy up here at this time of year. Its a slow climb to 26 at about 2.00 p.m. and it falls off sharply at 3.30. And I guess I'm out of luck 'cause I don't have the shades up yet ;-)

Who says ICF isn't for cold climates? The upshot here, if any, is that ICF isn't the mass wall of choice for the southwest. ICF is the only mass house I'd build in Calgary, but I'd want for its insulation and tight construction rather than its concrete.
there is no mass effect at minus30C. The concrete right under the exterior foam will be a degree or two warmer, the concrete under the interior foam will be a degree or two cooler than 21C. From a btu's perspective it's all downhill from there.
Yes you know your home's energy consumption. The only way to know if it is better than the identical low mass house next door is to build that house and compare them.
If you reject the knoxville ORNL/ICFA study as fatally flawed, seems to me you should be asking your trade group where they have been for the last 12 years. Spare us what the trades are trained to do. My dog is trained to find birds. That doesn't make her an ornithologist.

Posted By toddm on 11 Feb 2012 08:36 AM

If you reject the knoxville ORNL/ICFA study as fatally flawed, seems to me you should be asking your trade group where they have been for the last 12 years. Spare us what the trades are trained to do. My dog is trained to find birds. That doesn't make her an ornithologist.

It was also sponsored by Home for Humanity, so following your logic, I guess the homeless where the true experts.

Habitat for Humanity volunteers helped build the houses so, yes, that group was a sponsor as well.

Posted By toddm on 11 Feb 2012 08:36 AM
Who says ICF isn't for cold climates? The upshot here, if any, is that ICF isn't the mass wall of choice for the southwest. ICF is the only mass house I'd build in Calgary, but I'd want for its insulation and tight construction rather than its concrete.
there is no mass effect at minus30C. The concrete right under the exterior foam will be a degree or two warmer, the concrete under the interior foam will be a degree or two cooler than 21C. From a btu's perspective it's all downhill from there.
Yes you know your home's energy consumption. The only way to know if it is better than the identical low mass house next door is to build that house and compare them.
If you reject the knoxville ORNL/ICFA study as fatally flawed, seems to me you should be asking your trade group where they have been for the last 12 years. Spare us what the trades are trained to do. My dog is trained to find birds. That doesn't make her an ornithologist.

ICF is the better wall even in the southwest.   ORNLs DBMS tables show a clear advantage in Phoenix to internal mass over double insulated mass (ICF) but the the difference in R-value is just too great between say AAC and ICF for the DBMS effect to overcome it (even there).    

In other words you need to compare your R-10 wall AAC wall (on the chart) to an R-22 ICF wall (which is off the chart).  So if you really want to get down to it you can't really use these charts for an honest comparison.  Furthermore, depending on who you ask ORNL or ASHRAE -- AAC is marginally a mass wall at all with a heat capacity typically about half that of a 6" ICF wall.   In fact, ASHRAE's minimum of 7 Btu/sqft F leaves some of the lighter AAC designs of 5-7 Btu/sqft F out of the mix (not massive) and not applicable to ORNL tables for mass wall systems.

"There's no mass effect at minus 30C.  The concrete right under the exterior foam will be a degree or two warmer, the concrete under the interior foam will be a degree or two cooler than 21C."

This statement is not correct.   The first problem is that total delta T inside the concrete typically only a degree or two.   E.g.   17C +/- 2C.
The concrete never has more than a degree or two variance cold side to hot side.    Your example of a a steady state (been cold outisde for a while) wall with a huge temperature gradient of 50 degrees C is not possible for a conductor.  It (the concrete) will remain at a relatively constant temperature.  This is part of the reason you don't need set back with ICF. 

The second problem with this statement is that the concrete temperature is typically within a few degrees of the inside set point temperature.  In the many times where we've measured temperatures inside the wall the concrete typically varies no more than 8 degrees C from the set point (inside temperature).  This is true here in Texas and way up in Canada and is true regardless of outside temperature.   In other words, the concrete temperature generally parallels the inside temperature and is largely independant of the outside temperature.  

I know quite a few ICF folks in Canada that maintain that (when it's very cold) since their walls start on a concrete footer well below the frost line (e.g.  earth is at say 10C (50 F)) the walls are constraintly receiving heat from the earth.   I am in agreement with this as it reflects my thermistor studies here.   Clearly since it's so very cold outside heat is traveling up from the earth and is conducted by the walls.  I prefer to believe in heat traveling hot to cold instead of magic.

Posted By toddm on 11 Feb 2012 08:36 AM
The upshot here, if any, is that ICF isn't the mass wall of choice for the southwest. 

So for my area, southwest Arizona (Prescott) if I went with ICF, would I be throwing money into the wind?

Turns out TexasICF is right about the relative constant temp in an ICF concrete core. My bad. Toward the bottom of this page you'll find a link to a Canadian study monitoring probes in the walls of an ICF apartment building in Waterloo, Ont. http://gbt.buildcentral.com/Forums/tabid/53/aff/4/aft/49134/afv/Topic/Default.aspx You might jump right to the conclusions page where it states "No thermal mass impact or higher effective insulation value was observed."

I am linking the discussion rather than the study to demonstrate that we have here is not so much an ongoing thermal mass problem as a TexasICF problem. Facts bounce off the man like bullets off Superman. Density is less an issue than focus, I think. Green means energy savings here to most people. TexasICF has a different kind of green in mind.

Among the ricocheting facts is this chart I am showing TexasICF for the third time: http://www.ornl.gov/sci/roofs+walls/research/detailed_papers/thermal/figures/figure8.pdf
As you see, ORNL's DOE2 computer model predicts that R5 ICF will get you ~12.5 percent energy savings over regular stud wall in Phoenix. Ramp that up to R25 and your savings FALL to ~9 percent. And yet TexasICF continues to pretend that there's nothing wrong with ICF in Phoenix that more insulation wouldn't fix. TexasICF likes visuals so think of it this way: You're going to bed on a cold winter night and anxious to share body heat. Then you discover that your snuggle bunny is wearing a heavy down parka. That is ICF in Phoenix.

AAC gets you a bit less in effective R value. On the plus side the materials cost all in is roughly 2/3 the price of ICF block alone. Masonry contractors in Phoenix should have both experience and sharp pencils. As another plus you get 90 degree corners and straight walls without waves, dents or bulges. Stucco is a step easier and cheaper. You can paint AAC to pass code in nonpublic areas like the garage, mechanical areas and walls under cabinets, tile or paneling. My house took 3000 SF of stucco outside but only 1200 SF of plaster inside. Plaster costs all in were less than drywall cost along for every sf, which is a requirement for ICF. Acoustic and fire ratings are better: four hours for AAC in the latter case, making it the firewall of choice in coal mines. Finally, if you want your house to look like a wedding cake, complete with frosting roses and statuettes, hire an ice carver, hand him/her a very very good dust mask and step upwind. I'm guessing Rastra and Apex could make similar arguments.

Lbear, my advice is go with the flow in your market. There are very few areas in the US where ICF is common enough to promise consistent quality and competitive pricing. AAC is less common, although Arizona might be the exception. You'd want contractors who have done dozens of houses. If you can't find them, there is nothing wrong with CMU, which with recycled xps, would be cheaper than AAC.

Posted By toddm on 13 Feb 2012 10:48 AM
As another plus you get 90 degree corners and straight walls without waves, dents or bulges. Stucco is a step easier and cheaper... Plaster costs all in were less than drywall cost along for every sf, which is a requirement for ICF. Acoustic and fire ratings are better: four hours for AAC in the latter case...

Can't let this little disingenuous tirade pass without commenting...

(1) Polycrete proprietary corner guide system ensures corners are 90 deg. if they're supposed to be.

(2) Welded steel wire mesh within the foam panel prevents bulges, scalloping and snaking. Large size (2' x 8') allows 2 braces on each form. Forms withstand 1,600 lbs / sqft of lateral pressure, almost 2x that of the next strongest form. Forming capacity test results are on the website.

(3) Stucco is not a step easier or cheaper, it's the same. EIFS is a step easier on the ICF wall than the concrete block since you don't need the rigid foam board.

(4) Six inch Polycrete wall has a four hour fire rating -- those test results are also on the website.

(5) Acoustic ratings on a 6 inch ICF wall are STC 57. Can't imagine circumstances under which AAC is higher.

(6) Drywall is not a requirement for ICF, there are some fine veneer plaster products that perform beautifully on ICF walls.

Hope that clears things up. As Tex would say.... Regards

Todd,  Thanks for pointing me to this old link.   From your link -- I think mlevendo pretty much sums up my thoughts on cold weather ICF benefit and he or she sounds a lot like many I've spoken to that live where things get really cold.

"I have no doubt that thermal mass is still a benefit of ICF walls in cold climate because of what I have experienced so far. We have an ICF house in central Minnesota that will be finished in March. It is all closed up and the current heat source is an electric plenum heater (the two stage air source heat pump is not hooked up yet). We have had drastic temperature dips this winter with it dropping down below -20 F. I can view my per day electric usage via my utility providers website. The thermal mass defintely levels out these low temperature swings. Lately our temps have peaked in the single digits. Last week my project manager turned the temp from 66F down to 55F. Electric usage dropped to near nothing for almost 2 days. This occurred when we were on a 3 day cold stretch and the average outdoor temp was -17 F. It never got above -10 F during that cold snap.
In order for there to be no benefit of thermal mass the concrete in my wall would have to be equal to the outdoor air temps. I don't think that would ever happen with the concrete wall/footing in contact with the earth down below the frost line. Plus there is the heat from the interior that would also be heating the concrete."

Don't you want to listen to what people that actually live in these homes have to say? 

Regarding what a chart says about how an R5 ICF performs, I don't give this a lot of weight because as far as I've seen no such ICF exists (today or back 10 years or so).  Almost all ICFs are in the area of R22.   Also, although Phoenix is ideal location for internal mass Lbear is building a few miles north of there were climate zones 4 and 5 cross.   R-value and mass start to matter more and more as you get colder and get into higher temperature swings.   I'm with Bruce on this one, ICF is clearly the better system. 


Although, the material is still more commerical at this point I think googling "ASHRAE 50% Solution" for the DOE report will give you more recent data on thermal mass and for the eight climate zones including North Alaska.   Regards.

All I know is the icf contractor who built my foundation stem walls managed to make more mistakes and bigger mistakes in two courses (TWO courses) than my mason did in the rest of the house. The mason was appalled at how approximate the walls were, and this contractor came with the distributor's recommendation. Again, my advice is don't pick a wall technology that is rarely done in your part of the world.

Painting AAC walls is simpler and cheaper than anything you can do to bring ICF up to code.

My 8 inch walls are STC 47. They can be brought up to STC 68 at greater thicknesses and with an air gap. Interior walls panels are almost price competitive with stud walls and get you STC 40. With insulating and fire pluses as well, motel chains are liking AAC a lot.

Stucco over AAC doesn't require foam boards; the blocks are self insulating. By skipping the mesh, stucco is indeed one step simpler on AAC than ICF.

I have been careful not to generalize from my experience, which is not typical, or to impose my preferences on folks who are building different kinds of houses in different climates. You stop torturing the truth about ICF and you won't hear me from again.

TexasICF, if you put less weight on anecdotal evidence and more weight on scientific research, your posts would be worth reading. But that wouldn't do much for monthly sales, eh? Can't wait for you to publish your thermistor work.

Well, at least we can now trace the root of Toddm's anger at ICF technology. Another incompetent installer. Manufacturers can train installers and certify that they have completed the training course. Unfortunately, they can't verify their workmanship or diligence. That has to be up to the building's owner.

If you're acting as your own GC, get references from the ICF installer and then actually check the references. Go look at their previous work. If your GC is responsible for hiring the subs, don't accept shabby work.

Manufacturers can not refuse to sell their products to contractors, but they can stop recommending contractors that generate complaints. We have done that in the past and will continue to do so. Can you imagine Home Depot refusing to sell 2x4's to a lousy framer?

Todd, Oh well, your silent treatment lasted 10 minutes. I still think you should read some of the newer stuff from ASHRAE and DOE. That way, when you sit down to build again you'll have all the data. It also might benefit you to listen to folks who actually live in ICF homes. Bruce may be right about the installer being the anger source but I think it's also about trying to make the AAC decision seem like a good one. I don't think ACC is a bad system by any means -- I just don't agree that it's on par with the typical ICF. Regards.

Posted By toddm on 13 Feb 2012 01:33 PM
All I know is the icf contractor who built my foundation stem walls managed to make more mistakes and bigger mistakes in two courses (TWO courses) than my mason did in the rest of the house. The mason was appalled at how approximate the walls were, and this contractor came with the distributor's recommendation. Again, my advice is don't pick a wall technology that is rarely done in your part of the world.

My 8 inch walls are STC 47. They can be brought up to STC 68 at greater thicknesses and with an air gap. Interior walls panels are almost price competitive with stud walls and get you STC 40. With insulating and fire pluses as well, motel chains are liking AAC a lot.

Stucco over AAC doesn't require foam boards; the blocks are self insulating. By skipping the mesh, stucco is indeed one step simpler on AAC than ICF.

I have been careful not to generalize from my experience, which is not typical, or to impose my preferences on folks who are building different kinds of houses in different climates. You stop torturing the truth about ICF and you won't hear me from again.

That happens with ALL the trades; wood frame, SCIP, SIP, AAC, etc., all of them have bad installers and all of them have nightmare stories of bad installs. I know of wood frame contractors that cannot make a square wall. I currently live in a tract home that is made of wood and I have had tons of problems with bad framing and water leaks. The only good thing is that the builder came back and fixed the issues but the quality of the home will never be that great.

Out in my neck of the woods I cannot build with SCIP or AAC, as there is nobody out here who even does it. What I know for sure is that the area I will build my custom home in, wood homes do not do that well because of the termites, rodents and other critters. For me ICF is the clear choice, and I have one contractor that does ICF and does it very well. I have seen his work. If he is not available when I am ready to build, I can always get an ICF builder to come in from another state to do my project.

Each technology has its pros and cons, there is no "perfect" building technique. I am confident that if you had a qualified ICF installer, your walls would be true. I am also confident that the ICF guys on this forum build straight walls.

The thread I linked to a couple of posts ago began in January 2009, and my "anger" was evident then. I got my building permit on Nov. 1. 2009 so by your reckoning I am both clairvoyant to have anticipated problems with my slab 11 months later and dumb as a box of rocks to proceed. Nice try, though.

I couldn't find an ICF contractor who had done a slab on grade. Because slabs on grade are rare in the North and footers and stem walls are rare in the South, I am betting that most ICF contractors lack this experience, even though ICF is both far superior to CMU for this purpose and competitive in price. For the benefit of neophyte pros, DO NOT say, as the four of us did, "it's only two courses." Corners on low, unbraced walls are more likely to float rather than less likely. While you can true up rim boards and ledger boards, a slab is what it is. Happily my mason had it true in a single course of AAC. There is no substitute for 40 years of experience, eh?

You confuse me Lbear. You have conducted the world's longest courtship of a wall system, which apparently is ongoing, except you say on a different thread today that you have hired an architect and are passing along detailed questions about ICF. So.... shill for the ICF carney barkers on this site?

Not to worry about my silence TexasICF. You bring up the Mythical Earth Coupling Plug, pixie dust in the ready mix or Smart Foam (heat checks in but it doesn't check out) and I'll be here.


'

Give it up Toddy. You've been exposed and they've got your number. Now go back under that bridge like a good little troll.

Posted By toddm on 13 Feb 2012 07:18 PM

You confuse me Lbear. You have conducted the world's longest courtship of a wall system, which apparently is ongoing, except you say on a different thread today that you have hired an architect and are passing along detailed questions about ICF. So.... shill for the ICF carney barkers on this site?

 

The "architect" is a family member of mine who is a retired architect. He is doing the design of the home as a favor but he has a learning curve because he has not worked with ICF before.

When it came down to the wall systems, I researched all of them. When I contacted SCIP builders, only 1 returned my call, the others never got back to me. The one that did return my inquiry was not even that interested in my project as he is out of state. Then he quoted me some insane price tag which basically killed and buried SCIP. Plus I am not too thrilled with the SCIP interior wall finishes. Nobody out here does AAC. I don't like wood SIPs, but I will most likely use steel SIPs for the roof.

That leaves me wood frame or ICF for my wall system. The rural area I am looking to build has tons of burrowing pack rats and field mice. I have talked to homeowners out there who constantly have rodents getting into their homes by gnawing through OSB and even 2x4's. Just talked to someone the other day that had woodpeckers drill holes in their wood fascia which left holes for squirrels and rodents to get into their attics. I didn't even mention the scorpions which only need the width of a credit card to enter into the wall system of the home or the subterranean termites which would destroy the wood wall systems if not caught early.

Even if I still went with wood, how much $$$ would I have to spend on open spray foam for the walls to get an effective/true R-22 value? Blown-in cellulose or fiberglass is just a RSVP for rodents to come in and nest within the walls. In the end the cost to spray foam the walls and go with wood frame would be on par with an ICF wall.

Plus the area I will build in has a forest fire and seismic factor.

If you were in my shoes, honestly, which wall system would you choose?

I'm confused guys. Who's arguing what? Or are you just arguing for the sake of arguing?

Seems  to me the only ones in this thread who are making any sense are Dana, Lbear, and myself. And sometimes I wonder about myself!!

Where the hell have you been dmaceld? They're just arguing for fun. It's what they do. Lbear and Toddy throw out the bait and FutureStone and Polycrete keep coming after it. They can't help it. It's like the story about the scorpion and the frog... It's their nature.

Sorry, delayed double post