R values of ICF's

[carpenter]

I attended a seminar a couple of years ago hosted by one manufacturer and our supplier of that brand. The thing I remember is that they spoke in terms of effective R value. They claimed to have an effective R-50.

When I asked what the difference was between an actual and effective rating and how they could acheive such a high rating with a little stryofoam and concrete all I can recall is being lost in the explaination. If the resident scientist could take a stab at it I would appreciate it and reread it until I understand.

FWIW, I went to the seminar because we had sold a job to construct a shop building using ICF's for the foundation and haven't used them since. I am currently considering them for a personal project and want to get my facts straight. ( if possible ) TIA

Good Luck
Dave

[cblock]

Re: R values of ICF's

Try this - www.cemstone.com or www.rewardwalls.com
I believe their 9" has a steady R-value of 22, calculated w/ just forms and concrete. It has a Effective R-value of 32 using the entire wall assembly and calcs. for thermal mass, air infultration, and thermal wicking.

They can have up to 200 mph wind loading also. 1 - 4 hour fire rating, depending on size/thickness.

[RichAM]

Re: R values of ICF's

Most of what I've seen as far as documented information from the Oak Ridge National Laboratory shows that the true R-Value of the ICF is dependent on climate. The warmer the climate the higher the R-Value.
Here is the report from ORNL on Reward Wall forms - looks like they figure it at R16.1
http://www.ornl.gov/sci/roofs+walls/...rd/results.htm

[carpenter]

Re: R values of ICF's

Thanks for those links to get me started. In trying to find my answer I ended up here;
http://www.arxx.net/r50.htm. Oddly enough, the brand that hosted the seminar I attended.

If I understand it right the foam gives and actual R value of 22 and the thermal mass + reduced infiltration deliver the effective R value increase. The foam being equal on both sides means R-11 each, leaving the thermal mass somewhat exposed relatively.

I wonder if there would be a reasonable gain in performance by adding another layer of foam board on the exterior. Adding another R-5 for ex. would bring the exterior side to R-16, possibly forcing the mass to prefer to radiate to the interior rather than both directions.

Good Luck
Dave

[James Eggert]

Re: R values of ICF's

I have used, consulted and taught ICFs for many years, and I will say specifically that the term "effective" is used in the wrong context. The reason is everyone remembers the 32 or 50 or some of the other claims.

The simplest basis for comparison, and c alludes to this above, is that ICFs perform as an assembly, and when you take all the parts of that assembly, both tested and/or measured and/or totaled up as so much per part you end up with an assembly rated at say R26. Into the equation enters air infiltration, typically nil thru concrete, and thermal mass, or what I call the dumb house effect. These are the benefits which some companies have attempted to place a numerical value on and many times creates the creative math answer. Because of thermal mass, the outdoor temp swings take days to change the interior wall mass temp, so the interior constant temp isn't affected as rapidly as a wood frame wall!

However, when you do place a value onto the total in-place assembly, this is where a wood frame wall has to be built to very high in-place R values in order to provide the same performance that ICFs provide.

So, you need to build a wood frame wall to approx R50 to achieve the same performance that a lower R value ICF wall provides simply due to the performance characteristics of any ICF wall.

Now, once again....I did not say ICFs were R50. I'm only trying to explain the way the ICFs work!

[RichAM]

Re: R values of ICF's

Here is the test report for Arxx blocks -
http://www.ornl.gov/sci/roofs+walls/...XX/results.htm
I don't see anywhere that says R-50 under any conditions. Don't get me wrong - I like ICF's and have worked on several projects where they were used on the whole house and they work fine. Mostly used them on basements and crawlspaces though. I just don't like some of these claims of R-50 - maybe when all conditions are perfect in some climate.

[carpenter]

Re: R values of ICF's

Thanks for both of those responses. I want to be clear that the Arxx site only claims a rating of R-22 but then refers to a 1997 Illionois study that gives them an effective R-50 compared to wood or steel construction, much like Jim explained. I hope I've got enough sales experience to recognize the fluff.

My understanding of using a thermal mass is to regulate interior temps by slowly absorbing energy during the warmer end of cycle and then slowly releasing it during the cooler end of the cycle. If this mass is equally insulated on both sides it seems it would give off it's energy equally in both directions or even more to the cooler exterior.

The site that Rich links to demostrates a temp. differenc of almost 60 deg. F from the interior rebar to the exterior rebar for example.

What I'm really wondering is if would make any significant difference to add more insulation to the outside or am I over analyzing this?

What I'm considering is replacing my outdoor furnace with a heating shed that would contain a heated water tank. I want to try heating the water with solar panels and some sort of back up appliance.

Thanks again.

Good Luck
Dave

[Martin Holladay]

Re: R values of ICF's

I will join the chorus of suspicion at the term "effective R value."

According to the Federal R-Value Rule, there is no legal definition of "effective R-value," and material manufacturers put themselves at risk of federal prosecution when making marketing claims of "effective R-value." Certainly, "effective R-value" has no scientific definition.

Whether or not there is any net benefit from thermal mass in your wall is, indeed, very dependant on climate. In some areas of the Southwest, where night temperatures are chilly but daytime temperatures warm to a comfortable range, thermal mass makes sense. But in northern Minnesota or northern Vermont, where the temperature drops below 32 F and stays there for 5 months, all that concrete is doing diddly-squat. You still need BTUs to heat your house, and when the temperature is cold and stays cold, you're not getting any benefit from the concrete.

So those of us who live in cold, northern climates should be especially suspicious of inflated "effective R-value" claims.

[cblock]

Re: R values of ICF's

I want to be clear that the Arxx site only claims a rating of R-22 but then refers to a 1997 Illionois study that gives them an effective R-50 compared to wood or steel construction, much like Jim explained.

Nice! COMPARED is the key word in this "effective R-rating" idea.

[RichAM]

Re: R values of ICF's

I personally think SIP panels are the way to go if you are looking for a structural material with consideration for R-Value. It's a bit easier to add a window too :)
Overall I think the combination of SIP exterior and ICF foundation is the best solution for an affordable R-Value conscious home. When looking at the energy efficient "time" we are in, the 2x framed wall is losing some ground. Although I think exterior insulation on framed walls and the correct air sealing can be effective as well. It just depends on where you want to put your money at.

[Ted S.]

Re: R values of ICF's

I was waiting for Martin to chime in, he schooled me on the Insultarp. I agree with what he says, if you every build an ICF house just try and get that sucker up to temp with some salamanders, it seams to take 1/2 a 100lb tank of propane .

[stan54]

Re: R values of ICF's

I have client interested in building a house with ARXX
He is so excited about that r-50 claim
I just cant see r-50 with 6" concrete and 5 " styrofoam in upstate New York
LOGIX is knock off of ARXX I think guy who started ARXX later quit and started LOGIX
Anyway ,IMHO claims of r-50 in cold climates are exagerated
Besides cost of ICF home is much higher than frame

[carpenter]

Re: R values of ICF's

Thanks for all of the enlightening info. For me the "effective R-50" has been debunked and it will be back to the drawing board.

I am looking to construct a very small, very energy effiecient shed. The intention is to house a large tank of heated water and a back up heating appliance to pipe hot water to the house for heat. I'll need to maintain at least 150 degrees in the tank and overnight temps of -30 are not unheard of here.

Fire safety is also a consideration. Wood is my fuel of choice, although not averse to anything other than gas, oil or electric.

Good Luck
Dave

[Mark Parlee]

Re: R values of ICF's

Dave

why don't you consider the superior wall system and fill the cavities with foam?

http://www.superiorwalls.com/

[cblock]

Re: R values of ICF's

For me the "effective R-50" has been debunked and it will be back to the drawing board.

Wait,wait, wait. Debunked? Sure r-50 is a bit of a sales pitch but how far off do you really think it is? Even if "steady r-value" is 22, that ain't bad. You said "very small, very energy effiecient shed", AND, "fire saftey is also a consideration". You are going to store heating equipment in it, depending on size, that place could heat itself. If it doesn't, it would only take a candle or 2 to maintain decent heat.

You need to maintain 150 in the tank. Is the tank not insulated itself?

Have you checked into T-Mass construction aslo called sipcrete (poured wall-foam-poured wall). If the hang-up on ICF's is (foam-concrete-foam) the mass effect in cold weater, then T-mass would hold that mass effect where you want it. T-mass would have a much lower "steady "R", but can have a higher % increase of "effective R" because of the thermal break inside the wall.
http://www.sipcrete.com/
http://www.housingzone.com/article/CA6275261.html

The link below had a good article on this topic. It said everything that was posted above and a decent expalation for all of it.
http://www.buildinggreen.com/auth/ar...me=070401a.xml