Okay, I have been away for a while, but I came across something that has frustrated me, so I thought I would ask if I am misguided. A friend of mine is going to build a rather simple full basement and 2 stories above grade house that is about 2700 sqft. I strongly urged going ICF due to the few corners and well I feel it is the best way to build. I would also get decent windows, etc. Now, I run into the guy last night and asked for an update. Apparently he spoke to a passive haus guy who said the house (located in central Virginia) would be more efficient (and cheaper) if they go with 2 x 6 sprayfoam insulation, triple pane windows. Am I wrong or is the passive haus get a bit off, in part because they have their own agenda? It just frustrating to me to hear that the passive house guy says that he is very familiar with ICF...though never built with it, then says that 2 x 6 spray foam is better. I know I have been away for a while, but has something changed? Any input would be appreciated. Ren

Hi Ren. Glad to see you're still around.The sticks and spray foam vs. ICF debate has been raging unabated. Poke around in the other threads.

Some claim that you will get higher total R value in the wall with the spray foam, but you do not get all the other benefits of ICF. Durability, longer building life, lower maintenance, lower insurance, disaster resistance and the overall sense of well-being that comes from living in a very solid house.

My argument is that you can't separate those other benefits of ICF, so you have to account for them. If you just want a higher R value wall. Sticks are cheaper. But who wants to live in a cheap house? It's like comparing a BMW and a Kia that get the same gas mileage.

Passive house is about R-value. Using that as the measure success then yes 6 inches of closed cell foam will outperform the ICF in cost and energy savings.

This is what happens when you take your ICF plans to a contractor. They immediately try to turn you to something else - something that they can build.

Posted By jmagill on 28 Jan 2012 01:49 PM
Passive house is about R-value. Using that as the measure success then yes 6 inches of closed cell foam will outperform the ICF in cost and energy savings.

Yes ICFHybrid, you are correct.  

Passive is much more involved and complicated than just R-value.   In fact some passive systems use ICF but it's only a part of it.

R-value is not a measure of success for passive haus.

6" of closed cell foam (which is seldom done because it must be done in stages due to heat / fire risk) will not provide enought R-value for a 2x6 wall to beat  your typical ICF.  Due to the conduction of the studs, to beat ICF (in R-value) continuous insulation is needed in order to reach a higher R-value -- or double stud.

Lastly, there are other ways using less closed cell plus celluouse etc. but it you put 6" (5 1/2" really) of closed cell foam in a wall your costs will also exceed those of ICF -- at least here.

Regards.

Posted By jmagill on 28 Jan 2012 01:49 PM
Passive house is about R-value. Using that as the measure success then yes 6 inches of closed cell foam will outperform the ICF in cost and energy savings.

In general, no it won't.  This is because of the thermal short circuits provided by the wood framing which has an R value of ~R1.25/inch.  I calculated a 2x6 whole wall R value of ~R19 using 5.5" of closed cell foam with an aged R factor of ~6.0 and a 20% framing factor.  Most ICFs on the market today come in at >R20.

And that 5.5" of closed cell foam and 2x6 framed wall will cost about the same as the materials cost for a 6" ICF wall.

If you want a high R value stud wall, you have to have rigid foam applied over the framing to provide a thermal break.  1" of rigid polyiso insulation over the above 2x6 wall would bump the whole wall R value up to around R25.

Posted By arkie6 on 28 Jan 2012 09:52 PM

Posted By jmagill on 28 Jan 2012 01:49 PM
Passive house is about R-value. Using that as the measure success then yes 6 inches of closed cell foam will outperform the ICF in cost and energy savings.

In general, no it won't.  This is because of the thermal short circuits provided by the wood framing which has an R value of ~R1.25/inch.  I calculated a 2x6 whole wall R value of ~R19 using 5.5" of closed cell foam with an aged R factor of ~6.0 and a 20% framing factor.  Most ICFs on the market today come in at >R20.

And that 5.5" of closed cell foam and 2x6 framed wall will cost about the same as the materials cost for a 6" ICF wall.

If you want a high R value stud wall, you have to have rigid foam applied over the framing to provide a thermal break.  1" of rigid polyiso insulation over the above 2x6 wall would bump the whole wall R value up to around R25.

I do agree with Arkie6.
The thermal bridging of a 2x6 wall with closed cell foam will be significant and most likely will not outperform an ICF-wall

Passive House does not specify wall types or insulation types, although there is discussion about eliminating use of some types of foam due to the global warming potential. Thermal bridging is a big part of the insulation equation, so I doubt that any type of stud wall with no thermal breaks would meet PH guidelines. There are legitimate reasons to use other insulation methods (cost being one) but that would be true with or w/o PH. I'd suggest investigating the certified PH already built in the US and read about the reasons the builders used their particular insulation method.

Posted By Bob I on 29 Jan 2012 11:30 AM
Passive House does not specify wall types or insulation types, although there is discussion about eliminating use of some types of foam due to the global warming potential. Thermal bridging is a big part of the insulation equation, so I doubt that any type of stud wall with no thermal breaks would meet PH guidelines. There are legitimate reasons to use other insulation methods (cost being one) but that would be true with or w/o PH. I'd suggest investigating the certified PH already built in the US and read about the reasons the builders used their particular insulation method.

I agree. All my reading of PH has included no thermal breaks so I assumed that there would be an outer layer of insulation as a thermal break. I thought others would know that as well. My mistake.

it doesnt sound like the guy you talked to really knows much about PH. PH doesnt care nor specify a r value or wall type requirement. Instead they have a short list of target guidelines for energy use reduction and air tightness. However to meet a lot of those requirements, typically super insulation and thermally broken shells are needed. I would imagine ICF with proper air sealing details around windows and the roof structure would meet the air tightness requirement of .06, however I am not sure if it would reduce the heat load requirements compared to super insulated structures, which are typically double stud walls w/ dense packed cellulose. Spray foams are typically avoided, infact there was a recent article about the PHI proposing to ban the use of spray foams. To have a "PH" guy recommend spray foam and a standard 2x6 walls tells me he is not a PH guy at all.
I think your typical r24 ICF wall with the use of air tight ceiling deck and triple pane windows, plus the addition of exterior eps, you could make it work while maintaining the other advantages of ICF. This would get you a very good, strong structure, but at a premium price.

Posted By renangle on 28 Jan 2012 12:10 PM  Apparently he spoke to a passive haus guy who said the house (located in central Virginia) would be more efficient (and cheaper) if they go with 2 x 6 sprayfoam insulation, triple pane windows. Am I wrong or is the passive haus get a bit off, in part because they have their own agenda? It just frustrating to me to hear that the passive house guy says that he is very familiar with ICF...though never built with it, then says that 2 x 6 spray foam is better. I know I have been away for a while, but has something changed? Any input would be appreciated. Ren

That's the problem, you got a builder who NEVER built with ICF, so it is guaranteed he will recommend wood because he doesn't know how to build with ICF. If you friend wants to build with ICF he MUST go to a qualified ICF contractor, not a wood contractor.

Sprayfoam is expensive. In the end it's not always about R-Value, it is about strength, longevity, rodent resistance, air tightness, etc. If this is a home that he wants to live in for a long time, go with ICF. If this is a home that he wants to sell in 3-5 years, then go with wood.

boy Lbear...you are sure concerned about rodents!

"he MUST go to a qualified ICF contractor"
One of the things that drew me to the Passive House movement is that "they" are not selling anything except energy efficiency. There are many good ways to build; ICF is one, but certainly not the only one. I have friends that are ICF contractors, & others that are SIPS contractors - these people have a lot invested in that system and an incentive to use those products. I prefer to use the system that is most cost effective for the particular client and house; whether it be double walls, ICF, SIPS or something else. Some contractors are afraid to use anything new; some have good reasons for using or staying away from certain things.

Posted By Bob I on 29 Jan 2012 07:03 PM
  Some contractors are afraid to use anything new; some have good reasons for using or staying away from certain things.

I for sure would not want a contractor that never used ICF practice and learn to use ICF on my home. They would basically be learning on your dime and your home.

Would you want a new trainee mechanic fixing the plane that you and your family is about to fly in?

Posted By lzerarc on 29 Jan 2012 06:53 PM
boy Lbear...you are sure concerned about rodents!

In rural areas, rodents infesting homes is a big problem. I've seen in personally and even Animal Planet had the series "Infested" feature quite a few rodent infestations.

With a wood home it has to be detailed perfectly but even then wood cannot stop rodents. They will gnaw through it and make entry. For me personally, my home is my castle, I want it to be secure and keep out the elements along with critters.

I am also in scorpion country, they only need the gap of a business card to get in (1/16th of an inch). They will crawl inside the walls of wood homes and come out of the electrical outlets, bathroom vents, can lighting, or anywhere there is a gap of 1/16th of an inch. It is next to impossible to seal a wood home that tight because code requires the OSB to have gaps in it due to expansion rates. Wood is never 100% tight.

Long story short, I have lived in wood homes in the city and dealt with the constant problem with scorpions, ear wigs, crickets and everything in between coming in because there were so many gaps in wood. I don't want to deal with that in the country.

Talk to someone who had a rodent infestation, it is actually quite traumatic and has caused peoples "dream home" to turn into a "nightmare home". ICF solves that problem. Nothing is getting through 6" of reinforced concrete. Yes, I have to detail the doors and windows, but that is a given in any home, wood, SIP or ICF.

I think shotcrete homes with one inch of concrete on each side would also be resistant to rodents, bugs, critters, etc.