im so excited for you.

Hello there:

Having read some of the materials at CMHC regarding another Edmonton home built by this builder - especially his efforts to design a system that replicated typical framing cycles - I am a little curious that the 2 x 4 studs were not offset. I undertand it is easier to frame this way, and therefore likely to reduce the time spent by framers, and therfore the cost. Nonetheless, would it not be beneficial to offset the framing members so that any cold points would be reduced? Surely the framers could manage this once the little extra layout time had been spent?

I'd be interested in any thoughts.

Mississippi John
Mississippi Mills, Ontario

John,

I don't see any benefit to offsetting the studs. Remember, there is 9 inches of cellulite, over R28, between the studs. The benefit of having the studs offset is probably zero.

Conrad

Hello again - Sorry, I am inundating the system here with a lot of questions ...

I have read through and copied the general design of the interplay between the wall, floors joist, etc., and air-sealing details. The information from here, and from the CMHC pages outlining the Riverdale home, is very useful. All information and detail I have seen, however, addresses the relatively easy task of sealing the rims and joists where the joists run parallel to the wall. (This is the example that Peter AMerongen drew for the Riverdale specs).

What I am interested to know, is the opposite - where the joists are perpendicular to both the inside and exterior wall. In my dealings with a local green energy consultant here in town (http://www.homesolbuildingsolutions.com/ ), it has been pointed out that the real chanllenge will be sealing this area. For ease of reference, what I am refering to is shown in the first picture above - the wall on the right closest to the neighbouring house. How is that being sealed effectively?

I need to come up with an effective process here because these runs happen to be very long in my house design, and if it is done poorly, the house is going to be keaky ...

Any secrets would be welcomed.

Mississippi John
Mississippi Mills, Ontario

Hello again - Sorry, I am inundating the system here with a lot of questions ...

I have read through and copied the general design of the interplay between the wall, floors joist, etc., and air-sealing details. The information from here, and from the CMHC pages outlining the Riverdale home, is very useful. All information and detail I have seen, however, addresses the relatively easy task of sealing the rims and joists where the joists run parallel to the wall. (This is the example that Peter AMerongen drew for the Riverdale specs).

What I am interested to know, is the opposite - where the joists are perpendicular to both the inside and exterior wall. In my dealings with a local green energy consultant here in town (http://www.homesolbuildingsolutions.com/ ), it has been pointed out that the real challenge will be sealing this area. For ease of reference, what I am refering to is shown in the first picture above - the wall on the right closest to the neighbouring house. How is that being sealed effectively on the interior?

I need to come up with an effective process here because these runs happen to be very long in my house design, and if it is done poorly, the house is going to be keaky ...

Any secrets would be welcomed.

Mississippi John
Mississippi Mills, Ontario

Mississippi John
Mississippi Mills, Ontario

Hi John,

I was working with Peter today so I asked him about the difference between sealing on sides running parallel to joists versus sides running perpendicular. He said there was no difference. When you look at the exterior of a just-framed house, there is basically a box of 2x10's sitting on the foundation around the entire perimeter of the house. Some of these 2x10's happen to have joists attached to their inside faces and others do not, but as far as the air barrier is concerned it doesn't matter since the air barrier is on the outside of these 2x10's. Or were you referring to the vapour barrier?

B.

Mississippi John
Mississippi Mills, Ontario

Hi Bob - Thanks for asking my question. And yes, I suppose I am referring more to the vapour barrier, which looks to me like the more difficult to do in these situations.

I am assuming that both an effective vapour barrier and air barrier are necessary to achieve air-tightness that would result in less than 1 air-exchange per hour. Perhaps I am wrong here? If that is the case, then I suppose proper detailing to the air barrier is the more important and shold be achievable as per Peter A's answer.

Thanks again.

Hello there, I am happy to find that you are sharing your experience on internet, I plan on building in St.Albert this fall and take on the general contracting, wondering if your framing crew is willing to frame for me? could you give me phone number for Adam or Nick for me to talk to or If you have good trade people that will charge me reasonably, please let me know, thanks and good luck to your project, Alfred.

Alfred,

I've forwarded your comment to Adam.

Conrad

To ICF or NOT???

I'm about to build a house that has been influenced a great deal by the Millcreek and Riverdale homes. My double-wall is slightly less (15.5"), but then the Ottawa Valley is slightly warmer than Edmonton.

At present, we're pouring over cost projections with the builder in an effort to shoe-horn the project into our budget. In doing so my builder has advised that the foundation would be cheaper in ICF - he insists that in Ottawa, the cost of forming, concrete, and the extensive application of insulation will be more than the simpler ICF, which he can do without sub-contracting.I am ok with this so long as it shrinks one of the numbers on the estimate!!

Today, he heard back from the ICF supplier, and called to ask me if we would consider going ICF to the roof, with an extra application of 2" of foam on one side of the wall. He thinks it will save enough labour that the cost savings over the framing would be equal to the cost of the cellulose ($20,000). The ICF guys advise the wall will be R58. It will be 6" of foam and 6" of concrete.

Leaving aside the issues of embodied energy, does anyone here believe the ICF manufacturer's Rvalue estimates? I have a hard time believing this would be R58, but I concede it would be very good. And it would definitely be air-tight.

After considering that aspect, feel free to comment on the embodied energy aspect?

Cheers,
Mississippi John
Mississippi Mills, Ontario

Foam insulation is roughly R6 per inch so 6 inches of foam would give R36. Poured concrete is something like R0.1 per inch so its contribution to insulation is negligible. This means you're looking at around R37 for your walls - far less than the ICF supplier is telling you. The tricky thing about these walls is that the concrete has a very high mass which means it is slow to warm up and slow to cool down. Under ideal conditions, the concrete will absorb heat during the day and release it at night so that your home stays cooler in the day and warmer at night. Somehow the manufacturer has calculated that the effect of this thermal mass makes the overall wall behave like a low-mass wall with R58 insulation. They typically refer to this are "Performance R-value". While there is some truth to the behaviour of these wall, you should should be cautious about these claims.

In addition to the high embodied energy of both the foam and the concrete, foam insulation is flammable and the chemical reaction of spray foam produces heat which has actually caused fires. See http://www.greenbuildingadvisor.com/blogs/dept/green-building-news/three...

Having said that, you actually may want to consider ICF for one benefit: quietness. My first house was a brand new house with typical 2x6 construction and the house I'm in now is 2x4 construction with a full brick exterior. When we first moved in I couldn't believe how much quieter the 40 year old house is compared to our first brand new house. I live a block off the Whitemud freeway in Edmonton - a 6-lane road with a 80km/hr speed limit - and if we close the windows we don't hear any traffic noise. Conrad's house with the double wall system may be similarly quiet, I've never thought to ask. If you live somewhere that can be noisy and you're a light sleeper then you may want to consider ICF despite its flaws.

Ken

Hi Ken - you have summarized my apprehensions. At R36 or R37, it is still a good wall, but why would I want all that concrete if I could do the same thing with 2x6 and foam?

I think ICF may behave beyond the Rvalue, but I doubt that it would be equivilent to R58, especially here in a northern clime.

Mississippi John
Mississippi Mills, Ontario

This claim by ICF installers is frustrating to me.

Mass is only of value if you have a surplus of external energy. That energy comes in the form of solar radiation in a passive solar house.

The ICF people's claims are only correct if there is a surplus of energy sometime throughout the day.

So, if there are days when it is warmer than the interiour temperature for a few hours, and heat starts to flow into the house, then the mass is effective for the other hours, when the opposite is true.

However, that situation is virtually never the case in a cold climate such as Edmonton's. It goes below zero for months at a time, thereby rendering the mass, in my mind, completely useless.

Once the season has changed so that there are days that it is warmer than the inside for hours at a time, my house has already been heating itself with the sun for at least a month.

I personally only give stock to the R value of the styrofoam in ICF walls. The extra "R Value" claimed due to mass is a dishonest manipulation of people's understanding of how mass works in a passive solar home.

Ken, Conrad and Philip - thanks for this, especially the links! I am juggling a lot of things right now and you have summarized my misgivings so well. I appreciate that!

MY design is actually slab on grad, and the "foundation" I refer to is isolated from the pad (I prefer the stability of the foundation to an engineered pad). The north length of the house is built into a slight grade, and therefore requires 4.5' of concrete wall above grade. We will use ICF which will form part of the outer wall. There will still be an inner 2x4 wall and cavity filled with cellulose to make up the R54 wall.

I will give the OK for ICF foundation because it uses the same amount of insulation that I had speced (4") on the original ppoured design, and less concrete. It will eliminate moisture proofing and some other steps. My contractor says he can do it cheaper and that is also important.

We're working on a blog and will post a link eventually for anyone interested

Mississippi John
Mississippi Mills, Ontario

I agree with Conrad. The ICF industry tries to create this myth that somehow ICF walls are special and that normal R-values don't apply. Google 'the ICF effect' and you will see what I mean. Independent research from buildingscience.com and CMHC has shown that IN COLD CLIMATES the thermal mass effect of the concrete in ICF walls in negligible. See for example

ftp://ftp.cmhc-schl.gc.ca/chic-ccdh/Research_Reports-Rapports_de_recherche/eng_unilingual/Monitored_Performance(w)_dec12.pdf

In any case, you would want the thermal mass to be inside the thermal envelope, and thus insulation on the inside of the concrete reduces any thermal mass effect you may have. There are also some good discussions at greenbuildingadvisor.com. For example

http://www.greenbuildingadvisor.com/community/forum/energy-efficiency-and-durability/21312/thermal-mass-424-anyone-use-it

Bottom line:
ICFs for basements: maybe, but you may have to add more insulation if the goal is net zero.
ICFs for main floor: No, double wall framing is cheaper and has much lower embodied energy if using blown in locally sourced recycled cellulose.

Hello John

Ken's R value numbers for foam are a bit off. Most ICFs are made with 2 3/8 inches of Expanded Polystyrene (EPS) per side. This gives R10 inside and out.

In one research project, Jan Kosny and Jeff Christian of The Oak Ridge National Laboratory (ORNL) studied 18 different wall configurations. They said the claimed R-Value of most ICF walls was R 20. In their Hot Box Tests the ICFs performed at R 20 or R 21. The primary advantages of using ICF are the speed of construction, the strength of the walls, the air-tightness, the consistent R value with few thermal bridges, and the benefits of thermal lag. Quadlock makes an ICF with R10 inside and R20 on the outer skin. In the ORNL report, Larsen Truss and double stud walls get good ratings.

Durisol makes a 12 inch ICF which they say is rated at R28.
The Durisol product is made from a mixture of concrete and shredded wood. This product has a lower Global Warming Potential than foam ICFs. Ordinary wood screws can be used to attach lumber and drywall directly to the Durisol.

Building Science Corp has produced a very informative analysis which could help you. They assessed the qualities of a variety of High R-Value exterior walls. Their report details the thermal performance, the air tightness plus other factors such as the risk of condensation within the wall.

http://www.buildingscience.com/documents/reports/rr-0903-building-americ...

I hope this helps. - Jim