Hello all,

I am new to the site and this will be my first post.  (so be gentle :) )  So, first a little background and situation info.  I live in Alaska and my wife and I will be building a new house this summer.  Weather wise, we don't live in the extreme areas of the state, but in a more mild area (anchorage area).  Probably similar to MN or MT.  I know the temps can get extreme in both those states but think in general terms.  Our house design is 99% complete and the a large portion of the dirt work on the land has been completed.  The house will be a single floor with a full walk out basement (guess that would be technically two story) with a very large 44'x44' heated attached garage.  MY main concern is heating cost b/c we will not have access to natural gas and will have to use heating oil instead.  This can obviously be very expensive if little or no consideration is put into building materials.  Also important to note is I will be acting as my own general but do not plan on doing any of the actual work myself.  So...

I have always planned on using icf for the basement but the more i looked into the more i like the idea of using it for the entire house (outside walls only, the rest will be stick frame).  especially for the garage since it is a big blank box.  Everyone i talk to and everything i have read, including here, raves about the stuff.  but then i found this study,

http://www.buildingscience.com/documents/reports/rr-0903-building-america-special-research-project-high-r-walls

the info that caused concern is found on pages 44-47 (actual page numbers, not pdf page numbers) and the conclusions starting on page 60.  seems like a fairly legit study that doesn't seem to be pushing one method over another.  Although i didn't see who funded the study.  so why does this study seem to contradict everything thing else i have heard and read about ICFs in cold climates?  Did they not look at the thermal mass of the concrete?  Is this where the difference was?  This study specifically recommended NOT using ICFs in colder climates.

Other things to consider:

Roofing - Was planning on doing a standard truss roof with an insulated (R-42+) ceiling and a vented attic.  Although do sure if i can do this in the vaulted area? Although the icf roof looks interesting, don't know if i can do it with the complicated roof design i have.  haven't done much research yet.

Floors - All floors will have in-floor heating using the most efficient boiler.  how much and what type of insulation that compliments the icf walls?

Electrical - any one have an average cost increase when electrical is installed in icf?  do most use some sort of conduit?

Plumbing - i would think you would try to avoid plumbing in the icf, mainly b/c it is the outside wall?

Windows - will have to decide if triple pain is worth the money. (right now thinking no)  along the same lines, how useful is it to have high r-value walls if you have a number of windows on two sides?  a very large portion of both floors have windows to accommodate the view.  thankfully the view is to the southwest which should help a little in the winter.  although in the summer it will cause quite a bit of additional heat.  but the front, northeast, also has some windows and looking at the plans i wonder if i'll be defeating the point of using icf with the number and size of windows and doors?

Other methods i was considering, was going with the standard 2x6 construction but adding a couple inches of foam board to the outside and possibly using blown in insulation rather than batting.  going this route i am very concern with the insulation settling in the wall over time and water/mold issues inside the walls with the outside layer of foam, especially living in a colder climate,  but what would the cost difference be after adding the foam and blown insulation over icf?  i wouldn't think much but i really don't have any solid info on it.

well i think that is more than enough info and questions for my first post... :)  thanks, enjoy

pv

That's an interesting report. Wonder why table 17 on page 61 doesn't include the ICF wall. The description of table 17 is the last paragraph on page 60. I believe that is one of ICF's major strengths.

My take is that they don't recommend ICF just because the ones they tested don't end up with an R30 wall value. I guess you're in an area that they recommend R30 walls. If you used an ICF that had thicker foam, that reason would be eliminated.

There are at least a couple ofl brands that have thicker foam. Quadlock and Logix both advertise R values in excess of 30.

if i remember correctly from reading the article the first time, they didn't include icf in that table b/c they stated that they knew the number would be 0 due to the nature of icf.

yes, i could always go with thicker foam but i was hoping to keep my wall thickness reasonable.  i wanted to use 4'' of concrete and 4" total foam.  maybe that isn't a reasonable expectation.  but it starts to get prohibitively expensive.  if simply going thick with the foam is the only answer then i will probably just go with xps on the outside of 2x6 construction.  2" would get me to around r-25, higher if i can get the blown-in insulation to work.

pv

I don't see anything new in that study regarding ICF. Could it be that your perceptions of ICF were a bit off? They are not magic building blocks. If you want more R value in a wall than ICF can deliver, then you need to figure something else out. But, do you need more R-value? Heat loss at walls is only a small part of the overall picture.

Remember that ICFs have more value than just insulation and that you are looking for an efficient solution not just the highest r-value.

I also would not agree with your perception that "This study specifically recommended NOT using ICFs in colder climates.".

You are right on to be wondering about windows. My house is 6" ICF, (5" styro & 6" concrete). I installed Andersen 400 series casement wood frame windows. These are not the absolute best, but are some of the best windows on the market. In doing the heat load calculations I determined that each square foot of window was approximately equal to 4 square of wall in terms of heat transfer. Your greatest return comes not from super insulating the walls, but in reducing the square footage of your windows, and in using the highest R value windows you can possibly afford.

Unless you have extremely cold prolonged winter weather I see no problem in putting plumbing in an outside wall. However, I did not put anything larger than 2" pipe on an outside wall, and that I put in a channel in the foam, not in the concrete.

I used wood trusses for the roof. But instead of ceiling insulation I put spray foam on the underside of the roof deck. Attic space is part of the conditioned space.

I'm in SW Idaho where winter drops down to the 0° to 5°F range in winter.

You know, if you want more R value than a standard ICF form offers (typically R20-24), you can screw or glue additional foam board to the outside of the forms. Each additional inch of EPS adds about R4. XPS adds about R5. Polyiso about R6 (aged value).

EPS generally is the most R per $. Also, with EPS the colder it gets, the higher its R value. It gains ~10% R value as the temperature drops from 75F to 25F.

"I also would not agree with your perception that "This study specifically recommended NOT using ICFs in colder climates.".

Actually it said that someplace in the article.  Don't have it in front of my right now so I can't point to the actual page.  someplace towards the end.  sorry.

but yes i was slightly misinformed/misunderstood on a few specifics with R value with icf.  i think an r25 to 30 would be good for myself.  anything over that i think would be over kill for what i'm planning on building.  I like some of the other advantages of icf but i haven't made any decisions yet.  still comes down to cost to value ratio.  should be talking to an icf guy in my area this week so that should help.  trying to find numbers for adding foam to stick frame.  hard to get a solid number for a number of reasons but i have a few leads to check out.  might come down to who in the area is has experience with one or the other.  but my guess/instinct is telling me that by the time i spray in a couple inches of foam on the inside wall and add a couple of inches of eps to the outside to break the thermal bridging i'd be close to or over the cost of icf without the other advantages.   haven't had a chance to really look at windows yet, but thanks for the suggestion.  i'll check into those specifically.   haven't looked at different roof options much either but thanks for the method and numbers.  i'll check it out.  going to have an local energy rater do a plan check so i can change different variables and see what the cost/value difference is. 

pv

Actually it said that someplace in the article. Don't have it in front of my right now so I can't point to the actual page. someplace towards the end. sorry.

You might be talking about where they imply (on pg. 60) that ICF doesn't meet either their cutoff of R-20 or the IECC Zone 7 & 8 cutoff of R-21.

The study pegged ICF at between R16.4 and R20.6.

However, this study characterizes ICF as having 5" of EPS. As you know there are many different brands of ICF out there and I haven't done a comprehensive analysis, but nearly all the ones I looked at seriously have EPS at 5-1/2". Interestingly enough, this small difference is enough to get over R-21 which does include them in both categories. Moreover, ICF manufacturers use different foam materials with corresponding differences in R-value. There has been a lot of inflation of the R-value of ICF walls, but I think about R-23 is pretty reasonable, and I wouldn't be surprised if a number of manufacturers designed with the cold climate recommendations in mind.

ahhh, you are correct.  my apologies.  and yes, i agree.  that r-23ish + is what i'm thinking i'm looking for.  plus the extra benefits of icf. i sure would like to use it but i'm afraid the cost may be prohibitive.  but the jury is still out.

Pura vida,

If I were you, I'd recall Good Friday 1964 and rate seismic characteristics at least as high on my want list as R value. One of the advantages of ICF is the ability to put in just about any rebar schedule )or Helix (tm)) that you want. This is an important criteria regardless of what the local building codes do or don't say.

I'd put seismic high on the list for roof choices too ... I'd just as soon not wake up with it all on top of me.

I'm not a builder but there are several past contributors on this list who are, including several who build in California.

One of the advantages of ICF is the ability to put in just about any rebar schedule )or Helix (tm)) that you want.

It's true. I asked for seismic and got no changes in the ICF wall per se, but there is quite a bit of interesting steel in there.

If you were planning on 4"+4" of ICF/EPS and am concerned about cost, why not a 8" EPS SIP instead?

Victor
www.ecobuilthome.ca
A 4350sqft Net Zero Energy initiative

actually i am looking into that as i type.  very intriguing, especially for the garage.  other things to consider like wiring, roof, plumbing (hopefully avoidable), etc.  not sold on anything yet, still looking for that magic best cost/benefit.  as with icf i wonder if with my design i am going overboard with the walls with the number of windows i have... i have someone running numbers for icf vs sips now. very interested in how that comes out.

Posted By pura vida on 24 Jan 2011 10:01 PM
i have someone running numbers for icf vs sips now. very interested in how that comes out.

When I built my house I looked at SIPs. My conclusion, right or wrong, was that ICF was more amenable to DIY for wall construction. SIPs come as large panels and require lifting equipment, like a crane, to move into place. That requires qualified operators, etc., which on a per hour basis is more costly than DIY labor with skilled assistants. But time savings may offset that, I don't know. I don't remember what the approach is for wiring and plumbing for SIPs, if I even discussed it with the local SIP manufacturer. Those two are fairly easy with ICF. On the other hand, concrete work isn't for sissies either, and whoever does it has to know what they're doing.

Sounds like you're thinking this through pretty well and recognize already there are no pat answers that fit all situations.

How much of the work are you planning on doing yourself? And what kind of a time frame for completion are you looking at. If you're doing a lot yourself, and have plenty of time to do it, like a year or more, then ease of construction method becomes a high ranking factor. If not, then speed of construction becomes dominant. As you already know, it's all a trade-off, and not always easy to figure out.

"As you already know, it's all a trade-off, and not always easy to figure out"

Ain't that the truth! Actually we are in a fairly unique situation (i think). We have decent amount in cash to start the house after we pulled the money out of our current home (at a lower rate than what our first mortgage was at with only $125 closing cost!) and savings. we are going to start there and see where we get. Should be most if not all of the main floor which is what we are going for. So i don't really have any specific time frame but of course don't want it to take years. I am going to act as my own general but i don't plan on doing much if any of the work myself. I am not in the construction field and don't have a lot of experience with it. Plus the building season in AK is also my work season and i will be busy with my own business on top of the house (and a wife and two kids...) Figure the time it would take me to do my own building, how many times i would mess up, lost wages and focus on my business will more than make up for the cost of experienced, quality contractors. we shall see...

so all you icf guys, why is icf superior to SIPs? i see strength, little better sound proofing, slightly easier electrical, and ...?

Pura vida,

The Building Science folks are particularly interested in fairly high R-value walls, R30 or above. The only option available for adding thermal resistance with ICF is with rigid foams, EPS, XPS, etc. The cost per unit R-value of rigid foams is usually much greater than the cost per R-value for cellulose or fiberglass. You might check in your area at Home Depot or whatever supplier is available for the cost per square foot for R-19 fiberglass batts versus 4.5" or so of EPS. Assuming that you find the rigid foam is much more expensive than fiberglass, then you can see that for high-R walls, this gives a cost advantage to construction that can use cellulose or fiberglass.

budden makes a very good point regarding the 1964 quake, which was a monster. The strength and fire resistance of ICF is appealing, and it that area, the strength issue might be very important.

Posted By Lee Dodge on 25 Jan 2011 12:10 AM
Assuming that you find the rigid foam is much more expensive than fiberglass, then you can see that for high-R walls, this gives a cost advantage to construction that can use cellulose or fiberglass.

Pura vida,
Put fiberglass down low on your list of choices. Search these forums and you'll find guite a few comments about air movement inside of and through fiberglass and the attendant heat transfer that results. Cellulose is generally touted as having the best cost/performance ratio, but foam is a real contender in certain cases. For your ceiling an inch or two of foam provides a great air seal, and then cover it with inches and inches of cellulose. That is seen by many as the best approach.

If you have someone doing HVAC calculations for you have them run scenarios with various amounts of air changes. You just may astounded at how much of an impact air changes have on heating and cooling loads. In other words, avoid leaks any and everywhere. Like the new mantra in building science says, "Build it tight and ventilate it right!"

Getting the envelope tight takes less effort with ICF, although it can be done with SIPs.

yeah i am trying to find something that performs better than fiberglass but doesn't kill me on the cost. i really like the idea of cellulose. even in the wall if i end up doing stick frame but i don't know if there is any way to "guarantee" it not to settle in the top portion of the walls? i did find i can't use the sips in the basement b/c i guess you can't back fill it more than 6 feet and i will have 9 foot walls. so i'm thinking icf in the basement (which i kinda like better anyway but that might just be b/c the sips is fairly new to me) and maybe sips for the main floor. maybe. i really like the idea of sips or my garage like i said before. that could be really slick. i am also leaning towards doing a couple inches of foam in the ceiling and lots of cellulose on top. if i can get the house (walls) to where i want it i'm thinking the roof needs to be an r-50ish. i was even considering 2x8 walls with 2 inches of foam and r-21 glass on top of that. still have the thermal bridging with that though. so i prefer the idea of 2x6 with some ridged foam on the outside. so would it be weird if i ended up with an icf basement, sips garage, and 2x6 walls with foam on the main floor? that just sounds confusing. but i just feel there are economically smart choices that will be far superior to a standard wood frame 2x6 house. at least i have made some progress with finding people that work with the different options. i was getting frustrated with all the confused looks i was getting when asking about different options...

yeah, getting the CORRECTLY sized hvac system is going to critical in my final efficiency.

i was getting frustrated with all the confused looks i was getting when asking about different options...

Get used to it. I have found very few contractors with a wide enough variety of experience to be up to speed on all methods and products. That is not an indictment of contractors. I think it would be difficult and take a long time to become proficient in everything that is out there. Accordingly, it will be up to you and the effort you want to put into it to work through all the various options.

so would it be weird if i ended up with an icf basement, sips garage, and 2x6 walls with foam on the main floor?

No, but it won't be easy on you. When you start getting bids, you would be lucky to find a contractor well versed in all of those, so you will find that the pieces of the bid will get more and more chopped up, which means more and more work for you to figure out what is efficient and what isn't.

You may want to consider what the cost/benefit ratios of all those different methods will be to you. They make sense on paper, but there is a cost.

Pura Vida,

Based on my experience with my first high performance build, I'd be inclined to agree with your thinking, that is, ICF basement, SIP above grade. The SIP might be more in materials cost than 2"x6"+2"EPS outside and filling the cavity with dense pack cellulose (which supposedly won't settle), but the time to install makes up for it somewhat. The SIPs don't have to be craned, they can come in 4'x9' sheets that can be handled by two people. Thermal bridging is reduced, and if you want to reduce it further you could instead do 6" EPS and add another 2" on the outside, then EIFS over it. Where I am, an 8" SIP wall would costs about 2/3 of what an 11 1/4" (6" concrete plus 2 of 2-5/8" EPS) ICF wall would be, on an installed cost basis. The ICF is attractive because of the earthquake zone, but cost wise, the ICF basement + SIP above grade might be a good compromise in terms of strength, insulation/performance, and cost.

On the R20 windows, you must be referring to heat mirror, of which there's been a lot of cases of failure of the film. Plus, it's crazy expensive. There are lots of R7+ windows out there which are far more economical, and you definitely want to tune for solar gains. I was totally surprised at how much gain can be had with the sun, even with the triple panes we used (SGHC 0.46, R3.85).

After this build, I'm more convinced of SIPs than ICF in a cold weather environment. I've observed two things. The first is a section of wall where, at the second story, one section was ICF and directly adjacent to it was SIP (we couldn't easily bear weight with one section so we went with SIP instead). The interesting part is that when I take a temperature gun to it, the SIP (8" SIP + additional 2" outside for EIFS) is consistently over 1F warmer than the ICF, which would to me indicate that there's less heat conducted through the SIP than through the ICF. And since the SIP was cheaper by 35%, I'm more sold on SIP above grade than ICF, the seismic benefits aside.

The second observation is that we started in December being able to get to -12C on the ASHP we have before it couldn't keep up, but as we contined into the long cold stretch, that balance point is now higher than -12C by a couple of degrees. My theory is that the concrete inside is dropping in temperature, and is conducting more heat from the interior conditioned space. This of course would be reversed at the beginning of the cooling season where I would benefit from the colder concrete, so it's almost like a lag effect that the mass of the concrete is providing. But I'm of the belief now that the thermal mass of the concrete doesn't help as much for those of us that have long heating seasons, as the mass actually begins to work against us, and the ICF I think is much more suited for areas where there are wild temperature swings throughout the day where the ICF thermal mass acts as a stabilizer, and can then reduce the size of the heating equipment as well as keeping the interior temperature steady making the house more comfortable.

For the ceiling, Nudura makes a 2.5" and 3.5" EPS ceiling that's lapped and has built in straps so you can screw drywall directly to it. I think it's a great system of mounting EPS on the underside of the roof truss to eliminate the thermal bridging, and drywall installs the same way. You can then use cellulose above the EPS in the trusses to get to R-whatever you desire, and still get the air tightness and reduced thermal bridging qualities. Cellulose is cheap, so cost to get to even an extreme R100 isn't outrageous.

Victor
www.ecobuilthome.ca
A 4350sqft cold weather Net Zero Energy initiative