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ICF Construction

Posted by dreambuilder (My Page) on
Sun, Nov 11, 12 at 21:08

lzerarc I know you are in the middle of an ICF build, what are your thoughts so far? I've looked at the green building site and I didn't find it that helpful--geared more toward professionals. I also saw some people reporting they had used Superior Walls and had leaks. Obviously that is a problem--a huge one. I also fear that if the crew changes the concrete by adding water, etc...during the pour you are going to run into major trouble and need to call in Mike Holmes a couple years down the road. Basically sound proofing, withstanding weather, fire and bugs are main reasons to use ICF? My understanding is a stick house can be insulated to the same level as an ICF home for cheaper? If ICF is fantastic why hasn't it caught on more? I'm interested in doing it but makes me nervous for possible problems.


Follow-Up Postings:

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RE: ICF Construction

I'm building my own ICF house. I did the design, stacking, bracing, window and door bucks, and re-bar myself, but worked with an experienced ICF contractor, and hired him to do the actual pour. Pouring ICF is no different than pouring regular concrete foundations, but consolidation is more critical, since the forms aren't removed, so you can't tell if there are voids.

ICF isn't for everyone. It works well in a moderate climate; not quite as well in extreme cold. The reason being- All of those tons of concrete are connected at the bottom to the earth, which can work for you or against you depending upon the temperature of the earth in your climate. Here in SC, the earth is a very moderate temperature, so I have all those tons of concrete working as thermal mass.

ICF makes for very tight construction. Building a stick house to the same level of tightness requires great attention to detail to seal thousands of seams and small penetrations. If you trust your contractor (or yourself) to do a good job of it, yes, stick can be just as tight. There is some argument about whether the stick construction will STAY tight 10, 20, or more years down the road. My experience with the poor quality wood available today would not inspire confidence as far as stability is concerned.

Why did I go ICF? As a DIY, the foundation cost about the same as hiring a contractor for poured concrete, and Superior Wall was about the same. Going ICF for the basement was a no-brainer. I ultimately decided to go ICF all the way up because it was physically easier on this old man than building and erecting stick-built walls. The forms only weigh 7 lbs. each. The bracing IS heavy, though. Looking back, I would have had to hired help to erect framed walls. I'm a pretty stubborn DIY'er; the only thing I didn't do myself so far is the excavation and concrete pouring. I did hire a crane to erect the roof trusses, and had two friends help me set them.

So far, there is only one thing concerning me about ICF. Some of my forms were stacked in the woods for a couple months, sitting on cardboard packaging, and termites got into them. They only went in about an inch, but still, the potential is there. I have heard of them tunneling considerable distance through the foam to reach wood. They don't eat the foam, but it is an excellent cover for them to proceed undetected to wood. South Carolina is considered 'extreme' for termite infestation, and I have taken considerable pains to prevent them. The foam has two layers of protection below grade, and the soil was heavily treated under and around the foundation. We will maintain a termite contract, just as we have in FL.

There is a link to my build thread; the 'action' starts about 2/3's of the way down.

Here is a link that might be useful: ICF build


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RE: ICF Construction

I am looking into Superior Walls too, look closer, the owner of the company directly responsed to the big leak issue I believe. I have communicated with him and was impressed. I have had to put my build on hold for personal reasons, but when i re do the plans, i will certainly have them price it.


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RE: ICF Construction

dreambuilder-
I am not sure of your climate, but flg makes some good points. However, here are things to consider:

First off, the biggest goals for me in construction was the shell. I am in a heating dominate climate zone 6, with heat degree days of 7200. Typical ICF performs well in heating climates, but the faulty claims of "added r value" due to mass is simply not true for heating climates. In cooling climates, or climates where the diurnal tempertures stays above and below the interior house temp, then the concrete creates a buffering effect, thus the claims of added "r" value due to decreased temp swings (ok ok, its not r value at all, but typically a calculated u value, but I am keeping it simple here).
With that being said, why would I chose it for heating climates. Well, you still get a constant steady state r value of the EPS foam. EPS foam also increases slightly in performance as temps drop oddly enough. Even if you go with a "standard" stacked horizontal block, you are still hitting a constant (continuous) r of around 24. This is important, especially when comparing to frame construction.

Take a code min. 2x6 framed wall with crappy batts. The batts, advertised, gets you an r19. We all know this is not true. With perfect install (never happens) they are lucky to get near that. So you have an r19 (at best wall, already r5 below ICF) now factor in your studs every 16", headers, corners, etc. This is your framing loss factor, and its typically around 20%. This is almost an r4 whole wall hit to your structure. Your total wall r value drops to around 15. Again, ICF is now near an r10 higher since there is no studs or anything to interrupt the constant EPS foam. You can reduce the framing loss factor by adding exterior foam board sheathing, ranging from 1" at r5 and up. This boosts your cavity area up to r24 and your stud area up to r6. Your framing factor reduces quite a bit, but your whole wall r value is still around r20, again still under ICF.

Now the big kicker...add in the natural air tighness of ICF and framing as a lot of work to do. You need to caulk and tape any and all joints between studs, sheathing sill plates, top plates, windows, etc. All are places for air to get through. With ICF, you focus around doors and windows as well as the roof connection. Concrete also will not move as noted over time. Wind blows and racks the wood framing. The tape can pull off over the sears, caulk and stretch, shrink and lose bond. Your efforts to create the air tight wood framing is unknown in 5 years.

Depending on how you do it, you can hang your floor structure off of the basement walls. This is how I am doing it. So it is constant concrete and foam from footer to roof. No band joists areas for bugs, spiders, mold, dirt, etc. you also have some additional grading flexibility since technically you can run your grade and waterproofing above your floor line if needed for whatever reason.

You also add in the storm protection, quietness, and fire protection. Depending on your location and insurance, you could get a deduct on home owners because of it.

On my specific project, since super insulation was a goal, I got about as close as I could get on ICF. My forms are vertical forms with an average r value of 28. I was originally going to do double stud wall framing at an r40(whole wall r36) but decided on ICF for many of the reasons above. Running load calcs, the BTU hit in my climate between r40 and r28 was only about 1400 BTU. Total load for 3600 sqft condition (half below grade) is only 24k. 2x6 framing would require at least double that. This has upfront cost reductions in hvac equipment.

However it would be unfair to claim the BTU load is due to ICF, because there is a lot more to it than that. The design is heavily influences by solar temporing, and my glass is tuned to account for around 25% of the heat for the winter. Combine that with subslab basement insulation, r60 insulated attic, triple pane windows with u values at .22 and lower and placed only where needed (and only casements when needed, otherwise stick with fixed for air tightness), it all adds up to create the total package. For people who claim there is no payback, let me put it this way, in clear dollars. No one knows what energy costs will do to be in the upcoming years, however we do know they will keep going up. That is a given. Prelim energy audits and modeling is showing a total cost of conditioning (heating and cooling, over 12 months) will cost around $360. For easy math, that averages $30 a month to heat and cool 3600 sqft where temps get well below 0. My previous 1200 sqft 2x4 home cost $130/month just in gas with a new 97% furnace. Now lets add in rebates from local utility companies. I will get around $6k back in rebates from various utilities from appliances to Energy Star 3.0 ratings. That right there covers the upfront cost dfference. I am already a net below before I even factor in monthly energy savings. A wood framed house would not have qualified for the rebates unless a lot of extra work and exterior foam was added, which costs almost as much as the ICF did to begin with.

As far as your concerns, dont have any. Pouring the foam walls is not much different the pouring the formed basement walls. They can add water to that just as they can ICF. However any experienced ICF crew knows adding more water increases the change of a blow out, so they tend to not do so. A 4 or 5 slump is plenty to fill the forms depending on the aggregate. Mine was a 5 slump with 3/8 chip mix. I personally filled the walls with no issues at all.

THe biggest reason ICF has not taken off is it costs money. Not too many people care about their shell of their home unfortunately. My opinion is the shell is the only place that will ever give you payback. The shell is the area that protects you and your belongings. Why not put your money there? Make it the best, tightest, and most efficient you can. Do not rely on high dollar HVAC equipment for efficiency. It costs far less to boost shell performance with non mechanical items that can not go bad and need service in 5 years. ICF costs around 5-8% more than a typical code min. 2x6 framed house. This is quite small IMO. Some people spend this much on counter tops in their kitchen.

check out my blog and follow it throughout the construction phase if you would like. Also read more about the design, solar design, wall sections, etc.

Here is a link that might be useful: ICF house blog


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