View Full Version : Insulated Concrete Forms
montanadave
04-21-11, 11:44
So every now and again I get an urge to buy a little piece of property out of town and build a small vacation cabin/survival bunker. :sarcastic: I built a house about 15 years ago with the help of a contractor friend and we subbed out the electrical, plumbing, etc., but did all the rest. Sold that place after a divorce but have extensively remodeled my current home and have become reasonably proficient with residential electrical work. I guess what I'm saying is that I'm no contractor, but I'm pretty handy.
I'm intrigued by the idea of using ICFs because it would allow me to do much of the foundation work on my own until time to pour concrete, which would be advantageous given the remote area I would want to build in. ICFs seem like an efficient way to build both foundation and/or structural walls in a unique design while incorporating solid structural integrity, insulation, vapor barrier, etc. all in one stage.
Anybody have experience using ICFs or have any feedback regarding their cost, ease of use, functionality, or caveats?
A guy I used to work with did his own IC house up in Idaho. He did all the forms work etc and had someone come in and pour the concrete. It worked out well for him.
My goal is to build a house using ICF on a plot of land out in no where yet to be found and bought.
I think you are on the right track, but I have no personal experience. I have done a lot of reading in the past (but not recently).
My Dad is a builder (small time) mostly custom homes, and frames out houses for larger developers. and as a builders son, i have lived in a lot of homes in my life. 5yrs ago we were able to build an ICF home. i don't ever want to live in anything else again.
i don't have time right now to go into details. but i love it. its super quiet. we live by a busy road, and we only hear it if we are by our shitty windows.
i think they have an R value of 50. even our garage stays within 10° of the inside. we have to watch the weather otherwise we wouldn't know the cold front just went through (woke up to frozen pumps one day, and didn't know it was 27° out)
can't think of too many cons:
thick walls, can affect the layout(recessed) areas.
difficult to install plumbing/electrical on exterior walls.
i can't comment on cost. we were able to use a lot of left overs from past jobs.
on our next home i plan/hope to use ICF again.
this thread reminded me of this gif i made...
http://s-seriesforum.com/albums/album13/housebuild_sm.gif
The wife and I are discussing different building techniques in an effort to build a stronger home that is less reliant on the grid. ICF construction is one of the things we have been looking at. Pre-stressed concrete forms that are poured in a factory is another. ICF has some major advantages.
glockeyed, how does your house do in the summer? Any significant impact to the electric bill? Do they find that they can ren the A/C less often?
As a side note to our research we have found designs that, were it not for the humidity, you can build in Florida and not need A/C, However due to the humidity you still need A/C. But owing to the design, the A/C needs are minimal.
montanadave
04-21-11, 23:18
Thanks for the info, glockeyed. Photos are great. Looks like a beautiful home. I'm thinking ICF construction would work well in Montana for minimizing heating/cooling costs given our temperature extremes (20-30 below in the winter and over 100 in the summer).
Like HES, I've considered using ICF for exterior walls and prestressed concrete storm drain pipe stacked vertically for a central utility core. Seems like the versatility of the products could make for some real interesting designs.
It's cheaper than CMU below grade. You may want to hire someone to spec the concrete, it's not like pouring a garage floor. I'd guess in Montana you know about not putting plumbing in exterior walls :p Only downside is you cant really modify the exterior later.
I will say it does really well in the winter in typical FL winter the heat rarely comes on mostly at night becuase it holds heat well. and in dog days of summertime in FL it does well too.
I know how you M4 guys are, i will try and give more specifics later, but the wife pays the power bill. we have just over 2100 sq ft, and i think our bill is ~$150 energy rates keep changing on us. i know 5yrs ago when we first moved in(Oct) our bill was $96.
I will say it does really well in the winter in typical FL winter the heat rarely comes on mostly at night becuase it holds heat well. and in dog days of summertime in FL it does well too.
I know how you M4 guys are, i will try and give more specifics later, but the wife pays the power bill. we have just over 2100 sq ft, and i think our bill is ~$150 energy rates keep changing on us. i know 5yrs ago when we first moved in(Oct) our bill was $96.
Yeah please get us some more detailed information because your power bill is a metric ass-ton less than mine.
it will be a "bomb proof" house lol
No first hand experience since I have never designed a home like that up here in the NE, but the subject was covered in school [I am an Architect]
There are many pluses as mentioned before and many minuses, difficulty if running mechanical and electrical in exterior walls is one of them.
However, if you build the exterior walls with wood or metal furring on the inside, though the wall becomes thicker still, and you do loose a bit more usable floor area, you will not have those problems. The air space behind the furring will also prevent sounds from within the home from echoing in larger rooms.
Also, depending on the soil bearing capacity in the area you are going to build you may have to spend a lot more on foundation work that a traditional framed home. You may need larger spread footings to counteract the greater dead loads from the concrete walls, a traditional stick framed wall [8' tall] is about 10lbs per linear foot, at 150lbs per cubic foot a concrete wall will weight a hole of a lot more! The footing will need to be wider, and have more steel re-bar to counter the bending in the footing, this will all add to cost.
The return on investment in terms of energy bills will be only slightly better based on R-Value. The R value of pored concrete is pretty poor, only .008/inch of thickness since there are no air gaps to prevent thermal bridging, so a 6" concrete wall has an R value of .048... eh. Depending on the rigid insulation used in the form, you can have anywhere from R4/in for Expanded Polystyrene [most common] to R7+/in for Foil Faced Polyisocyanurate. With 2" on either side, you are talking about an R-Value of about R16 for a typical wall with 4" of insulation. [R4/in * 4"] If u use a 4" stud the batt insulation is R13, and with a 6" stud R19. The benefit is in the lack of studs acting as thermal bridging and air tightness of the structure compared to traditional framing.
Your roof will still be traditionally framed so there is no energy gain there.
Most heat is lost through windows and doors, do as the other poster with a ICF house mentioned, its cold by the "cheap" windows. Use a good quality window/door ie Kolbe, Marvin, Pella and sometimes Anderson 400 and you will minimize heat lose/gain in any structure.
Basically what I am trying to say, is that if you minimize energy lose in key areas which effect any home regardless of construction type, you will have an energy efficient home. Same goes for the garage statement, most of the heat lose will be through the door, get a good insulated door that is sealed on all sides when closed and your garage will not be cold regardless of construction.
The only area where the ICF is going to be better of course is structural stability, and wall penetration by flying debris in the case of a hurricane or tornado. Unless your roof will be concrete you will still be subject to the same uplift as any other home, so once again, no change there. Your windows if they are not hurricane "proof" can still be shattered by flying 2x4's and other stuff.
ICF will save on construction time, but once again, only on the parts of the home that are built that way. If you frame your roof traditionally, still takes the same time.
Not saying that ICF suck, they are great when time is of the essence, but they are not the end all be all.
For added fun, look up a program called ResCheck
http://www.energycodes.gov/rescheck/
Its free.
It is used by most States to calculate energy efficient of the home being built and the annalists you get from it is printed and submitted with the drawings when seeking a building permit. Same thing is done for commercial buildings using ComCheck.
Its pretty self explanatory when you use it... at least to me it is.
Enter the information for a concrete/rigid insulation wall framed house, then for a stick framed house. The difference will be minimal. However, change the type of window from a cheap double pane vinyl contractor grade POS to a high quality double/triple pane Low-E fancy shmancy window and watch the efficiency go up!
Play around with it, see what you get.
Once again, most heat loose is through windows/doors and roof, not walls. This program assumes perfect air tightness so of course the fact that most stick framed homes leak air like a sieve when compared to ICF is not taken into consideration.
ok i bugged the wife to dig out some past bills.
our home is 2100sqft. family of four (one baby) so we do a lot of laundry, and i can't get my wife to turn a light out to save her life.
our last bill was $83 for 860 kWh used 200 less than last year. but this is a spring time bill.
jan-feb of this year with days of freezing temps and my wife was home on maternity leave with the new one.
$169 for 1681 kWh used
she told me this is one of the highest bills she has had. and she as never paid a $200 bill.
montanadave
04-25-11, 10:59
What type of exterior finish did you use on your home, glockeyed? It looks like a stucco/dryvit type material but I've never worked with either. How difficult is it to apply, maintain, etc?
its stucco. i have never applied myself either. we sub-ed this out. they install sheets of metal lath that has a layer of felt paper attached to it. then add layers of "mud". most homes in FL have stucco. maintenance is every few years i pressure wash it.
glockeyed, do you know how thick your exterior walls were sans furring strips and dry wall? I'm playing with something in AutoCAD right now and was just wondering. Then again if you had a floor plan of your place in AutoCAD and were willing to share I would be your new best friend.
Alex V, you bring up some very good points. Please keep in mind that when it comes to roofs, Florida residential building codes take hurricanes into account. A typical Florida residential roof is a hell of a lot stronger than found in other areas to withstand with winds. Also a lot of us down here have invested in metal hurricane shutters to protect windows from flying debris.
I'm in the construction business, but commercial not residential. I also went to school for architecture as well as construction management. Just to toss that out there.
A friend of mine worked for a company building Section 8 housing in the ghetto. They used ICF for their houses, largely because of the time issue.
It's important to take into account the area you are in, and like anything else list the benefits you hope to gain by using one type of construction vs. another. If these Section 8 houses hadn't been ICF they would have been block because of the FL building codes (although there are ways to do it with stud framing, that most people down here aren't even aware of because it's cost-prohibitive).
FL roofs may be "stronger" in one sense of the word but that's not doing anything to increase your R-value. The current building code is almost entirely a reaction to the mess that Andrew left in Miami, and part of that is that roof elements are more securely attached to one another to help prevent them from flying off. Even then, many of the roof failures were really garage door failures because the open garage let the wind in and then up. Positive pressure inside + negative pressure above = roof flies off. Northern roofs designed for snow loads are just as strong, just in a different way. And again, none of this has anything to do with R-values or sound transmission.
An alternative to ICF that you don't hear much about anymore is aerated concrete (http://en.wikipedia.org/wiki/Autoclaved_aerated_concrete). I absolutely love this stuff, but it didn't really take off. I was a laborer on a house built using this back in the mid-90s and it was amazing stuff. More about it here (http://www.cement.org/homes/ch_bs_autoclaved.asp). The house I worked on was built with the blocks (IIRC they were still ~8" wide like aCMU but were taller and longer and still weighed less despite being solid) but you can also get it in panels which would be tits and make construction on-site go VERY fast if the builder is familiar with the material.
AAC is something like 80% air, and as such the insulating value is much better than traditional concrete. and floats!
http://www.cement.org/homes/images/AAC_floating.jpg
HES: i believe its 8in (2in foam+4in Concrete+2in Foam) the sheet rock is attached to the foam. there are a few fur strips, but that was only to "straighten" out a wall glued by a drunk.
also i will look to see if we have the cad file. i know we had one version, but not sure about a final.
and robs right, i remember when i first started with my dad. about the only metal fasteners were "hurricane clips". 8 nails 1 clip to attach the rafter to the top plate. when i left the business 10+ yrs ago it involved straps and clips both sides, walls were strapped every 4ft etc you get the point.
i think i have seen that AAC stuff once. not sure why it didn't take off.
Rob, thanks for the education. Question, could you lay the panels horizontally to serve as a sub roof? I'm thinking that you get additional insulation and you can more eaisly walk in your attic with out putting your foot through the dry wall?
Glockeyed, it is just curiosity on my part so don't knock yourself out. But if you find them, I would appreciate it.
montanadave
04-26-11, 13:13
The aerated concrete block is something I'd never seen. Because I would be building in a remote location and doing a lot of the work on my own, it certainly has some real advantages (e.g. lighter weight for one guy to easily handle, fewer steps as it could be finished both inside and out with just a stucco-type coating while still having a decent R-value).
What about running electrical and plumbing? Can these aerated blocks be channeled or do you need to fur out interior walls? Of course, given I'm wanting to build a "cabunker" (my wife's term-- cabin/bunker), I can always just run EMT or the like.
I'm trying to explore as many options as possible for building techniques and materials that are strong, fire-resistant (remote locations where range/forest fires are not uncommon), cost-effective, and suitable for a guy to use on his own and working at his own pace.
What about running electrical and plumbing? Can these aerated blocks be channeled or do you need to fur out interior walls? Of course, given I'm wanting to build a "cabunker" (my wife's term-- cabin/bunker), I can always just run EMT or the like.
What we did was use a router to cut channels. Personally I'd still want to stick conduit in the channels, but IIRC we just used Romex & the like. The link above shows a channel with conduit in it, or at the very least Romex & a box.
http://www.cement.org/homes/images/AAC_chase.jpg
what most people do is just attach drywall right to the inside or, if they want even more R-value they'll put up insulation and either furring or framing.
Business_Casual
04-26-11, 15:20
I find this fascinating, and I only did construction as a laborer, so I am not as knowledgeable. It does seem to make sense, though, to frame and insulate the walls on the interior. Just safer and more flexible.
B_C
Alex V, you bring up some very good points. Please keep in mind that when it comes to roofs, Florida residential building codes take hurricanes into account. A typical Florida residential roof is a hell of a lot stronger than found in other areas to withstand with winds. Also a lot of us down here have invested in metal hurricane shutters to protect windows from flying debris.
+1 on what Rob said.
The only difference between FL and NJ roof construction is the addition of "Hurricane Ties" from the top plate to the rafter/joist. Otherwise a FL roof may actually be weaker [in their load bearing ability] since roofs in FL do not have to support the snow live load. If you look at the ASCE 7-05 [Figure 6-1] the basic winds in FL are about the same as the rest of the Eastern seaboard so the wind design does not change much. Though you do have to design for a basic wind of 150mph in S. Florida, and down to 130mph in Central Florida away from the coasts you have to design for 120mph basic wind in NJ/NY/CT/MA and so on.
The point I was making with regard to windows/doors and roofs is that they are the main source of heat lose and gain in a building. Taking your wall construction from R13 [2x4 wall] to R16 [ICF] will not effect your energy usage much, and in that sense there is no grate gain in using insulated forms. Hell you can get R19 if you use 2x6's for exterior walls.
As Rob said, the benefit is time savings when building repetitive large scale projects such as low income housing. The same benefits are achieved by using most/any forms of concrete construction be it cast in place or pre-cast because you can reuse the same forms over and over. In a residential home where you may want more variety of forms to achieve the desired aesthetic, this cost savings goes away and you are just left with a bunker of a house.
In a residential home where you may want more variety of forms to achieve the desired aesthetic, this cost savings goes away and you are just left with a bunker of a house.
I don't know about cost saving but since the forms are basically big foam lego blocks that become part of the house you can build an infinite number of designs / layouts using ICF.
more info from a trade group: http://www.forms.org/index.cfm/buildingicf
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