Concrete home construction

[dmccarty]

I think Rat's append was addressed to me. I have not taken a class on ICFs but I have read quite a bit on the subject in the years before we built our house, talked to the manufactuers of ICFs, with doit yourself home builders, as well as several professional builders and I do have a valid opinion on the subject.

Fiberglass insulation, I think you mean batt insulation, is not the best for filling voids and in our attic we have blown insulation not batt to help fill in the voids. But most energy loss is in the attic/ceiling not through the walls. Our walls have one inch of rigid insulation to help the wall void insulation issue. I think its EPS. Our slab sits on top of two inches of rigid insulation while the edges of the slab has one inch. The brick veneer, ridgid foam and 2x6 walls really deaden the sound from outside the house.

Insulation is one reasons we did NOT go with the ICFs. Every major room in our house has at least ONE window that is 8'x6'. That is a BIG hole in the wall. Does the R factor of the wall assembly really matter when it has this huge hole? Why go spend 5% more on ICFs for energy effiiciency and then put a big hole that leaks more money? I had tough time justifing using 2x6s for just this reason but we used them anyway and I think we made the right decision but there is no way to really know.

Energy efficiency is a money issue. Our worst case house HVAC bill so far has been about $60 a month. And that only happens a few times a year. How much would an ICF wall reduce that bill? I don't think we would ever really know but would it drop it by 25%, 50%, 75%?

Lets say my house on average costs $30 per month for HVAC and it would cost $10,000 to use ICFs. Lets say that ICFs reduce my HVAC cost by 50%. So I'm saving $15 a month on my HVAC power bill. Thats 55 years to get the money back. Well not really since that that does not include the interest on the 10K or how much I could earn if the money was invested. Which would be reduced by the higher cost of energy. But its along time anyway you look at it. Given we only use the HVAC in the summer our HVAC energy use per month is most likely not $30 on average but more like $15 or $20 so the payoff is even longer.

Regarding ICFs in seismic zones remember Paddy wants a concrete ceiling/roof. That is going to take some engineering and money to build. And I would not want it over my head in my house. His last line of specs did not mention ICFs only poured concrete.

ICFs sound great for tornado alley. And given the threat of tornadoes and hurricanes it almost nullified the energy discussion above. BUT for us it came back to those pesky windows and doors. If we get hit a hurricane there is not doubt in my mind an ICF wall is going to stand up to wind borne debris. But what about the wndows and doors? Even if the window/door is boarded up, a 2x4 flying through the air is going to punch through the plywood. For our area we are not likely to get hit with hurricane winds the will drive a 2x4 through our current wall much less ICF. But a tornado would drive a 2x4 through the door and window and we won't have time to board them up for protection. So for us the ICFs again did not make sense from a storm protection point of view.

On thing I do favor for ICF's is the tree falling on the house scenario. But that was solved, I hope, by cutting down the trees that would fall on the house.

For a direct hit by a tornado you need a concrete storm room. See the FEMA site for design information. When we build the second phase of the house we will have a storm room to hide from tornado and hurricane threats.

Don't think I'm against ICFs. I'm not. I just think one has to look at how much they cost to use and what you get for the money spent. For OUR location and requirements it does not make money sense to use them. If our house was near the coast or where it really gets cold for months at a time then our decision might very well be different.

Later,
Dan

 

[_RaT_]

Yeah Dan, really don't know much about the concrete floor/roof system which is why Paddy may learn a little if he took the class as there are alternatives they offer. Man, I wish our electricity was as cheap as yours out here. AC is one big cost. Probably the highest energy cost we have. It is night and day when you find a well insulated home versus that is not as far as trying to keep it cool. Heating is not to bad though. My home was built in 1951 but has been remodeled a few times. They used TechShield for the roof sheathing. I don't understand why, but it really makes a dramatic difference in the ability to keep the attic cool and thus the house. I love all this stuff about homes and ways to make them better. I have yet to build a ICF home but know I could. As was mentioned, homes in the US are built for a few generations today, the rest of the world builds them for a substantially longer time span. Europe uses a lot of stone and concrete and it shows. Concrete has come down some around my area but then copper has gone through the roof. Labor is outrageous so in general, homes are just costly. Once you take a class on ICF, you can with a little knowledge on plumb and level techniques, set up a ton of form yourself in one day. It seems to be very user friendly. Nudura offers 8' forms, collapesable, reversable, universal 90's etc. sheetrock centers every 8" with the same pullout strength as wood. Anyway, I agree with much of what you say, I just like what ICF can do for posterity as well as the overall R value it has. Up in Canada they have built senior retirement buildings 6 stories tall out of both stick and masonary block as well as ICF. The cost savings to heat the nearly identical buildings are nothing short of unbelievable. Try to take a class from Nudura, it not much money and it is enlightening if nothing else. Here are some links.

http://www.nudura.com/Content.cfm?C=619&SC=1&SCM=0&MI=646&L1M=646

http://www.wealth4freedom.com/1-environment/IBT.htm

 

[dooleysm]

My inlaws are contractors and own a construction supply house. I believe they are a regional distributor for Reward Wall ICF's. We used ICF's for our basement. They were a cinch for my wife and I to install. We poured a footer and my brother inlaw laid the first row of ICF's to get us started. The wife and I put up the rest of the basement walls over the next 2 days. They snap together like legos. You SHOULD save on labor costs if you go with ICFs over a traditional poured wall.

My inlaws are really big on ICFs for the energy savings. Since only our basement is ICF (the layout of our home prevented their use above ground) I can't really speak to their efficiency. I do know that the inlaws have built all ICF homes and installed vent free fireplaces, only to have the buyer return the fireplaces because they heat the house too much to be of any value.

My brother in law is currently building his home using ICF's, so a Jasper area contractor thinks enough of them to use them, if that helps.

 

[ultrarunner]

I worked construction in Austria the summer I graduated. For most residential concrete projects, the concrete floor/ceiling girders are ordered the same way we would order manufactured roof trusses.

The girder is actually concrete "Beams", sized for the span, with 50% of the re-bar left exposed on the top side.

The floor for a typical room might require a dozen of these pre-engineered beams laid tightly side-by-side. Once lowered in place by a crane, concrete is poured directly over them... typically 6 to 8 inches.

The entire on-site process goes very quickly. Typically the beams are placed first thing in the morning followed by the concrete. The concrete ties everything together. The beams act as forms, contain 90% of the re-bar and provide a relatively smooth ceiling for the space below.

 

[dfkrug]

Paddy,


Will the house be in a sesmic zone? No way would I want to live in a house with a concrete walls or ceiling in CA. I'll take stick built with no bricks.

That is one of the biggest misconceptions about reinforced concrete
construction. I built 300 feet from the San Andreas Fault zone and
that is the PRIMARY reason I did go with concrete. UNREINFORCED
concrete and masonry is indeed unsafe (and illegal) here.

The 2 strongest forms of construction available for any building is either
structural steel or steel-reinforced concrete. Indeed those are the
only 2 ways you will see any large building or bridge constructed these
days. Wood frame has been heavily used for smaller structures in the US
primarily due to cost. New methods, incl ICF construction has made
the costs very close.

It is amazing to note that Florida (land of hurricanes and termites) has
thousands of ICF buildings, yet houses are fairly inexpensive there.

 

[dfkrug]

In California, ICF built homes fly through engineering. In the Bay area, the building departments kick the ICF design through much easier then the wood frame homes (not to mention title 24, our energy design requirements).

WHAT??!!

Virtually ALL my ICF projects had some difficulty with engineering, usually
because the PEs were used to stick frame and did not want to do any
concrete walls. Most in this region did not do basements either. The bldg
depts were sometimes trouble, too, despite all the approvals and
certifications. Since I consulted with the engineers and architects early
in the design stages, I saw their discomfort with concrete up close. Most
were in the Bay Area.

 

[dmccarty]

...
The 2 strongest forms of construction available for any building is either
structural steel or steel-reinforced concrete. Indeed those are the
only 2 ways you will see any large building or bridge constructed these
days. Wood frame has been heavily used for smaller structures in the US
primarily due to cost. New methods, incl ICF construction has made
the costs very close.

It is amazing to note that Florida (land of hurricanes and termites) has
thousands of ICF buildings, yet houses are fairly inexpensive there.

But we are talking about smaller residential houses. How much does it cost to build a house out of structural steel? I spent some time looking into using steel in a house for the same reason I looked at ICFs. The anwer I got back was only a few contractors do the work. The ones that do really want to do light construction not residential. And its expensive. Then you get into energy issues which seems like they can be overcome but again it costs more money.

Spending 5% more to use ICFs is not quite close. Its more expensive. And what does it buy me? From an energy perspective in my case not much that I can see. Now if my 5% number is wrong and the ICF house can be built for the same cost as ICF its a different story. But with new houses in my area costing around 300K to start 5% is alot of money.

I'm not sure I would call houses in Florida inexpensive. Maybe from the perspective of the NE or CA. Granted I have been gone from FL for a few years now but I did not see any/many ICF building going up. I saw lots of junk built stick homes and the usual CMU houses.

My area on NC has lots of building going on. I drive through areas where litterally thousands of home are being built. I have only seen one ICF building going up lately and it was for an animal hospital. EVERY house is stick built and mainly with vinyl siding. If you are lucky the front is brick. They cheapest of these developments has the lowest price home at $280,000. The builders and the buyers are going to look long and hard at anything the increases the cost on those homes.

Rat, a KW hour costs me an average of ten cents. We built the house to be energy efficient, get some passive heat gain in the winter and it seems to work. My power bill runs about $90-100 a month when we don't use the HVAC. My guess is that $30 is for the hot water heater. The rest runs the lights, washer, dryer, etc. If the outside temps stay in the mid maybe upper 80's we turn off the AC and open the windows. My power bill from 8/2005 was about $153 and I think that was a high. It will be interesting to see the bill this year since we hit the high 90's low 100s.

Again, my point(s) is not to beat up ICFs but look carefully at what things cost for what ye get.

As an example I have long wondered why home don't have fire sprinklers. Years ago when I was putting togather our requirements for the house I dug into the issue. At the time the code for putting in the systems for a residential house was the same as commercial which made the cost very high. And in a rural setting it would be even more so if the water source was a well. That has changed. NFPA if I remember the FLA correctly, change the code for residential and may it easy/cheaper. The best number I got was that it was going to cost me about $5,000 to put in the system. Roughly $2/sf. I called up the insurance company and asked what kind of savings I would get on my house premium. It was something like $25 a year. That tells me that the insurance company does expect the system to save them money. We don't have a sprinkler system. It just does not make money sense.

We made a similar decision about radient heat and solar hot water generation. We will have to revist the hot water generation because of the change in Federal tax law... But radient heating for us just did not make sense either. If we where up north I would have it in the house.

If I was living in FL I would strongly consider ICFs with the motorized window shutters along with hip metal clad roof and low/no overhangs. If I was in a fire prone environment out west I would do the same.

Later,
Dan

 

[Nat]

I'll have to back Dan's reasoning for NC. I am a building contractor, well really not anymore but have been one and around here finding someone to even have the concrete forms is like finding wheelbarow seed. I have had to do several jobs that required building my own forms because concrete was required. If building a house, and that's what we're talking about, it would cost nearly as much to build the concrete forms as it would to stick frame the walls. It would be nice if it were more often used cause I can see a lot of benifits to using poured concrete.
There is a company in Italy TX that sells a kit to build a dome house that is made of shotcrete. It has an inflatible "skin" that is inflated , then foam insulation is sprayed in place then rebar is hung from the suspended shell. After the rebar is placed the inside is sprayed with 5" of blown concrete, or shotcrete. That way you have the weather proof skin on the outside then the insulation next then the mass of the shotcrete on the inside.
I looked into trying to start building them here but NC is to conservitive for that.
Here near Lexington almost all the homes are build using stick framing with OSB sheathing, house wrap, then vinyl siding, maybe 40% will be brick veneer.
I have seen areas of the country where the 2 x 4 framing was sheathed with a 1/4" insulation board and then vinyl on the outside simular to the way mobile homes are sheathed here.
One of the best things about a board like this is to see the different ways that are called normal in different parts of our great country. Let's keep it coing maybe I will learn something, can't hurt, later, Nat

 

[_RaT_]

I'll have to back Dan's reasoning for NC. I am a building contractor, well really not anymore but have been one and around here finding someone to even have the concrete forms is like finding wheelbarow seed. I have had to do several jobs that required building my own forms because concrete was required. If building a house, and that's what we're talking about, it would cost nearly as much to build the concrete forms as it would to stick frame the walls. It would be nice if it were more often used cause I can see a lot of benifits to using poured concrete.
There is a company in Italy TX that sells a kit to build a dome house that is made of shotcrete. It has an inflatible "skin" that is inflated , then foam insulation is sprayed in place then rebar is hung from the suspended shell. After the rebar is placed the inside is sprayed with 5" of blown concrete, or shotcrete. That way you have the weather proof skin on the outside then the insulation next then the mass of the shotcrete on the inside.
I looked into trying to start building them here but NC is to conservitive for that.
Here near Lexington almost all the homes are build using stick framing with OSB sheathing, house wrap, then vinyl siding, maybe 40% will be brick veneer.
I have seen areas of the country where the 2 x 4 framing was sheathed with a 1/4" insulation board and then vinyl on the outside simular to the way mobile homes are sheathed here.
One of the best things about a board like this is to see the different ways that are called normal in different parts of our great country. Let's keep it coing maybe I will learn something, can't hurt, later, Nat

Hi Nat, the ICF system of concrete forming/insulation is very, very fast and very simple. If you can frame, you can form with ICF, it really is that simple. The rebar snaps in to the web, does not need to be tied because it is spaced apart. I do agree to a certain extent with Dan, you will probably want to do some calculating. He pays about 10 cents a KW. Well, I'm at about 15 or 16 cents/KW but that does not include tranmission or distribution cost. Thats another 12 or 13 cents per kilowatt. All said, its costly and I would venture to say, it will catch up with the rest of the country as various energy sources get scrubbed. Regardless, for right now, on a short term basis, I'm sure it is less to go stick frame. I just framed a place and was rather suprised at how relatively "cheap" wood is. The more extreme your climate, the more I think you will see ICF or the like appear. If I was building in Hawaii for example, I would like to consider ICF if for no reason then to keep the bugs from eating most anything alive. Anyway, I do realize it will be different for everyone not only because of where they live but because of the budget constraints. Good thread, great posts...

 

[Highbeam]

Our typical tract home here in the northwet is a concrete footing, short stem wall, then engineered floor joists above the crawlspace, then OSB flooring, then 2x6 framed walls with lumber prefabbed trusses on top. The walls are not wrapped in anything just painted T111 on the outside which is sheets of OSB with a pressed on exterior finish that looks like panelling, then bats of fiberglass insulation, sheetrock, and then the vapor barrier is painted on to the sheetrock on the inside. No plastic and no tyvek. The attics use blown in cellulose or fiberglass and then OSB roof sheeting, and composition shingles.

The homes are framed all year so you can imagine the water ponds on the OSB flooring held in by the bottom plate of the walls. Our concrete is cheap though.