Does anyone have thoughts on using SIPs vs: concrete filled styrofoam form homes for the second and third stories?
Does the thermal mass of concrete make much difference?
which goes up easiest?
What is the difference in cost by the time it is up?
Considering all factors which would you use in your own home?
Thanks,
Steven
Replies
Sip's is the way to go. I built a timber frame house and put all of the pannels up in one day. Great R- Value in the Pannels. Concrete has an R-Value of one per foot, wood one per inch, closed cell foam is five per inch. I heat my basement slab and it radiates heat to the rest of the house, but the temp of the soil under the slab is about 55 degrees. It is an efficant use of thermal mass to heat it to 80 degrees. Cost wise I dont know about concrete, but pannels are more expensive than a stick frame.
>Sip's is the way to go.
I don't agree. I think a case could be made for each depending on circumstances and needs.
>Concrete has an R-Value of one per foot
The benefit of concrete is not it's insulation value, but it's strength and conductivity. The concrete makes the house stronger than without the concrete. And the conductivity of the concrete serves to buffer internal and external changes in humidity and temperature. Foam insulation alone cannot do this. So, there are benefits to each style, and one has to balance their needs and budget, etc.
If I don't miss my guess, you're going to get a bunch of arguments for both.
What is important to you about the structure and function of this building?
DRC
I am looking for a comfortable home with low utility fees. However, I do not want to go insane and cross the line of diminishing returns and spend lots of money to save a few dollars. I am near Spokane Washington which is an area of fair temperature spreads from night to day although not as much as in the desert.
We have winds up to the 70-80 mph range on rare occasions. We did have a tornado the other day which was in the F0 range (the smallest as opposed to the movie which showed the F5 variety).
This home is for my family so I am looking for a nice one but am not going hog wild as money is an object.
Did this answer your question or did you need more info?
Thanks for your help,
Steven
My problem with either of these solutions is that I live in an area prone to wildfires and both the polysyrene and polyurethane foams commonly used in ICFs and SIPs are flammable, as is OSB which is commonly used as a facing on the SIPs. Flame retardants can be used, but they generally only delay rather than prevent damage to a structure from a long burning fire, and there is some question as to the ultimate safety of some of the flame retardants (some reportedly mimic hormones and can disrupt aquatic life - their effect on humans is being debated). The other drawback for my area is that I have a high population of carpenter ants which like to burrow into the foams.
I am investigating the type of ICF that encapsulates polystyrene in cement rather than having raw blocks of "Styrofoam". While I will probably use some type of foam insulation, I hope to have it protected from fires external to the building by concrete and from internal fires by gypsum board.
However, most of our building methods for single family dwellings are not that fire resistant, so either SIPs or polystyrene ICFs are probably at least somewhat of an improvement over the typical stick construction in that regard.
So, stucco the outside and limit air flow around soffits.
Thank you Casey,
Which brands have you studied? I only know of one and that is Rastra which has the disadvantage (or advantage if one wants to save concrete) of being a waffle design. This requires an engineer to stamp it to keep the building inspector happy. In addition one engineer said he liked solid walls better and they didn't require the time to engineer.
I have heard good things about Rastra thought as far as pouring has been concerned. A lot less concrete blowouts then styrofoam although they are heavier and harder to work by report. I have worked with styrofoam but not the cement ones.
If you know of any other brands please send me their names.
Thanks again,
Steven
The one I am looking at presently is called Tech Block. They are out of Arizona but have a couple of other locations, one in Marysville, CA. There is another outfit that originally manufactured Rastra under license but then split off to do their own. Don't remember the name. Techblock claims a calculated R of 35+, which I think may be rather optomistic, to say the least:
http://www.techblock.com
There have been a couple of threads on these types of blocks. One said that the Rastra they received had a lot of chips out of them that caused them to be hard to seat. I don't have the patience at present to fight the Breaktime "search" function, but you might be able to find something.
I ran across something called "Isoblock" but haven't really checked into it:
http://irc.nrc-cnrc.gc.ca/ccmc/registry/04/12713_e.pdf
There are also some blocks that use a mix of cement and wood. Don't know anything about them either. Faswall claims a R of 18+:
http://www.faswall.com/
I'm sorry, you need to do some research, I have a video of a sip built house that they built a bonfire in a corner of it and it came thru fine! no damage!
outside temp was only a few degrees higher than ambiant..
As for the problem with ants, it's called borax, AFM uses it in their foam and an ant/insect eats it and dies,,
In addition SIP construction while amazingly lite is 200% stronger than stick built.
To give you an idea of what that means... when I was building my house I placed a panel horizontal fom the roof panel. simply nailing it and foaming it in place as themanual staed. both ends and one side were free. totally cantalivered from those little 8 penny nails that are 2 inches long..
I wiegh 250 pounds plus my tool belt and stuff. My helper weighed similar. we built of of that panel and built a round tower! at any one time there were well over 600 pounds on the free end of the panel.. I'd put up a ladder and climb up to the top of the tower.
I'm willing to bet that I had as much as a thousand pounds on that cantalivered panel..
I have done the research and every spec sheet for polyurethane and polystyrene indicate that they are flammable with ignition temperatures between 700 and 800 degrees F. As far as I know, all codes now require foam insulation to be covered by at least a 30min. fire barrier, which indicates that code authorities also believe the stuff is flammable. I suspect that most of the demonstrations don't actually get the foam beyond its ignition temperature or that the sample happened to have effective fire retardants.
The MSDS for these foams warn that they are organic and when exposed to an ignition source with sufficient heat and oxygen, they will burn like most other organic materials. The MSDS sheets also warn against welding where sparks can ignite the foam.
"Polyurethanes, in the absence of flame retardants, are extremely combustible. In these tests, the pure polyurethane sample burned rapidly after exposure to the flame and was totally consumed within 40 sec, to leave a black char. "
http://research.chem.psu.edu/hragroup/flame_resistant_materials.htm
Even the suppliers warn that the materials are combustible:
http://www.huntsman.com/pu/index.cfm?PageID=351
http://www.huntsman.com/polymers/Media/EPS7-7.3.pdf
I don't know what percentage of foams used in construction incorporate fire retardants. I have seen their use mentioned on only a few of the ICF and SIP sites that I have visited. Fire retardants do slow the combustion process. However, the commonly used fire retardants may not be completely environmentally benign.
Additional reading:
http://www.monolithic.com/plan_design/fire_hazard/index.html
http://irc.nrc-cnrc.gc.ca/cbd/cbd178e.html
http://www.osha.gov/dts/hib/hib_data/hib19890510.html
Everything is flamable but not all flamable materials are easily ignited. The other key ingredient in a fire is air and there is no air cavity inside a SIP wall. Any fire that will damage a SIP, with a fire resistant coating such as sheetrock or stucco on both sides, will destroy conventional framing much more quickly. Concrete has some advantages here... unless it is inside an ICF with a thick foam coating on both sides that is.
Bottom line - any fire hot enough to destroy a SIP home will destroy pretty much any home.Kevin Halliburton
"Do you see a man skilled in his work? He will serve before kings; he will not serve before obscure men." - Solomon
Kevin,
"Bottom line - any fire hot enough to destroy a SIP home will destroy pretty much any home."
A most useful observation that homeowners, builders, and architects would all do well to bear in mind.
Fire resistance, especially in residential construction, is a somewhat odd concept, best approached with a certain degree of skepticism. The 30 minute rating we hover around in our design efforts really isn't much more than an attempt at creating a structure that increases the likelihood of successful occupant egress in case of fire. A secondary consideration is building a structure that is less likely to ignite the neighbor's house as well before the fire department can show up.
Whether there is anything useful left of the structure after the fire department overhaul is quite another matter. Whether that remaining portion of the structure with sufficient structural integrity to be useful will survive the economic phase of the autopsy is yet another question.
Contained within your observation is the consideration that regardless of the structural materials employed, the contents of most homes can provide more than enough BTUs to destroy the structure in case of fire (houses occupied by minimalists, ascetics, and existentialists notwithstanding <G>).
While it is not difficult to design a home that can survive a fire and remain useful, as you have pointed out, there is quite a bit more to the equation than material selection of the walls.
I'm glad you hang around here -- I always look forward to reading your comments.
DRC
While I normally agree completely with Kevin he is mistaken in at least one regard.. Many SIP homes are built around a timberframe, a wonderful symbiotic relationship.
In a a half an hour the typical 8x8 hasn't lost 1/10th of it's strength. surface or cosmetic damage only. Thus Evan after a half an hour a timberframe would most likely be fine with only superficial damage..
"Bottom line - any fire hot enough to destroy a SIP home will destroy pretty much any home."
Kevin,
While I agree with you, I believe that you are ignoring one of the key killers in a fire, and that is smoke. My understanding is that the various construction foams and adhesives, when burned, are far more toxic than plain ole wood. I'd rather crawl out through a cloud of smoke made by a chunk of solid wood than one made by a mass of foam. Not to say that I don't think SIPs are cool and safe and all that, I just wanted to point out that most people die from inhaling the smoke, not from getting crisped, and that the contents of that smoke are important in determinine what kills you quicker.
"While I agree with you, I believe that you are ignoring one of the key killers in a fire, and that is smoke."
Indeed, smoke and chemical vapors are the leading killer. However, (unlike us <G>) not all foam is created equal.
The foam that is used in ICF actually burns cleaner than white pine.
From: http://www.rewardicf.com/eform.htm
Fire Safety:
Omega Point Laboratory Tests (ASTM E84/ASTM E119)
Toxicity Fire Rating Flame Spread Smoke Development
24 (9 ¼") - 3 hrs.
(11") - 4 hrs. Less than 25 Less than 450 When burning, less than half the toxins of
burning wood (pine.) Self extinguishing
While I am not as conversant with SIP, it appears that the foam used in SIP has similar properties.
http://www.pbspanels.com/pansys.cfm?subtopic=FAQs§ion=panelsystem&faq=10#F10
The industry was thoroughly shaken up in the 1970s by the consequences of bad foam chemistry in fires, much has been done about that.
Of far deeper concern is any material containing PVC. The vinyl chloride, when burned, releases a gas that combines with the moisture in your lungs to make something similar to a contaminated version of hydrochloric acid. Death is a fairly common result. I've seen people who didn't die, and they looked terrible.
Other plastics are pretty bad, too. Synthetic fabrics are no fun, either.
Oddly enough, wool is another bad guy in a fire.
So while your concern is well-founded, it is also important to make these decisions on the basis of sound evidence.
DRC
In the video I got from AFM the fire they set didn't get the foam to the smoking point.
It's easy to understand how.. Think of conductivety..
The sheetrock used on the outside of the SIP is designed to be fire retardant.Gypsuim is a poor conductor of heat and it disapates the heat well while the foam acts as further heat sink.
Since there is no free oxygen to cause further combustion or allow a heat path to creat a air channel, the fire will slowly die due to use of all the available oxygen.
In my home the tempurature differance between the floor and the ceiling 28 feet above is about a 1/2 degree in the SIP portion of the house. That indicates that there is almost no conductivety or air transfer.
the other portion of my house which was stick built and sold as being "well insulated" (it even got a credit for energy savings at the time of construction) had over a 3 degree differance in just 8 foot rooms, indicating a clear transfer of air...
Casey,
Take the instructions that come with the purchase of SIPs and build according to those specs...
Now in the corner (to give it the best chance to catch fire) build yourself a bonfire. Light it and sit back and watch.. satisfy yourself....
Frankly it's not a gimmiick to sell you a dangerous product rather a demonstration to dispell such myths.. In today's litigous society the existance of such a video would be worth millions if your beliefs were valid..
You seem to fixate on the 700 to 800 degrees, would you please tell me how to achieve that temp and no higher?
Ok if you like that particular temp. Take a sliver of wood like you'd find from a split 2x4 and put it in a tube and heat it to that same temp.. No, Not from a fresh green 2x4 but one that has dried out to the degree that wood does after years in the house... after a while you'll notice that the wood is smoking, oops now it's glowing! I'll bet that with the correct degree of care (to not exceed 800 degrees with a heating source) and enough oxygen I can get it to burst into flame. (we did that in a fire fighting class I used to teach)...
To dispell one of your statements, there were no fire repellants as you define them, rather the use of common building materials that are readily available at Home Depot etc..
You seem to fixate on the 700 to 800 degrees, would you please tell me how to achieve that temp and no higher?
Not sure where the "fixation" comes in, the figures I have found for polyurethane ignition temperature were given as between 750 and 800 degree F, and polystyrene, if I recall, is about 750 degrees. MSDS for polyurethane:
http://www.auralex.com/testdata/test/foammsds.pdf
I agree that in a SIP, the fire danger is probably less than with standard stick frame materials. This is particularly true if it is covered with non-combustible materials. However, most SIPs that I have seen use OSB on at least one side, which probably doesn't provide much protection from a sustained fire. I just wanted to challenge the idea that the stuff is not flammable - as stated in the above MSDS "Once ignited, can produce rapid flame spread, intense heat, dense smoke and toxic gases."
My personal concern is to build a structure which can withstand a fairly major brush fire. I think that typical SIP construction would probably not do too well in the types of forest fires that have ripped through various parts of Oregon in the past few years. I am guessing that the Rastra type cement/polystyrene blocks filled with concrete probably stand a better chance of surviving.
If you read my first entry under "optional reading" (or something like that) in my prior post, you will get at least one person's opinion regarding the circumstances under which SIPs can be ignited.
Casey,
A while back Fine Home Building had an article on a house that survived the California fire of a few years ago.. While stick built (the most fire prone method of building) the outside was covered with stucco and the roof was tile..
What really saved the house was two things the speed of the fire (Santa Ana winds of 90 mph) and the house was surrounded by Ice plants which when exposed to fire give off it's water in the form of steam which cools the area temporary...
( and probably the fickle finger of fate)
Last winter I visited with some people who survived the San Diego fire. Their home was lucky and the fire went on either side of their house but because it was built on the outcrop of rocks it didn't burn (stucco and tile again)
They wished it had!
Their once great view is gone and their house which before was charming now looks like a pimple on the landscape. Everything smells of smoke and the have all the privacy of living on a freeway...
Phone and power lines are down and won't be replaced for a long time since they are the only ones to survive, everybody else has taken their insurance money and moved away.. Friends and neighbors all gone!
Their insurance has been canceled and the bank requires them to buy extremely expensive insurance to replace it which has made living there unaffordable.. yet there is no market now for their house..
If you still want to build ina high fire risk area, build with whatever method you want, cover it with stucco completely, tile roof (no vents) clear the are around the house by at least 30 feet (fifty would be better) no grass or brush of any sort,,
Make sure all trees are at least it's full fall height plus 20 feet away from the building..
(a 50 foot (when fully grown) tree should be 70 feet away from the house)
cross your fingers and I wish you luck
If you are looking for a result that is somewhat above the standard while containing costs to a reasonable level, I'd give serious thought to ICF on the first floor and double-framing the upper stories.
My experience with ICF says it adds about 4% to the cost of the job over what 2x6 frame would go for. For the value you will realize if you stay in this home more than 5 to 7 years, that's hard to beat.
Double-framing the walls does (at the very least) double the cost of the walls, there is no way around that. But in the big picture, we're not talking about a big chunk of the overall cost. Beyond the aesthetic benefit of thick walls and deep windows (great light if you splay the window openings), you can also install OSB shear panels between the inner and outer studs and never worry about that wind load again if the walls are spaced appropriately.
After installing those shear panels, you will notice a gap between the shear panel and the deck at the bottom plate. Be sure to point that out to your electrician, he will like that real well. Who knows, that might even be worth some money. Likewise for the plumber, especially if you are running PEX.
In my opinion, double walls need to be fireblocked more carefully, but that's not hard to do.
I would recommend consulting with someone who specializes in energy analysis before you buy too much insulation. There is a point of diminishing returns. Exactly where that is depends upon your climate, design objectives, and budget.
DRC
Thank you Dave for your insight.
Since you indicate that ICFs are about 4% more then 2x6 stick framing what do you like about double framing above ground rather then going all the way up with ICFs?
I just heard our local concrete company is bumping up prices by about $15/yard but I don't want to think about that.
Steven
Dave,
Did you mean 4% increase over the cost of the walls or 4% over the complete cost of the home?
Thanks,
Steven
It's about a 4% increase over the cost of the home. The hypothetical one-story $100,000 house made with 2x6 walls, unchanged except for ICF exterior walls, is going to cost about $104,000.
This presupposes a trained and experienced installer and sub-trades who have worked with ICFs before. If that is not the case, the cost can get badly out of control.
ICFs are pretty straight-forward at the basement and first-floor level. As you move up to the second and third floor, they get more expensive per unit, as does anything. Some things just get expensive faster than others.
Wood isn't bad -- it's easy to lift with nothing more than a set of pallet forks on the skid steer, and simple to stand up, even at heights. Enterprising builders have been known to sheathe the walls, install the windows, and put most of the siding on before the second or third-story wall is stood up.
You can go as high as you want with ICF, but as more than one unhappy customer will attest, the bracing is essential, no matter what the manufacturers say. Likewise for the window and door flanges. The higher you go, the slower the process. It just seems to work that way. At some point, it's hard to justify the cost.
As for the ICF versus SIP, it's difficult to make a useful comparison without considering your own design intent. They are very different materials, each designed to address a different question. They both do their job well.
The best characterization of the philosophical difference between them was described to me as SIP being "light and tight" and the ICF as "mass and class." (This was by Joe Lstiburek's wife, Betsy.)
Attempting to analyze ICF solely on the basis of the published R-value ignores the significant benefit that can be gained in certain climates from mass-compensated thermal performance. R-value is only part of the picture.
If you consider that up to a third of the heat loss from a modern home can be due to air leakage and convection, it's easy to see that more R-value isn't the answer in every case.
Speed of construction with SIPS is only part of the picture if your electrician and plumber walk off the job because they have never seen such a thing before.
It's worth figuring out exactly what you want the finished product to do for you, and then figure out the best way to get there.
DRC
Regarding the use of SIPs and electricians and plumbers..
first you won't ever put plumbing in an outside wall in my climate.. to do so would be to ask the pipes to freeze.. Inside walls aren't built with SIPs so plumbing isn't a problem.. wiring is a piece of cake.. you tell the manufacturer where you'd like the wire chases and they are molded into the panels at the factory.. if you should want to change your mind later there are plenty of easy ways to put wire chases into panels in the field that are easy and cheap..
(face it, how difficult is it to drill into a foam coffee cup?)
A conversation with your electrician up front a should help you confirm his ability to work in a media..
Cool -- thanks.
DRC
Cloud is right - I strongly favor SIPs but the real answer is probably, "it depends."
Concrete:
IF IT IS BUILT RIGHT, concrete is stronger and will generally outlast just about any other form of building. It also has greater thermal mass that will make for a little quieter and possibly more energy efficient home.
On the downside concrete is very difficult to work with, compared to SIPs, it is significantly more expensive, takes a lot longer to build with, the walls will not be square or plumb by any stretch of the imagination and, once poured, changes are very, very, very difficult and expensive.
While concrete tends to be more efficient the additional expense does not usually pay out very quickly on the energy bill savings, if it pays out at all. While concrete tends to last longer, how much longer and what that means to you is debatable. Any house that is well built and well cared for will significantly outlast its occupants. Any house that is not well built and is not well cared for will not - even if concrete is one of the main structural elements involved.
SIPs:
IF THEY ARE BUILT RIGHT, I am convinced that SIPs are the best bang for your building buck on the market today. They are tight, strong, easy to work with, fast, they are more flexible in the construction phase, straight as an arrow when finished and they provide far superior energy efficiency to conventional framing. I could go on but those advantages are the biggies.
On the down side, they must be special ordered and, depending on where you are located, lead time may be significant and shipping may cost quite a bit. If there is a problem you can't run down to the lumber yard and replace a panel. I don't care what anyone says, electrical is going to be more difficult (expensive) than traditional framing and you will need some big equipment to errect the panels which you need to factor into the budget. The roof panels in particular will kill you if you don't have the equipment on site to do it right. (speaking from experience here)
If you go with conventional OSB type SIPs I recommend R-Control but Thermasteel makes a steel stud and foam version I am pretty fond of as well. I just saw an article recently about a SIP panel that was built with cement board instead of OSB. I like the concept but don't know enough about them to recommend them yet.
Here is the biggest "it depends" consideration... Both forms of construction are still pretty specialized so the most limiting factor in my opinion is who is working in your area and what they are working with? Hope that helps and best of luck to you.
Kevin Halliburton
"Do you see a man skilled in his work? He will serve before kings; he will not serve before obscure men." - Solomon
Just caught the fact that you are asking about second and third story applications in particular. SIPs are sure going to take a lot less first floor structure to support them than concrete in any form. Arguments could probably be made in both directions, but once you pour past that first floor, concrete gets less and less affordable by the foot.
Kevin Halliburton
"Do you see a man skilled in his work? He will serve before kings; he will not serve before obscure men." - Solomon
asking about second and third story applications in particular
That caught my eye, too.
The ICF can really only go up a 'floor' at a time. So, there will be the additional man/hours for that. There will have to be some sort of access or scaffolding just to get the forms up. Then, you are calling for the pump truck to get the concrete in for each new floor level.
An extra day or two of crane rental ought to be a lot less. And the 'stand up' time ought to be shorter over all, too.
ICF up to one (a/some) level, then SIP above that could be a compromise--but there are a ton of factors to judge that.Occupational hazard of my occupation not being around (sorry Bubba)
I know some will not agree---
I would do neither one--- I built a 2400 sqare foot home using double stud walls, for both floors. The walls were insulated to R 50 and the roof to R100. Wrapped in poly, and used a water source heat pump for heating and cooling. had 30 feet of glass on the south side for a great view of the smokies... I will say that the double stud design is cheaper than either of the other two designs. And my wife LOVES the deep window sill created by the double stud walls.
I studed up the outside walls and and then moved in a foot and studed up the insdie walls--- VERY warm and QUITE.
I'm with you on this one. I have always been an admirer of the newest products, but I tend to ultimately seek the simplest solution. The look of the deep exterior jambs satisfies my need to make the house look as though it is from an era long ago.
I am curious how you get to R-50 and R-100. Is this all fiberglass or cellulose or is there foam in there as well ? Where are your electric bills ?
carpenter in transition
Brother Tim
I put 3 1/2 inches offaced fiberglass in hte outside wall then 6inch batts horz in between the stud walls and then 3 1/2 in batts in the inside wall.
in hte ceiling i used 6 inch batts and roatated their posisition every layer till i reached 3 feet of insulation
for those that say this is overkill--- they are right but the added cost was very little when looking at the whole house.
I also put insulation inbetween every single wall inside the house and between the first and second floors--- and every wll in the house is wrapped in poly
this was 15 years ago and the house is great!!!!!!!!!!! it is on a slab facing south. and at 10 degrees outside the house was 75 inside with nothing on except the fan that passed that solar heat around.
the house is VERY quite from the outside and VERY quite between rooms
yes the deep walls are great
good luck
OK the math is simple. ICF's have 2 inches of foam on the outside and two inches of foam on the inside. total foam is an r value of 20 add the conrete's r value and you are talking of a total r value in a 10 inch wide panel of 28
a SIP of the same thickness would have an r value of 50
thermal mass only works if it's inside the heated space since half of the concrete would be on the inside and half on the outside of the center of insulation your total gain would be zip..
Dramatic differance in cost.. the SIPs would cost about $3.50 a sq.ft. plus labor while the ICF"s would only be half of that, plus the cost of rebar, (Not cheap now) plus cement, plus something to mount the siding on (inside and out). I've used both and while it is relatively easy to build with ICF's SIPs are a breeze!
I used ICF's for the foundation on my home and SIPs above ground..
View Image
SamT
If you or anyone else here has done this, what the most it's safe to pour at once--10'? 8'? less?
I've poured 10'-8" with no problem. Just put a loop at the end of the boom to slow things down and go easy.
Start in a corner, slide the pour along so you are actually placing it on the slope that is formed rather than dropping it, and work in lifts.
A little SP in a fat 3/8 minus mix batched at slump 4 and you have no problem with segregation.
I know it breaks a few rules, but it really does work just fine.
DRC
Dave,
Slump of 4"? (I have always poured wetter.) Do you vibrate it? What forms do you prefer?
Ron