SIPS vs ICFs
Ann Henning| Posted inGreen Building Techniqueson
What is more economical and energy efficient for climates like northern Minnesota? I have read that ICFs are best for the foundation work. SIPS are easier to install. Assuming the home owner is the builder, are SIPS or ICFs a better choice if the goals are ease of installation, cost and energy efficiency?
Thanks for your suggestions.
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Replies
I vote for neither.
For ease of construction and cost, an insulated slab on grade with thick stick-framed walls will be hard to beat.
Concrete is expensive.
ICFs or SIPs will require specialized tools and equipment.
Stick framed structures can perform as well as anything else and will be much more straight-forward and forgiving for an owner-built project.
Given MN requires R-19 for above grade insulation, you can find adequate stick-frame construction. However, it would take quite a bit of work to get an equivalent R-value of what a SIP or ICF wall can provide right off the shelf. Those two wall systems have very similar energy savings potential.
If the home owner/builder has carpentry training, ICFs aren't very tough to learn. Most, if not all, of the "specialized tools and equipment" can be rented.
For me, the big difference between ICFs & SIPs is the disaster-resistance of ICF walls. Disasters might not seem like something to be concerned about in MN, but tornadoes do happen there, as do storms that blow debris like twigs, branches and loose material. Wind-borne debris can't puncture through concrete.
Just don't make the mistake of looking solely at up-front cost. You're not buying a shirt; you're making an investment. Take into consideration what will go out of your pocket on a monthly basis: mortgage, insurance, utilities, taxes, etc. Your mortgage may go up based on your choice of building materials (or other sustainable choices), but if you reduce your operating costs, that's going to outlast the life of the mortgage.
Finally, ask yourself this question: Do you think electricity/heating/water costs will go up or down in the next 5-10-20 years?
我看着使用,对我来说,他们已经virtually no advantages above grade, if that is what you are thinking as an option. Yes, they can withstand (I think) more of Ma Nature's forces, so it becomes a probability game for you. IMO, if they were "a more probable to survive" home, then the insurance companies would reflect that in their coverages. Do they? I don't know; I've never checked. If they don't give you any discount for "endurance", than there is no argument, IMO, for their being "better" in that regard. Insurance companies are all about probabilities, and they pay people well to figure these things out. In my experience w/ ICFs, and thinking about what they are made of, they are likely not the best choice for a heating climate. They don't have great R value, and the thermal mass argument is confused; the mass should all be on the inside of the house. They are expensive, lots of embodied energy, and require a lot of bracing when putting them up. An 8' high liquid wall is not going to sit still w/out help. I did not find them to be particularly fast, and the wiring is not a snap; you need to plan meticulously, and modifications down the road will not be a cake walk. How are you going to get any R value appropriate for Minn? Doable, but what is the cost vs a double-stud wall w/ dense packed cellulose (something, as a diy guy, that appeals to me)? I have no use for ICFs above grade; you may. In 1980 we built our basement w/ all-weather wood; still standing, but maybe we got lucky.
Ann,
When it comes to SIPs and ICFs, the advantages are well known, and the manufacturers will tout these advantages in their brochures. However, the manufacturers don't usually discuss drawbacks -- so I will.
1. The exterior OSB facing on SIPs is cold during the winter and subject to moisture accumulation and rot, so builders need to seal seams meticulously and worry about rainscreen details.
2. ICFs provide a low R-value compared to most systems being considered by builders of superinsulated homes. In Minnesota, there is absolutely no advantage to the thermal mass in the center of an ICF wall.
I am with Martin, John and Lucas. Stick with standard construction and consider a double wall with blown cellulose insulation. Minimum R-40 walls for northern MN with R-70 to 80 ceiling, make sure the roof trusses have energy heels for full insulation at the plate line.
John:
A homeowner can get a reduction in premiums in the range of 8-25%, depending on the carrier. The low number comes from their classification as a masonry wall (compared to stick wall) as it pertains to fire ratings. The high number comes from any carriers that recognize their disaster-resistant characteristics.
Hello John
Many ICF manufacturer's that I had reviewed (2 years ago) made claims of R40 performance because of their thermal mass, however independent testing done by our national lab (Oak Ridge National Lab), confirms that they only insulate as well as the thickness of their foam and the mass adds nothing. It is possible to do ICF's yourself but it is time consuming and because of the concrete, expensive, and makes interior finishing more complex, not to mention running wires, plumbing etc.
SIP panels don't require special tools but it is more difficult than standard framing for sure, although it could be done if you have help and and get some instruction. Also concerning the issue with the outside layer of OSB, I would concur with Martin that if not sealed well with mastic you can have issues, however one of the major advantages to SIP's is that if installed and sealed well with LOTS of mastic, you get a very tight building, capable of passing even PassivHaus standards. Again passing utitilies is more difficult than a double wall as well, so this is not for novices.