ICF's for storage

[djblech]

Has anyone ever built a storage unit using ICFs and a liner? I use Logics for footings and basement walls that have about 2 3/4 inches of insulation on both sides and either 6" or 8" of concrete. They make corners so a box would be easy, rebar in every 16" course and vertically for strength. The hardest part would be placing the concrete, but it could be pumped if necessary. It would be kind of permanent.
I have a number of forms left over from my last job and I got to thinking.

 

[DaveBP]

I think you need to look into the maximum service temperature of the expanded polystyrene that's used on the forms. I don't think it's rated for the kind of temps you would be aiming for in a heat storage tank for a wood boiler. I suppose you could line it with 1" polyisocyanurate on the water side to protect the EPS.

There was a recent post about a 5000 gallon tank built from ICFs.

https://www.hearth.com/talk/threads/39073/

 

[djblech]

I hadn't seen that thread, that is much bigger than I was thinking. Could I spray foam over the expanded polystyrene? I was thinking of putting this in my basement in a corner, about 1000 gal.

 

[DaveBP]

It's really hard to get spray foam installed to a consistent thickness and anywhere near smooth. I would worry that the hills and valleys in the surface would put a lot of stretching in the liner that might not be helpful to its service life . 1" rigid isocyanurate board is probably cheaper and certainly easier.

 

[SE Iowa]

Isn't the Dow-Corning ICF an extruded polystyrene that can tolerate higher temps? In addition, so what if the inner styrofoam deteriorates? Wouldn't it still have 2.5 inches of styrofoam on the outside as well as alot of extra thermal mas in the concrete?

 

[DaveBP]

Isn’t the Dow-Corning ICF an extruded polystyrene that can tolerate higher temps?

I don't know much about newer ICF systems but the first two different products I saw in the field were expanded (beadboard) polystyrene and I have never taken ICFs seriously since. Makes sense that by now they are using the better stuff. Beadboard soaks up water like a sponge and loses a lot of its insulation value.
Extruded polystyrene, as I remember, does have a little higher service temp limit than the expanded product. But when I was thinking about building my own unpressurized tank I tried to find technical info on Dow's website. 160F was what I remember being their best recommendation for long term service. Someone on this forum posted some pictures of an experiment they did on boiling and 190F water temps on a couple brands of extruded stuff. The boiling water wrecked it but the 190F(?) looked OK after overnight. But this is from my memory and that wasn't a long term test. A lot of folks with unpressurized storage tanks don't get above 160F or maybe 170F very often. Probably much ado about nothing. Not the first time for me.

so what if the inner styrofoam deteriorates?

I would just be concerned that the liner would stretch in the corners and I don't know how much that would affect the lifespan.
The more insulation the less standby loss you have. I believe you can't have too much insulation, especially outdoor installations. And it would tear at me to pay good money for it knowing it might be wasted even if it didn't hurt anything.

 

[tom in maine]

Use 1" polyiso to cover the ICF's and don't even think about Styrofoam. 2" would be better and even with a 1,000 gallon tank, the investment is not that much.
Don't forget to use it over the base and cover as well. If this is a freestanding tank, be sure to use rebar that overlaps the corners. You are trying to hold back over 8,000 pounds of water!

Install the liner carefully and fill it slowly. If it is not fully supported by the shell. STOP and empty the tank and start over.

Some common sense and a little guidance can go a long way.

Tom
americansolartechnics.com

 

[DaveBP]

Thanks for weighing in, Tom. I was hoping someone who was personally experienced with these materials in these applications could give a more authoritative opinion than my 'informed speculation'.