Insulation on a DIY drain back tank like Gary's

[mbeland]

I posted this as part of another thread but had no answer.

It seems like the insulation is the most expensive item in those tanks. Has anyone ever thought of using just a minimal (maybe 1 inch) thickness of polyisocyanurate under the EDPM liner and using cellulose loose fill insulation which I assume would be much cheaper than rigid boards between the studs? The way I thought one could do that without having the thermal bridges would be to build the tank out of 2 layers of 2" x 3" instead of one layer of 2" x 4" just like in superinsulated houses. The 2 layers of 2 x 3 would be perpendicular and could thus be made pretty rock solid. That could be one layer of 2 x 4 and one of 2 x 3.

What do you think?

Martin

[ghurd]

It would be a lot cheaper.  Take up more space is the only draw back I can see.

An addition on my house did not have enough space over it for a reasonable amount of insulation.  I put 1.5" (IIRC) on the ceiling joists, then drywall, then blew in cellulose.  No problems that I am aware of.

G-

[clarsondd]

i would guess it depends on where your tanks are located.

gary's are outside his house so any heat loss from his tanks is unuseable for heating his house. But, if your tank is inside your home, any losses are still heating your home.  One only needs enough insulation to be able to regulate the temperture.  i.e. superinsulating exterior walls probably good, interior walls probably overkill.

[mbeland]

My tank would be inside. I understand your point but even inside the home, I don't want it to heat the house in the Summer.

My other concern would be for protection against moisture. In Gary's web site, water leaking out or evaporating out does not seem to be a problem, but I wouldn't want that cellulose ending up damp and rotting.

I would be glad to hear Gary's opinion on that.

Thanks,

Martin

[SparWeb]

Gary checks Fieldlines often, but who knows if he'll see this message.  If you send me an e-mail, I can give you Gary's e-mail address.  You could contact him directly.  My address is in the header line.

(I would just do so here, but posting e-mail addresses directly on web pages - it tends to attract spam).

[jondecker76]

I started building my solar water system from Gary's plans a little over a month ago. All in all, the insulation isn't really the most expensive part. On my list, the 2" poly-iso is about 3 or 4 down from the top as far as price goes.

In my opinion, you will be best off with at least some sort of hard board insulation that won't compress from the weight and pressure of the water (thus losing its R-value and risking breaching the liner). Sure, poly-iso is a little pricey (I spent about $95 to line my tank with 2"), but i think its worth the investment. In fact, If I could, I would go back and get 3" board instead of 2". In all, my 4'x4'x4' tank will cost around $450 total. $90 or so for insulation isn't so signifigant that its worth skipping on to save a few bucks, IMO.

Good Luck!