home made, energy star rated water tank idea.

[trooper Tdiesel]

ive got an idea,

that came to mind having a modern electric hot water tank that has the plastic liner and foam filled out side....


how about taking a older tank and removing the insulation and using the ins-ta spray foam around the tank versus the old house type insulation.

and you have a used tank that is now much better at holding heat....
how much better i have not a clue other then just tossing around ball park numbers.

the other thing i been thinking about is, does the stuff that exspands less have a better R value then the sruff that exspands many times the size of the can

[Ryland]

If you used small cans of foam you'll spend a ton of money insulating the tank, you'd be better off leaving the insulation on and building a small box around it and filling that with cellulose insulation, you'd get a higher R-value and spend less.
To spend even less, put your water heater on a timer so depending on how much hot water you need it's either turning on for an hour before you need water then turning off so any hot water you are using is not being reheated, or at the very least have it turn off while you are at work and while you are sleeping.

[trooper Tdiesel]

the cans range from $4.00 to $7.00 for the fire resistant one.

the original is $4.00
large expand is $5.00
the min expand is $6.00
and the fire resistant one is $7.00

there are larger 24oz cans, but they seem to have a higher cost per OZ for some reason. they clam to have less splatter and wast thus the higher cost.


im thinking, for a 38 gal tank. using the min expand, one can each for top and bottom. and one can for every 6" of height or would it be more like one can for every 4" of height

its about 3 foot high so 8 cans total, at a cost of $48.00
or using the 4" rule its 11 cans total, for $66.00

using the max expanding, it would be more like 6 cans at a cost of $30




clearly covering it on the out side and turning it off when not in use, would be much easier.
id do this mod, but we all ready have a marathon tank and its foam from the factory.

[benphyr]

Hi all,

Please take the scientific sound of this post with a grain of NaCl as it is from my memory of sprayfoaming my header space in my basement and other renos.

Most of the foam in a can type are isocyanurate foams, a polymerization process that produces a closed cell foam. Insulation values are high and they also provide a vapour barrier making them a great insulation. The insulation values between the low expansion and high expansion is insignificant in the case that you gave. That is, you should

use the high expansion low density foam for your suggested case because it will cost less and be easier to use. Also, the pressure built up by the low expansion high density version can pop drywall off of walls so low density version should be used for filling any enclosed space. Best practice says to allow one can to fully expand and cure before using the next in the same area because the chemical process at work produces heat. Sometimes this type of foam is labelled as suitable for windows and doors because the low pressure build up will seal but not bow the window/door frame.

Other extraneous information: Even the fire retardant added ones are not good in a fire (the fire retardant decreases/stops the spread of fire/flame by them but the smoke produced by heating them is still mucho toxic). That is, don't breathe unless the other option is death by another route so avoid using them anywhere in any quantity larger than just filling cracks and holes unless they are covered by a fire stopping material such as drywall. A brick size chunk of polyurethane foam that is in a fire situation can fill a small house with not-so-good-for you smoke. Anyway that is just an aside for those who, like me, try to take into account all of the factors in a decision (and sometimes therefore never get around to accomplishing the task .

Cheers,
Benphyr.