Storage tank insulation

It's all about R-value and how well you sealed out any air currents. Even the high dollar European tanks rarely have more than 3, maybe 4" of insulation. Some are sprayed, some you wrap after the tank is moved into place.

What drives heat transfer is the delta T, the temperature difference between the tank, and the ambient temperature around it. Not counting drafts of course.

Typically rigid foam is r-5 per inch, plus the batt you added. No amount of insulation stops the heat transfer completely. It comes down to how many dollars worth of r-value, to reduce how much loss.

hr

That does seem a bit excessive. 5 degs would be more acceptable. The spray foam seems to be the ticket. Alternatively, use polyisocyanurate foam boards and seal the seams with spray foam. Good luck.

One thing that could be a possibility, is how the sheets of fiberglass were installed. They should be installed with the face of the sheet facing the heat source in this case your storage, so if you laid them flat & simply kept on adding to the pile this will make it easier for the heat to escape. If you stood the sheets on their edge then they are in correctly & you will only get more R value by adding more insulation.

Here is a good link that gives some r-values to the different products http://www.homeconstructionimprovement.com/foam-board-insulation-values/ . I have 3 inches of polyiso on all sides and then I also laid a layer of r-19 fiberclass over the top. There are absolutely no gaps anywhere and with no use over night, I see maybe 1* of loss. You should check for any ghost flows out of the tank. I have a DHW coil in my tank, so if I am not charging it in the off season I have to close a valve in the main line in order to not have the hot water cycle through it on its own...

chuck172,

What would you think of building a sheathed framework around the whole tank, maybe a 6" to 18" perimeter shell, (depending on how much insulation you want), and fill the gap between the tank and the shell with cellulose? An inexpensive build could even be done with 1 x 3s and luan plywood or scrap since you're just using the "shell" to hold the insulation and there should be very little stress on the shell.

-David H.

What is an acceptable heat loss depends on the individual situation.

If the tank is inside a space that requires heating anyway, it isn't really a total loss.

Storage outdoors in unheated space makes you a lot more vulnerable.

Depending on what temperature water you can effectively use, 10 degrees loss per day might be from 15% or up to even a 50% loss of your usable storage energy per day. If you had a radiant heated home and could use water down to 90 or 100 degrees, the loss from a fully charged tank at 180 (which is higher than some storage setups can reach with unpressurized storage) losing 10 degrees/day is about 1/8 of your stored heat that you can actually use. If you have baseboards that were designed for 200 degree water and can't keep up with a cold night with less than maybe 170 water you might be losing half or more of what is usable each day.

chuck172 said:

I don't really think my tank insulation is up to snuff. I framed out my 500 gallon propane tank with 2x4's and sheathed it with 2" blue Styrofoam
I laid down batts of unfaced fiberglass insulation over and around the tank and put the foam roof on.
Seems like the temp isn't holding too well. It's more noticable now in the spring because I'm only using domestic hot water.
Would I be better off with some other type of insulation? I do want to keep the blue sty. framing though.

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Chuck, I'm experiencing a similar situation where I'm loosing more of my storage in the spring than I was during the winter.In my case I built a box around the water storage tanks(2-330 gallons)with more than 12" of loose filled insulation blown in around them.One thing I neglected was the bottom of the tanks which is probably only 3 - 4" off of my concrete slab in my garage,my thinking it was all inside the box so why worry about it.Well after reading a book called The Superinsulated Home Book by J.D.Ned Nisson I discovered that during the fall and winter the ground underneath my garage was most likely dried out and may have even helped insulate the tanks,but now that its spring the soil is very wet and this area underneath is acting more as heat sink and drawing my heat into the Concrete slab and Earth at a much more rapid rate.Looks like I may need to jack up my tanks so I can get more insulation under it.

On our houses, we like 6" insulation on the sides and 15" on top. The temperature difference between a hot storage tank and the outside is twice as much - my thought is that storage tanks should have more than twice as much insulation as a house. I think 12" on the sides and 30" on the top wouldn't be too much.

Chuck,not sure if that's the type of insulation others are talking about but that it is the type that I used in my tank storage.Yes I am a big fan of the Fiskars,while I was on a 13 week laid-off this winter I split 18 full cord of ash with my pair of Fiskars.It's amazing how much can be accomplished in small increments of time.

NoFossil, I believe the reason we stuff so much insulation in are attics is because warm air rises and the convenience of space,not many of us have 12" - 24" walls to insulate.As far as our storage tanks are concerned the hotter water sits on top(stratification)so it makes sense to add more insulation on top to prevent our heat from radiating out.What I'm wondering is that by adding 2-3 times as much on top we aren't just forcing any heat loss we might have out the sides or bottom.It certainly would be interesting to know what would be the "perfect" ratio of insulation to put around the top,sides and bottom of our tanks ,that way we could get the most bang for our buck.I suppose there are a lot of variables to consider,temperature of water,size of tank,horizontal, vertical,square or cylinder shaped like a propane tank .If anyone has seen or done a study on it I certainly would be interested.

Storage tanks have to be insulated underneath just the same as any other exposure. Every Garn we do sits on 2" of foam and a couple owners have used 4". Martin Lunde told me that he once measured a concrete floor that was running 82* nearly 5 feet away from an Garn with no insulation under it.

If using an insulation that is applied directly to the tanks and leaves NO room for air such as spray foam I would say that there is little reason to apply much more to the top as to the bottom as the tanks will loose heat equally in all directions by radiation. If building a box and filling it with an insulation such as loose fill cellulose or fiberglass batts which will allow air movement it is crucial the the box is as air tight as possible due to the convective movement of air (hot air rising) which will constantly be pulling hot air out the top of the box and cold air into the bottom of the box if given the opportunity. In this case it probably also makes sense to put more insulation at the top of the box.

A question of my own--- those of you who have gone the cellulose route --- What do you do when you need to get at your tank to fix/add something?

Cheers,
Augie

(2 inches of snow here today)

I'm glad that this thread was started as I will soon be insulating a 1000 gallon storage tank. I will place it in an outside building because I cant get it inside my basement where the boiler will be located. I was planning on asking several of the questions that were answered here. Thanks Guys.

no experience, just a lot of hot air here.

Air sealing is the first priority, which is what makes spray foam so effective. Especially with a relatively small cylindrical tank, applying insulation directly to the tank give you the benefit of reducing the square footage right from the start vs filling a box with fiberglass which allows air currents to transfer heat to a larger surface area even if the box is airtight. If the box was strong enough to blow cellulose with enough pressure that would be a close second behind spray foam, or blue/pink/polyiso foam "scales" attached and sealed with can foam (Great Stuff etc.)

churchillrow said:

A question of my own--- those of you who have gone the cellulose route --- What do you do when you need to get at your tank to fix/add something?

Cheers,
Augie

(2 inches of snow here today)

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I hope to never have to gain entry to my tanks. If I do have to I know I'll have a big mess but being fairly dense packed, hopefully it'll stay if I have to open the wall. At the narrowest point I have 14 inches of cellulose so what I did was installed the tanks and then got them up as high in temp as I could to check for leaks. To monitor temps I took 10 inch pvc piping and inserted them through the wall to the sides of the tanks as if I ever have a probe failure I can just reach in the tube all the way to the tanks.

sdrobertson said:

churchillrow said:

A question of my own--- those of you who have gone the cellulose route --- What do you do when you need to get at your tank to fix/add something?

Cheers,
Augie

(2 inches of snow here today)

Click to expand...

I hope to never have to gain entry to my tanks. If I do have to I know I'll have a big mess but being fairly dense packed, hopefully it'll stay if I have to open the wall. At the narrowest point I have 14 inches of cellulose so what I did was installed the tanks and then got them up as high in temp as I could to check for leaks. To monitor temps I took 10 inch pvc piping and inserted them through the wall to the sides of the tanks as if I ever have a probe failure I can just reach in the tube all the way to the tanks.

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I like the PVC pipe idea. If I get the boiler up and running this fall I will probably spend a chunk of the winter using my tanks as a huge radiator so that should give me a chance to trouble shoot everything. Speaking of which I've been meaning to get some pics of my tanks posted. I followed advice gotten here and made the two 500 gallon tanks into a hydraulic separator. I'm excited to see how it works and I get the impression that I may be a bit of a guinea pig in this respect.

Augie

chuck172 said:

I don't really think my tank insulation is up to snuff. I framed out my 500 gallon propane tank with 2x4's and sheathed it with 2" blue Styrofoam
I laid down batts of unfaced fiberglass insulation over and around the tank and put the foam roof on.
Seems like the temp isn't holding too well. It's more noticable now in the spring because I'm only using domestic hot water.
Would I be better off with some other type of insulation? I do want to keep the blue sty. framing though.

Click to expand...

Are you sure you are really dropping that much temperature?
The reason I ask is that I have a well insulated 500 gallon tank and during the heating season only burn one fire a day then shut down the boiler so I have plenty of time to observe what is going on. At first glance you would think that I was losing heat quite rapidly. I have wells for probes in the top, center and bottom but the only one I usually monitor is the top probe to keep the temperature from going over 185*. The pipe exiting the flat plate is constructed to evenly and easily distribute hot water to the top. After the heat has been purged from the boiler and the circulators have shut down, the temperature on the top may drop about 5*. What I found was the water is mixing in the first hour or two then the temperatures stabilize and the mixing appears to stop until the zone circulators start. I believe what I have is temperature differences that the nature of the water cannot sustain.

chuck172 said:

Fred, are you saying that the hot water in the storage tank is stratifying?

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Well, I don't know. I had always assumed that stratification meant that heat rose to the upper portions of a body, whether it is steel, concrete or a bucket of water. I run my boiler at a pretty high temperature. My circulators don't start 'till 180* and shut down at 169* (boiler temp.) (Unless over ride by Tekmar 156 differential) and boiler temp will reach as high as 205* during the burn so I'm laying some pretty hot water on the top of the tank. What's happening is that the heat is mixing, meaning that some of the heat in the uppermost layer of water is mixing with the cooler water in the lower layers as it sits there, because the temperature difference is so severe.

Fred, I'm also in Southeastern VT (Weathersfield)
How long have you used your 500 gal storage tank? I just installed one, not real happy with the way it seems to be loosing heat. Up the chimney of the WB, up the chimney of the Oil Boiler etc. any chance I could steal some info from you? Possible guided tour of your system sometime in the future?
Sorry for the thread hijack.

Outlaw said:

Fred, I'm also in Southeastern VT (Weathersfield)
How long have you used your 500 gal storage tank? I just installed one, not real happy with the way it seems to be loosing heat. Up the chimney of the WB, up the chimney of the Oil Boiler etc. any chance I could steal some info from you? Possible guided tour of your system sometime in the future?
Sorry for the thread hijack.

Click to expand...

I sent you a PM!