Insulating storage tanks question

[nctacoma]

So I have two 300 gallon vertical tanks to box in and insulate.
They are set against the back wall if my basement which is lined with 3" of xps insulation. So that wall is already taken care of. My plan is to build 3 more 2x4 walls around the tanks and box them in. The inside of the walls will be lined with 3" or 4" of rigid polyiso insulation and the ceiling will be lined as well. The outside will be plywood and taped for air sealing. I plan to fill the inside of this insulated box with cellulose. My question is Should I just blow it in loose like an attic or should I try to dense pack the whole thing? I know it will already be very well insulated with the rigid foam, but I want to do it right and as good as possible. I already have all the rigid foam and framing materials laying around so there is no cost there. I will only have to purchase the cellulose.
What do you think?
Also any chance of the tanks condensating if it is all well insulated?

 

[maple1]

I can't see the tanks making condensate - should be a non-issue.

I would leave space between the tanks & basement wall for more insulation - 3" isn't a lot. But is that 3" on the inside or outside of the basement wall?

With cellulose I would just kind of dump it in from the top, and tamp it down as much as I could around the sides, as long as there is space around the sides - I am picturing it going all over the place if you try to blow it in to a small space like that, but I could be wrong on how it would react. If it settles over time, you could just add more on top.

And make sure you insulate under the tanks. I stuffed 2 layers of 1.5" foam board under mine in pieces when I put them in - and spent last Saturday trying to fill some voids that made by jamming in as much cellulose underneath as I could from the sides. That didn't go as smoothly as I thought, that stuff is messy & kind of wants to go everywhere when you try to push it. But I got it done eventually. At least that stuff doesn't itch.

Are your tanks hooked up yet? I think if I was doing mine again, I would put down a good few inches of foamboard, then a layer of plywood, then put my tanks on that.

And, on other hint - if you have enough headspace over your tanks, and room around the side, you can make a very decent DHW pre-heater out of a couple of rolls of pex coiled around the outside of the tanks & laid in the top, as long as the pex is under the insulation. I did that and I think that alone heats most of my DHW during infrequent use periods - laundry day is another matter though.

 

[woodsmaster]

I'd dense pack the cellulose. it will take a little more, but give you a better R-value

 

[JP11]

Mine is dense pack. I spray foamed them before boxing them in.

I'm a bit disappointed even with that.. but I think it's the TOP of my tanks, that is right at floor joist level which is letting the most heat out. Need to do something up into the truss area.

JP

 

[stupe]

I used blown-in Owens Corning fiberglass insulation. Got everything from Home Depot. I can't remember why Mark from AHONA told me to use that instead of cellulose. Something about the cellulose breaking down with high tank temps. Anyway, its about foot thick around the tank (more in the corners) and I left it fluffed up. Its incredible how well the tank holds heat. No signs of heat escaping anywhere. The outside of the plywood is cool to the touch.

 

[S.Whiplash]

Cellulose and steel are not a good combination because of the acid contained in the paper reacting with the steel. Better to use blown in fiberglass or rockwool.

 

[heaterman]

Cellulose is a poor choice. It you're going to loose fill the space use the blow in fiberglass stuff made by Owens/Corning and others. Cellulose will draw moisture and the product itself is slightly acidic. Not a good combo next to ferrous metal. (always wondered about some of the places I see with steel studs and blown cellulose used for insulation)
How did you insulate the floor under the tanks?

 

[stupe]

My tank stands on end with legs welded to keep it off the floor. My tank is located in my basement (I have 10 ft ceilings) and the basement floor has radiant heat with 2" rigid foam board underneath the concrete (so I'm not concerned about losing heat to the floor). However, I did put some wooden blocks under the legs to provide a thermal break. So at the lowest point I only have about 4" of insulation under the tank but its a curved bottom and that's the coolest part of the tank anyway.

 

[Clarkbug]

You can get borate free cellulose insulation. That would alleviate the issue of moisture and acidity.

 

[woodsmaster]

im ca

Cellulose is a poor choice. It you're going to loose fill the space use the blow in fiberglass stuff made by Owens/Corning and others. Cellulose will draw moisture and the product itself is slightly acidic. Not a good combo next to ferrous metal. (always wondered about some of the places I see with steel studs and blown cellulose used for insulation)
How did you insulate the floor under the tanks?

I'm calling bullshit... Id choose cellulose over fiberglass any day. there wont be any moisture for one thing. fiberglass will also draw and hold moisture if there where any. Cellulose dosn't itch when you work with it. It's not going to hurt the steel one bit. The acidity of it keeps rodents out unlike fiberglass that they LOVE to nest in.

 

[woodsmaster]

Cellulose and steel are not a good combination because of the acid contained in the paper reacting with the steel. Better to use blown in fiberglass or rockwool.

you have to have moisture for rust. there just wont be any unless you have a leak. if you have a leak it will need fixed and again you will have no moisture.

 

[woodsmaster]

Cellulose and steel are not a good combination because of the acid contained in the paper reacting with the steel. Better to use blown in fiberglass or rockwool.

Maybe if you have completely bare metal tank with no primer or paint. I still find it hard to believe it would be an issue.

 

[woodsmaster]

I used blown-in Owens Corning fiberglass insulation. Got everything from Home Depot. I can't remember why Mark from AHONA told me to use that instead of cellulose. Something about the cellulose breaking down with high tank temps. Anyway, its about foot thick around the tank (more in the corners) and I left it fluffed up. Its incredible how well the tank holds heat. No signs of heat escaping anywhere. The outside of the plywood is cool to the touch.

I'd like to see some real proof that the heat breaks it down. Mine looks the same as it did four years ago.

 

[ewdudley]

I'd like to see some real proof that the heat breaks it down. Mine looks the same as it did four years ago.

Because afraidium buildup.

 

[Fred61]

I used blown if fiberglass once in an old one room schoolhouse and the heat loss was horrendous. Two years later, after it settled it was like having no insulation. Nearly unable to heat in the winter and like being under a broiler in the summer. Re-insulated with cellulose took care of the problem.

If you have any moisture around your tank, something is wrong regardless of what it is insulated with. If you're concerned about the boric acid corroding the surface wrap the tank with fabric first.

 

[DaveBP]

Most, if not all, brands of conventional cellulose insulation use various boron compounds to make it fireproof and insecticidal. Some brands also add sulfates to the mix. I would stay away from sulfate containing brands if you're concerned about corrosion. Call it a preemptive precaution.

How much humidity will condense in there at the normal heat storage temp range? Might be good to run a fire every few weeks in the summer just to keep it well above ambient.