Give me advice on tank top layer insulation

[goosegunner]

Please give advice on the final layers over my tank.

I made a blanket with some pole barn insulation. It has a vapor barrier on it so I am trying to decide if I should cut it or not. It is on top of 12" fiberglass.

Here is the plan do I need a barrrier in here some where? Outside layer of OSB will be unheated space for several years. .


You can see the layers in the pictures

From the top down

1/2" OSB
1.2" foam board
R19 fiberglass
R6 Pole barn blanket with vapor barrier (not sealed around edges)
12" fiberglass minimum
Tank

gg

 

[maple1]

The only thing that comes to my mind, is that generally speaking, I think barrier is supposed to be on the warm side of insulation.

Maybe turn it over so the barrier is on the bottom? But I guess you can't get it on the very bottom, since there is lots of fiberglass right on top of the tank.

I guess that talked around in a circle and didn't help much. I think maybe if I was doing this, I would put all the insulation around the tank, with no vapour barrier, then maybe a wrap of house wrap around all of that before the OSB goes on - or at least think about it. Is the box open a bit around the bottom somewhere so a leak would show up fairly quick? That tank should hold heat forever, that's a lot of R's.

 

[Nofossil]

Don't think the normal vapor barrier rules apply when there's no moisture generated on the warm side of the insulation.

However, I think that the vapor barrier could serve a useful purpose in slowing or preventing airflow through the insulation - convection cells and/or 'chimney effect' where warm air rises through the insulation and out the top, drawing cooler air in at the bottom.

 

[Frozen Canuck]

No barrier there Goose. It will only serve to trap any moisture that may be present & hold it causing rust on your storage tank/iron pipes as well as rotting any wood sheathing & framing.

In this situation (where one plans to finish in stages as budget allows) it would be fine to lay a plastic sheet over the tank enclosure when it is complete. You can monitor visually which side of the plastic the water vapor is condensing on. If it is condensing on the other surface, leave it in place as it is helping the situation with excess moisture most likely from the snow melt of vehicles parked in adjoining rooms. If it is condensing on the underside of the plastic (against the tank enclosure) then remove it as it will hold the moisture there for the wood to absorb eventually causing rot.

You may have to alter plastic on/off with the seasons as that is when we get the biggest swings in atmospheric M.C.

Once the building is finished & all rooms are conditioned spaces you will not need the plastic as you will then be in control of the building conditioning, rather than mother nature as is now the case.

Hope this helps Goose.

 

[goosegunner]

I think it would take a while for a leak to show. I have access to both ends where the fittings are on the bottom. I will probably check it once or twice a year. The bottom plate of the interior wall does not have sill seal under it so it might work its way out eventually. There is 8" of foam under the tank though.

I have considered buying one of the inspection cameras with the feel exile head to look things over.



gg

 

[goosegunner]

No barrier there Goose. It will only serve to trap any moisture that may be present & hold it causing rust on your storage tank/iron pipes as well as rotting any wood sheathing & framing.

In this situation (where one plans to finish in stages as budget allows) it would be fine to lay a plastic sheet over the tank enclosure when it is complete. You can monitor visually which side of the plastic the water vapor is condensing on. If it is condensing on the other surface, leave it in place as it is helping the situation with excess moisture most likely from the snow melt of vehicles parked in adjoining rooms. If it is condensing on the underside of the plastic (against the tank enclosure) then remove it as it will hold the moisture there for the wood to absorb eventually causing rot.

You may have to alter plastic on/off with the seasons as that is when we get the biggest swings in atmospheric M.C.

Once the building is finished & all rooms are conditioned spaces you will not need the plastic as you will then be in control of the building conditioning, rather than mother nature as is now the case.

Hope this helps Goose.

Are you saying no barrier under very top layers?

Or

Are you saying I should remove the pole barn blanket?

Could you cut it randomly with a knife to still use the layer?


Gg

 

[Frozen Canuck]

Yep Goose, just cut with knife to defeat vapor barrier effect & use as is. No need to throw it out, you just want to defeat the vapor barrier so it can't condense on the inside of the tank enclosure. Once your up & running with the tank & it is enclosed & leak free it should be the driest place in that building as it will have a permanent heat source (the tank), so you "want" it (the tank) to be able to drive out any moisture that may have been trapped there during construction.

As an example set a piece of wood in your boiler room off of the floor, check it's MC when you put it in the room. Then check it monthly after that. I am willing to bet that it will lose 1% per month at a minimum, until it gets down to 4-7% (depends on species) but in any event ready for millwork at that MC. My point is that framing material by code must be 19% MC max here, prob there too & that 13% that is lost has to go somewhere. You want that somewhere to be away from your expensive heating system, not held in & condensed by a piece of plastic. The rest of the building will have no issues dealing with that slow release of additional moisture so let it. Only real issue I see as possible & that would be during your worst winter weather is possible icing in the garage area when you drive in a hot vehicle. Most of that can be avoided by kicking the snow/slush off before driving in.

Hope this helps.

 

[goosegunner]

Yep Goose, just cut with knife to defeat vapor barrier effect & use as is. No need to throw it out, you just want to defeat the vapor barrier so it can't condense on the inside of the tank enclosure. Once your up & running with the tank & it is enclosed & leak free it should be the driest place in that building as it will have a permanent heat source (the tank), so you "want" it (the tank) to be able to drive out any moisture that may have been trapped there during construction.

As an example set a piece of wood in your boiler room off of the floor, check it's MC when you put it in the room. Then check it monthly after that. I am willing to bet that it will lose 1% per month at a minimum, until it gets down to 4-7% (depends on species) but in any event ready for millwork at that MC. My point is that framing material by code must be 19% MC max here, prob there too & that 13% that is lost has to go somewhere. You want that somewhere to be away from your expensive heating system, not held in & condensed by a piece of plastic. The rest of the building will have no issues dealing with that slow release of additional moisture so let it. Only real issue I see as possible & that would be during your worst winter weather is possible icing in the garage area when you drive in a hot vehicle. Most of that can be avoided by kicking the snow/slush off before driving in.

Hope this helps.

Thanks for your help!

I will slice away with a utility knife before I put the final batts in the joist space. Foam board and then OSB. Thought about taping foam board joints but that would be the same as vapor barrier.

I do get lots of slop on the floor in my garages. They use a lot of sand/salt mix here.

Already notice a difference in tank holding heat. Had a 25 degree night and in the low 30's today. I had the tank at 175 yesterday evening. It was 168 this morning and it is 147 now, time for a fire 24 hours later.

gg

 

[jebatty]

Vapor barrier - none required, makes sense to me.

Already notice a difference in tank holding heat. Had a 25 degree night and in the low 30’s today. I had the tank at 175 yesterday evening. It was 168 this morning and it is 147 now, time for a fire 24 hours later.

Now that you have storage, you may be able to do some interesting things. If your tank mixes pretty well as it is being drawn down (assumed average temperature for the entire tank), when your boiler is "off" you can calculate your actual heat load by measuring the drop in temperature over a time period: temperature drop x #gallons x 8.3 / hours = btuh. Similarly, if all demand is "off" and your boiler is firing to charge the tank, you can measure the btuh output of your boiler through the rise in tank temperature. And, if you do weighed wood burns, you can calculate your btu's in and btu's out to calculate boiler efficiency. Have fun.

 

[barkeatr]

i agree with other folks but will add my own spin....vapor barriers are always on warm side in heating climates regardless of it being occupied space or not. warm air always has more moisture than cold air...i.e. the cold air cannot "hold" the moisture. the goal of a vapor barrier is to stop moisture from getting into insulation and the condensing when you get cold enough for dew point as you get closer to outdoor temperature. for protection of your storage enclosure from exposure to water being that its in a garage, you shoudl use more of what is called a rain screen or simply put a layer of steel or plastic that is a tiny bit above the entire assembly protecting it from water, but allowing any moisture that is trapped in the insulation layer, out. with all thsi said, your probably fine...i would just keep an eye on it to make sure you dont get condensation build up on one of your layers in the insulation system. with your highly closed system im not sure how you could check on it, maybe after a few months of full on heating season, use your nose to smell mold or some such. if moisture is condensing on a surface it will make insulation soggy and you will loose more heat in that spot..FYI condensatoin will not happen in the middle of insulation, it needs a surface to condense on. congrats on a great project.

 

[goosegunner]

i agree with other folks but will add my own spin....vapor barriers are always on warm side in heating climates regardless of it being occupied space or not. warm air always has more moisture than cold air...i.e. the cold air cannot "hold" the moisture. the goal of a vapor barrier is to stop moisture from getting into insulation and the condensing when you get cold enough for dew point as you get closer to outdoor temperature. for protection of your storage enclosure from exposure to water being that its in a garage, you shoudl use more of what is called a rain screen or simply put a layer of steel or plastic that is a tiny bit above the entire assembly protecting it from water, but allowing any moisture that is trapped in the insulation layer, out. with all thsi said, your probably fine...i would just keep an eye on it to make sure you dont get condensation build up on one of your layers in the insulation system. with your highly closed system im not sure how you could check on it, maybe after a few months of full on heating season, use your nose to smell mold or some such. if moisture is condensing on a surface it will make insulation soggy and you will loose more heat in that spot..FYI condensatoin will not happen in the middle of insulation, it needs a surface to condense on. congrats on a great project.

That would be one advantage of cellulose right? I have been told that cellulose will wick away moisture to dry over time.

The disadvantage of cellulose for me would be future access. How would I move or shovel it and to where....

gg

 

[Gasifier]

That would be one advantage of cellulose right? I have been told that cellulose will wick away moisture to dry over time.
The disadvantage of cellulose for me would be future access. How would I move or shovel it and to where….
gg

How did you make out on the final insulation of your tank GG? Have you had any time to work on it?

 

[goosegunner]

Yes I have worked on it some but not done yet.

I have everything in place I just need to fasten osb down.

I did slice the vapor barrier on the pole barn blanket. I ended up with 20" of fiberglass on top. With 1.2" foam board then OSB. I have enough foam board to put 6" on the top but that would probably be pointless.

You know what sucks about building? Hindsight, if I were to do my same building now I would not do the lean area where the tank is. I would make the main building trusses wider there. It would have given me enough headroom in the future to stack another 1000 gallon tank on the one I have. It also would have given me a lot more space to work on the piping and the enclosed box.

The building wouldn't have been as appealing to the eye, but it would have probably been cheaper and faster to build that way.

gg

 

[Gasifier]

Yes I have worked on it some but not done yet.
I have everything in place I just need to fasten osb down.
I did slice the vapor barrier on the pole barn blanket. I ended up with 20†of fiberglass on top. With 1.2†foam board then OSB. I have enough foam board to put 6†on the top but that would probably be pointless.
You know what sucks about building? Hindsight, if I were to do my same building now I would not do the lean area where the tank is. I would make the main building trusses wider there. It would have given me enough headroom in the future to stack another 1000 gallon tank on the one I have. It also would have given me a lot more space to work on the piping and the enclosed box.
The building wouldn’t have been as appealing to the eye, but it would have probably been cheaper and faster to build that way.

I hear ya GG. But I think you will find that the 1000 gallons of storage will be plenty. You don't have to take a bath in that pool you know. :lol: (Weren't you heating your pool with that? To make your swimming season longer. I hope I didn't confuse you with someone else. ;-) )