Sweating

[spam4us]

Please see post #7. What I wrote here is confusing. Thanks

I have a 40x40x14 pole building. Walls are insulated with 4x8 foam panels. I have not installed any finish material on the walls or the flat ceiling yet. Ceiling is not insulated at this point.

I am leaning toward osb walls and metal liner panel ceiling. I am only planning to heat the interior once in awhile only when I am in there working.

Once the ceiling is installed, it will be insulated with blown in insulation and have a vapor barrier.

I live in the northeast.

1. Will the metal liner panel sweat when I heat the building in the winter?
2. Will the metal panels sweat from the heat produce from the car engines just by parking the cars in there during the winter without the heat turned on?
3. Will the ceiling sweat if I go with osb or drywall?

Thanks

 

[spam4us]

Anyone?

 

[MEngineer]

The metal roof panels should not sweat if you have an insulated attic since they will have the same temp air on both the outside and within the attic.

The walls are something else entirely. Your walls will only sweat if there is an air gap AND a temperature differential. If you have hot air on the inside touching your metal wall panels then you will have condensation on the interior of the panel and they will "sweat". If you have an air gap and the air on both sides of the metal is unheated, then you will not likely have a condensation issue.

I am hoping that your wall metal is attached to 2x purlins which then has a continuous layer of foam board affixed to the purlins, and then your sheetrock/osb attached over the foam. If you have this build up, you shouldn't have much of an issue as the wall won't be so cold... If you follow

 

[firebirdparts]

It'll have to get humidity to sweat (more humidity than the weather outside) If you heat it with direct fire, then you would generate some humidity. If you don't, then you wouldn't.

My wife runs a humidifier in the house, and yes, stuff sweats all the time. Walls, ceiling, windows, doors, you name it.

 

[Falcon67]

I saw the Hardipanel on my shop sweat during the build phase, before insulation and wall covering but the conditions were somewhat unique (OK maybe not) as in very warm and a little humid (maybe 40~50% RH) one day and suddenly nearly freezing the next. OK, not unique around here as it was 90F yesterday and 42 this AM LOL, 90 last week on Friday and 31 Saturday morning.

I have not looked in the walls but I have not noted any specific moisture issues once the R13 was in the wall cavities and the OSB covering put up.

 

[TractorJeff]

OP is asking about interior walls sweating, not exterior walls. (if I read it correctly)

 

[spam4us]

Thanks everyone for the replies. Sorry for any confusion. Looking at my post I wasn't too clear.

All of my questions relate to the interior of the building only.
The following is for the walls.
The interior walls most likely will be osb or drywall. I have already insulated the walls with 4x8 foam panels. The walls look like this

(Exterior Metal) - (exterior girt) - (4-1/2" foam) - (3/4" air gap) - (1-1/2 interior girt) - (vapor barrier) - (OSB or drywall)

..............................................^----------5-1/4" post--------^......................................

My post are 5-1/4" wide. So the space between the exterior girt and the interior girt is made up of 4-1/2" of foam plus 3/4" air gap (or dead space). I will then attach the interior girt creating another 1-1/2" air gap. I am not planning on installing any other insulation in this space(3/4 + 1-1/2"). I will then put up a vapor barrier and then osb or drywall.

Will this be ok for the walls or will it create any sweating or moisture problems????

This next part is for the interior ceiling and not the roof.

I have 4/12 trusses with a flat bottom for the interior ceiling. It has vented soffits and is vented at the peak.

I am planning on the following.
r30 insulation blown in:
vapor barrier:
Metal liner panel or osb or drywall attached to the bottom flat side of the truss.

So for the interior ceiling....
1. Will the metal ceiling liner panel sweat when I heat the building in the winter?
2. Will the metal ceiling panels sweat from the heat produce from the car engines just by parking the cars in there during the winter without the heat turned on?
3. Will the ceiling sweat if I use osb or drywall instead of metal?

Again, sorry for any confusion.

Thanks

 

[spam4us]

Can anyone that has an interior metal liner ceiling provide some answers concerning the ceiling?
This is for the interior ceiling and not the roof.
thanks

I have 4/12 trusses with a flat bottom for the interior ceiling. It has vented soffits and is vented at the peak.

I am planning on the following.
r30 insulation blown in:
vapor barrier:
Metal liner panel or osb or drywall attached to the bottom flat side of the truss.

So for the interior ceiling....
1. Will the metal ceiling liner panel sweat when I heat the building in the winter? I plan to only turn on the heat when I am in there (maybe 4 hours per day). The rest of the time it will not be heated at all.
2. Will the metal ceiling panels sweat from the heat produce from the car engines just by parking the cars in there during the winter without the heat turned on?
3. Will the ceiling sweat if I use osb or drywall instead of metal?

Thanks to all who have answered.

 

[finn]

1 no

2 no

3 no.

As long as you have adequate insulation and a vented attic, there won’t be sweating on your metal ceiling.

 

[850xpeps]

Put the air gap to the outside of the foam insulation. Or you will have frost. The foam should be against the vapour barrier for the walls.

 

[850xpeps]

1 no

2 no

3 no.

As long as you have adequate insulation and a vented attic, there won’t be sweating on your metal ceiling.

He’s correct

 

[Showkey]

Google metal building sweating............you will get 100 of hits ( some leading back toGJ) .........it’s a BIG issue. The reasons and prevention are numerous and one size does NOT fit all because the root cause can be complex, environmental and related to construction techniques and materials used.

https://www.whirlwindsteel.com/blog/bid/238023/tips-to-prevent-condensation-in-metal-buildings

http://blog.abcmetalroofing.com/simple-solution-metal-panel-condensation/

http://www.rhinobldg.com/how-to-avoid-condensation-problems-in-steel-buildings/

I have been in metal buildings where it looks like it’s “raining” inside and worse where it is “raining” in the attic caused by severe condensation issues.

“Conditioning” the air on occasion makes controlling the moisture, dew point and temperature almost impossible which in turn makes controlling the condensation more difficult if not impossible under certain conditions. This not only comes up on Wall and ceiling sweating but also floor sweating.

 

[HoosierBuddy]

I'm with ShowKey on this. This is a complicated question.

It would seem to me that if the metal surface temperature is lower than the dew point of the air in the building then it is likely some of the moisture in the air will condense on the walls.

We don't see this where we heat the building all the time, because the metal temperature on the interior is kept above the dew point. It's not just siding that's an issue, it's any metal surface.

The floor under my mustang would end up drenched when I kept it in an unheated barn and then went out there on a cold day and cranked up the heat. Same thing for my table saw which has a large cast iron table. It would stay colder than the dew point for a long time after the air started warming up. Once it got warm, the condensation would stop.

Complicated problem to predict!

Phil

 

[Showkey]

In case you did not see the possible complications of foam:

https://www.garagejournal.com/forum/showthread.php?t=374702

 

[finn]

I'm with ShowKey on this. This is a complicated question.

It would seem to me that if the metal surface temperature is lower than the dew point of the air in the building then it is likely some of the moisture in the air will condense on the walls.

We don't see this where we heat the building all the time, because the metal temperature on the interior is kept above the dew point. It's not just siding that's an issue, it's any metal surface.

The floor under my mustang would end up drenched when I kept it in an unheated barn and then went out there on a cold day and cranked up the heat. Same thing for my table saw which has a large cast iron table. It would stay colder than the dew point for a long time after the air started warming up. Once it got warm, the condensation would stop.

Complicated problem to predict!

Phil

That doesn’t make much sense to me thermodynamically, unless you are using a heat source that dumps the products of combustion, ie water in to the space being heated.

Were you using an unvented heater?

On the other hand, single pane glass frosts over, but the insulation behind a metal ceiling takes care of the issue.

 

[HoosierBuddy]

That doesn’t make much sense to me thermodynamically, unless you are using a heat source that dumps the products of combustion, ie water in to the space being heated.

Were you using an unvented heater?

On the other hand, single pane glass frosts over, but the insulation behind a metal ceiling takes care of the issue.

I'm not sure what you mean by "thermodynamically" as Thermo was a class I took in 1989...and that was a lot of brain cells ago.

I think the process is simply moist air being pulled into the building as make up air for combustion OR previously frozen condensation liquefying and then vaporizing in the warm air produced by the heating appliance...and then recondensing when the moisture-ladden air meets a cold surface (less than the dew point of the air).

Either of these would lead to condensation. If an unvented heater was used, it would likely be worse due to the water dropping out of the combustion products.

Phil

 

[finn]

If you are exhausting the products of combustion through a flue, they aren’t adding water vapor to the inside of the building, so that shouldn’t add to condensation on the metal ceiling.

Warm air holds more moisture than cold air, at least it did when l took thermo in 1972, so the relative humidity of the room when heated will be lower than when unheated. When it is cold outside, the relative humidity tends to be low, and, in fact, that is the reason most forced air home furnaces have an add on humidifier in cold climates.

Properly insulated metal panels on the ceiling will be roughly the same temperature as the room, and won’t condense water vapor from the air.

An uninsulated ceiling will be the same temperature, roughly, as the outside ambient temperature, and will frequently sweat, given high enough indoor relative humidity.

My garage floor sweats in early summer when the ground and high thermal mass uninsulated slab are still cold and we get warm, high humidity days. My shop and other garage have insulated slabs and don’t sweat.

Neither of my heated buildings with well insulated metal ceilings sweat from the ceiling. One is heated regularly and one is heated sporadically.

The lean to is not heated nor is it insulated and the ceiling sweats, given the right conditions.

In the end, l thing we’re probably pretty close to being on the same page, ie a cold ceiling is the issue. I don’t think make up air is much of a factor, though. One could always use a heater with an outdoor combustion air source, if it is a major contributor.

 

[HoosierBuddy]

I
Warm air holds more moisture than cold air, at least it did when l took thermo in 1972, so the relative humidity of the room when heated will be lower than when unheated. .

When I took Thermo it was all steam tables and carnot cycles. Turbine efficiency. Enthalpy and Entropy. YIKES! About midterm I went home for a weekend and had a long talk with a friend of my parents that went through the navy's nuclear engineering program for submariners. In two hours I learned more than I had in 6 weeks of class. Got a B. Moved on.

I have found no practical use for anything we learned since, including trying to predict an unheated garage's reactivity to sudden heating.

Our Heat Transfer class probably applies more...but your curriculum wasl likely more practical. It couldn't have been less practical than ours...I'll say that. I think the main point was to weed out marginal Sophomore ME's.

Phil

 

[spam4us]

Thanks everyone for all of the responses. You all have a lot more knowledge about this then I.

As for the walls, I am using 4x8 rigid foam panels. The wall will be covered with either osb or drywall.

So what I am concluding is that a metal ceiling with a vapor barrier and insulation may or may not sweat depending on how cold it is and also the dew point when it is heated.

In other words, am I safe in saying it's a **** shoot as to the sweating when heated?

I will probably go with at least r30 or better above the ceiling.


Thanks

 

[Firebrick43]

If you put a vapor barrier under your slab and have good drainage and good insulation it's highly unlikely for the walls or ceiling to sweat. The slab and high mass items still might sweat however (ribbed lining panels are not high mass).

If you have a vented furnace and maintain some heat it's unlikely that anything at all will sweat.

 

[finn]

Firebrick is correct.