Opinion on Condensation control

[mic575]

Hi All,

I’m looking for opinions regarding potential condensation control in a post frame I am planning.

I am planning a 30x48 with 11’ wall height. Concrete floor. 8’ on center truss. Steel siding and roof

I am not planning to insulate or heat/cool. It will be storage and work area as weather permits.

I will be building myself, location in central Iowa, 4 seasons of climate.

What are your opinions regarding interior condensation control?

My plans: vapor barrier under concrete. 12” overhang with vents on eave ends. Vented ridge.

I view my options as

• Do nothing and deal with it after build if it occurs at all
• Add a house wrap type product (KC Blockit) over purlins. Menards offers this as part of the kit but I’m not sure of the benefit.
• Add a radiant barrier over purlins, then a 1x4 furring strip, then steel. I worry about bubble type degrading over time, would probably use Bluetex. Extra cost and don’t know if its worth while. Plus it adds complexity to the build.
• Do something different?

 

[Uncle murph]

Hi All,

I’m looking for opinions regarding potential condensation control in a post frame I am planning.

I am planning a 30x48 with 11’ wall height. Concrete floor. 8’ on center truss. Steel siding and roof

I am not planning to insulate or heat/cool. It will be storage and work area as weather permits.

I will be building myself, location in central Iowa, 4 seasons of climate.

What are your opinions regarding interior condensation control?

My plans: vapor barrier under concrete. 12” overhang with vents on eave ends. Vented ridge.

I view my options as

• Do nothing and deal with it after build if it occurs at all
• Add a house wrap type product (KC Blockit) over purlins. Menards offers this as part of the kit but I’m not sure of the benefit.
• Add a radiant barrier over purlins, then a 1x4 furring strip, then steel. I worry about bubble type degrading over time, would probably use Bluetex. Extra cost and don’t know if its worth while. Plus it adds complexity to the build.
• Do something different?

One thing is for certain,any time the temperature of your slab is below the dew point,your slab is going to be wet no matter how much vapor barrier you use.If your not going to heat/cool the building you need to make sure it’s well ventilated.

 

[mic575]

Hadn't thought about that, thank you.

 

[larry_g]

I used the 2" stuff from here; http://www.metalbuildinginsulation.com/newconstruction.html

more of an insulated vapor barrier. Have it in two buildings and happy with it.

lg
no neat sig line

The above is what I used on 2 of my buildings. I recommend it.

 

[AdamMopar]

You can get dripstop on the roof steel if you are concerned.

 

[RPH]

Build wrap stops the snow and rain from being driven in the wind. Roof insulation, I have the plastic coated roll’s of fiberglass on mine.
No condensation issues or snow drifts inside. Concrete condensing is hard to cure without heat. Moving air will help but the physics are against you at least a few days a year.

 

[AC-WC]

Definitely vapor barrier under the concrete. It's cheap and you'll never have a chance to do after the concrete's in. Depending on budget....foam insulation underneath and on the sides. Probably not going to help too much if you're not heating/cooling it.
I agree with option 2 (what I did on the walls) and some variation of 3.
You need some kind of thermal break to prevent condensation whether it's house wrap, thin insulation/bubble wrap etc on the ceiling.
You may get lucky with a coated roof panel. I don't know where the Amish guys came up with it but on mom's new barn the roof panels have some kind of 'flock' coating on the bottom to help prevent the condensation/sweating. It was up late summer/fall and I haven't seen any condensation yet

Like Outbuilding's post STEEL structures seem to have more issues with sweating than wood structures. My swag (scientific wild a$$ guess) is you get just enough thermal break with the wood to steel panel. I know mom's old barn like his sweated like crazy and that was with full ridge vents at the cap.

 

[theoldwizard1]

Insulation and ventilation.

At least 2" below the floor. If you do two 2" layers and seal and stagger the seams, you won't need a vapor barrier.

2" of spray foam on the ceiling and around all joints

Yes, this cost a lot of $$$, but it won't sweat.

 

[silvermonte]

I live on the east central side of iowa so same weather as you. In the spring when the ground is cold and the weather warms up its going to sweat regardless. If you have electricity in the building run a dehumidifier in there in the spring for a few weeks once temps stabilize to keep the concrete dry and use the shed as needed.