Humidity control: what to do first?

[Rusty Pilot]

I'm in NE Indiana (in the middle of this heatwave) and my barn has not handled humidity very well. The floor condenses like crazy. After fixing a separate issue this past month, I noticed the barn doesn't have a vapor barrier or even a tyvek house wrap. It's literally exterior metal then insulation. I'm assuming that is the source of my problem.

My wall now:


Being in Indiana, I see stupid hot weather and stupid cold weather (and sometimes in the same day). I'm assuming a vapor barrier in my case should be on the inside (interior wall, vapor barrier, insulation, exterior metal) as I do heat it in the winter. Is the house wrap worth it?

I do have 3 wall mounted oscillating fans to help move air. What makes it tricky is the I have an interior wall that separates the front to the main garage area. I'm not really sure what to expect when I remove the plywood or paneled walls. This issue makes the house wrap more appealing since the exterior panels need to come off rather than working around an interior wall and attic. (Not really sure how to slip the vapor barrier through the interior wall)



(Pardon the mess. Working on building a workbench and purging things at the same time)

In your opinion, what should I do first? Any contractors you would recommend in the NE IN/NW OH/S MI area?

Is double bubble useful? I have a source that will give quite a lot of it.

 

[BillK]

How large is this building ?

 

[mikedodge]

Is there any ventilation to outside? If you're sealed well you'll still have humidity problems if there's a lack of ventilation and the fans only move around air that's already there. I need to run a dehumidifier to keep mine under control.

 

[Dagny]

You need to raise the temperature of the floor above the dew point or get the moisture out of the air with dehumidification.

 

[zimman]

Ventilation. Lot's of it.
Zim

 

[AC-WC]

I don't believe housewrap would help your current situation. Since the sheet metal is already up that's a ton of work to remove just for housewrap. Short of removing all your paneling I don't know of another way to install the vapor barrier to the interior.

I have the same condition in this weather as you. The floor is cold compared to the air and will continue to 'sweat' until the temps equalize. Fan is on with a couple windows open....

 

[zkdiesel]

Big ac units

 

[Rusty Pilot]

How large is this building ?

2400 sq ft.

Is there any ventilation to outside? If you're sealed well you'll still have humidity problems if there's a lack of ventilation and the fans only move around air that's already there. I need to run a dehumidifier to keep mine under control.

Outside of a couple windows and 2 garage doors, the soffit goes above the panel ceiling and to the attic area. What kind of dehumidifier to you use? Should I consider an exhaust fan/vent or something like that?

Big ac units

Considering it

 

[Dagny]

An exhaust fan will cause more sweating on the floor because you are bringing in new humid air.

 

[Shiftless]

Mechanical dehumidification and/or big air conditioners is your only hope. Sorry.

 

[BillK]

2400 sq ft.

Outside of a couple windows and 2 garage doors, the soffit goes above the panel ceiling and to the attic area. What kind of dehumidifier to you use? Should I consider an exhaust fan/vent or something like that?

Considering it

I dont think the lack of vapor barrier has much to do with it. The condensation comes from temperature changes.

I think AC/heat is going to be your best bet and might actually be the least expensive in the long run. If you cant swing that right now then a small exhaust fan might keep the air moving enough to help in the short term.

 

[racecougar]

In agreement with everyone else here. I'd take the time/money you would invest into vapor barrier and funnel that toward AC.

 

[finn]

The problem is that the slab is a large cold mass, and the warm humid air this time of year releases water when it contacts the slab, which is below the condensation point.

The water isn’t coming up through the slab, so a vapor barrier won’t help. It’s condensation.

I had a similar situation on a garage with an overly thick slab (whoever poured it must have been of the Garage Journal thicker must be better crowd). It would take forever to warm up in the spring since the door faced north, and never got sunlight, and the walls were insulated. The soffits were ventilated, though. Leaving the doors open when the weather started warming up after a cold winter brought the slab temperature up, and by July the floor was dry, with no condensation.

A larger garage within three hundred feet of that one, but with windows and SW facing doors and windows gets some sunlight and the floor doesn’t condense, as it heats up faster in the spring.

My shop, a mile away, is heated in the winter with in floor radiant, so the slab temperature never drops. It’s perfectly dry during hot humid days like we’re seeing now.

 

[imagineer]

Air flow. Create more of it.

 

[Rusty Pilot]

AC it is... anyone have any recommendations? I am not sure if a mini split would suffice. Just the quick google search suggests that a 5 ton unit is what I would need.

Favorite (or hated) brands?

 

[racecougar]

I'd run a load calc to determine sizing.

When I chose my mini-split, I compiled a spreadsheet to build out a comparison of specs. I went with a Gree unit (basically a non-DIY version of Mr. Cool) and have been nothing but pleased with its performance.

 

[pembol]

Air flow. Create more of it.

A lot of folks are suggesting more ventilation, but that may actually make the issue worse. A others have said, the root cause of the condensation is the temperature of the floor dropping below the dew point of the air. Just looking at the weather for Indianapolis, the dew points are often in the mid 70s (ugh). If your floor is cooler than this it will condense the moisture from the air. If you ventilate the garage and bring in more moist air, you are just bringing in more water to condense. Later in the season, when the floor warms up the problem will likely fix itself.

Sealing up the garage on its own may help a little bit, as the air the air that is in the garage will condense, but without new air coming in there won't be as much moisture coming in to condense, but probably not a huge amount on it's own. Warming up the slab by opening up the garage at the hottest part of the day may also help some, but makes the garage less pleasant to be in. Or you could actively heat the floor, but also not great for the working environment.

Your best bet is probably AC/minisplits AND air sealing. The minisplits will reduce the humidity in the garage and keep the dew point above the temp of the floor. Air sealing will stop more moist air from entering the garage and make the minisplits have to work less hard.

 

[mikedodge]

2400 sq ft.

Outside of a couple windows and 2 garage doors, the soffit goes above the panel ceiling and to the attic area. What kind of dehumidifier to you use? Should I consider an exhaust fan/vent or something like that?

Considering it

If the windows and doors are open regularely with your fans going that should handle the issue but im guessing you probably dont have that liesure (i dont). My space is maybe 1200sq feet? It's a normal dehumidifier I use.

 

[Paycheck]

Increasing airflow doesn’t work if all that air is coming from the outside. If you just recirculate inside air then the humidity doesn’t go anywhere. You need a big dehumidifier/HVAC system. And even that won’t work well if the space isn’t well sealed because of outside air coming in.

 

[pembol]

AC it is... anyone have any recommendations? I am not sure if a mini split would suffice. Just the quick google search suggests that a 5 ton unit is what I would need.

Favorite (or hated) brands?

Do a real load calculation, and decide if you want the mini just for cooling/dehumidification or heating as well. If you want heat (which I am guessing you do) that will probably drive the sizing as I am sure your heat loads are much higher than your cooling loads.

Also, remember this is a garage, not your house, so you don't necessarily need to plan for the worst possible scenario. If it is -10F out, I am not working in garage so it is fine if the garage is only 50F. If you are above 3 ton, then two independent systems may be your best bet - it is more versatile and efficient than a multizone system, and not much more expensive.

 

[Rusty Pilot]

Do a real load calculation, and decide if you want the mini just for cooling/dehumidification or heating as well. If you want heat (which I am guessing you do) that will probably drive the sizing as I am sure your heat loads are much higher than your cooling loads.

Also, remember this is a garage, not your house, so you don't necessarily need to plan for the worst possible scenario. If it is -10F out, I am not working in garage so it is fine if the garage is only 50F. If you are above 3 ton, then two independent systems may be your best bet - it is more versatile and efficient than a multizone system, and not much more expensive.

I already have a heater in there. I'm looking for cooling/dehumidifying.

 

[pembol]

If the heat is the wall heater in the photo, you may find heating with the minisplit to be better, also the cost differential for a unit that heats well is small and gives you options for heat. Either way, definitely consider 2 units if you end up needing more BTU - also addresses the 2 room issue.

 

[Rusty Pilot]

I got a gas heater in the corner. It keeps the barn pretty warm in the winter. I keep the barn at a min of 50 when I'm not in there.

 

[finn]

A lot of folks are suggesting more ventilation, but that may actually make the issue worse. A others have said, the root cause of the condensation is the temperature of the floor dropping below the dew point of the air. Just looking at the weather for Indianapolis, the dew points are often in the mid 70s (ugh). If your floor is cooler than this it will condense the moisture from the air. If you ventilate the garage and bring in more moist air, you are just bringing in more water to condense. Later in the season, when the floor warms up the problem will likely fix itself.

Sealing up the garage on its own may help a little bit, as the air the air that is in the garage will condense, but without new air coming in there won't be as much moisture coming in to condense, but probably not a huge amount on it's own. Warming up the slab by opening up the garage at the hottest part of the day may also help some, but makes the garage less pleasant to be in. Or you could actively heat the floor, but also not great for the working environment.

Your best bet is probably AC/minisplits AND air sealing. The minisplits will reduce the humidity in the garage and keep the dew point above the temp of the floor. Air sealing will stop more moist air from entering the garage and make the minisplits have to work less hard.

I agree. In my experience wth the garage I had a spring / early problem with the floor sweating opening the door actually made the problem seem worse, at first.
However, after a number of years of trying different things, opening the door and dealing with the floor sweating for a while was the lesser of all evils. sort of hold your nose and bite the bullet. Once the floor warmed up, everything was fine until the next spring, and it only took a week or two to get there if the door was open as much as feasible.. Keeping the door closed, using fans, etc just prolonged the agony, although I think a really high airflow like from a Big *** fan or the like would speed the floor slab warm up past the dew point.

 

[racecougar]

Local dewpoint is going to play a role in whether or not that approach is reasonable. Getting the slab above 75F whilst still attached to the massive heatsink that is the Earth is a bit of a struggle here in MO, not to mention, entirely unpleasant. It looks like the dewpoint up in the UP is in the 50's-60's right now, by comparison.