ideas to solve moisture problem in shop

[1hawkeye]

I have a 45' x 64' pole building with 18' ceiling. The walls are sprayed with closed cell foam and the ceiling has blown in fiberglass insulation. I only have one end (45x32) of the floor poured. I have plastic down, then 2" of styro foam insulation with pex tubing under the 6" thick slab. The other end is still dirt. It is not taking much to keep it 50 degrees in the shop but my problem is moisture. It is always 70-80% humidity. I have condensation on my doors and windows. I am attributing it to the dirt floor. I live in central Iowa, so normally between 0 and 30 degrees F. in the winter. I am looking for ways to control the moisture until I can afford to put concrete in the whole thing. Thanks in advance

 

[BlackTalon]

Can you put down poly sheeting over the exposed soil area? Maybe weigh it down with some sang bags, etc. Tape the poly joints and seal it at the perimeter.

If you need to walk/ drive over the exposed soil area then good luck addressing the moisture issue in a reliable manner; you'll just have to live with it until you can complete the slab installation. Either that or invest some $$$ in some honking big dehumidification system.

 

[wssix99]

Just putting down the plastic will probably save you its cost on heating. It should give you a little bit of a barrier to heat escaping through the unpaved/uninsulated area.

Do you have a dehumidifier you can try out?

Are you really getting 70-80% humidity? That sounds way high. If that is an actual reading, then I'd expect you have some sort of water leak in there or that your building is too tight. If you are really that air tight, you might want to check out putting in a HRV to improve your air quality. That should also get rid of some humidity by air exchange and they also have some dehumidifying effects.

 

[boobag]

how are you heating the shop? running a ventless propane heater for example, lets out a lot of moisture.

 

[1hawkeye]

I do need to walk in the area and drive on it. I have thought about putting down heavy plastic or even tarp and covering with limestone rock.

I am heating with electric boiler floor heat. I got the reading off of a cheap humidistat (?). It is very humid as I can tell papers and cardboard are damp. I think you are right about it being very tight.

Thanks for the input-- keep it coming

 

[SALIV8]

What about the runoff ? Do you have gutters, downspouts directing away from the structure?

 

[911mike]

Get some fans and ceiling fans and move the air. All the heat is at the ceiling and the moisture is on the floor as the air cools.

 

[olytdi]

If you have moisture, you have to:

stop the source (plastic, rock),
vent the moisture (exhaust fan).

I (stupidly) failed to put a moisture barrier under my slab when I built. As such, I get a damp floor when it's warm and rainy out. I built a vent that has an in-duct fan in it. It's intake is about an inch off the floor and moves the air off the floor and out of the building. Makes a big difference. I find also that a ceiling fan helps in general.

If your building is really tight, you're contributing a significant amount of moisture while breathing. Also, if you store things in there that were wet (like vehicles), that will bring lots of unwanted water into your building.

 

[Chris705]

How about a 15mil Steigo VB a layer of fine stone dust & then a layer of more course layer. If your not turning equipment, just in and out I think it would hold up.

 

[wssix99]

I do need to walk in the area and drive on it. I have thought about putting down heavy plastic or even tarp and covering with limestone rock.

That was one thought I had. You could put down your permanent vapor barrier and then your permanent stone and then compact the stone. You'd be all set for concrete when you are ready, but you'd just have to take on the initial expense for the base.

Another thing, if the soil is loose, is that you might use a tiller to mix in some portland cement. That could "cap" things so less moisture gets through. But... that sure would make a dusty mess!

I think you are right about it being very tight.

The closed cell foam will make the walls air tight. Do you have a vapor barrier under that blown-in insulation. If so, the effect could be like running a 10 miler wearing a garbage bag - it will get and stay pretty humid in there.

If you are tight, the HRV is going to be the way to go. I'm in a concrete house, which is totally air tight and will give off moisture for a few years as the concrete and drywall dry out, etc. We have a HRV to make the place habitable and keep up the air quality. We went from a sauna to a normal house the day we turned the HRV on this summer.

 

[1hawkeye]

Yes, I have gutters and down spouts all the way around.

 

[1hawkeye]

I also have two ceiling fans running all the time. I have used a temp gun and the temp varies very little from the floor to the ceiling.

 

[1hawkeye]

Could someone explain this HRV system? I have considered putting a small exhaust fan close to the ceiling that could be used to vent exhaust fumes, welding smoke, dust etc. I hate to vent out my heat but think that may help some.

 

[MagKarl]

Could you put down heavy plastic over the dirt, then crushed rock over that? Then you need ventilation, your building needs to breath to let the moisture out.

 

[JACDes]

Radiant heat does not create any moisture,
the moisture is coming up from the unfinished floor.



FWIW
The vapor barrier goes over the stone not below it.
By the time you place and compact the stone you will destroy the plastic sheet

 

[1hawkeye]

FWIW
The vapor barrier goes over the stone not below it.
By the time you place and compact the stone you will destroy the plastic sheet

That is what I was thinking, I wish there was an economical way to seal off the moisture below the rock.

 

[JACDes]

you can try using rigid insulation below the stone, but that means removing more soil or adding less stone fill to make up the difference..

A 6" slab for residential use is super-overkill unless you have 20 ton punch presses in there.

 

[1hawkeye]

A 6" slab for residential use is super-overkill unless you have 20 ton punch presses in there.

It is a farm shop and I hate cracks in concrete. It has rebar and fiber mesh, and so far (cross my fingers) no cracks.

 

[JACDes]

If you laid out the control joints correctly and cured it properly it should not crack.

It also should never crack because it is frost protected (insulated) & heated.

If it did not crack within 28 days, odds are it never will.

 

[boobag]

It is a farm shop and I hate cracks in concrete. It has rebar and fiber mesh, and so far (cross my fingers) no cracks.

concrete WILL crack, the thing is to control it. thats why saw cutting the floor soon after its poured is necessary. then it will crack in the cut.

 

[wssix99]

FWIW
The vapor barrier goes over the stone not below it.
By the time you place and compact the stone you will destroy the plastic sheet

It doesn't matter where the vapor barrier goes for this kind of thing. The weight of the concrete on top isn't much different than compacted stone.

There is some debate over where the barrier should go, but PCA recommends under the base. http://www.cement.org/images/defaul...ion/vapor_fig2_large.jpg?Status=Temp&sfvrsn=2

That recommendation is for concrete quality issues that really don't come in to play for the situation we are talking about here - but for an industrial application, it would be more important.

Could someone explain this HRV system? I have considered putting a small exhaust fan close to the ceiling that could be used to vent exhaust fumes, welding smoke, dust etc. I hate to vent out my heat but think that may help some.

The HRV is just that - it's an exhaust fan with a heat exchanger so you aren't pumping your heat out of the building. They are sized for the volume of the structure and the number of air changes per hour you want. Some even have multiple speeds, so you can boost the ventilation when you need it. They also have a furnace-type air filter to filter the air coming in to the building, that you have to switch out just like any other filter.

http://www.popularmechanics.com/home/improvement/interior/1275121

I'm using one in my garage to deal with CO and exhaust ventilation. (Code requires is to have holes cut in our walls and I'm using the HRV to get a variance for that. It comes on whenever my garage doors operate or the lights are turned on.)

The only worry I'd have in your situation is if any of your fumes are corrosive. Some welding fumes could hurt the HRV heat exchanger and in that case, you'd probably want to put in a welding fume extraction system/fan to deal with those specifically before they get to the HRV.

 

[JACDes]

Since most slabs on grade are poured before the roof ever goes on we place the vapor barrier over the stone base.

because we cannot predict if the stone sub-base will be subjected to water infiltration the barrier goes over the stone base.....

Typically concrete is placed with the chute, a pump, or with wheel barrows. once placed the finishers work by hand.. the damage to a 12 mil visquine is negligible..

stone base is normally placed with small equipment (bobcats) and then compacted with plate compactors the weight of the skid steer or turning the machine is enough to ruin the membrane if placed beneath the stone. when the stone is compacted this punctures the membrane even more.

Common sense: we always do method #2 to preserve the integrity of the barrier.

 

[JACDes]

Very few buildings actually need a ERV / HRV system, highrises are an example.

For OPs' barn: try cracking open a few windows to help

or lowering the temp.

it may sound silly but if you can drop it to 45-40 degrees you will not have condensation.

just raise it to 50+ when you are working out there until you finish the slab.

 

[wssix99]

stone base is normally placed with small equipment (bobcats) and then compacted with plate compactors the weight of the skid steer or turning the machine is enough to ruin the membrane if placed beneath the stone. when the stone is compacted this punctures the membrane even more.

Obviously, if one doesn't have the right base material, equipment, or process to lay the barrier under the stone, it shouldn't be done. That doesn't mean that it can't be done or shouldn't be done.

Very few buildings actually need a ERV / HRV system, highrises are an example.

From the time man discovered fire to the 1980's, this was true. As smaller buildings started getting tighter and more energy efficient, the scales started to tip.

For OPs' barn: try cracking open a few windows to help or lowering the temp.

This doesn't sound comfortable or economical.

 

[JACDes]

I would prefer to crack open a window and have controlled air leakage / fresh air when I want it than run a contraption 24/7.

What sort of energy savings do you gain with a ERV that runs all day every day?
The answer is none (or a 90 year pay back if you bother to crunch the data )

You have the upfront cost of the equipment then the operating cost.

not needed for single family residential construction, it's a crutch for poor HVAC design or an excuse to use grant money.

 

[JACDes]

Cracking open a few widows will exchange some cold dry winter air with the warm damp air lowering the humidity which should stop the condensation.

Depending how "green" the slab is and the saturation of the bare ground where there is no slab this will not be resolved until the floor is completed and the humidity stabilized.

Suggesting an ERV is like hammering nails with sledge hammer.

 

[BlindViper]

I have a 45' x 64' pole building with 18' ceiling. The walls are sprayed with closed cell foam and the ceiling has blown in fiberglass insulation. I only have one end (45x32) of the floor poured. I have plastic down, then 2" of styro foam insulation with pex tubing under the 6" thick slab. The other end is still dirt. It is not taking much to keep it 50 degrees in the shop but my problem is moisture. It is always 70-80% humidity. I have condensation on my doors and windows. I am attributing it to the dirt floor. I live in central Iowa, so normally between 0 and 30 degrees F. in the winter. I am looking for ways to control the moisture until I can afford to put concrete in the whole thing. Thanks in advance

Can you build a plastic wall on the poured side?

 

[wssix99]

What sort of energy savings do you gain with a ERV that runs all day every day?

Not much. That's why they come in different sizes, with multiple speeds, timers, and controls. They are sized, set up for, and run on cycles for efficiency and do not run all the time. (unless you have an atypical need and set them up that way)

not needed for single family residential construction, it's a crutch for poor HVAC design or an excuse to use grant money.

They are needed for advanced/tight residential construction. This type of construction is not common because it's expensive. You are correct that a "typical" inexpensive spec house will not need an ERV/HRV.

Highly energy efficient houses (like houses with vapor barriers on all 6 sides and houses with closed cell foam insulation) do need mechanical ventilation in order to be comfortable.

BTW - The OP, in this case, would need a HRV and not an ERV. This is a good article that covers the basics, so you can educate yourself on the technology if you've never used or had the need for one before: http://www.homepower.com/articles/h...ent-products/heat-energy-recovery-ventilators

Cracking open a few widows will exchange some cold dry winter air with the warm damp air lowering the humidity which should stop the condensation.

How would exchanging air like this (in an uncontrolled manner without heat recovery) a beneficial thing? If you can control the amount of ventilation and recover the heat, wouldn't that be better? Or should the OP live out in the barn full time and go crack the window whenever its needed?
http://www.homepower.com/articles/h...ent-products/heat-energy-recovery-ventilators

 

[Scott mcguire]

The condensation is from the air not from the ground. Houses with ch&a do not have the condensation because the moisture is removed from the air.
All concrete will crack eventually from ground movement and expansion and shrinking of the concrete itself.

 

[911mike]

Could someone explain this HRV system? I have considered putting a small exhaust fan close to the ceiling that could be used to vent exhaust fumes, welding smoke, dust etc. I hate to vent out my heat but think that may help some.

Most fumes are heavier than air so vent at floor level not the ceiling. I have seen many auto shops where they pull in fresh air up at ceiling height and pressurize the building and then they have several adjustable vents at floor level for the dirty air to excape. This also helps pull the hot ceiling air down to floor level.