Moisture/Humidity Issue

[Showkey]

Would the dehumidifier work better than a mini split? I'm waiting on a friend to get back to me who owns an HVAC business on what it would cost to get set up with one of those (or maybe multiple needed?).

No Will not “better”..........AC will dehumidify and cool.
Difference is the cost, dehumidifier at Costco might be $150. Install 10 minutes and cost of operation is 400-700 watts for the dehumidifier.

If your not there much right now the cooling effort and comfort level goes unappreciated.

 

[glentre]

Using my cheapo humidity meter, it's showing 74% humidity and 82 degrees inside. Nothing sweating, like the floor, etc. Outside it's 93 and muggy.

At 74% and 82 degrees, the dew point is 72.9 degrees so you will not have any condensation but I agree that 74% over time will result in mold in your garage so dehumidification is advised either with a dehumidifier of HVAC. Hate to be repetitive but your garage is so air tight that ventilation through introduction of fresh outside air and exhausting that same amount of air is advisable. You can check on line for recommended air changes for the activities you will be doing.

Just as an interesting aside regarding humidity, some crowded night clubs feel clammy and moldy because the room temperature is low but the RH is very high due to all those sweaty bodies. In these instances, good clubs will use the HVAC system to overcool and remove this excess moisture and then use a reheat coil in the duct work to raise the temperature so the RH stays at comfortable levels.

Glen

 

[Showkey]

At 74% and 82 degrees, the dew point is 72.9 degrees so you will not have any condensation but I agree that 74% over time will result in mold in your garage so dehumidification is advised either with a dehumidifier of HVAC. Hate to be repetitive but your garage is so air tight that ventilation through introduction of fresh outside air and exhausting that same amount of air is advisable. You can check on line for recommended air changes for the activities you will be doing.


Glen

Repetitive and wrong.......... bringing in outside air that it hot and humid will NOT solve or cure anything !!!!!!

You have got to be kidding on the air exchanger or recovery unit for this shop situation.

An air exchange system or recovery system is a whole nother cans of worms and costs. Starting at $600-$1500 and 99.8% of the time they installed in complete HVAC system.

https://www.ecohome.net/guides/2362/ventilation-air-exchangers/

An air exchange is actually and air exchanger. ... The installation of an air exchanger inside the house removes stale and polluted air from the house to the outside and replaces it with fresh air. Generally, an air exchanger system installed properly will renew the air of all the important parts of your home.

Air exchange recovery systems are designed to save the cost of heating or cooling the structure by recovering the heat or cooled air while exchanging the air and some determined rate. Since the shop has no heat and no AC there’s no conditioned air to recover. WHICH IS THE REAL PROBLEM IN THIS SHOP !

 

[glentre]

Repetitive and wrong.......... bringing in outside air that it hot and humid will NOT solve or cure anything !!!!!!

You have got to be kidding on the air exchanger or recovery unit for this shop situation.

An air exchange system or recovery system is a whole nother cans of worms and costs. Starting at $600-$1500 and 99.8% of the time they installed in complete HVAC system.

https://www.ecohome.net/guides/2362/ventilation-air-exchangers/

An air exchange is actually and air exchanger. ... The installation of an air exchanger inside the house removes stale and polluted air from the house to the outside and replaces it with fresh air. Generally, an air exchanger system installed properly will renew the air of all the important parts of your home.

Air exchange recovery systems are designed to save the cost of heating or cooling the structure by recovering the heat or cooled air while exchanging the air and some determined rate. Since the shop has no heat and no AC there’s no conditioned air to recover. WHICH IS THE REAL PROBLEM IN THIS SHOP !

I don't disagree with you when the shop has no HVAC. In post 26, I advised the OP to review with his HVAC contractor when he installs his system that ventilation air be introduced through the HVAC system. I neglected to say again in my above post that the ventilation air should be part of the new air conditioning system so if you did not see post 26, your comments are understandable. I am not advising an air exchanger or recovery unit for this application, only that some outside air be introduced when he has his system installed so he can get some fresh air into his building which he says is extremely well insulated and airtight, allowing for no outside air to get in.

Glen

 

[pcmeiners]

Just as to the mold/funk. Purchase a $50 ozone generator, a cheap timer, off Ebay. Hook it up, set it to go on at 2 am for 30 minutes. Ozone is almost as powerful as chlorine, breaks down in a few hours so you will not breath it.

 

[jkohnz]

Well, I bought a 50 pint dehumidifier (per new measurements, 70 pint per old, not sure what that means) that had a $40 coupon on Amazon, started it up yesterday. It's been 16 hours, and it has gone from 82% humidity to 65% this morning. Not sure how much of that is just simply the overnight temps dropping down 20 degrees. I reset the gauge so that the 65% is the registered high. We'll see after this afternoon's high humidity outside. I'm pretty thankful that the mold was limited to 2 shelving units and a pair of leather seats. The seats can be cleaned up fortunately. Funny thing is, I have another pair of leather seats sitting on the second floor loft of my shop that don't have a single spec of mold on them. So, I'm thinking I caught it pretty early on. I can definitely tell a difference in how the shop feels now. I appreciate all the suggestions and comments!

I'm hoping to put a 3 to 4 ton mini split in there for the winter time (money money money). But, if the humidity is down, and I put in a big ceiling fan, I think the summer temps will be very much bearable without needing A/C running 24/7.

 

[Jeepster04]

The temp dropped 20 degrees inside of the building overnight? If thats the case, thats exactly why you were getting the mold. Anytime you have big temp swings, everything in the building slightly lags behind which puts that surface below the dewpoint. Condensation forms on whatever is below the dewpoint and over time, you get mold/rust.

To keep this from happening you can either stop the temp swings or like youve done, remove the moisture. The temp shouldnt drop by 20F in a spray foamed garage though, so thats odd. And fans only can indeed help depending on the situation. Often times things down low will be below the dewpoint while things up higher will be above the dewpoint. If you have fans running it will move the warm air around and keep everything at the same temp, which could be above the dewpoint. So having a fan running along with the dehumidifier could be a good idea. Ive always had a dehumidifier in my garage but sometimes Ill open my garage door and condensation forms on the lower portions of the vehicles in my garage. Its kinda wild, you can see a very defined line in the condensation along the vehicles. The vehicle above that line is above the dewpoint while below the line is obviously below the dewpoint. If I had a fan running then the lower portion of the vehicle wouldnt be cooler than the top portion.

 

[jkohnz]

The temp dropped 20 degrees inside of the building overnight? If thats the case, thats exactly why you were getting the mold. Anytime you have big temp swings, everything in the building slightly lags behind which puts that surface below the dewpoint. Condensation forms on whatever is below the dewpoint and over time, you get mold/rust.

To keep this from happening you can either stop the temp swings or like youve done, remove the moisture. The temp shouldnt drop by 20F in a spray foamed garage though, so thats odd. And fans only can indeed help depending on the situation.

The building temp drops only a few degrees when the outside temp drops like that. Even when it was 98 outside the other day, it was only 81 inside. I've kept the big door shut this whole time to try and prevent bringing the moisture back in again. But, I'll have to open it here soon to do some work lol. We'll see how it goes. Planning to put in a 10ft ceiling fan probably next week to help with that air flow, once I get the humidity down AND get the mold spores cleaned up. I don't want them circulating.

 

[jkohnz]

It's been holding steady at 55-56% humidity for the last 36 hours, at 77 degrees. Today it's mid to upper 70s and 83% humidity outside. I'm hoping that, once I get a fan put in, I can get it to around 50%. I might pick up another dehumidifier and put it on the other side if not. I've read that mold starts above 60%. But not sure how accurate that is.

 

[Hank11]

Go ahead and buy another dehumidifier. When you have the humidity down to 35% or so and 77 degrees inside you will love it and your stuff will stay nice.

 

[Showkey]

50% is a goal......not an absolute critical point.

Move the humidity meter around the numbers many move 3-6 points.

70% plus is where bad things start happening.

 

[jkohnz]

Go ahead and buy another dehumidifier. When you have the humidity down to 35% or so and 77 degrees inside you will love it and your stuff will stay nice.

The one that I have seems to be doing a good job maintaining. The separate gauge is tracking high vs low. Low was 52% this morning, and hasn't gone back up again since. The machine is set for continuous mode, and I'm not able to see in the book what this will take it down to. It also has a Comfort mode, which will take it down to 50% when the ambient temp is between 65 and 77. So, I'm not sure how much lower it would take it. And with that, I'm not sure buying a 2nd one will help any.

If 50-55% is good enough to stop mold, I'm happy. I'm putting in a 10ft fan next weekend when it gets here. It's actually pretty comfortable right now, but a little warm at 78 degrees inside the shop. It's 86 and muggy out again today right now.

 

[jkohnz]

Well, it's been almost 2 weeks since the last update, with the single dehumidifier running 24/7. It's now down to 41% as of a couple hours ago. The fan isn't helping with the effort, but it does create a nice little breeze while I'm in there. Still sitting at 77 degrees. It's a little warm for my liking still. I mounted up a small fan on the wall and it works nice for some spots to cool off quick. Still probably going to have to put in a split unit I think.

 

[Hank11]

It takes a while for the mass of the building and contents to come to equilibrium with the air inside the building. After that the dehumidifier will maintain the humidity pretty well until you open the doors and leave them open too long. But you have things dried out and that is the important thing here.

I think you will be pleased with 35ish% and high 70s. Its will be pretty comfortable and there won't be any tendency to mold or mildew.

Just based on the square footage I'd buy another dehumidifier and get the humidity knocked down.

 

[My Old Tools]

East Texas is similar in humidity. My MrCool 3 ton went in over a week ago. The first 12 hours it pulled gallons of moisture out of the shop. Now it's just a trickle. Once the shop cools down the AC just idles to maintain it. I bet it doesn't use a lot more power than your dehunidifier.

 

[jkohnz]

East Texas is similar in humidity. My MrCool 3 ton went in over a week ago. The first 12 hours it pulled gallons of moisture out of the shop. Now it's just a trickle. Once the shop cools down the AC just idles to maintain it. I bet it doesn't use a lot more power than your dehunidifier.

What size shop do you have? I've been told I need a 3 ton mini split, with low ambient heat for the winter by a friend who owns an HVAC company. But, he's so busy he doesn't respond very quickly. He told me I can get them online much cheaper than he can sell them for. Been trying to find the right one to get, but am thinking I best just pay an HVAC company to come do it right.

 

[Shovelhead]

Very interesting read to me as I am not convinced this spray foam totally sealed shop is the "nutts" for how I operate in my shop, and the next one I have built. I'm really tryin to learn about it and make an educated decision on my next shop. In my location HIGH humidity is a daily occurrence and way of life.

I see the only real benefit of spray foam is if you air condition the entire shop and never open the dang overhead doors.

I work in my current shop (red iron frame / vinyl back insulation) with the doors open ALL the time unless it's cold outside. I have no heat or A/C.

I also have a small dehumidifier used only when we had to move our entire house and clothes out there due to being flooded in hurricane Harvey.

That dehumidifier works fine as long as you don't open an overhead door, then yer tryin to dehumidify the whole County.
The way I see it yer gonna be chasing yer tail unless you air condition and heat the thing and rarely ever open any doors. Fine for a house or an office, but for a "Shop" ?????????????
I don't get it.

Spend the money on a totally sealed foamed shop only to fight the humidity forever?

 

[My Old Tools]

What size shop do you have? I've been told I need a 3 ton mini split, with low ambient heat for the winter by a friend who owns an HVAC company. But, he's so busy he doesn't respond very quickly. He told me I can get them online much cheaper than he can sell them for. Been trying to find the right one to get, but am thinking I best just pay an HVAC company to come do it right.

30x40x12 with a 6/12 pitch, 22 feet to the peak. Conventional roll insulation,, double on the roof. 7 windows, 3x5, double pane low E fiberglass, one man door, 12x12 insulated overhead door. The 3 ton MrCool is cooling it easily, just idling at 75 degrees on a 95 day. Installed in 2 half days, maybe 5-6 hours total and that was working around all the **** in my shop. Very easy install, no gauges or instruments needed. 3.5" hole saw and a couple of wrenches will do it.

 

[My Old Tools]

Very interesting read to me as I am not convinced this spray foam totally sealed shop is the "nutts" for how I operate in my shop, and the next one I have built. I'm really tryin to learn about it and make an educated decision on my next shop. In my location HIGH humidity is a daily occurrence and way of life.

I see the only real benefit of spray foam is if you air condition the entire shop and never open the dang overhead doors.

I work in my current shop (red iron frame / vinyl back insulation) with the doors open ALL the time unless it's cold outside. I have no heat or A/C.

I also have a small dehumidifier used only when we had to move our entire house and clothes out there due to being flooded in hurricane Harvey.

That dehumidifier works fine as long as you don't open an overhead door, then yer tryin to dehumidify the whole County.
The way I see it yer gonna be chasing yer tail unless you air condition and heat the thing and rarely ever open any doors. Fine for a house or an office, but for a "Shop" ?????????????
I don't get it.

Spend the money on a totally sealed foamed shop only to fight the humidity forever?

I don't think foam is required in Texas. Mine is red iron with vinyl backed roll. I did have them double it on the roof and that makes a huge difference. I worked wide open too, but never again after I got my MrCool. Huge difference. It doesn't take long to cool down and lower the humidity if you have to open the doors to move something in.

 

[Shovelhead]

I don't think foam is required in Texas. Mine is red iron with vinyl backed roll. I did have them double it on the roof and that makes a huge difference. I worked wide open too, but never again after I got my MrCool. Huge difference. It doesn't take long to cool down and lower the humidity if you have to open the doors to move something in.

I can understand that but my point is I don't want to get in a situation where I have to run an A/C or dehumidifier just to fight the moisture problems a sealed up Shop would create.

I'd want to run an A/C when I wanted to, not when conditions warrant it.
From what I'm getting out of it, it seems a foam job would warrant constant conditioned environment.

 

[Shovelhead]

jkohnz sorry for butting in on your predicament.
I’m just trying to learn more about it and your situation is providing a lot of info for everyone considering foam insulation.

 

[firebirdparts]

Well, if the shop was really easy to heat and cool, there is a lot of benefit in that. I would happily run a dehumidifier and enjoy it. In fact I do. The basement under my shop is like that. Always temperate.

 

[TonyG109]

I'm a bit late to this party, but I'll add my real life experience. My garage is a 30' x 50' x 12' pole building with dense packed cellulose in the walls (8 1/2" thick) and about 10" blown in cellulose in the ceiling. The building is pretty well sealed. Before I had any environmental controls I would get condensation on the floor, bare steel was getting rusty and the musty smell was starting to set in.

I put in a 70 pint Frigidaire dehumidifier from a big box store, routed the hose under the garage door and said goodbye to all the issues. Relative humidity was kept around 50% and the unit would actually cycle and not run continuously. This worked very well for about 2 years. Now, I must add that this is a home garage and not a working shop so the doors didn't open and close all day long.

Happily, I just installed a 24k Mr. Cool unit and now have low humidity AND cooler temperatures. Contrary to most advice, the 24k unit seems to be plenty enough despite mid 90 deg. temperatures.

 

[My Old Tools]

I can understand that but my point is I don't want to get in a situation where I have to run an A/C or dehumidifier just to fight the moisture problems a sealed up Shop would create.

I'd want to run an A/C when I wanted to, not when conditions warrant it.
From what I'm getting out of it, it seems a foam job would warrant constant conditioned environment.

If you don't ventilate and stir the air I'm afraid any closed space with humidity would be the same problem. Before I got my AC I kept a window cracked and a box fan blowing 24/7.

 

[Showkey]

^^^^^^^^^Ventilation will NOT work if the air outside has a humidity level. It can actually make things worse. Especially at night when has the temperature drops the air becomes more saturated. Very dependent on the climate.

Temperatures are close in the examples below. Often the temperature are not close and can be 20-40* spend.
Example ventilation on this day would not cause a concern:



Ventilation on this day would be a complete waste of time energy and make things drastically worse.



Also these values are variable day to day and hour by hour. Again depending on climate, location and weather conditions that minute.

Reality is there’s no real substitutes for conditioning the inside air.

 

[jkohnz]

jkohnz sorry for butting in on your predicament.
I’m just trying to learn more about it and your situation is providing a lot of info for everyone considering foam insulation.

No problems at all!

 

[jkohnz]

So far, I've been running the dehumidifier on continuous mode. This past week, we've had some milder days in the upper 70s. The temps inside the shop have been about the same, and the humidity has dropped down to around 38% overnight, then back up to 42 or so during the day. This is a workshop for me. I like to work on cars. But, I don't open the big door if I don't have to. It's comfortable if I have multiple fans going, but I prefer it to be a bit cooler. It's working for now, though, until I can get the $$$ for a 3 ton mini split.