de-humidification for garages

Gary Knox

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There has been a thread about this a while back, and currently there are some posts in the 'What did you do xxx'' thread. I'm posting this separately, as it is a slightly different (but much more flexible) approach to de-humidification. I installed a 'split' heat pump system in my hobby garage about 12 years ago. Cheap Chinese system, but it has worked beautifully for these 12 years, summer and winter.. It puts out 120 degree air when the outside temps are in the low teens, and 40 degree air today when it's 95 degrees. Of course when it is on the cooling mode it also dehumidifies beautifully. BUT, it has a 'dry' mode, which allows it to function as a de-humidifier. And, it operates on DC (converts 220 AC to DC), which means it has variable compressor speed, based on thermostat demand (designated as Inverter Technology). This is much more energy efficient than the heat pump systems that turn the compressor off and on to achieve the thermostat setting. The ones available now are about 25% cheaper than the one I purchased (installed it myself).

Here is a link to an 18K BTU unit on eBay fro <$1K (I think i bought the 24K BTU size): https://www.ebay.com/itm/18-000-BTU-KLIMAIRE-19-SEER-Ductless-Mini-Split-Inverter-A-C-Heat-Pump-220-V/401821086659?hash=item5d8e6733c3:g:-2MAAOSwffBdMixL

Just posting this, so anyone looking to keep the humidity down might consider an option that provides even more functions.

Gary--
 
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Michael Kaye

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Thanks Gary, sounds interesting.

However I'm still trying to work out whether a de-humification is even worth it for me.

I live in London. The garage is concrete floor base, with brick walls, Unheated and small (as in the E9 just about fits). It is pretty well sealed with an electric garage door and a door into the house hallway.

Temps in London range from around 0 c (32 f) in winter to 25 c (80 f) in summer.

Any thoughts whether it would be beneficial?

Anyone else (especially those based in the UK and similar climates) have any thoughts/advice?

Thanks, M.
 

autokunst

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There has been a thread about this a while back, and currently there are some posts in the 'What did you do xxx'' thread. I'm posting this separately, as it is a slightly different (but much more flexible) approach to de-humidification. I installed a 'split' heat pump system in my hobby garage about 12 years ago. Cheap Chinese system, but it has worked beautifully for these 12 years, summer and winter.. It puts out 120 degree air when the outside temps are in the low teens, and 40 degree air today when it's 95 degrees. Of course when it is on the cooling mode it also dehumidifies beautifully. BUT, it has a 'dry' mode, which allows it to function as a de-humidifier. And, it operates on DC (converts 220 AC to DC), which means it has variable compressor speed, based on thermostat demand (designated as Inverter Technology). This is much more energy efficient than the heat pump systems that turn the compressor off and on to achieve the thermostat setting. The ones available now are about 25% cheaper than the one I purchased (installed it myself).

Here is a link to an 18K BTU unit on eBay fro <$1K (I think i bought the 24K BTU size): https://www.ebay.com/itm/18-000-BTU-KLIMAIRE-19-SEER-Ductless-Mini-Split-Inverter-A-C-Heat-Pump-220-V/401821086659?hash=item5d8e6733c3:g:-2MAAOSwffBdMixL

Just posting this, so anyone looking to keep the humidity down might consider an option that provides even more functions.

Gary--
Hi Gary,
I plan to install the same/similar system in my new garage. It is great to get an endorsement, as the idea was the builders and I wasn't 100% confident in the performance of this system. Thanks for posting!
 

autokunst

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Thanks Gary, sounds interesting.

However I'm still trying to work out whether a de-humification is even worth it for me.

I live in London. The garage is concrete floor base, with brick walls, Unheated and small (as in the E9 just about fits). It is pretty well sealed with an electric garage door and a door into the house hallway.

Temps in London range from around 0 c (32 f) in winter to 25 c (80 f) in summer.

Any thoughts whether it would be beneficial?

Anyone else (especially those based in the UK and similar climates) have any thoughts/advice?

Thanks, M.
Hello Michael,
Nothing beats some actual data. I would recommend putting an accurate hygrometer in the space so you can see what the RH (relative humidity) is in there. Perhaps even a digital model that can record changes over time/various temperatures. Personally, I like to keep the car storage at 40% RH, but I let it go to 45% in parts of the year. Anything above 60% allows steel to corrode more rapidly. Not sure what the magic number is for mold/mildew, but I would be suspect of anything over 50%. I've attached it before, but here is a brochure for a car dehumidification system from a company in the UK - for reference.

Stephen
 

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Michael Kaye

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Hello Michael,
Nothing beats some actual data. I would recommend putting an accurate hygrometer in the space so you can see what the RH (relative humidity) is in there. Perhaps even a digital model that can record changes over time/various temperatures. Personally, I like to keep the car storage at 40% RH, but I let it go to 45% in parts of the year. Anything above 60% allows steel to corrode more rapidly. Not sure what the magic number is for mold/mildew, but I would be suspect of anything over 50%. I've attached it before, but here is a brochure for a car dehumidification system from a company in the UK - for reference.

Stephen
Hey Stephen, great advice thank you. I'm also one for empirical data so will get a hygrometer bought and see what it tells me. I'll report my findings here soon. Thanks, M
 

Ohmess

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Thanks Gary, sounds interesting.

However I'm still trying to work out whether a de-humification is even worth it for me.

I live in London. The garage is concrete floor base, with brick walls, Unheated and small (as in the E9 just about fits). It is pretty well sealed with an electric garage door and a door into the house hallway.

Temps in London range from around 0 c (32 f) in winter to 25 c (80 f) in summer.

Any thoughts whether it would be beneficial?

Anyone else (especially those based in the UK and similar climates) have any thoughts/advice?

Thanks, M.
Not sure about the climate specific stuff, but both the concrete in your floors and to a lesser extent the brick in your walls will soak in moisture and leach it out into the air in your garage. If you want to try to dehumidify the air in your garage, you should seal both the floors and the walls. I had to do this in my basement.
 

Drew20

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I had noted rust spots blossoming on my garage's previous resident (mk2 Golf) and so bought an inside/ outside humidity meter to monitor humidity levels. At a basic level, this worked well as I was able to open the garage door if humidity outside was lower than inside. However during the UK winters humidity inside and outside is consistently high.
So I bought a de-humidifier to actively control the situation. It's one that uses desiccant material, and heat to dry the desiccant, rather than a normal heat-pump one as I had read that heat-pumps do not work well at low temps.
I reckon this costs £1 per day in running costs (it runs full time in winter but it's mostly not on in summer), and it pulls a scary amount of moisture from the air when running. With it I can keep humidity down to ~50% year round
 

Michael Kaye

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So I bought a de-humidifier to actively control the situation. It's one that uses desiccant material, and heat to dry the desiccant, rather than a normal heat-pump one as I had read that heat-pumps do not work well at low temps.
I reckon this costs £1 per day in running costs (it runs full time in winter but it's mostly not on in summer), and it pulls a scary amount of moisture from the air when running. With it I can keep humidity down to ~50% year round
Hi Drew, any chance you could post details of the one you bought so I can do a bit of googling for it or similar.

Thanks, Michael.
 

Drew20

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It's one of these:

the one thing I find annoying about it is that when I switch it back on it doesn't remember the settings from when I switched it off, so I have to reset the fan speed and humidity "target"

a small niggle

but otherwise it's fine. It is relatively low capacity, but that's fine for me as my garage is not particularly damp. If it rains solidly for a few days humidity will creep up towards ~60%. But we live in the UK and so those days of relentless and unending rain are very rare.... ahem!
 

Michael Kaye

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It's one of these:

the one thing I find annoying about it is that when I switch it back on it doesn't remember the settings from when I switched it off, so I have to reset the fan speed and humidity "target"

a small niggle

but otherwise it's fine. It is relatively low capacity, but that's fine for me as my garage is not particularly damp. If it rains solidly for a few days humidity will creep up towards ~60%. But we live in the UK and so those days of relentless and unending rain are very rare.... ahem!
Thanks Drew that looks good value. I'll get one ordered :)
 

JayWltrs

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My experience with dehumidifiers.
1. As with most things, buy the most powerful one you can stomach or will fit into your space. If it is too small, it will run constantly and generate significant heat. They can use a surprising amount of energy.
2. Compare operating temps as some will work down to 40F and others don't work well blow 60F.
3. Make sure it has drainage hose connection and you have a place to drain, as emptying the pans will get old fast.

Didn't read entire thread and sorry if I've duplicated others.
 

Gransin

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I have a Mitsubushi FH25VE-E1 in my garage, which can handle -25C° and still give heat, and it's doing a great job of de-humidifying the garage while it's humid outside. Not the cheapest but it's a very nice machine that I can recommend to anyone.

MSZ-FH25.jpg
 

JayWltrs

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I have a Mitsubushi FH25VE-E1 in my garage, which can handle -25C° and still give heat, and it's doing a great job of de-humidifying the garage while it's humid outside. Not the cheapest but it's a very nice machine that I can recommend to anyone.

View attachment 69060
I'm jealous, and I also want this for my next garage/shop. I looked at mini-splits during round 25 of never-ending old home renovations, and they're just all-around smarter options. Also saw some good sales & discounts in the off-season. But I only had one available wall, and I couldn't stomach more work to navigate around obstacles. So I stuck with my stand-alone de-humidifier, which runs nearly non-stop during summer and makes me feel like an eco-criminal. I have a near-constant stream of drain water from May to September. But I have to heat up the garage in our relatively mild winter to get it to work. I'm confident I'll spend more on increased utility bills over the life of a mini-split unit than the difference in the price.
 

JayWltrs

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Funny thing I learned today. Marijuana grow and dispensary ops seem to use mini-splits quite a bit for some reason. My state’s foray into legal weed has been accompanied by an influx of supplies from failed dispensaries in other states, including mini-splits. The market here is wildly over saturated with new weed shops and we’re already seeing failures in the first 6 mos as the market sorts itself. So, although I can’t use it now, I’ll probably grab one or two in the distress sales that are popping up while they’re stupid cheap.
 

Michael Kaye

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So I've been measuring the humidity in my garage this last week and with an average temperature of around 75 °F (~24 °C) I'm seeing a maximum relative humidity of on average 56/58 .

According to this chart, this is outside safe storage conditions i.e. metal will start to react and rust.


IMG_2438.png



Therefore I've just ordered a Meaco DD8L Junior Dehumidifier (Multi Award Winning) (thank you @Drew20 for the recommendation).

I'll let you all know how I get on and what effect the dehumidifier has over time.
 

Michael Kaye

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So been away for a few weeks and left the Meaco going and it’s worked pretty well so far.

Would highly recommend to use the drain if you can.

Here’s the model I bought :


Some pics showing humidity and temperatures over the last 24 hours and since resetting it 2 weeks ago. Pretty good.
0F6FDBB9-7F74-49A8-ACA5-D7E19E46E08A.jpeg
B4E3A9A8-97D9-48A0-B27A-E424F6632645.jpeg
 
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