Garage dehumidification

Scuzi

Scuzi

Scuzi

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Joined
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I have a single skin brick wall detached garage. The cold and damp weather recently has meant that condensation has built up on all cold surfaces. I have an old chest freezer which has a puddle underneath it due to dripping condensation. The motorbikes are all wet, and all containers of liquid are also wet. I figure a dehumidifier is the answer.

Does anyone else run one in a similar setup and if so, what sort of spec should I aim for? Would a “20l per day” spec do the job. One of my concerns is that the tank capacity of these is around 4l, meaning it would need to be emptied 5 times a day. Is that right? I’d prefer something I could leave running and pretty much forget about - or at least have a few days between emptying.

Also, what’s the ballpark cost of running my one of these in a garage throughout the winter months?

What do you recommend OcUK?
 
I hadn’t considered ventilation. There aren’t any air bricks. The only ventilation I can see is the gap beneath the garage door. All of the walls are solid and there doesn’t seem to be any ventilation built into the pitched slate roof.

It was built new in 2019 so I’d expect it would be compliant with any regs...if there are any?
 
Opening the door could work most of the time, but there are times when we get a front of warmer moist air after a cold spell that still results in condensation on the cold surfaces, even outside in the open. I’m thinking if I plugged the gap under the garage door that a dehumidifier could take enough moisture out of the air to keep it in check.

The ideal situation I think would be to convert to a double skin construction and put a radiator in there but I’m guessing that would cost a lot and impinge on the available space.
 
Tube heaters look like a possibility I hadn’t considered. How many do you think I’d need for a single garage?
 
SPG said:
Very easy job to put on insulated layer just did half my sectional for that very reason for cycling room.

It does sound more like and airflow issue more than anything else though. Waste of time putting in a de-humidifier in though you will be trying to dehumidify the earth.
Click to expand...

What did your insulation job involve?

I think part of my problem is the sheer amount of stuff in there preventing good airflow.
 
Welshman said:
Insulation is easy to put up......1” x 1” buttons on the walls, 25mm insulation boards in between and then either plaster board or osb board over the top. But I would then insulate the roof too and also add an extractor fan, to help with air movement and the removal of damp air. Again put it on a timer to run for 10mins or so every hour
Click to expand...
Can that be done on a single skin wall? During driving rain some damp makes it through the brick.
 
So I had an architect friend have a look while he was dropping off an Xmas card. He thought ventilation wouldn’t cut it alone. His recommendation for a ‘proper job’ was to batten, 75mm insulation for the walls and 100mm for the ceiling. Ballpark estimate for a DIY job was £1.5-2k.

That’s more than I want to spend and I don’t want to lose the space. Realistically I won’t be able to do it until next summer anyway so still leaves me with the problem for the next 3-5 months.

I continued looking for other options and spotted this:
https://www.machinemart.co.uk/p/ecor-pro-dryfan-8-dh800-8-litre-deciccant-dehu/

What do you think? Would putting something like that up in the rafters keep the condensation at bay? I get that it would be “dehumidifying the world” but the garage is relatively air tight so maybe it would be enough?
 
I’m tempted to just try an extractor fan and some airbricks to see what that does. Trouble is that I’ll have holes to plug if I do go down the insulation route.

So the temperature here now is 13C. The dew point is 12C. Everything in the garage is soaking because it was colder over the past few days meaning that all of the surfaces are below the dew point. The more I think about this, the only way out of this is to make sure the temperature of the air and the contents of the garage stays above the dew point.
 
Welshman said:
Then he’s ripping them off.....I fully insulated a 3.5mtr x 2.5mtr man cave with Board, batten and insulation for a few hundred pounds....plaster board is as cheap as chips these days and double foil sided insulation is too......trust me I know
Click to expand...
What insulation did you use and where’d you get it from? He recommended at least 75mm for the walls and 100mm for the roof. The roof insulation would go on the pitched surfaces to maintain loft storage.
 
Welshman said:
Double side foil insulation at 50mm......it’s not a house. Local builder suppliers it was around £6 for 1200x450 board and I used around 25 boards with cutting around windows and doors, about 30 2x1 battens £1.40 each and around 10 sheets of plaster board 2.4mtr x 1200 £7 each...

so that’s £265.....give or take and a box of dry wall screws
Click to expand...

Not bad at all.
 
It’s that time of year again. Earlier in the week my tools and motorbikes were dripping with condensation so I took the plunge and bought a dehumidifier. It’s this one: https://ecor-pro.com/product/dh1200-dryfan-12-litre-desiccant-dehumidifier/

It seems to be designed for this sort of application so fingers crossed.

Part way through the install:
NFl6YuS.jpg

Can you guess when it was turned on?
LOy9rql.png

The ambient RH is sitting at around 80% outdoors. My shed which is attached to the garage is showing around 88% RH and the garage was trending very similarly to the shed at night time before the install. So the conclusion from day 1 is that it is knocking the RH down by about 10-15%. Is it enough to keep the garage condensation free? I’ll see how it goes over the coming weeks. The real test will be on the warm damp days after a very cold spell where the temperature of the garage contents is very low but warmer humid air comes in.

I’m going to experiment with various levels of external ventilation and ducting of the inlet and dry outlet to see if it makes much difference.

You may ask why I didn’t go down the route of insulating the garage. In short, too expensive, too many compromises with space, and little guarantee it would actually solve the problem without continuously heating the garage throughout winter.
 
CaptainRAVE said:
Why does it suddenly stop reducing the RH? Does it switch off? Is the garage well sealed?

45-50% is the target to apparently stop all corrosion. Below 60% seems essential.

It looks like a neat setup.
Click to expand...
Good question. The humidistat was set to target 50% so I’m not yet sure. The obvious reasons would be either the dehumidifier is operating at its maximum capability or the influx of the external air mass through leaks is levelling it out. Or both. Or maybe the contents of the garage (cardboard boxes etc.) are still drying out? Having spoken to the manufacturer before buying they suggested the unit should be more than capable of bringing the RH lower so I’m leaning towards the air leaks. I’ll plug it up and see if that has any effect.

This morning the shed contents were soaking in condensation but the garage contents seemed completely dry in comparison. The indicated humidity level seems high but, acknowledging it is early days, it seems to have done the job last night.
 
Last night and this morning have provided the perfect test conditions. The garage started off cold and a warm front of heavy rain came through significantly raising the outside relative humidity to 96%. The RH in the garage increased markedly overnight despite a slight increase in temperature but it managed to stay below 80%. The contents are condensation free which is the main objective, however I’ll be looking to seal it up better as it has to be leaking quite a lot based on the data.

Garage:
YFM1Xj4.png
You can see from the trend graph at the bottom where the dehumidifier was turned on. There is a step decrease in humidity but I’d still like it to be less volatile to weather events like we have just had.

For comparison, here is the shed:
cM0NXUd.png

Next steps:
- Get up into the roof and look for air leaks. If necessary, board it up.
- Look at roller shutter garage doors. I have a standard cheap up and over which despite lots of plugging, still has gaps everywhere.
- Ventilate the shed.
 
So far so good. The dehumidifier has consistently dropped the RH by 10-15% throughout, so even on the warm days of 99% RH after a really cold spell it has lowered the garage to the mid-80s which has been sufficient to prevent condensation. Because it is doing the job I haven’t really bothered doing much else.

The built-in humidistat is terrible so I have been manually switching it on and off using a smart plug. I might look at smart hygrometers to act as a humidistat with the smart plug but that’s quite low on the priority list.

I’m happy with the outcome. My bikes and tools are dry!
 
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