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Garage Dehumidifier for winter
ash_hammond - 6/10/15 at 12:49 PM

I was wondering if people use a dehumidifier in their garage over winter?

My garage is pretty water tight, the roof does not leak, but the concrete sections that make up the sides do let some water in, albeit a small amount. Last winter i monitor the humility and it got to 80% to 90%, I would prefer it to be more like 50% to 60%, given the car now as come expensive electronics and my tools are in there.

If people do use a dehumidifier which ones are recommend?

- Compressor or Desiccant. Apparently Desiccant do work more efficiently at lower temperate due to the way their implementation is designed.

Thoughts welcome.

nick205 - 6/10/15 at 01:14 PM

Don't use one myself as my garage is integral to the house, but I understand your desire. From what I know they are expensive to run and need attention to empty etc. That said, I'm not sure what other options you have bar external cladding of some sort!

ash_hammond - 6/10/15 at 01:23 PM

The model that i'm looking at has the ability to install a constant drain, so very little maintenance on that from will be required. As for the running costs, I kinda of agree, the one i'm looking at has a max consumption of 350w. I guess it will take around £5 to £10 per month to run, assuming is it on for between 3 to 6 hours per day. For piece of mind, i'm willing to pay that. If it turn out to be on more like 15+ hours per day then i will need to look at other options.

ian996 - 6/10/15 at 03:17 PM

If this is the first car you have in there I can understand your concern. I was worried about mine and I think the car coon would be the better option but I didn't bother in the end. And nothing rusted or degraded. It was quite alright

ash_hammond - 6/10/15 at 04:05 PM

quote:
Originally posted by ian996
If this is the first car you have in there I can understand your concern. I was worried about mine and I think the car coon would be the better option but I didn't bother in the end. And nothing rusted or degraded. It was quite alright


I'm not over keen on that idea, looks like it will take up more space than the car. Plus I have two cars in there and both would not fit in the garage in those bubbles.

The garage goes not leak from the roof. But it is an old garage, so there are small pin holes in the walls and where the wall meets the floor etc. Over summer I have tired to seal as many of them as possible to stop the water getting in, but i dont think i will ever win the battle. The car has been in there for a few years now with no real issue. Just big metal objects like my tool chest and pillar drill do attract more condensation than I would like.

JMW - 6/10/15 at 04:52 PM

I have installed one in my wooden garage. The cheapest I could get from Argos, condensate piped outside. Has a humidistat but I also have it on a timer plug.

I cannot say whether it does any good, but it does produce condensate down the pipe.

I know absolutely nothing about air-conditioning or dehumidifying so the benefit may be purely psychological.

Somewhere in the back of my mind though I have a recollection that the colder it gets the less efficient these devices become. Something to do with the dew point I think.

But if I know this BB there will be someone who knows about these things along shortly.

cliftyhanger - 6/10/15 at 05:39 PM

For a dehumidifier to be effective you need to get the garage airtight. Virtually impossible, and I suspect it will be running full time. And possibly fail to make a huge impact.

Surely a more viable alternative is good ventilation and airflow?

Irony - 6/10/15 at 06:52 PM

I have one. The colder it gets the more they become less effective. You either need a warmish air tight room or a huge dehumidifier. They will also need regassing. Your probably better off putting a wall fan in to get good airflow through the garage. You'd be surprised how much more water is in the air inside than out. During the winter months condensation never forms on the outside of your windows.

Bluemoon - 6/10/15 at 07:23 PM

quote:
Originally posted by Irony
I have one. The colder it gets the more they become less effective. You either need a warmish air tight room or a huge dehumidifier. They will also need regassing. Your probably better off putting a wall fan in to get good airflow through the garage. You'd be surprised how much more water is in the air inside than out. During the winter months condensation never forms on the outside of your windows.


As said depends on how warm the air is, I use a regenerative desiccant one in the caravan after a mildew incident that I don't want to repeat, it will dehumidify a 3 bed house and is over kill, it has a humidity stat (essential) and can operate to close to 1C. Drain is plumb in permanently and I monitor it with a remote humidity and temperature sensor. Works well but the caravan is "sealed" (minus gas drop out holes) much more than a draughty garage. The issue that caused the mildew was that the caravan is always in the shade, and that area is a damp trap, i.e. it's in a location that moss and the green algae tends to grow. The only option was a to dehumidify, creating drafts made it worse (but this is the exception no the rule good ventilation is normally the best option)...

Compressor ones are good at room temperature but become inefficient as the temperature drops, they are also noisy. You have two options:

1) Get some air flow. Nateral air flow may be best option, A humidity controlled extract fan might be worth a look, but you only want it operating with the dew point is less outside than inside or you will make the dam worse.

2) Seal the garage, and use a dehumidifier. If the garage is cold you will need to use a regenerative desiccant unit (these units are less efficient than the compressor units but do also warm the space with the wast heat generated). Will only work if no drafts.

One garage we have had was so damp all I could do was lay a rubber floor matt to keep out the rising damp and add ventilation, running a dehumidifier was not an option it was that bad. Ventilation worked to a point, but not without rust corrosion issues on tools.

Dan

v8kid - 6/10/15 at 07:25 PM

I took a different route insulating the garage and installing underfloor heating fed from the house boiler. The underfloor heating has a very low return temperature increasing the boiler efficiency and back of fag packet sums gave running costs same as dehumidifier. been installed 15 years noe and stuff in garage does not rust plus its nice to lay on the floor under the car - not that I need to these days!

ash_hammond - 7/10/15 at 09:00 AM

Last winter i took notes of where the moisture, was gaining entry, Don't get me wrong it was not a lot. Mainly a few dripples under the concrete sections where it was not 100% flush with the base. I've now sealed those and they look fine so far. Also, there were also few hairline cracks in the wall sections. These have now been filled with cement and the whole garage has been painted with proper masonry paint.

I know this may have initially caused the condensation issue or not helped, but i have blocked up all the gaps between the roof and the sides to stop new moisture entering. I think the biggest culprit was for getting water into the garage was the guttering fall pipe. This just simply lets the water run towards the garage given the natural slope of the floor. This is now being caught by a water butt, so hopefully the major sources are dealt with.

I might try blasting the walls with a hose pipe to see if i have covered all bases.

I have ordered a desiccant style one, as I got a decent deal, so it should be more effective at lower temperatures. I like the ideal of putting it on a timer, this way i can control how much electric it uses.

Thanks for the help.
Ash

garyo - 7/10/15 at 12:26 PM

Probably not the low effort approach you want, but I dealt with my condensation issue last year by lowering the ground level all around the garage by 20cm, and extending the roof so that it has eaves to prevent the walls getting rain on them and so that the slab doesn't pick up water that can creep under the walls. The difference is like night and day.

phelix - 7/10/15 at 05:47 PM

A dehumidifier in a detached garage that isn't sealed will pretty much run 24/7.

The concept of making your whole garage into a carcoon is the right one. You need ventilation so that the temp and the humidity inside and out are roughly the same. That will prevent condensation.

v8kid - 7/10/15 at 09:45 PM

quote:
Originally posted by phelix
A dehumidifier in a detached garage that isn't sealed will pretty much run 24/7.

The concept of making your whole garage into a carcoon is the right one. You need ventilation so that the temp and the humidity inside and out are roughly the same. That will prevent condensation.


Sorry but I don't think so. You will get condensation when the relative humidity at the surface approaches 100%. The vapour pressure of water is fairly constant from inside to outside, if you remove water inside the vapour simply leaks in through the smallest of opening like a hole in a boat.So to reduce the relative humidity raise the surface temperature is heat the space. Heat will not leak like vapour as it is dependant on the average u value.

If you want a more elaborate description Google is your friend.

Cheers!

Peppapig101 - 8/1/16 at 10:47 AM

Hi Guys,

I have written a garage dehumidifier guide however I won't link to it as I don't want to be accused of spamming.

Very briefly;

The best type of dehumidifier to buy for 'outdoor' use is a desiccant dehumidifier.

Compressor dehumidifiers become fairly useless at temperatures below 10C or so (depending on the model of course). In fact compressor units improve in extraction the higher the temperature goes (well up to 35C anyway). Desiccant models increase their extraction the more the temperature falls (although the extraction rate is much more even than that of compressor units) and are able to operature in temperatures down to 1C.

Given that garages are often cold it therefore pays to get a desiccant dehumidifier.

Desiccants are also lighter and quiter than compressor models and due to lack of compressor parts don't give of any cfc gasses.

Look for dehumidifiers with a continuous drainage feature (CDF) so that you don't have to run out to the garage to empty the water tank. Also choose a gravity led CDF over an motorised one as in my opinion motorised ones tend to break more often (haven't done any scientific research on that though just general observation).

Another feature to look for is auto restart which enables the dehumidifier to restart in the correct setting after a power outage.

Anti-bacterial filters are great for those with allergies but a garage dehumidifier can do with a standard dust filter (make sure to clean regularly by washing it or vacuuming it).

The big issue that everyone talks about is running costs.

Well here is a great solution;

The best Meaco dehumidifiers have a feature called Control Logic which is basically an energy-saving feature.

You set the humidity level that you want the dehumidifier to run at (say 50%) and the dehumidifier operates until this humidiity level is reached.

The dehumidifier then automatically goes to sleep for half an hour before resuming fan only mode for 5 minutes to check the humidiity level.

If the humidity level stayed the same the dehumidifier goes to sleep for another half hour before testing the air again for 5 minutes.

If the humidiity level has risen then the dehumidifier automatically toggles into the most appropriate setting to tackle the humidiity level to bring it back down to the set level. The unit will then go to sleep again.

You can see that once the set humidiity level has been reached the unit will only operate in fan only mode for 10 minutes out of every hour.

Other makes of dehumidifier with these feature leave their units in fan only mode for the full hour so there are great cost benefits to be had by choosing a Meaco.

If you find my Ultimate Garage Dehumidifier Guide you will read that my choice of garage dehumidifier is the Meaco DD8L Junior which contains all the features mentioned above and more.

* I must state that I do not work for Meaco nor do I receive any compensation for advertising their units*

The above is only my personal opinion but I hope that some of you will find it helpful.

ash_hammond - 8/1/16 at 03:35 PM

Thanks PeppaPig.

I think I did pretty much exactly what you said and bought the same product.

I have the unit on a timer for a few hours per day and the drain runs out of the side of the garage on a downward slow. I'm also planning to slope the guttering in the opposite direction and this should also remove some water building up near the garage.

The garage now runs at 50% humidity and is fine for that i need. It should not break the bank to run either as its on the eco setting.

Cheers
Ash

Bluemoon - 8/1/16 at 06:36 PM

We also run a Meaco unit, use this in the caravan, running for 1.5 years now continuously no issues, humidity stat is a must.

Dan

Peppapig101 - 9/1/16 at 01:03 AM

quote:
Originally posted by ash_hammond
Thanks PeppaPig.

I think I did pretty much exactly what you said and bought the same product.

I have the unit on a timer for a few hours per day and the drain runs out of the side of the garage on a downward slow. I'm also planning to slope the guttering in the opposite direction and this should also remove some water building up near the garage.

The garage now runs at 50% humidity and is fine for that i need. It should not break the bank to run either as its on the eco setting.

Cheers
Ash


Hi Ash,

Good job in bringing the humidity down from 80%-90% to 50%.

I'll bet the garage is a much more comfortable place to be in now.

It's interesting that you have the unit on a timer....be carefull though!!

The Meaco DD8L Junior (and other desiccant dehumidifiers) need time to cool down as it were.

Proper procedure would be to press the 'off' button on the dehumidifier. If you do this you will notice that the fan will keep on spinning.

Only when the fan has stopped spinning should you unplug the unit from the wall socket not before.

What a timer does is it switches of the unit prematurely and could result in a much shorter life of the unit.

Bear in mind that Meaco's warranty does not cover damages of this type.

Granted the unit gets turned of prematurely in power failures but these (should) only occur once in a while. The timer turns the unit off prematurely on a daily basis.

Your best bet would just be to run it 24/7 and let the Control Logic energy-saving function do its work. This way the unit should only be in fan only mode for 10 minutes out of every hour with the occasional blast to bring the RH back down.

Hope that helps a little.