Best dehumidifier models for cold garages

by Maxine
(MN)

We have two large garages at our lake home in northern MN...neither has a floor drain

The detached garage floor is painted and always cold inside. The attached garage floor is epoxy finished and, particularly when it's humid outside, tends to bead up with moisture, literally that of a slip and slide, and has actually caused mold to grow on the lower parts of the wall. We're only there on the weekends.

Is there a dehumidifier that is

1) safe to leave running,

2) can sense when to turn on and off,

3) can drain outdoors,

4) and where can we buy the right unit ???

Thank you.




Answer

Hello Maxine and thank you for your question.

There are four numbered issues in your question plus two more that arise from the information you have given. The additional issues are:

  • The ambient temperature within each garage


  • The size of each garage


Temperature

Northern Minnesota has cold winters and cool summers but if your lake home is close to Lake Superior the summer is cooler still while winters are a little less harsh.

You describe the detached garage as "always cold inside". If the temperature inside one or both of your garages is below 65°F for extended periods (which it almost certainly is) a portable unit, such as a Frigidaire or Danby, will be largely ineffective. There is a second reason for ruling out portable models to which I'll return a little later.

This means that we are talking about industrial quality dehumidifiers, either basement/crawl space models or small commercial units. I'm sorry to say that this type is considerably more expensive.

The choice of model will depend on just how cold each garage is. At around 55°F or above any basement model will be fine. From 45-55°F most crawl space units will manage, but check out the individual specifications to pick the right one. At lower temperatures, down to 33°F, you will need a unit with a more effective defrost function, usually described as "hot gas defrost" or "hot gas bypass".

Size

Dehumidifiers are often described as being suitable for "x square feet" of space. These descriptions are useful if the enclosure has a ceiling height of around 8 feet but if the ceiling is significantly higher allowance needs to be made for the additional air volume. If the ceiling is 12 feet (50% higher) for example, you will need to increase the actual floor area by the same 50% to arrive at a notional floor area and select a unit that is powerful enough for the larger (notional) area. I'm sorry if I'm stating the obvious but I like to be thorough :).

If the detached garage is close enough to the attached garage it may be possible to use a single unit located in one garage to control humidity in both by using ducting. I cannot comment further without more information but I will suggest a source of advice on this towards the end of this answer.

Returning to your numbered issues I will take each in turn.

1.) Is there a unit that is safe to leave running?

The least safe type is the standard portable. These units are relatively inexpensive but the build quality reflects the price. Fires started by dehumidifiers occur every week in the USA and this is, by far, the greatest risk.

Minimizing this risk depends on paying scrupulous attention to the manual, ensuring free flow of air around the appliance and cleaning or replacing the air filter at the recommended intervals.

I would not recommend a portable model for use in your circumstances on this ground alone. Taken together with your need for low temperature operating capability I would rule out this type entirely.

Purpose built basement and crawl space units are much safer. The build quality is an order of magnitude better and they are designed to operate unattended for long periods, particularly in crawl spaces. Attention to location and maintenance is just as important.

Commercial models are at least as good as basement/crawl space units and many have "hot gas defrost". They are robust and reliable and some are designed for use in remote locations, such as pumping stations, where they may remain unattended for considerable periods. Location and maintenance remain important.

2.) Can it sense when to turn on and off?

All basement/crawl space models and many, but not all, commercial units have an adjustable humidistat. This device senses the relative humidity and switches the compressor on and off to maintain the level you select. 50% and below will stop the mold growth, 40% will largely prevent corrosion of metal tools, cars and other objects.

3.) Can it drain outdoors?

All basement and commercial models are configured for continuous drainage, usually by gravity feed. To propel the water to the outside you will almost certainly need a condensate pump. Some commercial models have an internal condensate pump but I would not make this a major issue in coming to a decision. Separate condensate pumps work just as well and, if they fail, can be more easily replaced than an internal pump.

4.) Where can we buy the right unit?

I would suggest two suppliers in particular, sylvane.com and dehumidifierexperts.com. Let me say before continuing that I have no commercial relationship with dehumidifierexperts.com. I have an indirect commercial relationship with sylvane.com as I am an affiliate partner of amazon.com and have links on my site to amazon.com which lead to products sold on behalf of sylvane.com. I only benefit from this relationship if a visitor to my site clicks on one of these links and purchases through amazon.com. I am stating this to make it clear that my advice to you is not influenced in any way by the prospect of financial gain. To be plain; if you contact sylvane.com directly and buy from them I don't get a cent! :)

Both of these retailers have a sound reputation and sell the types of dehumidifiers I have been talking about. For basement/crawl space models I would recommend the Santa Fe brand (made in the USA); for commercial models Ebac (made in the UK) is hard to beat.

My suggestion is that you have a chat with a sales advisor at Sylvane. You may call this number - 1 (800) 934-9194 - 24 hours a day, 7 days a week.

I have the highest regard for this company and I am confident that an advisor will be able to help you. There is so much information that I don't have that it is difficult for me to make a specific recommendation of one or two models that would precisely meet your needs.

What I hope I have done is to add to you understanding of the type of dehumidifier(s) you need, the issues you need to consider and the questions you may need to ask and answer to get the best advice during a consultation with an advisor from Sylvane or any other company.

Tom (Webmaster)

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