I frequently notice standing water in my garage when I pull in during a rainstorm that will sit for a couple of days. The garage also suffers from condensation on the floor at times. I have been wondering if I need to install a dehumidifier in my garage to prevent mold and structural damage.
If you are facing a similar decision, I have done a lot of research on putting a dehumidifier in the garage and this is what I’ve learned.
I want to share with exactly what I’ve learned about the importance of keeping humidity levels in a garage under control, how to choose and size a dehumidifier for a garage, and how you make your dehumidifier essentially maintenance-free.
Reasons For Moisture In a Garage
Garages, by design, usually lack ventilation. Aside from the large garage doors, this part of the house is essentially a cave with no way for air to flow freely through it.
This can result in higher humidity levels for long periods of time depending on weather conditions. Without a way for the humidity to escape, moisture can build up on floors and walls. Over time, this can have devastating results. The Department of Energy cites proper ventilation as a key component to moisture control.
There are three primary ways that this problem is usually identified; condensation on the garage floor, standing water on the garage floor, or in later stages, evidence of mold of wood rot on the walls and ceiling.
Ideally, we want to address these issues early and prevent damage to the structural integrity of your home.
Why Does My Garage Floor Sweat?
A garage floor “sweating” is usually the result of moisture in the air settling on the cold garage floor. In a well-ventilated area, fresh air is continuously circulating but in a garage, the warm moisture makes contact with the cool garage floor and condensation droplets appear.
It is possible that a vapor barrier was not properly installed under the garage slab when it was constructed. If that was the case, moisture can actually be coming up through the slab.
Note: There is a great deal of debate over whether or not the lack of a vapor barrier contributes to condensation appearing on the surface of a garage slab or whether or not condensation can seep from the ground. Regardless of the reasoning behind it, I can only say that from my experience, the lack of a vapor barrier does seem to play a factor. I offer the below as an example.
A family member has an old shop that did not have a vapor barrier installed under the original slab. A couple of years ago, she expanded the garage, installing more concrete but this time adding a vapor barrier first. This picture tells the story:
There’s not much you can do about this with a slab that is already poured though, so I prefer to focus on what we can do to prevent you from having problems with humidity in your garage.
Standing Water In Garage
Condensation is one thing, but some homeowners like myself deal with a much more frustrating and concerning issue and that is standing water in the garage. I don’t mean from a flood. Standing water is often the result of driving into your garage during a rainstorm. As your vehicle sits, rainwater and moisture fall off of it onto the garage floor.
If you are fortunate enough to have a drain in your garage with the floor sloping to facilitate drainage, then you are in a good position here. Unfortunately, my garage does not have a drain. So when water accumulates on the garage floor, it sits there.
Over time, this stands to do serious damage to the structure of my home. If you have a similar situation, you are going to want to address this!
How To Identify Mold Issues In A Garage
One of the first things you may notice is not what you see but what you smell. If your garage consistently has a musky, stale odor, you likely have excessive moisture levels and potential mold issues.
Peeling, deteriorating paint is often one of the first signs of high moisture rates in a garage with sheetrock walls. If you do have sheetrock in your garage, you want to be proactive in preventing moisture and mold. Not only will the moisture itself degrade the sheetrock but studies like this one have identified very dangerous forms of mold that grow on moist sheetrock.
If you have OSB siding on the inside of your garage as I do, then look along the corners (especially the lower corners for evidence of deterioration and “peeling”, where the layers of wood are no longer tightly adhered to each other.
See OSB Versus Sheetrock In A Garage: Pro, Cons, And Fire Code
Mold in your garage is more than just an eye sore, it is evidence of physical damage occurring to the structure of your home. As the American Society of Home Inspectors explains, mold also reduces your home’s value.
If you actually see mold on the surfaces of your garage walls or ceiling, you need to take action now. This report gives an overview of mold on walls and specific steps you should take to get rid of it. However, we still have to deal with the cause itself and that is the humidity level in your garage.
If you have any questions about whether or not the moisture levels in your garage are too high and may be causing problems, a moisture meter is an inexpensive and simple way to accurately gauge the moisture levels in a structure. You simple press the pins against the wall or stud and the meter will show the moisture level. My friends and I used these extensively while helping families renovate their flooded houses following Hurricane Harvey.
Why A Garage Needs A Dehumidifier
We’ve already addressed the reasons for condensation on the floor of your garage and the potential impact on the structural integrity of your home resulting from mold and wood rot. Now it’s time to address the problem.
A dehumidifier is the most direct way to deal with humidity in a garage and prevent condensation and mold. It will keep moisture levels in check and reduce the moisture that mold spores require for growth as well as preventing tools from rusting and structural wood rot.
How Does A Dehumidifier Work?
A dehumidifier works by pulling air through it and separating the moisture from the air. It then exhausts dehumidified air back into the garage. Over time, this reduces the overall moisture levels in the garage.
What Features Should I Look For In A Dehumidifier For My Garage?
You will want to ensure that you purchase a dehumidifier with an automatic mode. This will allow the device to automatically turn on when moisture levels are too high and shut itself off when the levels return to normal. Manually managing this process would be very difficult as it would require constant checking of moisture levels and wasted energy use if you failed to turn the device off when levels returned to normal.
I also recommend purchasing a model that allows you to connect a discharge hose directly to the back of it. By doing this, you can place the dehumidifier against an external wall, drill a hole through the wall for the hose to discharge through, and automatically dispose of water without having to manually empty the tank.
How Much Electricity Does A Dehumidifier Use?
According to this report, the average energy consumption of a dehumidifier is 459 watts when actively running and between 0-2 watts when in automatic standby mode. The impact on your electric bill will depend on several factors including, the model of dehumidifier you select, how often and low long it needs to run to keep your garage’s moisture levels in check, and your electric provider’s cost per kWh charge.
I strongly recommend an Energy Star model as this will be the most energy efficient approach, using 30% less electricity
What Size Dehumidifier For My Garage?
It’s also important to select the proper size dehumidifier for your garage. Sizing too small will result in ineffective moisture control. Oversizing, on the other hand, could have the side effect of the system turning on and off more frequently than necessary.
As for square footage, the average two-car garage is around 700 square foot, maybe a little less. Based on this information, a 50-pint dehumidifier is a common size for most garages that are defined in the chart as moderately damp.
Recommended Dehumidifier Models
I’m going to share with you two different options. One meets all of the criteria that we’ve outlined and is the one I purchased for use in my garage. The other is a less expensive model that meets most of the criteria. I purchased two of these for my sister to use in her house after it was flooded by Hurricane Harvey.
Best Option – Frigidaire 50 Pint Model FFAD5033R1
This Frigidaire 50 Pint Dehumidifier checks all the boxes. It is Energy Star Certified, has the ability to attach a drain hose for continuous drainage without the hassle of emptying the tank, and can be set to automatically turn on and off as needed to ensure the moisture level in your garage is controlled.
If you don’t have the ability to run a drainage hose through an exterior wall, the unit has an automatic shut off that will activate when the tank is full.
Understand this. There are countless websites with “dehumidifier reviews” where they go over the specs for systems. I own this unit! I have it in my garage right now! What I am sharing with you is not theoretical comparisons of specs from manufacturer websites. I am a product owner and user. What I am sharing with you is from
Good Option – hOmeLabs 50 Pint Dehumidifier Model HME020006N
I purchased two of these dehumidifiers (the 70-pint versions of the same model) around December 2017 following Hurricane Harvey. My sister’s home flooded along with hundreds of others. Furniture, appliances, and sheetrock were destroyed in these homes. Once those were removed, we needed to eliminate and prevent moisture buildup in the walls and ceilings.
We set them up with one on a chair draining into the bathtub and another sitting on the kitchen counter draining into the sink. We did this so that we could leave them for days or weeks at a time and not have to worry about them shutting off due to the tanks being full.
I am happy to report that both units worked flawlessly and in fact are still in operation today at that same house due to a standstill with the insurance company. They have never given us a single issue and continuously cycle on and off as needed to keep moisture levels in check.
Why Is the Frigidaire the “Best” Option
Although I have used both of these units and found them both to function flawlessly, Frigidaire gets a brand reputation edge over the hOmeLabs unit. But I would recommend either of these units. I’ve been very pleased with the performance of each. I favor the Frigidaire unit simply because there is more online documentation available in the event that I do run into issues and need to figure out how to repair something. Additionally, Frigidaire repair parts and service is widely available across the country.
Ultimately, you will be well served by either of these units. I cannot recommend any other brands as I have not used them. These, however, have been rock-solid performers.
Regardless of which unit you purchase, I encourage you to address the condensation issue in your garage soon. Rust, mold, and wood rot can become expensive consequences of procrastination. You could face serious damage to your home and it’s value. By installing a dehumidifier you can easily control the moisture in your garage and protect your home investment.
Below are links to each of the dehumidifiers on Amazon so that you can check current prices.
Frigidaire 50-Pint Dehumidifier with Effortless Humidity Control
Take control of high electricity costs by learning which energy efficient home upgrades are worth the investment. Click here to read Energy Efficient Home Upgrades – Which Ones Are Worth It?
As a homeowner, I am constantly experimenting with making the structure of my house more energy-efficient, eliminating pests, and taking on DIY home improvement projects. Over the past two decades, my family has rehabbed houses and contracted new home builds and I’ve learned a lot along the way. I share my hard-learned lessons so that you can save time and money by not repeating my mistakes.
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