The Ideal Garage Humidity Level (And How to Get It!)

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Struggling with humidity in your garage? You’re not the only one. In this article, we’ll cover the ideal humidity level to have in your garage to help prevent rust on your tools and keep you comfortable while you’re working.

I’ve been fighting high humidity in my own Florida garage, so I’ll show you why garage humidity control matters and how to do it effectively. Through trial and error, I’ve learned what works. 

Whether you’re a DIY enthusiast, a car lover, or just looking to protect your garage, this article is for you.

Key Takeaways
– Try to maintain garage humidity between 30-50%. 
– Use a hygrometer to accurately measure relative humidity.
– Poor insulation, water leaks, environmental factors, and even the type of garage floor contribute to increased humidity.


What Causes High Garage Humidity Levels?

At a basic level, the relative humidity is the amount of water vapor in the air. If there’s 100% humidity, the air can’t hold any additional moisture and

you’ll see it as fog or condensation. 

That makes sense outdoors, but what causes high humidity levels inside your garage? 

Ideal garage humidity levels range between 30% and 50%

Here’s a breakdown of the common reasons:

  • Insulation Issues: Insulation and weatherstripping help keep unwanted moisture out. Without them, moisture from the outside air permeates your garage, leading to temperature changes. This results in condensation and increased humidity levels.
  • Water Entry and Leaks: Leaks in your garage door, faulty plumbing, damaged roofs, foundation cracks, or snow-melt off your car can lead to accumulated water in your garage. As it evaporates, the amount of water vapor in the air increases.
  • Stored Items: Stacked firewood or cardboard boxes are more than just clutter. Some materials act like sponges, absorbing moisture from the air or releasing it as they dry out. This can significantly increase the humidity level in your garage.
  • Appliances: Poorly vented washers & dryers in your garage will add additional moisture to the air.
  • Environmental Factors: Humid climates, recent rainfall, or stagnant air can all elevate your garage’s humidity. Here in Central Florida, it’s common to see relative humidity levels between 70% and 90% during the summer.
  • Type of Garage Floor: Unsealed or poorly sealed concrete floors can trap moisture. A clogged floor drain can prevent proper water drainage, contributing to the overall humidity. 

What is the Ideal Garage Humidity Level?

Try to maintain garage humidity levels between 30 – 50%. This range prevents condensation on metal surfaces and makes it comfortable for people. Humidity levels above 50% risk mold growth, possibly damaging tools, electronics, and other items stored in your garage.


How Does Humidity Affect Different Materials?

Metal Tools

Water and metal don’t mix. Got it. We’ve all seen rusty steel tools before, so this shouldn’t be a surprise. 

Moisture in the air causes oxidation, a chemical reaction where metal, oxygen, and water create a brownish-orange flaking. For steel and iron, this is commonly called ‘rusting.’

Did you know that stainless steel can rust?

I didn’t.

Stainless steel isn’t pure steel but a mixture of several metals. Some, like Chromium, help make the resulting metal resistant to rust.

It’s not entirely rust-proof, however.

Cougartron, which is a US-based company that makes stainless steel coatings, sets the record straight:

The reality is that stainless steel does rust. The word “stain-less” does not imply free from stain or “stain-impossible.” It simply means that the alloy stains less.

Given the suitable set of circumstances, any metal can rust or corrode. It’s essential to keep moisture and humidity under control to prevent your tools from rusting in your garage.

Electronics 

For simplicity’s sake, we’ll define “electronics” as anything with circuitry or wiring.

This includes large items like your garage TV, a sound system or speakers that you store in your garage, or any exercise equipment you store or use there.

It also includes any power tools or your classic car sitting under a car cover in your garage.

The challenge is that even electronics designed to be water-resistant are still exposed to the air. If humid air can get in, it can bring water vapor.

Water-resistant and water-vapor-resistant are NOT the same things. 

When water vapor in the air cools down, it changes into a liquid. This is how we get dew on the grass in the morning or frost in the winter.

Semikron, one of the world’s largest semiconductor manufacturers, released a study on the effects of humidity and condensation on electronics back in 2016.

They found that condensation poses a severe threat to electronics because the water molecules are attracted to the electrical circuits inside the devices.

As they put it: “the resulting failures from these effects are usually catastrophic, and it can be very difficult to identify humidity as the root cause.”

Condensation vs. Lubrication

We’ve all heard the saying that oil and water don’t mix. That also applies to any lubricants you may be using in your garage.

One key element in maintaining our tools and lawnmowers is lubricating moving parts with oil.

When water vapor (humid air) condenses and turns into liquid water, it eventually starts to break down any oils it comes into contact with.

We all know how destructive it can be when sand or metal shavings get into your gearbox.

Consider what J. C. Fitch and Simeon Jaggernauth said in their paper on the effects of moisture on machinery:

“Moisture is generally referred to as a chemical contaminant when suspended in lubricating oils. Its destructive effects in bearing applications can reach or exceed that of particle contamination.”

According to their study, moisture can be as damaging – or MORE DAMAGING – than any physical particle rattling around in your gearbox.


How to Measure Humidity in Your Garage

In this section, we’ll cover some easy ways to monitor the humidity level in your garage. Remember, the ideal humidity level for a garage is between 30% and 50%. 

The most reliable tool for this task is a hygrometer, which is specifically designed to measure the relative humidity in the air. 

In my garage, I use a digital hygrometer\thermometer that records minimum and maximum humidity levels over a specific period. 

High humidity readings in garages can damage items

If you don’t have a hygrometer, you can check for moisture or ice at the bottom of garage windows on cold days. This indicates that warm, moist air inside is hitting the cold window surface and condensing. 

Similarly, condensation on windows or glass panes is a telltale sign of high moisture levels in the garage, suggesting the air is saturated with water vapor.

Humidity levels can fluctuate with seasonal changes, weather conditions, and different activities. Consistently monitoring your garage humidity levels can help prevent issues later on. 


Garage Humidity Control Tips

Once you’ve identified a humidity problem in your garage, there are some steps you can take to try to fix it. 

Here are some quick tips:

  • Add Insulation & Weatherstripping: Outdoor air coming in through gaps around the door and walls significantly contributes to high humidity. Add insulation on your garage door and walls rated at least R-12 for thermal resistance. Add weatherstripping around the garage door to seal gaps and ensure an airtight barrier.
  • Improving Ventilation: Use fans, vents, or windows to introduce fresh air and expel moist air. Fans near windows create a cross breeze that dries out the space. Installing vents in walls or ceilings aids in natural air circulation and moisture control.
  • Fixing Leaks: Use concrete patching caulk or mortar-type cement for repairing garage floor or wall cracks. Fix leaking faucets or pipes to prevent moisture accumulation.
  • Dehumidification: If you still have high humidity in your garage, consider adding a dehumidifier. Choose between home or commercial-grade models based on your garage size and humidity levels. 
  • Seal Concrete Garage Floors: Apply a concrete seal to the floor to block moisture absorption. Choose between penetrating seals for deeper protection or topical seals for surface-level barriers.
  • Temporary Solutions: For mild or occasional humidity issues, simple solutions like airing out the garage with a cracked door and fan or using moisture absorbers like silica gel or other desiccants can be effective.

Wrapping It Up

Maintaining your garage’s humidity level is crucial for protecting your tools, electronics, and even the garage structure itself. Aim for a 30-50% relative humidity level. This range helps prevent rust on metal, ward off mold growth, and keep you from sweating while working in your garage. 

Living in Central Florida, I’ve learned some tips to keep my garage humidity levels under control. 

Using a hygrometer is the best way to keep track of humidity levels. You can also look for signs like condensation on windows, which indicate high moisture levels.

Key factors contributing to humidity include poor insulation, water leaks, and even the type of flooring in your garage. Some simple fixes for garage humidity control include adding insulation and weatherstripping, improving ventilation, and fixing leaks. Consider using a dehumidifier or sealing your concrete garage floor for more stubborn humidity issues.

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Tim Wells

Tim Wells, the founder of Garage Transformed, has been featured in dozens of home renovation publications, including BobVila.com, Home Stratosphere, House Digest, Livingetc, and SFGate. Since 2018, he has helped over two million people transform their everyday garages into something they can be proud of. He lives in Central Florida with his wife and bulldog.

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