Adding an exhaust fan to your garage can keep the summer temperature down, especially in areas that aren’t insulated or well vented. My garage has a shed that’s separate from the garage. I designed it this way to have a place for all the things that are for yard maintenance and some storage. This area is not insulated and gets hot during the summer from sun heating and ambient temperatures.
The way the shed roof connects to the garage roof prevents convection cooling through the garage ridge vent so heat just hangs in the high part of the shed’s roof. It seemed like the best way of dealing with it was to install a powered exhaust vent fan.
The Benefits of a Powered Exhaust Fan in a Shed
Garages and sheds often suffer from one major drawback: poor ventilation. A powered exhaust fan can be a money saving addition, offering a range of benefits that protect both the structure and its contents while also making the space more usable and comfortable. Here’s a few reasons why an exhaust fan can benefit your garage or shed.
1. Improved Air Quality
Garages and sheds tend to accumulate dust, fumes, and odors. A powered exhaust fan actively pulls stale air out and brings in fresh air, reducing the buildup of harmful particles and fumes. This creates a healthier environment, particularly important if you spend long periods working inside.
2. Temperature Regulation
In warmer months, sheds can turn into ovens. The sun heats the walls and roof, causing internal temperatures to soar—especially in metal or dark-colored sheds. A powered exhaust fan helps to vent out the hot air, allowing cooler air to enter. This not only makes the shed more comfortable but also protects heat-sensitive items like paints, batteries, or gardening supplies from damage.
In my case this was my biggest problem. On a summer day even by 10 am I could see temperatures 20-30 degrees warmer than outside. The fan drastically reduced the temperature especially if the fan started off early to keep the temperature down.
3. Moisture and Mold Prevention
Moisture buildup is a common issue in garages and sheds, particularly in areas with high humidity or poor air circulation. This can lead to condensation, mold, and mildew damaging tools, rusting metal, and promoting wood rot. A powered exhaust fan helps maintain proper airflow, keeping humidity levels in check and reducing the risk of moisture-related problems.
4. Increased Longevity of Stored Items
From tools and electronics to gardening chemicals and seeds, many items stored in garages and sheds are vulnerable to damage from heat, humidity, and poor air quality. By ensuring consistent ventilation, a powered exhaust fan helps protect these items, potentially saving hundreds of dollars in replacements or repairs.
5. Enhanced Usability and Comfort
If you use your garage or shed as a workshop or hobby space, comfort matters. High temperatures, unpleasant smells, and stuffy air can make it unbearable to spend time there. A powered exhaust fan makes the environment far more pleasant, turning a hot, stale shed into a productive space where you can work year-round.
6. Energy Efficiency
Compared to the cost of air conditioning or frequent repairs due to mold or heat damage, powered exhaust fans are relatively inexpensive to install and operate. Many modern fans are energy-efficient and can be paired with thermostats or humidity sensors to run only when needed, minimizing power usage while maximizing benefit.
7. Fire Safety
Garages and sheds that house flammable materials such as gasoline, solvents, or propane benefit greatly from improved airflow. It might be difficult to find a garage or shed that doesn’t have flammable materials. A powered exhaust fan reduces the buildup of flammable vapors, lowering the risk of accidental combustion and improving overall safety.
Selecting an Exhaust Fan
There are many options and capacities when it comes to powered exhaust fans. Below are some key factors to consider when selecting an exhaust fan.
1. Shed Size and Fan Capacity (CFM Rating)
Exhaust fans are rated in CFM (cubic feet per minute), which measures how much air the fan can move. In general recommendations for the proper size fans are.
- For basic ventilation, aim for 1 CFM per square foot of floor space.
- For garages or sheds with heat-producing equipment, you may need 2–3 CFM per square foot.
2. Power Source
Most powered exhaust fans require electricity but how you get that electricity can vary.
- AC-powered fans: Best for sheds with existing electrical wiring.
- Solar-powered fans: Ideal for off-grid or remote sheds.
- Battery-operated fans: A temporary or backup solution, usually with lower airflow.
3. Installation Type
Fans can be mounted in different locations depending on your shed’s design:
- Wall-mounted: Common and relatively easy to install; best for pulling air directly outside.
- Roof-mounted: Good for removing rising hot air, but installation is more involved.
- Gable-mounted: Fits into the triangular wall section of many pitched-roof sheds.
4. Noise Level
Check the decibel (dB) rating if you’ll be working in the shed often. Some fans can be quite noisy, especially high-powered models. Look for quieter fans (under 60 dB) if comfort is important.
5. Weather Protection and Durability
Outdoor conditions can be harsh. Choose a fan with:
- A weatherproof housing (especially for roof or wall installations).
- A backdraft damper or shutter to prevent rain and pests from entering.
- A metal or UV-resistant plastic construction for long life.
6. Thermostats, Humidistats, and Timers
Some fans come with built-in controls:
- Thermostats: Turn the fan on automatically when temperatures rise.
- Humidistats: Ideal for humid climates; activate based on moisture levels.
- Timers: Allow for manual control of ventilation cycles.
What was Selected?
I had a few parameters I needed to satisfy physical size, volume and damper style. Since this was going to require a hole to be cut in the outside wall and the garage is a pole building with steel outer walls that have ribs. I wanted to not have to cut out a rib and stay within the flat area between ribs, about 8 inches. The fan measured in at approximately 6 inches which would fit nicely.
I also wanted the fan to have some sort of damper that would auto close to prevent a backdraft and keep out pests. This fan has a spring loaded damper that opens and closes by air moving across it.
The shed area of my garage is small so the CFM of this fan will do the job. Fans that are similar sized that moved more air generate more noise since the fan has to move faster. I was satisfied with the 308 CFM rating of this fan.
Installation
Cutting a hole in a wall of a brand new garage is a bit unnerving but I dove right in. I picked a high spot on the peak of the side wall and marked the cut out area using the fan as a template. A small hole was drilled in the wall to get started and using an air nibbler the large hole was cut out.
I created a mount for the fan using a piece of plywood. This mounted the fan away from the wall allowing the duct to reach the outer part of the wall. The exterior vent required a bit of modification before it was mounted. Duct tape was used to seal up the connection of the duct to the exterior vent. The exterior vent was caulked to prevent water from entering.
Finally it was a matter of getting power to the fan. This particular model used a plug with a switch and luckily there is an outlet within reach of the cord. I used one of the Kasa Smart Plugs to program the fan to turn on and off at a set time each day. This fan makes a big difference in both temperature and odor.
Conclusion
Adding a powered exhaust fan to your shed is a simple upgrade with outsized benefits. From enhancing comfort and usability to preserving your tools and preventing mold, the fan pays for itself in both convenience and protection. Whether you’re a weekend gardener, a DIY enthusiast, or just want to extend the life of your shed, investing in a powered exhaust fan is a smart, cost-effective decision.
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