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The first rusted wrench is how most people find this site.
The house felt fine. The thermostat said 74. The garage ate a toolbox in one summer. That is not a mystery. An attached Florida garage is a metal box with a west wall, no return air, and a door that leaks. House AC does not condition it. Treating it like a closet with a $20 hanging bag is how the rust starts.
What the garage is actually doing
Summer garage air in Volusia and the rest of the peninsula often sits 75–85% relative humidity (RH) with ambient temperatures in the 90s. Cardboard softens. Fasteners bloom. The shared wall pushes moisture toward the laundry. A hygrometer on the living-room bookcase will not see any of that.
Read three numbers, not one:
- Living space (target about 45–55% relative humidity (RH))
- Garage wall, not on the dehumidifier exhaust
- Outdoor shade
If the garage is 15–20 points above the house, it is its own zone. Guide: Florida garage dehumidifier. Size from the pint chart, not from the bedroom aisle.
What people buy first — and why it fails
A 35-pint cube. A bedroom unit with a bucket. A hanging absorber on a hook by the golf clubs.
Those fail the same three ways: not enough pints, no high-temp rating, no continuous drain. You will empty a bucket. Then you will stop. The rust will not.
Santa Fe Compact70 is the USA-built garage/crawl pick on this site. Hose downhill. Add a pump if the drain is uphill. Confirm with a logger, not with “it feels drier.”
The morning check after you notice rust
Put a hygrometer on an interior garage wall for a week. If it holds above 60% with the door closed, you have a machine problem, not a “I’ll crack the door” problem. Cracking the door in Florida is how you import more wet air.
Do not set the house AC to 68°F to “help the garage.” See AC vs dehumidifier.
If rain blew under the door, pin the first two feet of drywall on the shared wall: moisture meter after a leak.
Run this, in order
- Measure garage relative humidity (RH) for seven days.
- Size 50–70+ pints, high-temp, continuous drain.
- Drain to a downhill hose or a pump. Never a bucket as the plan.
- Keep the house door closed. The garage is not a return-air closet.
Reed Lang writes these notes from coastal Florida. Specs and rooms, not a lab. Rust is a humidity reading you can see. Believe it.