Here are some rusty metal registers. It happens and it happens quite a lot.
Q: So why does this happen?
A: Excess humidity! Humid settings can cause rust quite easily. When you are not running your A/C all the time, your home gets extra humid, but when you turn it back on, the registers along with your duct work get cold which condenses the moisture on the surface and in turn, will cause your metal registers to rust. Another humidity issue is when your attic gets hot and that hot air will meet with your cold metal registers. Also, humid cities are a great cause for constant moisture which induces rust on your registers. Lastly, of course, restroom grilles tend to be the rustiest and moldiest registers due to the moisture in the air.
Q: What can be done to prevent mold growth and rust in your vents?
A:
1) Level your condenser.
2) Use resin vent covers.
We hear a majority of complaints from the very humid prone cities looking for an alternative to their rusty metal registers. Here is a list of the overall most humid cities here in the U.S:
New Orleans, Jacksonville, Houston, Orlando, Tampa, San Francisco, Seattle, Miami, Portland, Rochester, Raleigh, Nashville, Los Angeles, Birmingham, Milwaukee, Buffalo, Cleveland.
Beach homes are also very susceptible to constant rust causing you to change your vent covers every couple years!