How to prevent mold using a humidistat

Asked on: September 1, 2011 by Roger H. – Fort Myers

What is your opinion on using a humidistat as a means of controlling mold?

That’s a great question, Roger, and one that many customers raised in response to my recent post on how to save energy and prevent mold when away from home.  No one wants mold inside their home, so finding ways to prevent it in Florida’s muggy climate is of interest to many of our customers.

Why it happens
Mold can begin to take root inside your home when the relative humidity (RH) exceeds about 68 percent. A humidistat, which directly controls indoor relative humidity, is one way to prevent mold. Dehumidifiers and some central air conditioners have a built-in humidistat that tells the system to dehumidify the air to a desired point.

Setting your humidistat or dehumidifier
Set the controls of your humidistats and dehumidifiers to 58 percent RH to maintain acceptable humidity, since some humidistat sensors are inaccurate by as many as 10 percentage points.

Better ways to control mold
If you don’t have a humidistat, another way to control mold when you’re away is by programming the A/C to run at 72 degrees for just two hours before sunrise and at 88 degrees the rest of the day.

But what if you don’t have a programmable thermostat? In that case, set the A/C at 77 degrees for condos or apartments and 80 degrees for single family homes and townhouses. (Remember to have the fan switch set to auto.)  Thermostats in condos and apartments should be set at 77 degrees to make the air conditioner run enough to provide significant dehumidification.

If you live in Florida seasonally or leave for extended periods of time, the most economical way to prevent mold in a vacant home is by using stand-alone dehumidifiers instead of A/C. Use one for every 1,000 square feet.

We also recommend repairing any leaks around doors, windows and in your A/C ductwork, which will help minimize the amount of moisture getting into your home.

Visit us online at http://www.iaq-usa.com (Air Duct Aseptics)

(see the original blog at http://www.fplblog.com/?p=734)


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