People are so confused about de-humidistats and I don't blame them. Everyone seems to tell a new homeowner what to set them at..45%..50%..55%..60%. Which one is correct?
Well, what is a de-humidstat? It is an energy saver. It will only have your air conditioning system come on when it hits the percentage the de-humidistat is set at. Humidity is all we care about so we can keep mildew and mold out of our homes. Many owners set their de-humidstat at 60 or 65 percent thinking that will save them a lot of money in energy costs. That is partly true. It doesn't save a lot of money, but it saves some. However, according to the University of Florida's Professor Lee, the ideal setting is between 30-50%. I attended a seminar recently given by Dave Borowski, Vice President of Wiegold Air Conditioning and he said 50% was ideal.
At 60%, mold and mildew can have a open door to your home. Many owners think setting their AC at 80 degrees will keep their home free of mold and mildew. But if their de-humidistat is set at 60%, the AC will not come on until it senses 60% humidity in the home. These homes can get up to 88 degrees! When the AC finally kicks on, it is already warm and moist in the house. This is a disaster just waiting to happen. You could set the AC at 60 degrees at the AC will still not come on until the humidity is 60%.
Most de-humistats are not digital and are not very accurate. These dial types should be set a little less than your optimum setting to make up for the inaccuracy. For example, it you want the humidity no higher than 55%, it should be dialed to 50%. Remember, even if it 100 degrees inside your home, the AC will only come on when it reaches that humidity setting.
A home should have air flow to keep moisture down. If the AC doesn't come on, that's not going to happen. One of the things we do during our inspections is leave all closet doors open and all doors under sinks open. This air flow is critical for areas with water pipes. Another thing we do is we carry a weather station with us and take it into every house to measure the humidity. This is reported on their Inspection Report, along with the temperature in their home.
So what do we recommend? We recommend a de-humidistat setting of 50 and the AC set at 82 degrees. When in residence, the de-humidistat should be set to 'On'. Not to any percentage..just On.
Why take chances with your home? Mold and mildew is harmful to health and very expensive to eradicate. The cost of having your AC come on at 50% versus 60% is very small..especially compared to mold and mildew removal.