An energy-efficient home in a hot, humid climate should have a tight envelope, thick insulation, energy-efficient appliances, and low-solar-gain windows. If you include these features in a new home, your air conditioner won’t run as often as your neighbor’s. That’s good.
But there is a downside to the fact that your air conditioner runs rarely: during the hours that your house has no active cooling, it also has no active dehumidification. As a result, your indoor relative humidity is going to rise.
This problem is fairly well understood. In hot, humid climates, a run-of-the-mill house has better control of indoor humidity levels than an energy-efficient house. If you live in an energy-efficient house in a humid location like the Southeastern U.S., you may need a dehumidifier.
Why do some homes need supplemental dehumidification?
To figure out whether you need a dehumidifier, it’s worth considering the factors that raise indoor relative humidity levels. Some of these factors apply to all climates: indoor humidity levels rise when there are many people or pets living in the house; when residents take many showers; when there are lots of houseplants; when residents cook frequently; and when someone mops the floor.
Other factors — some of which are counterintuitive — apply particularly to houses in hot, humid climates:
A study of homes in Houston