Handyman: Right A/C unit, lower humidity equals comfort

Glenn Haege
Special to The Detroit News

The outside air gets hot and humid, you crank up the A/C and…your house still doesn’t feel cool. So is there something wrong with your air conditioner?

That is a scenario I discuss with people all the time. Obviously, getting your air conditioning unit tuned up regularly by a company with North American Technician Excellence ( certified technicians is recommended. But even if your A/C unit is working properly, controlling your indoor humidity is the way to indoor comfort, and to do that your air conditioning needs to be able to “condition” the air. That means your A/C should run frequently to do its work by first dehumidifying the air before it reduces the air temperature. Therefore if you keep turning your air conditioning on and off, or you set the indoor temperature too high, the A/C won’t have a chance to do its job and the humidity will build up in your home, making you feel uncomfortable.

It may seem like turning the air completely off when you aren’t home and then turning it back on when you return would save energy. In fact, energy costs peak at startup, so keeping a comfortable temperature range won’t cost you much more. Instead, when leaving home for more than five hours, raise the thermostat setting an additional 5 or 10 degrees. This will make the air conditioner’s job much easier when you turn it back down when you arrive.

“If a unit is oversized, it will cool the home off too quickly but won’t run very long, so it will leave the air clammy because it won’t get rid of the humidity,” said Matt Marsiglio, operations manager for Flame Heating, Cooling, Plumbing and Electrical, (888) 234-2340,

Marsiglio said ideally your A/C should run around 45 minutes per hour to enable it to condition the air properly.

“Your A/C should work just like your outdoor grill does when you are barbecuing; low and slow,” he said.

Marsiglio said when Flame is replacing an air conditioning unit in a home, they do a heat gain calculation and use the Manual J from the ACCA, the Air Conditioning Contractors Association (, which is an industry standard that describes a method for determining how big your air conditioning system should be for the size and type of house you live in. In addition to the square footage of the home, Marsiglio said they also look at a variety of other factors that could impact the size of unit needed for a home, including the amount of insulation, type of siding and windows and which direction the home faces.

A properly sized air conditioner should keep the humidity level in your home below 50 percent in the summer to maximize your comfort. But even if your unit is sized properly and is doing its job, you may have certain areas in your home like the basement that are still damp and require you to run a dehumidifier in addition to the A/C.

To determine how humid your indoor air is, I recommend getting a digital hygrometer from the hardware store to check various rooms throughout your home. If it is too high in certain areas, adding a room dehumidifier can really make a difference in your comfort level.

In some cases, you may need to run a dehumidifier 24 hours a day to get rid of the moisture in a room that is always damp, especially a basement. That’s why it is important to have an EnergyStar-rated dehumidifier with an automatic humidistat that senses the moisture level in the area around the unit and shuts the unit off once the desired humidity level is reached. Because basements are also colder than the rest of the house, especially if you are running the A/C, make sure you also get an ultra-low temperature Energy Star model.

In addition to making sure your A/C is doing its job of conditioning the indoor air, here’s a pair of things you can do to help keep your home cool this summer. Keep the sun out by closing your blinds, shades or drapes where the sun beats in the most, and by running either a ceiling or oscillating fan in an occupied room to make you feel cooler.

So the next time you feel hot and sticky in your home even with the A/C running, remember to give it a chance to do its job and giving it some help to lower the humidity if you have moist areas of the home. That combination will greatly improve your indoor air quality this summer and keep you cool.

If you would like to suggest a question for this column, e-mail If you want to talk to Glenn Haege, call his “Handyman Show” on WJR-AM (760) at (866) ASK GLENN, (866) 275-4536 between noon and 2 p.m. Saturday and Sunday. “The Handyman Show” can be heard on more than 130 radio stations.