The only reason for putting the air handler (indoor unit) of an air conditioner in an attic is to free up usable floor space in the living area of the home. But the additional square footage comes at a cost. Here are four reasons why it is actually not such a good idea:

1) An attic is hot in the summer and cold in the winter, with energy loss around the cabinet that results in increased utility bills, despite manufacturer-installed insulation. Summer attic temperatures in our North Florida area, for example, reach 130º F and above on a hot afternoon.

2) Attic installation is more expensive because the air handler requires a catch pan under the unit and drain pipe running down to the ground, a structural support to hold it without cutting any roof trusses, a floor in front of the unit for a service tech to work, with a work light and receptacle, and a minimum two-foot wide walkway from the attic hatch opening to the unit.

3) Out-of-sight also means out-of-mind. An air handler with a filter located in the attic is more likely to get changed less often because of the inconvenience of climbing into the attic for it and, if there is a condensate drain line backup that overflows into the catch pan below the unit, it can remain undiscovered for weeks or months—creating a small pond of brown scum water sitting in a rusty pan, like in the photo above.

4) An air handler in the attic has a shorter life expectancy and is more difficult to remove and replace when the time comes. 

    “The worst thing you can do is install furnaces and air conditioning systems in vented attics,” according to Joe Lstiburek, a nationally known professional engineer that does extensive research in construction methods and materials for Building Science Corporation. “The attics are way hotter than the outside in the summer and cold and miserable in the winter—and in hot humid climates it gets ugly”

   But, if you insist on putting your air handler in the attic, there are specific code requirements for attic installation. You can read about them at our blog post ”What are the building code requirements for installing an air handler in the attic?"

    Also, there are a couple of ways to give your attic air handler a more hospitable environment. Some builders create a small, insulated attic room with a door to reduce the energy loss. Another alternative is to insulate the underside of the roof in the attic with spray-on polyurethane insulation. This technique is often used for energy-efficient new homes and, although the attic is not a conditioned space, it will not be much warmer or cooler than the interior of the home, and this also reduces the energy loss from attic ductwork.

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  To learn more about heating and air conditioning systems, see these other blog posts:

• How can I find out the SEER of my air conditioner? 

• My air conditioner won't turn on. What's wrong? 

• How can I find out the size of my air conditioner? 

• How can I tell whether the condenser (outdoor unit) is an air conditioner or heat pump? 

• Where is the air filter for my central air conditioner and furnace? I can’t find it? 

• Does an old air conditioner use more electricity as it ages? 

• How did homes stay cool in Florida before air conditioning? 

• What is wrong with an air conditioner when the air flow out of the vents is low?

• Why has the thermostat screen gone blank? 

• Why does it take so long to cool a house when an air conditioner has been off for a while? 

• Why is my air conditioner not cooling enough? 

• What are the most common problems with wall/window air conditioners?  

• Will closing doors reduce my heating and cooling costs? 

   Visit our HEATING AND AIR CONDITIONING page for other related blog posts on this subject, or go to the INDEX for a complete listing of all our articles.