What size air conditioner do you need for a 1454 sq ft home?

Answer 1

Depends on the relative quality of the house (insulation, glass, etc) and location (Atlanta vs Maine).

Most air-conditioners generate about 400 CFM per ton, but don't confuse Square Feet with Cubic Feet. A sunny South-facing room in Nevada will take more CFM to cool than the same size room facing North in Maine.

1) The proper way to size HVAC systems is with the calculation process described in ACCA Manual J. There are some approved software programs that do this for you and there are some freebies on the web that can give an approximation. It takes into account things like windows size and types, insulation in walls and ceilings, location of the house.

However, it takes a little time to do this so often there are "rules of thumb" that contractors use to get a quick estimate. However, if you get a quote from a company for new HVAC and they don't offer to perform a Manual J as part of the job, then find another HVAC company because this one is cutting corners. If you are replacing an existing system and have made improvements to the insulation, window, air-seal, etc. then a new Manual J load calculation should be performed.

Many HVAC companies will try to install systems much larger than needed. Partially because they can charge more, but also because it covers builder and installer errors and can reduce complains on the hottest days that the system is not working or is not big enough.

However, it is important to know that a too large system will cool your house too quickly and not dehumidify well. So in a humid place (like Atlanta or Houston) your house will be cold but very clammy.

2) A newer house, reasonably well built in a moderate climate may be just fine with 2 tons for a 1454 sq foot house. However, you must understand that a 2 ton system in a 1454 sq foot house in a humid environment like Atlanta will be different that a 2 ton system in the Nevada desert.

3) If you are considering a replacement, think about when the system was operating well, In the hottest afternoons did it run the full hour and keep the temperature under control? Did it cycle of and on? Did it run for less than 30 minutes of each hour?

If during the hottest weather the system ran the full hour or nearly the full hour and kept the house comfortable, you probably have about the right size. If during the late afternoon of the hottest summer days it ran for 40 minutes or less of each hour, it is very possible you may benefit from a size reduction. A Manual J load calculation can confirm your experience.