In order to achieve comfortable cooling and dehumidification, the system must be correctly sized. The size of central air conditioning is measured in tons. (1 ton = 12,000 BTU/HR).

As a general rule of thumb, you need one ton of cooling for each 750 square feet of living space. This ratio assumes that the space you are cooling has standard 8 foot ceilings, that windows make up less than twenty percent of southern facing walls, that your windows have drapes or blinds and that you close them during the heat of the day, and that your walls and attic are insulated.

Keep in mind that this is only a guideline and that skylights, type of insulation, the number and size of south facing windows, protective shade trees, etc. can significantly effect the size of system required. Ideally, the technician should perform a load calculation to determine what size unit would best suit the space to be cooled and heated.

Note that when it comes to air conditioning equipment, bigger is not always better. An over size unit will lower the temperature too quickly and will shut off before it has an opportunity to properly dehumidify the air being conditioned. Excessive humidity can create an environment which facilitates the growth of mold.

The chart below offers a general guideline for sizing residential systems in the Miami Valley.