Under certain conditions, a thermostat can be a misleading indication of comfort level – your eyes are telling you one thing while your body is telling you something quite different.  “It’s 70° in here and I’m burning up!”

That’s because a thermostat (thermometer) is a device for measuring temperature only.  However, your body is responding to the heat index (HI), a combination of temperature and relative humidity.  The heat index, oftentimes referred to as the “apparent temperature”,  is a measurement of what heat actually “feels like” or what your body perceives the temperature to be at any given time.  For example:

• If the thermometer reading is 90°F and the relative humidity is 90% - your body reacts as if the temperature is 122°F – a full thirty-two degrees above the actual temperature reading on the thermometer (Heat Index Calculator).

• If you were to lower the relative humidity to 39% - your body would adjust and react as if the temperature was 90°F – the very same reading on the thermometer.

 HOWEVER, at a certain point, lowering humidity alone would no longer be a factor.

• At 90°F (temperature) and absolute 0% relative humidity – your body perceives the surrounding temperature to be 87°F – a drop of only three degrees.

• Also, drying the air too much has adverse effects: it creates static electricity which causes painful shocks and could harm computers and other electronic devices; it causes wooden furniture to dry out and develop cracks and wooden floors to separate at the seams; it causes wallpaper to peel at the edges; it causes dry skin and hair, and itching and chapping.

On the other hand, allowing humidity to remain at high levels and reducing the temperature impacts your body in the opposite direction – your skin feels cold, damp and clammy.  If the humidity is high enough, moisture may collect on window panes and other smooth surfaces such as refrigerators, countertops and shower enclosures.  And, over a period of time in such an environment, mold, mildew and resultant property damage is inevitable.

In order to be truly comfortable and protect your property from damage, it is necessary to regulate both temperature and humidity.  That is the reasoning behind proper sizing for air conditioning units.

• An oversized air conditioning unit will rapidly drop the temperature level, satisfy the thermostat and shut down without removing the proper amount of moisture from the air.  A low temperature combined with high humidity is distinctly uncomfortable – you feel cold, damp and clammy.  Many people, especially older folks, develop joint aches and pains.

• An undersized air conditioning unit will run constantly, draining moisture, but it may never satisfy the thermostat and shut down – you feel warm and there’s a possibility you may develop dry, itchy skin along with a scratchy throat and other symptoms associated with drying out the mucous membranes in your nose and sinus cavities.

Improper sizing, too large or too small, will cost you money as well.

• The up-front cost of a larger unit is greater.  It also takes more energy to operate larger units and the constant on/off cycles create unnecessary wear and tear on the compressor motor, fan motor, switches and other internal components.

• The up-front cost of a smaller unit may be less expensive but if the unit is too small to adequately cool the area, it will run constantly at full-speed, consuming excessive amounts of electricity while wearing itself out in the process.

An air conditioning unit properly sized for your home or business will turn on, run long enough to remove sufficient moisture and cool the premises – then, shut down long enough to recuperate before restarting the cycle.

• A properly sized air conditioner will keep you comfortable.

• A properly sized air conditioner will perform stronger and last longer.

• A properly sized air conditioner will keep moisture levels within a range that will not damage your property or injure your health.

• A properly sized air conditioner will treat your pocketbook with respect by not consuming excessive amounts of energy.