Window Units


VAV System
Window Units



A basic window air conditioner unit puts the abilities of a normal air conditioner in a small space.  The unit fits into a typical window frame and is held in place by the window itself.  The window air conditioner is typically used to condition the air in smaller areas and is best suited for single rooms.  The window unit can be removed from the window during the off season to prevent heat loss around the edges of the inactive unit.

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Inside of the unit are a compressor, condensing coil, evaporator coil, blower, controls, and a small amount of ductwork. The ductwork and possibly a damper will allow the unit to draw fresh air in or re-circulate 100% of room air.

The efficiency ratings (EER ratings) are not as high as central air conditioning systems and versatility is limited because all of the cooling is blown into one room, but they get the job done when needed.

This kind of unit needs to be maintained like any other air conditioning unit.  The filter needs to be cleaned routinely as well as the condenser coil, which may require a chemical bath.

One major problem with this unit is the fact that the efficiency and performance decreases when air flow over the evaporator and condenser coil.  If the airflow decreases too much, the unit will burn out.  Another problem with the unit is that half of the unit is exposed to the outside.  Birds, rodents, and insects have the ability to nest inside of the unit causing the unit to work less efficiently and potentially ruin the unit to the point that it will not function at all.

The unit does not cost a lot to install and does not cost a significant amount to operate. 

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When selecting a window air conditioning unit, size is a very important consideration.  First off, the room that is being conditioned must be taken into account.  A small window unit will not require much energy to run but if the room it is trying to condition is too large, it will need to run all day for the desired comfort level.  This will not cool the room in an efficient manner.  A large window unit on the other hand will require a lot more energy to to condition the same room.  This will cause the room to cool rapidly and the unit will turn off and on more than if the unit and the room were more compatible, wasting energy.  Humidity must also be taken into consideration.  The room may cool quickly but the humidity will still be present causing it to feel damp and uncomfortable. 


To cool this area

Look for this size air conditioner

100 to 150 square feet

5,000 BTUs

150 to 250 square feet

6,000 BTUs

250 to 300 square feet

7,000 BTUs

300 to 350 square feet

8,000 BTUs

350 to 400 square feet

9,000 BTUs

400 to 450 square feet

10,000 BTUs

450 to 550 square feet

12,000 BTUs

550 to 700 square feet

14,000 BTUs

700 to 1,000 square feet

18,000 BTUs

1,000 to 1 400 square feet

24,000 BTUs


  • If the room is heavily shaded, you can reduce the BTU capacity by 10%

  • If the room is very sunny, you should increase the BTU capacity by 10%

  • If more than 2 people regularly occupy the room, add 600 Btu for each additional person

  • If the unit is for a kitchen, increase the capacity by 4,000 Btu/Hr.


For instance,  there is a 100 S.F. room that is heavily shaded and normally has 3 people in it.  According to the table above, a window air conditioner of 5,000 BTU’s should be used.  Since the room is heavily shaded, the needed BTU usage would be 4,500 BTU’s since that would be a 10% decrease.  Next, there are 3 people in the room which would increase the needed BTU usage to 6,300 BTU’s because of the additional 600 BTU/person.  One can now take that information and find a suitable window unit.  In this instance, the Sunpentown WA8010 Window Air Conditioner - 8,000 BTU unit would be a good choice.  This particular unit has the following specifications:

  • Function: Cooling
  • Power supply:1Ph,115V,60HZ
  • Capacity: 8,000 BTU
  • Refrigerant: R22
  • 4-Way Air Flow
  • Airflow: 320 (M3/H)
  • Noise Inside/Outside: 50/57 db(A)
  • Dimension: 19X14X18 Inch
  • Weight: 75 Lbs


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This site was last updated 11/10/04