Your Home's Air Demands

Listed below are some typical appliances which exhaust indoor air to the outside = cause drafts
Gas Forced-Air Furnace and Hot Water Tank
(Non-Sealed Combustion)
100 - 200
Bathroom Exhaust Fan60
Kitchen Exhaust Fan75
Fireplace150 - 300
Whole House Vacuum150
Jenn Air Range325
Total: 1,060+ CFM

A home with 1,400 square feet and eight foot high ceilings has 1,400 ft2 X 8 ft = 11,200 Cubic Feet. This is the amount of air avaliable in the home during winter with all the doors and windows closed. When any of the above appliances are operating, there will be less air in the home.

11,200 ft3 / 1,060 CFM = 11 minutes!

Your 11,200 ft3 of air would be entirely exhausted in only 11 minutes!
Even without all these appliances operating, most homes built before 1995 have one complete air exchange every 1 - 2 hours.
Therefore, all homes need a controlled way for outside air to enter in order to have a healthy and energy efficient home.