2 ms·

I don't think that's correct (and it's certainly not correct for my system). Not drawing in outside air from time to time will make the indoor air quality very

• SketchySeaBeast 8y ago
  Is your furnace high efficiency? Older models take in air from the house and then blow it out the chimney, but it's different in newer systems. The intake/exhaust are both pressurized and at least exit outside the house (in most setups they pull and exit outside, but I have seen where the intake is inside). The cold air return is usually in the basement and then just blows hot around your house. And yes, the air does get stale in winter.
• theluketaylor 8y ago
  Modern furnaces take in outside air for combustion. Using up inside, warm air for combustion is doubly inefficient since you expel exhaust air you already sunk energy into and you are sucking cold air that has to be heated from a much lower temperature. Modern code for cold climate houses is to be air sealed. A heat exchanger draws in fresh air, raises the temperature with existing heat and then expels cold, stale air outside. Very efficient. When air sealing was new many buildings developed longevity issues like mold since any moisture issues couldn't dry. All those problems have been worked out and there are homes in extreme cold climates that don't need any energy from the grid they are so efficient.