So I have been having trouble heating my home. I noticed today that there is a vent blowing hot air outside. It is not the return, chimney or venting. Any ideas other that the builder thought we should all play our part in global climate control?

  • 3
    Do you mean that one of your air ducts leading from the furnace goes to the outside of your house? If so, I don't think any of us can answer 'why' it was done that way. It does seem illogical.
    – DA01
    Feb 18, 2013 at 5:07
  • Sounds like you need an HVAC expert who knows the brand of equipment in to have a look and make sure it was properly installed. Feb 18, 2013 at 16:40
  • 2
    Are you sure it's not a vent, or an exhaust fan from a bathroom or something?
    – Hank
    Feb 18, 2013 at 16:45
  • Either your installer is an idiot or that's the combustion exhaust pipe.
    – ssaltman
    May 28, 2015 at 20:03

1 Answer 1


All gas furnaces require a flue to exhaust carbon monoxide outdoors, the reason modern units require a fan to do it is due to the circuitous design of modern heat exchangers that extract more heat from the unit before exhausting it outdoors, natural venting will no longer happen if the induced draft motor is not running, So much heat is removed these days they can be vented using PVC flue rather than metal and moisture condenses making an acidic condensate that is drained just like the AC condensate is. It is normal,if it were not so you would/ could die by operating the unit in that condition.

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