Is it ok to have high efficiency condensing furnace in the garage or attic of a house in an area that experiences below-freezing temperatures? I've heard that having a furnace in a spot without "conditioned air" can lead to frozen components that somehow break the furnace.

  • What make/model of furnace are you looking at? Commented Jun 16, 2017 at 1:14
  • Only Carrier at this point.
    – Megatron
    Commented Jun 16, 2017 at 1:15

2 Answers 2


A condensing gas furnace needs to discharge it's condensate "waste" water. If the furnace is in an environment that experiences freezing temperatures, this can become difficult. Typical condensing gas furnaces don't have provisions to protect the condensate line against freezing temperatures, so the line can freeze up and break.

This is one of the reasons you won't typically find furnaces installed in attic spaces in cold climates.


My high efficency condensing furnace in the attic freezes when it gets to zero or lower. I have been going into the attic on cold mornings and thawing the line and the tank in the unit with a heat gun. This winter I have built a shroud out of a large aluminum roasting pan, attached it to the side of the furnace Put a heat lamp under it and plugged into a thermostat contolled receptable. Supposed to get to -5 this next week. Hope it works.

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.