I've got an electric dryer currently vented outside:  current setup

Behind the door to the right is our heat pump furnace: picture from other side

I was thinking about, during the winter, venting the dryer (properly filtered for lint) into the furnace return (which would then be filtered again by the furnace filter) instead of outside.

My thinking is that it will act somewhat as a humidifier (the house is very dry in the winter) as well as conserving a bit (not much) of heat from the dryer output.

Can this setup work? What dangers would I need to address? And of course will I actually be doing any good at all?

2 Answers 2


Can you do this? ABSOLUTELY NOT!!

Aside from (likely multiple) code violations you will never filter the lint out and will create a dangerous situation inside the furnace plenum, aside from clogging the furnace filter probably weekly.

  • 3
    Yeah, you'll at least wreck your heat pump with all that lint, not to mention a dozen other reasons why this is a bad and dangerous idea.
    – iLikeDirt
    Feb 6, 2015 at 16:33
  • Well in my defense, I did say properly vented to remove the lint before it enters the return. I haven't really done much research to see if that is feasibly possible but if you guys are saying that it isn't I'll trust your judgement. Btw, what code violations would there be? I don't see this as much different than one of those inside vents for a dryer they sell at Home Depot and/or a humidifier hooked to the return (which my hvac guys said was standard when they installed the unit but I opted not to get it for now)
    – kinar
    Feb 6, 2015 at 17:24
  • 4
    The code violations are 'dryers must vent outside' because of the significant fire hazard presented. The indoor vents they sell at Home Depot are probably not legal to use either, but if they are, the difference is that the kit has passed some testing standard and does not potentially exhaust highly combustible material into the furnace.
    – Zhentar
    Feb 6, 2015 at 19:53
  • 1
    Fair enough. I suppose even if I could do it safely, the cost involved to put in the necessary failsafe checks would probably outweigh any potential gains. Plus once those failsafe checks are in place, that may well remove the efficiency gains as well.
    – kinar
    Feb 6, 2015 at 22:32

You could build (or possibly buy) a heat exchanger for the dryer exhaust. This way you could extract the heat without mixing the air (and lint). This wouldn't be as efficient as what you wanted to do, and you wouldn't get the humidifier effect. But it would be safer.

DIY Example: http://www.alkeng.com/AL/dryer

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