After living in the German-speaking world and becoming accustom to having a Trockenraum, which can be thought as a dedicated room of a building for line-drying laundry indoors backed by a blowing dehumidifier (e.g., Secomat), I would like to replicate this concept in a house in the United States.

I could install a direct dehumidifier in a room. That said, I am curious if I could effectively dehumidify while fulfilling some side-goals (listed below): using a air source heat pump water heater (HPWH). Would a typical HPWH remove humidity satisfactorily for laundry drying in a room?

To help clarify "satisfactorily," note that the Trockenraum concept is not designed to support rapid drying of items but rather provide faster than line drying alone (e.g., fully dry a sopping duvet in three-to-five hours). I plan on having a heat pump laundry tumbler for things that require more rapid drying but can tolerate the beating from the tumbler.


  • Decarbonization of the house (HPWH would further this among many other activities)
  • Keeping basement dry (it's already very dry — thankfully)
  • Supporting accelerated line drying of laundry (particularly large, bulky, and delicate things)

Clarifying information:

  • Cold climate
  • Will eventually have solar
  • House has ducted AC/heating but the basement is not hooked up into the climate loop (plan on retrofitting the HVAC with ERV and ground source heat pump soon)
  • What is your climate? Hot/cold/dry/humid? Does the house have AC in the summer? What ventilation system? Solar panels? Do you plan to use this in winter only or all year?
    – bobflux
    Oct 3, 2023 at 16:28
  • You could hang the laundry outside in the summer to further reduce your energy usage.
    – FreeMan
    Oct 3, 2023 at 17:16
  • @FreeMan: Outdoors is certainly a possibility for warm periods, but I'd like to mitigate dust/contaminants on the laundered items still.
    – mtp
    Oct 3, 2023 at 19:38
  • if the heat pump pulls from outside air, i don't see how it would condition the room. If it pulls from inside, it's going to make the room cold, which lowers evaporation and raises humidity, making the clothes take longer to dry.
    – dandavis
    Oct 4, 2023 at 3:17
  • @dandavis: It would use indoor air. While it would lower the ambient air temperature (how much, even), HPWH are touted for their dehumidification capability. My intuitive understanding was that dehumidification was to be proportional to water usage, which some material seems to confirm. The real question is how much ambient dehumidification they provide, like keeping the tanked water warm. As I said, the house has no moisture problem, and I would like to avoid introducing one! I'm not sold HPWH is necessarily sufficient.
    – mtp
    Oct 4, 2023 at 5:34

1 Answer 1


It should work fine. Anything that will raise the temperature or lower the dew point of the air will help it work faster. I have seen this done many times commercially to dye many different items, not all were clothes but some furniture etc. It is not instant but you say you are not in a hurry so have fun and enjoy dry clothing.

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