What kind of unvented tumble dryer will reduce indoor humidity?

Question

We had a humidity issue in our rental flat last winter - every morning all the windows were wet, and we had mold in the corners and behind the couch. (Despite venting 3+ times a day for 10+ minutes - which was really uncomfortable because of the cold.) The apartment has 55m2, is floor-heated, family consists of 2 adults and a toddler. We had to hang our clothes inside to dry, because outside they only would get damp. The humidity sensor I installed showed up to 80%RH, with 10+ minutes of venting I could barely get it under 60%RH.

This winter we'll try to remove all the houseplants from the flat and buy a tumble dryer for the clothes. Questions are:

1. what kind of tumble dryer do we need?

   Vented dryers are not an option (unless it stands outside in the cold) because the apartment is not ours and I'm not allowed to make modifications for the vent. So I guess I'm left with condensation dryers and heat pump dryers. Efficiency is less of an issue, but I'd like to avoid damaging the clothes. Also don't know what kind of air circulation they need - if I have to vent the whole apartment to keep them working, then they are a no-go. Can any of them be installed in a bathroom with no direct ventillation (no windows, only some kind of an inefficient active ventillation)? Can the condensation dryer get hot enough to injur a toddler?

2. will it reduce the humidity at all?

   I'm not sure how humid the exhaust air will be. I guess it should contain less water, than if we dry the clothes in the living room. But not sure if it will work at all, if the living-room humidity is constantly (hopefully) between 60-70%RH.

Answer 1

A more compact alternative worth a mention is a dehumidifer. I dry my washing indoors in UK winters, without a tumble drier. For efficient drying, shutting the damp washing and dehumidifer in a room works well; at other times, allowing air to flow between rooms drops the humidity in all of them.

Unlike a tumble drier it will also deal with cooking or shower steam if you don't have a good extractor fan.

Another space-saving option I should mention for completeness, though I haven't used one myself, is a washer/drier in place of your washing machine. They're probably better for occasional drying rather than being your main method.

Whatever you use, you can help the process along by making sure your washing is spun as hard as the care instructions and your washing machine allow. Really wet things that can't be spun benefit from a couple of hours to start with outside unless it's raining or freezing.

Answer 2

Heat Pump or Condensing Dryers will not add meaningful moisture to your apartment.

Both Heat Pump and Condensing Dryers are closed loop systems, recirculating air inside the unit. Both use a refrigerating system to create the cold surfaces for condensing.

• Condensing Dryers use a heating element to increase the temperature inside the drum to release moisture to the air. The moist air is passed through a condenser which turns the water vapor into droplets that are either collected in a pan or drained.
• Heat Pump Dryers use the ambient air temperature as the heat source. It collects the heat from the room to create the heat source to dry the clothes. It removes the moisture in the same way as the condensing dryer.

Heat Pump Dryers take a little longer to dry clothes because they do not add extra heat to the drying process. They will be cheaper to run because they do not use resistance heaters.

Both will do the job.

If you use the machine's pan and forget to drain it, you will be adding moisture to your apartment.

I used a Heat Pump Dryer on a recent trip and found the dry times acceptable. Your experience may vary.