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Comment by locallost | Hacker News Reader

I watched a report on a block of "passive houses" in Germany and the people liked it, but had a complaint that the air is too dry, so they dried their laundry indoors. I'm a fan of the idea, so not really critical, but I wonder what it's really like to live in one.

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Instead of a heat recovery ventilation you can use energy recovery ventilation which gets back some of the humidity, otherwise just buy a cheap electric boiling humidifier and it you get the job done. What is important that in the coldest part of the winter you can turn down the ventilation to a minimal, something like 0.3 hourly exchanges per hour.

> winter you can turn down the ventilation to a minimal

The problem is that the Heat exchanger actively draws moisture out, as it has a huge cold surface area that forces water out of the air. If you don't change the air it feels stuffy.

You can buy heat exchangers with very high efficiency and good moisture reclamation or suppression for a slightly higher cost. The problem is usually that the customer does not look into the details and the construction company can increase profits by buying cheaper versions.

A good modern ventilation energy exchange unit for a 300m2 house can be <30dB, >90% efficiency, and return a lot of humidity.

Yes, the ventilation system inside a passive house needs not only a heat exchanger, but a humidifier as well. Actually, I'd rather dry my laundry to humidify the room than rely on a humidifier that can grow bacteria and mold inside.

> [...] than rely on a humidifier that can grow bacteria and mold inside.

That's down to maintenance and care; change the filters and clean it regularly. Like everything else in your house. You need to change and maintain filters in a heat exchanger as well.

>>than rely on a humidifier that can grow bacteria and mold inside.

There are humidifiers with UV-C lamps inside that sterilize themselves as they run. Dyson makes some, but I've seen them from other brands too.

Indoor plants are also useful in this regard, as the plants (and their containers) will return humidity to the air.

Modern heat exchangers allow you to set the air humidity.

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