ᐅ Central ventilation system – is humidity recovery necessary?

Created on: 30 Dec 2019 16:17
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ludwig88sta
Hello everyone,

for our planned single-family house with 2 floors and a basement, we have decided on a central ventilation system for all rooms with heat recovery within the thermal envelope. The brand and model are not yet determined.

I have read here on the forum a few times about an additional moisture recovery feature (MRF?), since otherwise the indoor air tends to become too dry (of course, the ventilation system also removes the moisture that naturally occurs in the room, which usually makes the air feel comfortable). I wanted to ask if anyone can confirm these issues and whether this is more common in timber frame houses or also occurs in brick houses?

Did you install additional moisture recovery in your ventilation system? How much extra cost does it involve? I assume there are also additional maintenance costs because it involves another motor and related components.

Best regards
ludwig88sta
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haydee
3 Jan 2020 09:01
I have a test system, so data is transmitted to the manufacturer daily. The difference with or without an enthalpy heat exchanger is about 10% humidity after last winter.
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bernie
3 Jan 2020 09:21
tomtom79 schrieb:

I can hardly believe it! We have 10 plants between 30cm (12 inches) and 2m (6.5 feet) tall. We cook regularly, and there are 4 people living here.

Either you have no air exchange or an enthalpy exchanger.

Believe it or not – we do not have an enthalpy heat exchanger. You just have to familiarize yourself a bit with your device, like with the heating system, and experiment. I can set the fan speed in percent for three levels as I like. Accordingly, I have set the "low" and "medium" levels lower and programmed them over the day using a timer. Currently, we have an air exchange rate of 0.3. That’s more than enough – 0.5 is not absolutely necessary.
face263 Jan 2020 09:47
Maybe it doesn’t depend solely on the mechanical ventilation system but also on the building itself (has the construction drying period already ended?) and how it is used. How many people live there? Is there a lot of cooking? Laundry drying, and so on?

Just as an example… a large building volume, dual-income no kids (DINKs), cook rarely, send most laundry to the cleaners, and shower every other day at the gym, compared to a more compact building with two adults, three children, daily cooking, laundry drying, and five people showering. Both have mechanical ventilation without enthalpy recovery... do you think the average indoor humidity would be the same?
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bernie
3 Jan 2020 09:55
You are absolutely right, face. There are 4 of us, showering and cooking daily. On the ground floor and upper floor, we have regular houseplants. Of course, in winter we hang wet laundry indoors on the drying rack to dry. When it’s raining or foggy outside, the laundry just doesn’t dry.
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ludwig88sta
4 Jan 2020 13:24
Maybe consider getting a ventilation system that can be easily upgraded with heat recovery (ET) later on without major costs, because as @face26 already mentioned, it really depends on the circumstances.

There should be options for retrofitting without significant expenses, right?
opalau4 Jan 2020 13:30
The heat exchanger is easily replaceable in all central ventilation systems known to me.

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