Komfovent Domekt R400V MVHR

[Street654]

Hello, I was wondering if anyone has had any experience with a Komfovent Domekt R 400 V MVHR unit please? I am about to replace my Frankische unit which we are having issues with the Komfovent Domekt R 400 V. It will be located in the loft, and I'm told the Komfovent Domekt R 400 V is designed for cold installations (hence popular in Scandinavia). The current Frankische doesn't like the cold despite being well insulated, and should really only be installed in the warm floors in the house. We can only place the unit in the loft, hence having a specialist take a look, and they are recommending the Komfovent Domekt R 400 V. Thank you in advance for your advice :)

[JohnMo]

32 minutes ago, Street654 said:

designed for cold installations

Not really it's designed for cold climates which isn't the same thing. It has a Condensing rotary heat exchanger which us better at heat recovery in cold climates - or so they say.

 

A very quick look at the install manual and it clearly states, 

 

DOMEKT units are designed for installation in household or technical rooms with an air temperature of 0 °C to +40 °C, relative humidity 
from 20% to 80% (non-condensing). It is recommended to install the air handling unit in a separate room or in an insulated attic

 

So not sure it's suitable for your location - most units aren't really well suited for a cold or very hot loft space. Hence the issues you currently have.

 

I would remove insulation from under MVHR and then build a box from 100mm+ PIR or insulated stud walls and box the whole unit in. Make a wall removable or add a door for maintenance. Then the unit is in loft, but within a heated envelope. Then just keep the unit you have. Other option is every time it's cold you have issues.

[Mike]

+1. If the Frankische unit is in good working order, then there is nothing to be gained by replacing it. Just build a well insulated enclosure around it - something that should have been done when it was installed and something that your 'specialist' should know. And something that a replacement unit should have too.

 

Several Frankische units have PassivHaus certificates confirming their suitability in cool temperate climates. The larger version of the Komfovent has a similar certificate (and similar-ish performance - compare the Efficiency Ratios), so there's no particular reason to choose one over the other on those grounds.

 

The common reason for choosing an MVHR unit with a rotary heat exchanger (such as the Komfovent) is that they can - if the right materials are used - recover moisture from the outgoing air and transfer it to the incoming air, preventing the air within the building from becoming too dry (which can be an issue in cold climates where the air already has low relative humidity). Komfovent suggest that their units can do that (they "regenerate[s] humidity in winter"), however the PassivHaus certificate for their larger unit makes no mention of this - which suggest that they didn't get that aspect tested & raises a doubt about how effectively it can do it. It also introduces another mechanical moving part which can go wrong. Perhaps, due to their large commercial range of rotary MVHR units, it was just easy for them to scale down their existing rotary technology for their domestic products?

 

BTW, if the Frankische needs replacing for other reasons, then that PassivHaus database is a good place to look for quality alternatives.

 

Edited October 26 by Mike