Enthalpy exchanger and timber construction

[davidc]

I am looking at getting an MVHR system with an enthalpy exchanger as I have chronic (non-allergic) rhinitus that seems to be triggered by central heating drying out cold winter air. The build type is to be timber frame and blown woodfibre with Wraptite on the outside. Regarding the wall type and moisture management within it, should I be concerned that in winter the humidity will be higher than it would otherwise have been without the enthalpy exchanger ?

 

 

Edited January 28, 2021 by davidc

[andy]

Hi

 

I have a Zehnder ComfoAir Q350 ST on a timber frame with airtight layer on outside, foil backed plasterboard on external walls without the enthalpy exchanger (but you can retrofit that if you need to AFAIK) and my MVHR is as follows right now:

 

Extract Air 22.6C/50%

Exhaust Air 13.6C/90%

Outdoor Air 11.0C/89%

Supply Air 21.4C/51%

 

https://www.zehnder.co.uk/products-and-systems/comfortable-indoor-ventilation/zehnder-enthalpy-exchanger

 

Whilst I am not capturing this data yet to drag it into InfluxDB, it is pretty constant humidity, around 45-50% supply I think.

[ProDave]

I have one of the Mistubishi / Kingspan enthalpy mvhr units in a timber framed house.

 

I don't have any humidity metering but just what issues are you expecting?  I have no condensation issues anywhere so what problem do you anticipate?

[PeterW]

Mitsubishi Lossnay 35 running an enthalpy heat exchanger over the past couple of weeks and this is the output (courtesy of the Shelly monitoring)

 

 

Sits between 51-58% humidity

[SteamyTea]

Remember that you are using RH not AH

 

Taking @andy's data, there will be 10g.m^-3 of water in the air.

[davidc]

Thanks for measurements, I guess what I don't know is what the RH would be during cold snaps without an enthalpy exchanger.

 

@ProDave my concern was that I'll be reliant on the inside VCL more than if the airtight layer wasn't on the outside which to my mind sounded like a potential cause of increased moisture if the internal AH was higher than it would be for four months of the year than without the exchanger.

Edited January 29, 2021 by davidc

[davidc]

So have I understood correctly in that an enthalpy exchanger operating at 50% moisture recovery would take out 5gm.m^-3 of water from extract air at, say, 10gm.m^-3 and put that back into the supply ?