Central and distributed dMVHR

[mvhrishard]

I'm in a 1960s concrete brick cavity wall house. I hope to have it clad with rockwool in future to improve insulation.

 

CO2 levels get quite high when the windows are closed so I'd like to have MVHR with filtration.

 

Upstairs (the bedrooms) its very easy to run ducting in the loft that can access each room (and vent to the outside). However, all the walls in the property are concrete so its very difficult to run anything downstairs (a lot electrical wiring etc has been done on the outside of the property for this reason).

 

I'm wondering about having a central MVHR for upstairs and dMVHR (single room) for downstairs. Has anyone done anything like this? bpcventilation discouraged me from using MVHR if I can't reach every room and suggested PIV but then I'll loose a lot of heat in winter and also at night the bedroom doors will be closed.

 

Any advice?

[JohnMo]

There is no reason not to use a split system, a couple of things to think about.  You generally supply to dry room and extract from wet rooms.  The extract and supply rates should be equal.

 

But I am not thinking of any reason why you couldn't supply or extract from bedrooms the important thing is having a movement of air, sweeping stale air away and replacing with fresh.  So if you have only bedrooms upstairs, supply 45m3/h to two bedrooms and extract from the other two.

 

Get a unit that has a holiday function and run a timer so the unit ticks over during the day, and goes to normal duty at night.  Get an oversized unit so it's near silent.

 

Another thing you could do with MVHR, if you have a cupboard upstairs is run a single supply similar to PIV, through the cupboard to a downstairs ceiling and then an extract in each bedroom. To get a through ventilation, but with heat recovery.  The supply use a coanda effect terminal, so the air clings to ceiling, a move out as far a possible.

 

Just need to think a little out the box.