MVHR external vent location

[Conor]

Our design has a partial basement that is only open to the south side. Space is precious on the ground floor and ceilings are vaulted on the first floor... So basement is only option.

 

Architect is proposing inlet and outlets of MVHR to be on the southern basement wall. Not ideal, but not a huge issue. ASHP also to 3b close by.

 

Issue I've raised is that these are all underneath a ground floor balcony. It will be 3m above the basement ground level and will only project 1.5m out and will be a slatted deck. Is air recirculation a potential issue here? We can still get the pipes 2m apart, but both will be under the covered area. ASHP can be about 4m away, but still under the covered area.

 

Very rough sketch landed in there now. MVHR ducts would be around the area annotated "E" on the drawing. 

 

Thanks

Edited August 22, 2019 by Conor

[Jeremy Harris]

I'd say there's probably a pretty high risk of some recirculation by having the external terminals under a covered area.  The main issue might be drawing in cooking smells, plus having cooking smells trapped under the covered area, I think.  I don't think there's an issue with having the fresh air intake under cover, the main concern I'd have is with the exhaust.  Is there any way you can somehow extend the exhaust beyond the covered veranda, or maybe up through it somehow (might look a bit messy, though)?

 

The ASHP will be fine under a covered area that's fairly open, but it may well locally cool the air a fair bit in winter (ours does, and that's in an open pathway about 2m wide, especially on still days).  Having the MVHR draw in air that's cooler than ambient is going to reduce its effectiveness a bit, so my inclination would be to try and position the ASHP as far away from the MVHR fresh air intake as you can.

[PeterW]

@JSHarris What’s the optimum spacing (vertical and / or horizontal) for MVHR..? I’ve got an option as to how to split some vents and can’t decide on the best split

[Jeremy Harris]

5 minutes ago, PeterW said:

@JSHarris What’s the optimum spacing (vertical and / or horizontal) for MVHR..? I’ve got an option as to how to split some vents and can’t decide on the best split

 

Optimum is probably as far apart as you can get them, on the same wall, but not near a corner, I suspect.  Genvex MIs have the following diagram which seems pretty reasonable:

 

[PeterW]

1m vertical would work - I’m assuming it’s exhaust at the top and intake bottom...??

[Jeremy Harris]

4 minutes ago, PeterW said:

1m vertical would work - I’m assuming it’s exhaust at the top and intake bottom...??

 

Yes, as there will be a slight tendency for the exhausted air to rise, although I'm not wholly convinced it's that critical.