MVHR Grill placement for supply / extract

[Wookie_73]

Hi all.

 

I am in the midst of designing my MVHR system for my house I am renovating.

I am happy with he design on the whole but I have one room that I am not sure about the vent placement, indeed even if I should have supply vent in that room at all.

I have attached my proposed layout / vent placements for the first and ground floor. Any comments are more than welcome.

I have also attached a ground floor layout marked up with a 3.5m distance between a supply and extract vent.

My question is this a great enough distance to prevent short circuiting?

Also do I even really need this vent? I added it to help bring down the air velocity in the main air supply vent on the ground floor.

I realise the ducting takes a convoluted route on the ground floor. This is because I am dropping the ceiling level every where on the ground floor by around 100mm to accommodate services except in the hallway.

All vents located near corners are 350mm away from walls.

 

Also would you normally put the vent in the bathroom above the bath / shower area?

 

Thanks for any advice.

Dave

 

EDITED TO REMOVE PLANS, PLEASE SEE POST FURTHER DOWN FOR PLANS

 

Edited 7 hours ago by Nickfromwales
Plans removed to anonymise project

[Nickfromwales]

Hi. 
Firstly, you’ve left the address on public view, do you want to upload anonymised versions instead? 
 

Secondly, are you making the property airtight and are testing it with an aim to get a target result? Eg <1 ACH. 

[JohnMo]

16 minutes ago, Wookie_73 said:

would you normally put the vent in the bathroom above the bath / shower area

Mine are directly over baths or shower areas. But other will say the complete opposite, so make your choice.

 

Difficult to tell from the drawing is it one large kitchen diner? You seem to have 2x extract one over island and other over sink? If one room one extract is fine, but not above hob, as you will fill the system with grease.

[Mike]

8 hours ago, Wookie_73 said:

All vents located near corners are 350mm away from walls.

I wouldn't put the ceiling supply vents right in the room corners & so close to the walls, particularly in the bedrooms. Many such vents use the Coanda effect (which is recommended) so that the air disperses evenly across the ceiling. However, if a wall is in the way, the air will be deflected down the wall and may cause an unwanted draft; from memory 750mm is the recommended minimum distance from a wall. Zehnder's Luna S (and probably others) have an optional deflector that can be inserted to get around that.

 

8 hours ago, Wookie_73 said:

I have also attached a ground floor layout marked up with a 3.5m distance between a supply and extract vent.

My question is this a great enough distance to prevent short circuiting?

Also do I even really need this vent? I added it to help bring down the air velocity in the main air supply vent on the ground floor.

What @JohnMo says. Just add a double pipe to the extract over the sink.

 

7 hours ago, Wookie_73 said:

Also would you normally put the vent in the bathroom above the bath / shower area?

Zehnder's advice is to place the extract near a shower, but not within / over it.

 

[Wookie_73]

On 24/01/2025 at 12:48, Nickfromwales said:

Hi. 
Firstly, you’ve left the address on public view, do you want to upload anonymised versions instead? 
 

Secondly, are you making the property airtight and are testing it with an aim to get a target result? Eg <1 ACH. 

Yes I would like to remove the address, silly mistake on my part. How do I edit my original post?

 

Yes I am trying to make the property as airtight as I can. It is a 1930's house so there has / is a lot of sealing done or to be done.

[Wookie_73]

On 24/01/2025 at 12:49, JohnMo said:

Mine are directly over baths or shower areas. But other will say the complete opposite, so make your choice.

 

Difficult to tell from the drawing is it one large kitchen diner? You seem to have 2x extract one over island and other over sink? If one room one extract is fine, but not above hob, as you will fill the system with grease.

Yes it is one large kitchen diner.

The extract over the island is close to where the hob is. I could ditch this and just have one extract.

[Nickfromwales]

20 minutes ago, Wookie_73 said:

Yes I would like to remove the address, silly mistake on my part. How do I edit my original post?

Just post the plans again in your next post, please. I have removed them from the original, as it's the documents themselves that need editing before posting vs the post  

[Wookie_73]

On 24/01/2025 at 21:16, Mike said:

I wouldn't put the ceiling supply vents right in the room corners & so close to the walls, particularly in the bedrooms. Many such vents use the Coanda effect (which is recommended) so that the air disperses evenly across the ceiling. However, if a wall is in the way, the air will be deflected down the wall and may cause an unwanted draft; from memory 750mm is the recommended minimum distance from a wall. Zehnder's Luna S (and probably others) have an optional deflector that can be inserted to get around that.

 

What @JohnMo says. Just add a double pipe to the extract over the sink.

 

Zehnder's advice is to place the extract near a shower, but not within / over it.

 

I was looking at the Zehnder ComfoValve Luna S125 for the supply. The recommended minimum distance from corners is 350mm in there documentation. They have what looks like a foam segment that you put in to slow the flow pointing toward the corner.

This is where the 350mm came from.

I quite like the look of these valves and they seem affordable.

However what I would like is a plaster in type diffuser so I don't have anything protruding down from the ceiling but I cant seem to find any that don’t cost stupid money. Any recommendations?

[Wookie_73]

11 minutes ago, Nickfromwales said:

Just post the plans again in your next post, please. I have removed them from the original, as it's the documents themselves that need editing before posting vs the post  

Thanks Nick

MVHR Layout First.pdf MVHR Layout Ground - With notes.pdf MVHR Layout Ground.pdf

[Mike]

22 minutes ago, Wookie_73 said:

I was looking at the Zehnder ComfoValve Luna S125 for the supply. The recommended minimum distance from corners is 350mm in there documentation.

I'm using the same model and that is indeed their minimum distance. However I've seen it recommended that Coanda-effect vents should be >750mm away from walls, though I can't give you a reference for that. But since they disperse the air across the ceiling in all directions, there is no need to squash them in a corner.

 

23 minutes ago, Wookie_73 said:

what I would like is a plaster in type diffuser so I don't have anything protruding down from the ceiling but I cant seem to find any that don’t cost stupid money

I'd prefer that in principle too. However if they don't protrude from the ceiling you don't get the Coanda effect; instead the air will blow in whatever downward direction the vent deflectors dictate, albeit gently. That's not a problem if you have space to site them away from where they may cause a draft, but not so good in a smallish room where you don't have that freedom.

 

At lest the Zehnder Luna protrudes less than most and they look reasonably good.