Locations of MVHR extracts in bathroom and kitchen?

[oranjeboom]

Great time to be doing the final ducting work in the loft. Probably 50c in there at the moment....

 

Kitchen:

This will have a re-circulating hob extractor, so no connection to MVHR. Is the location of the MVHR extract in the best location? Probably 1m from hob?

 

 

Bathroom:

 

Should the extract be closer to the shower or more central in the room? I was going to go for position A.

 

 

Both rooms will have a 'boost' switch to cater for cooking/showering periods.

 

[Jeremy Harris]

The general rule for all MVHR terminals, either extract or supply, is to make the path length that the air has to travel across the room as long as possible.  This allows the best chance of there being no "short cut", where the ventilation air only crosses a part of the room, leaving corners less well ventilated.

 

For example, if the fresh air to a room like a kitchen enters through a door (more likely under a door) then fit the extract terminal as far away from the door as possible, whilst making sure it's not tight in a corner (around 300mm to 400mm away from the walls is about right).  Our kitchen door, where fresh air comes in, is near one corner, so I fitted the extract terminal diagonally opposite it, in the corner.  The same goes for other rooms, so the living room, which has a door to the hall in one corner (which is the air extract point for this room) has the fresh air supply terminal in the opposite corner, so air has to flow diagonally across the whole room.

 

Try not to have terminals in the centre of a room, as you have shown, unless it's a small room like a WC, as they may not work as well, in terms of ensuring even diffusion, as ones where the air path length is as long as it can be.  For a shower, I fitted our extract right above it, as far from the door as possible, and that works pretty well.

[Cpd]

So would the best place in the bathroom be directly above the shower ? Or could you put two terminals in one above the shower and one above the bath ? 

[oranjeboom]

Thanks @JSHarris! I have used the longest path principle for most rooms where practical. The eaves in some rooms meant that some vents had to be some distance closer to the doors but on the whole I am happy with most of the positions, taking into account potential placements of future tall wardrobes, bookshelves etc.

 

Just thought I would check on the bathroom and kitchen positions as was not convinced the positions indicated by BPC were optimal. So will re-locate the vents for both rooms. Was a bit concerned of having a dead zone in the bathroom at the bath end, so planning to move the vent closer to that end of the room.

 

At least it's only 34c in the loft now!

[Jeremy Harris]

21 minutes ago, Cpd said:

So would the best place in the bathroom be directly above the shower ? Or could you put two terminals in one above the shower and one above the bath ? 

 

I'd put it above the shower, as the shower produces lots more water vapour than the bath.

[Adam2]

On 24/08/2019 at 20:07, JSHarris said:

 

I'd put it above the shower, as the shower produces lots more water vapour than the bath.

Is there any concern with being directly above a shower with the vapour being too wet? I thought I read somewhere (manufacturer or possibly on here) about having the extract just outside of the shower area so you had the heat and the water vapour was more gradually removed?

[Onoff]

On 24/08/2019 at 17:54, JSHarris said:

fit the extract terminal as far away from the door as possible, whilst making sure it's not tight in a corner (around 300mm to 400mm away from the walls is about right).

 

So have I done wrong here? Currently an extractor fan but with a view to this being the MVHR extract position later on.

 

 

A bit constrained up in the loft:

 

 

As it was I had to cut into the side of the joist:

 

 

 

Bringing it nearer to the shower head wasn't possible due to the joist & pipes. I suppose I could redo the pipework.

[Jeremy Harris]

I doubt it makes much difference, but the most common MVHR terminals are the mushroom type, that draw air in from their edges mainly, with a fair bit of the flow being close to horizontal all the way around their periphery.  Ideally there needs to be a clear area all around to allow the terminal to draw air more or less evenly around the peripheral opening, but given that the air flow needs to be throttled down a bit in almost all MVHR ducts, it probably doesn't make too much difference if flow is a bit restricted on one side.

[phatboy]

I was advised to fit extracts near to the centre of the room, and supply close to the farthest corner to the internal door.

 

I hope it's right, as it's done now ?