MVHR for a small 2 bed ground floor flat in a terraced house

[Adsibob]

I'm thinking of installing MVHR in a flat which comprises two bedrooms, a bathroom, an open plan lounge/kitchen and a hallway which links each of these rooms together. The flat is only about 780 sq feet. Here is the layout (though the room at the bottom of the drawing, labelled "living room" will be a bedroom):

 

My first question is where to install the actual MVHR unit itself. The current options are:

1) There is a large cupboard that sits above the bathroom. It is about 45cm tall and has the footprint almost as big as the whole bathroom (which is about 1.8m by 2m). That cupboard is, accessed from the smaller of the two bedrooms, though it's slightly awkward because the cupboard doors are about 2.1m above floor height. Apart from the access issue, the main disadvantage of this location for the MVHR unit is that it will be audible from the small bedroom, and that is a big problem. So unless units operate close to silently, I don't think this is viable.

2) There is a cupboard which houses the tumble dryer which has enough space to house another laundry machine, on top of the tumble dryer, but that second laundry unit went into the kitchen instead, leaving that space available. That cupboard is at the bottom of the staircase within the flat, just to the left, before entering the kitchen. The advantage of that location is that it's not adjacent to anything other than the kitchen. This would be my preferred location, although I'd still want a quiet machine if possible, as the kitchen will be in regular use and in combination with the open plan "morning room" area will form the only communal living area, as the "living room" is actually a second bedroom.

3) I could build a small external insulated cupboard outside in the garden, up agains the external kitchen wall (shown to the right). The downside of this is that there aren't any PD rights with flats, so we'll need planning permission probably, even though it will be a small addition. It will also need to be detailed carefully to ensure it's sufficiently well insulated, and it might need its own heat supply, which would be a bugger.

So my questions are whether people think option 2 is viable from a sound insulation perspective. How quiet can a machine for a 780 square foot flat be? Ceiling heights are about 2.65m at most (and less in some places, e.g. the bathroom). But assuming an average of 2.55 throughout, the cubic volume of the flat is 2.55 x 72.5m^2 =184.875 m^3. Rounding up to 200m^3 to be safe.

I'd like to aim for very low air velocities, generous duct sizes, proper attenuation between the MVHR and distribution system, and low-noise terminals, like the Lindab airy ones. 

My second question: is a machine with 250m^3 per hour output sufficient? If so, can anybody recommend a quiet one?

Edited 7 hours ago by Adsibob

[JohnMo]

49 minutes ago, Adsibob said:

780 square foot

Either use ft2 or m2/m3/m. Mixing makes it rubbish to read without us having to convert from imperial to metric.

 

If your airtight do dMVHR, if your not airtight do dMEV 

 

[Mr Punter]

+1 for a couple of dMEV fans.  You could also have humidity trickle vents or through wall vents for fresh air.  Get rid of the tumble dryer and use a decent dehumidifier with plumbed in condense.  Put a drying rack or rail in the same room / cupboard as the dehumidifier.

[Mike]

4 hours ago, Adsibob said:

There is a large cupboard that sits above the bathroom. It is about 45cm tall and has the footprint almost as big as the whole bathroom (which is about 1.8m by 2m). That cupboard is, accessed from the smaller of the two bedrooms, though it's slightly awkward because the cupboard doors are about 2.1m above floor height.

I'd probably fit a horizontal MVHR unit in that space, but block the access from the bedroom, accessing it instead through trap(s) in a new bathroom ceiling. Unless I'd only just renovated the bathroom.

 

dMVHR is certainly worth considering, but there are downsides too:

 

 

4 hours ago, Adsibob said:

My second question: is a machine with 250m^3 per hour output sufficient? If so, can anybody recommend a quiet one?

You'd need to do some calculations to check the size - one option here. Good units are fairly quiet if run at less than 2/3 capacity.

 

The list at https://database.passivehouse.com/en/components/list/ventilation_small includes the noise level and shows which are horizontal. These units are independently tested to more accurate standards than normal (a higher efficiency ratio = better economy). Other cheaper options exist.

 

[Nickfromwales]

Brink Sky units are very good.

 

Here’s one I fitted in a garden annex, which the clients lived in whilst we built the main house on the same site.