MVHR retrofit upstairs only for leaking house?

[gambo]

A bit complex situation because house was renovated small couple years ago so want to limit the damage. I really want MVHR with some nice/good filters. The reason is I want cleaner air inside + kids close doors in their bedrooms which causes lots of bad air during nights in winter. 

House is a usual late 80s build with loft above and positioned in such a way that in order for summer bypass to work well I need to run external ducting through the roof or sofits.

1) Can I run inlet/outlet through sofits? I think I can fit 100mm but could I split the ducting into 2x 100mm to make the flow better? I want to avoid scaffolding for lifting roof tiles.

2) Does it make sense adding MVHR unit to a leaking house? I guess I can do some improvements around windows but am not planning anything massive. I don't need a huge efficiency, it's more about getting some fresh air well filtered + some recovery of the heat.

3) Can I install MVHR working only for upstairs? I would size the unit so that we can at some point extend it to downstairs too but initially we want to do it as simply as possible and DIY (got an offer for supply and installation of £12k for 110m2 house whereas supply only is around £3k).

4) Anything specific to look at when looking for a very quiet unit? I hate noises generated by fans when trying to fall asleep? Any good places where I could see units working?

[JohnMo]

If you are doing MVHR, the inlet on the smallest will be 125mm dia, but normally 150 to 160mm dia. You need to maintain those Mon cross sectional areas, other noise is going to be an issue.

 

1 possibly

2 air passing through MVHR will be in addition to air leaking in or out elsewhere. It will be likely heat recovery of additional ventilation over and above your normal ventilation.

3. Both your prices sound excessive.

 

If it was my house this is what I would do.

1. Install moisture activated trickle vents, only open when needed, closed automatically all other times 

2. Under cut the bedroom and living doors, so therecis approx 10mm gap always open.

3. Install a MEV system to the vet rooms - this extract only and they also can come with moisture activated flow control at the nozzle and fan speed.

 

There is no heat recovery but only active when needed, only extract ducts needed , so way simpler to install.

[gambo]

3 hours ago, JohnMo said:

If you are doing MVHR, the inlet on the smallest will be 125mm dia, but normally 150 to 160mm dia. You need to maintain those Mon cross sectional areas, other noise is going to be an issue.

What do you mean here? Outside air to mvhr or mvhr to room? I don't have space for 150mm in soffits but mvhr -> room can be whatever I want as everything will sit in the loft.

3 hours ago, JohnMo said:

There is no heat recovery but only active when needed, only extract ducts needed , so way simpler to install.

It won't filter the air in the rooms as well as mvhr and there is lots of noise coming from the road which is another reason for not opening windows. Mrs also likes idea of having cleaner air and less dust on flowers.