Partial MVHR

[JoeA]

I'm in the middle of adding a fairly large extension (2 stories out the back + dormer in loft onto a 1930s semi.

We're trying to do somewhat better than build regs in terms of energy efficiency, and hopefully improving the air tightness of the house in the process.

 

We've been debating MVHR for about the whole planning time, and have been though several loops including

BPC system design with radial ducting (This got removed because the architect (now parted company from) was adamant that we couldn't trust a BPC design.  Also the initial design for this put the MVHR unit in the loft eaves, and we were  (still are) concerned about noise

Green Building Store designed system with branch ducting (removed from the contract because, a) the metal ducting lost too much space in various ceilings, b) the cost of a installation pushed us over budget.

 

I'm now debating a third approach where I put in MVHR just for the bedrooms and upstairs bathrooms.  This feels like it would achieve much of our aims, while making the installations much easier, as all ducts could be run along the joists of the loft, and it save the challenge of where to do drops down to the ground floor.

 

So our basic aim was to bring fresh air (which the other half loves) into the house, without the drafts.  This was particularly for the bedrooms, where the can't really open the windows anyway due to the noise (we live close(ish) to a dual carriageway).  It also gets us away from having to put in those horrific noisy extractor fans to the bathrooms (which currently have no extraction - and aren't being dealt with in this.

 

Does anyone have any experience of partial MVHR?