The build team are off on another job (again) so I’m going to suspend the automated daily updates (again) to avoid clogging up the timeline with lots of identical posts showing no progress.
(For the record, this would have been Week 78, Day 1)
Daily Blog Updates On Hold (Again) by Marsh Flatts Farm Self Build Diary is licensed under a Creative Commons Attribution-ShareAlike 4.0 International License.
Hi, can you give some feedback on living with MVHR ?
Planning a new build to passive and some family members not so keen on the MVHR part of the solution, citing issues such as:
– noise transmission through ducts
– noise transmission through door vents need for air movement
– ability to control heat room by room
– noise of fans
– noise of MVHR unit itself
– feeling of draughts.
– Poor record of installation recorded across the industry (a key one, one article quoted about 15% get it right)
– running costs (compared to opening windows/trickle vents)
As someone who now has experience i wondered if you could provide some feedback ? Thanks.
Hi Jonathan,
Those are all excellent questions so it’s evident you’ve done some thorough research and homed in on the key areas of potential concern.
As my project nears completion I’m intending to turn this website into less of a chronological record of the build and more of a summary of the design choices and things I might choose to do differently, so I’ll address those points when I create a separate Page for the MVHR system.
Some partial responses in the meantime:
– It’s imperative to have any MVHR system designed and commissioned by MVHR specialists. That will address many of the potential issues: no draughts, no audible fan noise at the ventilation outlets, good reduction of inter-room cross-talk through the ducts. The commissioning will also check the installation aspects – like you say there are many horror stories and it’s evident most builders don’t understand MVHR yet. I used the Green Building Store for Design and Commissioning and I highly recommend them.
– Running costs are an important consideration since most people aren’t used to paying for good-quality ventilation. I have quite a big MVHR unit moving quite a lot of air and on the Normal setting (fan speed 2) it’s consistently using 66 kWh (£10) of electricity a month (I have a sub-meter on the dedicated electrical circuit for the MVHR unit). Then there are the filters which I’m expecting to change 3 times a year, at roughly £30 a set. All-in that’s a shade over £200 a year for running costs.
– My MVHR unit is in the Plant Room on the 2nd floor and the noise level right by the unit is significant – around 50 dB. The (huge) silencers do a great job of keeping the noise out of the ducts but you can hear some slight noise in adjacent rooms. It’s not a problem on the landing or in the bathroom but in the bedroom below the Plant Room there is a slight rustling and rumbling noise. It would be best to position the MVHR unit where there is no bedroom immediately adjacent to it. (Having said all that I find the noise much preferable to that from standalone extractor fans.)
– Noise through the ventilation gaps under doors hasn’t been a problem for me but then I’m not living with a large, noisy family. It’s possible to form ventilation slots in the door frames instead of leaving 15 mm gaps under doors, which might help. It’s tough to say how this compares with noise transmission through the doors, walls and floors.
– Per-room control of heat is interesting and it’s not practical to have bedrooms at 18 degrees with other rooms at 22 degrees using MVHR. Relative temperatures can be controlled to some extent by managing how the heat is delivered – e.g. omitting any heating on the MVHR supply duct and adding radiators or UFH in living rooms and bathrooms instead. I’ve been slightly surprised by just how useless air is at moving heat around.
The really big question is what would you do instead of MVHR? All the studies I’ve seen show that most homes are under-ventilated leading to higher-than-desirable levels of CO2 and VOCs.
David