MVHR, PIV or just a bathroom fan?

[Bugtownboy]

As a general rule I would expect the single room units with the largest fan and heat exchanger size to be the quietest, and for a living room I'd still be a bit sceptical about the noise level being a bit too high.

The noise level with our VentAxia, in normal low speed operation, isn’t ‘too noisy’, but, if you had one in a living room and wanted to sit quiet/read/relax, it’d be damn annoying !

I’m ok with loud rock/metal music as background when reading/relaxing, but something quiet and continuous

[marshman]

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[ducabi]

Thank you everyone for contribution. Now I'm a bit confused what I want, so maybe will give more details in case it helps.

If i go for MVHR it would sit in a cold loft and would probably be used only upstairs (to simplify the installation). There are 2 rooms belonging to kids (not used by 4pm) and 1 office used most of the time, the biggest is bedroom and used in late evening.
Atm I try to keep opening windows whenever it's needed but the rest of the house struggles to remember to do it.
We have no signs of mold upstairs and next to nothing downstairs even though laundry is drying in living room quite often.
My thinking is that by installing MVHR upstairs we are dealing explicitly with humidity upstairs but it will also have some positive impact on downstair, so perhaps no need to rip the walls to install it everywhere. However, I read that installing it in cold loft makes it less effective. So, I wonder if given only 1 room is used through most of the day upstairs will we benefit from having MVHR? The longest showers are usually taken 2-3hrs after kids are in beds, so we don't really need to recover that heat as the thermostat during the night is set below what the actual temperature indoor is at that time.

The other thing is that I would love to install cavity wall insulation, but I'm puzzled whether it's a good thing, even after reading all pro's of EPS beads. If it is then, to make ventilation future proof we would probably need MVHR anyway.

[Oldgreybeard]

If it's any help, the ducts don't need to be large if a radial duct MVHR system is used. I used 75mm diameter round ducting from BPC (good supplier, I'd recommend them), this stuff: https://www.bpcventilation.com/airflow- ... al-ducting

For rooms where a higher airflow is needed (in our place only the kitchen extract) then two parallel ducts can be used. Being relatively slim means that this size of flexible ducting can easily be fitted under suspended floors, or even run down inside partition walls (there's an oval version that's slimmer and better for this): https://www.bpcventilation.com/airflow- ... ng-airflex

The way a radial system works is that every room has its own duct, either extract or fresh air feed, and these are led back to two plenum chambers, one for extract, one for fresh air. Those plenum chambers connect to the MVHR unit (which is fine in a loft, as long as it's insulated) using large bore ducts (160mm in the case of ours): https://www.bpcventilation.com/10-point ... 160-spigot

I also added silencers in these large ducts, to reduce the very slight fan noise to an inaudible level in the rooms: https://www.bpcventilation.com/quiet-ve ... ncer-range

What marshman says above about air quality is very true. Even if the MVHR didn't save a great deal of heat, I'd still have it just for the fantastic air quality. Also, being able to fit a fine filter on the intake air means that the air coming into the house is pollen free, a real boon for those with hay fever.

[marshman]

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[ducabi]

That's not sort of help I was hoping for. I thought you would convince me to go with extraction fans
Have you guys done it yourself of used someone for installation/calibration. I'm happy to pay but I don't have any positive experience recently with delegating work I'm afraid, so I guess I would need to do it myself.

Perhaps there is a good online shop doing lots of work to workout what the client needs to supply a proper DIY kit.

[Stig]

If you want to do a lot of DIY
https://camelot-forum.co.uk/phpBB3/view ... f=21&t=463

[marshman]

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[marshman]

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[ducabi]

If you want to do a lot of DIY
https://camelot-forum.co.uk/phpBB3/view ... f=21&t=463

I've seen it and, nope, that's not the route I'm keen to take .

Does it make much difference if i initially do MVHR for upstairs only and add downstairs later on? Is it just extra ducting that is required and making sure the unit itself is fit for this, or is there anything else I should be worry about?