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I was planning to topup loft insulation but got stuck a bit. I can't decide what to do with ventilation in bathroom upstairs. Since we dropped temperature feels like we are wasting to much heat by keeping windows open for too long in bathrooms.
The houses was built 30yrs ago, cavity wall detached house with no cavity insulation.
Does MVHR make any sense here? I was thinking about just doing something upstairs but the airtightness isn't probably great. Other option is PIV but I read that it will just be blowing cold air into house and it's already quite cold upstairs. So, maybe just install 2 bathroom fans above showers, running through loft to sofit.

I believe for whole house MVHR air tightness is essential.

A single room MVHR in the bathroom might work.

PIV into your bathroom might make your situation worse.

Bathroom extractor fan will work and is the cheapest option.

Nowty Towers uses a ceiling vent in the bathroom and shower room running through ducting to an axial fan in the loft and then out through a vented roof tile. Comes on with the light switch and over runs for 15 mins. Its inobtrusive and is practically silent. Similar to what your thinking.

The single room MVHR units work well, and although a lot more expensive than an extractor fan they are no harder to install. Options might include these:

https://www.extractorfanworld.co.uk/ven ... -130-c.asp

https://www.extractorfanworld.co.uk/env ... -255-c.asp

nowty wrote: ↑Wed Nov 30, 2022 10:26 pm Nowty Towers uses a ceiling vent in the bathroom and shower room running through ducting to an axial fan in the loft and then out through a vented roof tile. Comes on with the light switch and over runs for 15 mins. Its inobtrusive and is practically silent. Similar to what your thinking.

Do you have MVHR? I don't really need MVHR in bathroom. I would consider it to use the warm air from bathroom to heat other rooms but then it probably makes it more expensive.

Oldgreybeard wrote: ↑Wed Nov 30, 2022 10:30 pm The single room MVHR units work well, and although a lot more expensive than an extractor fan they are no harder to install. Options might include these:

https://www.extractorfanworld.co.uk/ven ... -130-c.asp

https://www.extractorfanworld.co.uk/env ... -255-c.asp

The trouble is my shower is on the left from entrance and the window is on the right, so ideally I need something above the shower.

ducabi wrote: ↑Wed Nov 30, 2022 10:46 pm

nowty wrote: ↑Wed Nov 30, 2022 10:26 pm Nowty Towers uses a ceiling vent in the bathroom and shower room running through ducting to an axial fan in the loft and then out through a vented roof tile. Comes on with the light switch and over runs for 15 mins. Its inobtrusive and is practically silent. Similar to what your thinking.

Do you have MVHR? I don't really need MVHR in bathroom. I would consider it to use the warm air from bathroom to heat other rooms but then it probably makes it more expensive.

I did put a single room one in my lounge, there is a bit about it here as part of my aircon thread.
https://camelot-forum.co.uk/phpBB3/view ... =75#p13625

But I unplugged it soon after turning it on as its just too noisy, much more than the aircon unit even in tickle mode. But it would not be any worse than a bathroom fan so it might work there.

That was a good test of my loft insulation, its freezing up there.

Why through tile rather than sofit? I read somewhere that it's easier for the inline fan to suck the air than blow.

ducabi wrote: ↑Thu Dec 01, 2022 12:11 am Why through tile rather than sofit? I read somewhere that it's easier for the inline fan to suck the air than blow.

It was easier and shorter distance.
The tile is a special plastic vent tile that replaces your normal concrete tile.

It sucks from the bathroom and the ceiling vent is where the most restriction is, so I think that's still right. It works as when I bought the house there was terrible mould on the ceiling which I could never get rid of until I installed the fan a few years later.

We went with both - single room MVHR in the main bathroom, in line axial in the ‘guest’ en-suite - out through soffit. Much easier for us as the roof has sarking boards, though it does have wide soffits.

In some ways, I prefer the MVHR as it’s on all the time (agree with Nowty, too noisy for a living room) and has a Humidistat to activate boost (as well as being activated by the bathroom light switch).

The MVHR is opposite the shower, and further away from the bath.

Never had a problem in it not managing humid air when the bathroom is in use - the advantage with the humidistat is it obviously doesn’t require the user to remember to switch the light on.

The axial fan works fine too - it’s in a windowless room, so no probs with forgetting to switch the light on.

The MVHR does constantly introduce ‘fresh’ air upstairs that has been reasonably pre-warmed.

nowty wrote: ↑Wed Nov 30, 2022 10:57 pm I did put a single room one in my lounge, there is a bit about it here as part of my aircon thread.
https://camelot-forum.co.uk/phpBB3/view ... =75#p13625

But I unplugged it soon after turning it on as its just too noisy, much more than the aircon unit even in tickle mode. But it would not be any worse than a bathroom fan so it might work there.

I've only seen (and heard in action) one silent single room MVHR, and that was a Dutch made unit that seems to have disappeared now. PIty, as it seemed to be a really good unit. Only downside was its size, it needed a rectangular wall cut out that was about 2ft high and a foot wide. I think that its size was the key to it being silent, it used large diameter, slow turning fans for the intake and exhaust.

Our centralised MVHR is very quiet, silent when not in boost mode (it gets boosted to deal with baths, showers and sometimes cooking) and that also has large fans, centrifugal ones about a foot in diameter, that only turn pretty slowing 99% of the time.

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.