Extractor Fan or Single Room MVHR?

[Onoff]

Looking to fit an "extractor fan" to a small bathroom extension. Rental and really nice tenant. 3 kids, lots of bathroom use so some black spotting on the ceiling above the bath. Bathroom window directly above the garden box:

 

 

Access into the roof space above the bathroom is likely doable, through the airing cupboard where the gas boiler is (lucky I'm slim):

 

 

Looking from the hatch to the end wall above the garden box:. There's a smattering of old fluffly insulation between the ceiling joists. As the outside is all brick thinking this must be a cavity wall on the end. Looks like a line of Celcon blocks just above the joists. Not sure how those ceiling joists are "fixed", looks like L brackets rather than proper hangers. I was thinking I might as well put a crawling board up there and maybe re-insulate whilst in there. Going over there at the weekend so will look then.

 

 

Going to get some better internal pictures. Thinking mabe a SELV extract directly above the bath but have to check heights to the ceiling ref Zones. Pretty sure it's all Zone 1 above the bath height wise. Saying that, an inline fan in the loft space would I think negate any requirement for SELV/PELV?

I can fit an isolator above the bathroom door entrance on that grey bit of wall to the left, behind the chandelier. The door in the picture is the airing cupboard door open against the bathroom door:

 

 

Rough sketch of the bathroom. There's a shower rail and folding screen the towel rail end. Mulling a single room MVHR unit above the sink exiting out into the "alley", first picture above:

 

Only photos I have:

 

 

 

[Redbeard]

(permanently-running + humidistat-controlled over-ride) dMEV?

[JohnMo]

Greenwood CV2GIP, low background ventilation, easy setup, smart boost when humidity rate of rise is above a given threshold - almost silent.

 

Mounted in ceiling and duct away, if that's easiest.

 

Pulls about 2Wh electric.

 

Normally get them on eBay cheap enough.

[ProDave]

My top tip.  Do NOT fit an accessible fan isolator in a rental.  I have known tenants turn them off because they are noisy then complain about the condensation.

 

I do not believe they are legally necessary (I have asked several times for someone to point me to the reg that says you must fit one and nobody has) but if you really feel you need to fit one, put it up in the loft close to that loft hatch.

 

Check how air will get into the room to replace what is extracted, you may need to plane a bit off the bottom of the door for instance.

[Onoff]

A Vent Axia MVHR unit here? Would draw the warm, wet air across to it and out the wall?
 

 

[JohnMo]

1 hour ago, Onoff said:

A Vent Axia MVHR unit here? Would draw the warm, wet air across to it and out the wall?
 

 

Not sure about that, it would push new air in to the room and pull air out of room.  Believe that are not the quietist units available, so more likely to get switched off, as annoyance

[Onoff]

Went over today and had a look. Definite mould spots  Need to sort asap really.

 

Bathroom is nom 9m3.

 

Height from floor to ceiling is 2170mm. Inside bath to ceiling is 2100mm so Zone 2 all the way to the ceiling above the bath and 600mm past the bath. 

 

 

 

 

 

 

 

Interesting outside, an old air brick blocked up with a very weak mix. There's no matching vent inside though, cavity vent? 

 

 

 

 

Edited May 25 by Onoff

[Dave Jones]

The dreaded cranked ceiling. No insulation there and sure enough mould grows.

 

those cranks should have trickle vents , would 100% fix the issue 

[Onoff]

8 hours ago, Dave Jones said:

The dreaded cranked ceiling. No insulation there and sure enough mould grows.

 

those cranks should have trickle vents , would 100% fix the issue 

 

Never had an issue until now in about 15 years. Now there's 5 people using the bathroom.

 

Got any links to this and where the vents should go?

[FuerteStu]

On 23/05/2024 at 09:13, ProDave said:

My top tip.  Do NOT fit an accessible fan isolator in a rental.  I have known tenants turn them off because they are noisy then complain about the condensation.

 

I do not believe they are legally necessary (I have asked several times for someone to point me to the reg that says you must fit one and nobody has) but if you really feel you need to fit one, put it up in the loft close to that loft hatch.

 

Check how air will get into the room to replace what is extracted, you may need to plane a bit off the bottom of the door for instance.

It always comes down to interpretation of localised isolation. 

 

Some define it as within the area it's installed, others count the breaker as such. 

 

[Onoff]

Still got to do this so thinking on options and tbh ease of install and maybe future planning:

Option 1:

Simple extractor fan. place directly above the shower end of the bath here (Zone 2):

 

 

Duct through the wall:

 

 

To vent here:

 

 

Or ducted to a tile vent:

 

 

 

With the above, potentially no drilling. No MVHR though.

Option 2:

Vent Axia Lo Carbon MVHR unit, 12V:

 

Mounted here, again in Zone 2:
 

Ducted through the wall to here:
 

Thinking the heat recovery aspect and bringing fresh air in would be good.

Or a combination of the above, or something else...no drilling is appealing.

How about. A "proper" MVHR up in the loft space.

Fresh air intake and warm, wet extract tile vents on the roof, one each end. Warm, wet intake in the bathroom, same place,  above the shower. Fresh air ducted into the lobby ceiling just outside the bathroom?

 

 

Would I need to insulate any ducts?

Edited May 31 by Onoff

[JohnMo]

5 minutes ago, Onoff said:

Fresh air ducted into the lobby ceiling just outside the bathroom

Or better still as far from bathroom as poss and get plenty of cross ventilation 

[Onoff]

10 minutes ago, JohnMo said:

Or better still as far from bathroom as poss and get plenty of cross ventilation 

 

Not easy. To get a duct to the other side of the kitchen would mean clearing an upstairs bedroom, carpets up etc. Possibly an option for later though. Would have to drill though the wall where the copper pipes go through. Not sure on joist levels etc. 

 

Would my idea of the fresh air duct just outside the bathroom work?

 

 

[Onoff]

Any links to a good, cheap MVHR unit that would do the one bathroom? Room volume nom 9m3.