toilet smells vs humidity

[hendriQ]

I'm a newbie to MVHR but I have largely been converted and am looking forward to installing a system later this year.

 

One thing I'm trying to work out is the optimal positioning of the extract vents in the bathrooms. I got one of those free designs from a company, and they have put all the extract vents in the bathrooms directly above the bathtub/showering area as they are obviously trying to mitigate the humidity from the hot water. These positions are somewhat sheltered from the rest of the bathroom due to large floor to ceiling shower screens. For the smaller bathroom in our house, I'm not too bothered, but for the bigger one, which is our ensuite, I'm wondering if that is an optimal way to ventilate the whole bathroom, or if it will result in leakage of smells into the bedroom. My husband will regularly leave what can only be described as "nuclear" smell in the bathroom and so I had asked him to install a regular extractor fan like we have at the moment in the bathroom as well as the MVHR. He says this is a no-no because it will completely unbalance the system as well as introduce a potential air leak. I think there are some clever extractor fan covers that close to be fully airtight such as the airflow icon range, but he says it still will mess up the MVHR. So a second option is to either move the MVHR extract vent so it is directly above the toilet, or have two vents, one for the toilet and one for the shower.

 

The bathroom I'm thinking about is about 7.5m2 with a floor height of about 2.6m2, so a volume of 19.5m3. The radial ducting kit we were going to get has two size options:

1. 65mm diameter which are rated for 23m3 per hour max flow
2. 75mm diameter which are rated for 30m3 per hour max flow

There is also a larger diameter ducting pipe available, but I don't think we have room for it. Alternatively, a third option is an oblong pipe with is sort of a smoothed out hemispherical shape and only 52mm high but much wider (about 150mm) which offers a maximum flow rate of 45m3 per hour, but I'm assuming that it's shape means it's not as efficient as a circular option

 

We are planning on running the MVHR unit on its lowest setting to minimise noise and save energy, so I doubt we will get very close to those maximum flow rates. Would it make sense to have 2 x 65mm ducts for that bathroom, or will it make it too noisy? The distance from the MVHR unit (which I understand is a factor in noise calculation) is not much. Maybe 3m to the position in the ceiling just above the shower area, or 4.5m to get it closer to the site of nuclear explosions.

 

I know there is a boost function, but I'm keen not to rely on this as when my husband has a late night nuclear explosion, the boost noise might cause noise that will bother others. During the day, that's less of an issue, but he is more of a night time pooper.

[ragg987]

You need to balance inflow with outflow. So if you increase outflow in the bathroom you need to input more in adjacent bedroom. Not really ideal as will increase noise and waste heat.

 

If the bathroom door is kept shut, there should be no leakage of smells or humidity as the it will create a one way airflow from under the door.

 

I suggest you locate exhaust at furthest point from the door. And agree that an additional local extractor makes little sense.

 

Regarding fan noise, suggest you install a sound attenuator (like a giant car exhaust pipe) after the mvhr and before your room outlets.

[ProDave]

There is always a gentle slow flow of air from a bedroom to a bathroom so smells should not migrate against that.

 

The normal is to run the MVHR at trickle speed most of the time where is should be silent, but boost it to a much faster speed when showering.  Some (us) do that with a manual activated timer, others use a humidity sensor.

 

If you are worried about wc smells, some connect a branch of the bathroom extract to the WC cistern which will extract some air directly from the pan via the flush pipe. this is known as an "odourless WC"

[joe90]

Solution.....(sorry ?)

 

Edited February 7, 2021 by joe90

[ProDave]

16 minutes ago, joe90 said:

Solution.....(sorry ?)

 

SWMBO flatly refused to enter an outside Dunnie while at a restaurant in Queensland, prefrirng to "hold on" until we got to somewhere with indoor facilities.

[hendriQ]

41 minutes ago, joe90 said:

Solution.....(sorry ?)

 

This is brilliant. I would absolutely love it if my husband did all his toiletting outside. Not sure today is the best weather for it mind you.

[Mr Punter]

Seriously has he considered a change of diet?  An occasional upset is fair enough, but if this is a regular occurrence It may be worth thinking about his digestive system before trying to compensate with the ventilation system.

[hendriQ]

1 hour ago, ProDave said:

There is always a gentle slow flow of air from a bedroom to a bathroom so smells should not migrate against that.

 

The normal is to run the MVHR at trickle speed most of the time where is should be silent, but boost it to a much faster speed when showering.  Some (us) do that with a manual activated timer, others use a humidity sensor.

 

If you are worried about wc smells, some connect a branch of the bathroom extract to the WC cistern which will extract some air directly from the pan via the flush pipe. this is known as an "odourless WC"

Interesting option @Mr Punter. A similar, but fairly different idea is the Geberit DuoFresh Odour Extraction Module. This recycles the smells through a carbon filter, and neatly fits concealed behind the flush button plate.

 

Anyone have any experience of this sytem?

[hendriQ]

10 minutes ago, Mr Punter said:

Seriously has he considered a change of diet?  An occasional upset is fair enough, but if this is a regular occurrence It may be worth thinking about his digestive system before trying to compensate with the ventilation system.

I think it's more to do with his larger than average colon (he had a colonoscopy a few years ago and they discovered this - apparently completely safe genetic abnormality).

[Timedout]

I would not worry too much about the smell thing. Perhaps try it and see how it goes for a while. To give a bit of confidence I did the following on a bungalow a few years ago.  We used a DIY ducted PIV into the living area and passive stack ventilation in the bathroom and shower room. The passive stacks had Aereco ceiling terminals that modulate relative to humidity. Like you, we were anxious about smell but it in practice it was fine.

 

 

[Seeoda]

Did you ever find a solution to this? Did you try a odourless toilet?

[hendriQ]

On 12/09/2021 at 11:01, Seeoda said:

Did you ever find a solution to this? Did you try a odourless toilet?

So more than six months on from my original post we are now a week away from our MVHR install first fix and we still haven't figured this out. We didn't go with the odourless toilet in the end because builder hadn't installed one before and wanted to charge extra and budget is already stretched.

We decided instead to have boost switches in the bathroom and to install sound attenuators to deal with the extra sound issue.

But now that we're coming to the install someone has pointed out that BCO might object to a retractive boost switch being installed in the bathroom.  Would it be okay if the IP rating of the retractive switch module was high enough. I've found an IP20 which is probably not high enough, but maybe this IP66 would work (if I can find a compatible face plate): 

https://www.tlc-direct.co.uk/Products/KBOP21.html?source=adwords&ad_position=&ad_id=415703895087&placement=&kw=&network=u&matchtype=&ad_type=&product_id=KBOP21&product_partition_id=963257115964&campaign=shopping_switches_sockets&version=finalurl_v3&gclid=CjwKCAjw-sqKBhBjEiwAVaQ9a8RaocJ_oVgq-bPkPjtdR3nrAMlpemYZDzKyhWofGEsKhISb9RqrMBoC0loQAvD_BwE

 

[ProDave]

Are you proposing a boost switch in each bathroom?

 

I solved the problem by having the boost switch on the landing so you press it before you enter either the bathroom or en-suite.

 

But I think that IP rated switch should be okay in a bathroom.

[Olf]

Why not using a remote switch? I installed NineLeaf Portable Mini Wireless Switch from Amazon in place of bli%&ing string in a bathroom, 30 minutes job and it has not failed me once.

Battery powered (or for few quid extra you can get kinetic ones) so zero chance for electric shocks risk mitigation. And of course no running of the cables, making holes etc!

[TonyT]

https://www.tlc-direct.co.uk/Products/QUWS1W.html

[Andehh]

OP, could you let us know how you get on once installed & trialed a few times please?