Bathroom Ventilation

Dwaegon

I'm living in a 25yo house, and I have noticed some mould building up on the bathroom walls and they are often damp and it's getting quite disgusting. I have complained to the landlord, but he tells me that there is sufficient ventilation for two people living in the property and sharing the bathroom.

I asked him to install a bathroom extractor fan as we cannot have the window open to vent the air out in winter for long periods of time, but he has told me that it would not be possible due to the high cost involved (he had gotten a quote a couple of years ago), and that in 20 years of renting to tenants he has never had a complaint about the damp problem.

The bathroom has a 1.5mSq opening window, and he says that it is big enough and high enough (1.8m) to allow for moisture from showering to exit the window. Is there any regulation that provides for minimum ventilation standards in a bathroom just by window?

Atlantic Dawn

How long are you leaving the window open for after a shower/bath?

Dwaegon

https://www.boards.ie/discussion/comment/118536538#Comment_118536538

Generally leave it open until there's no humidity noticeable in the air, which doesn't normally take too long, but there is still moisture on the mirror and the shower panels and tiles. It's tricky in the winter, if you leave it open too long it's absolutely freezing. Surely I can't be expected to leave it open for hours?

10-10-20

Here's the 2019 specification and the points of note are 1.2.4.3 and table 3.

https://assets.gov.ie/100200/36644c6f-ce8a-4bb2-976e-20fbf39ef6fb.pdf

A window is defined as "purge ventilation" and there is no size requirement for such. It looks like a window is considered sufficient in a bathroom.

Ray Palmer

https://www.boards.ie/discussion/2058229916/bathroom-ventilation

Weird. A powered fan is not expensive and knocking a hole in a wall is easy stuff. About €250 total. Anyway a window should do but you also have to clean it off regularly. Opening the window during the winter is generally going to bring in more moisture making the issue worse. Very few building in Ireland have no damp issues and it requires maintenance by the resident which many tenants don't understand or accept

Atlantic Dawn

https://www.boards.ie/discussion/comment/118536557#Comment_118536557

Perhaps trickle ventet windows might be an option if say you were having a shower in the morning and then leaving home to go to work, probably more expensive than the electric fan ventilation though.

https://www.youtube.com/watch?v=6_2SdLEbHcM

Sleeper12

A bathroom fan won't be able to do anywhere near as good a job as the window that is already there. The real issue is insulation or lack of it. Condensation is warm water /steam hitting a cold surface.

mickdw

The requirements vary by year of build.

It varies from opening window or extractor in earlier years to extractor being required in all cases later.

If it's early 90s house, an opening window would meet the regs for bathroom but the house should have vents in all habitable rooms also.

Ray Palmer

https://www.boards.ie/discussion/comment/118536719#Comment_118536719

Not really true. An insulated wall is still cold to water vapour as is the ceiling. Only way is to expel the moist air whether through ventilation or dehumidifier. An open widow will bring moisture in the winter so a fan is best in most situations and will function better than a window as it doesn't let the outside air in.

No matter what you must clean regularly to stop damp and mould.

J_1980

Get a dehumidifier. Easy to keep rH in low 40%. Costs €20 a month to run, but well worth it. Best thing I bought.

Emma2019

I have a 1940s house with no insulation. After showers the bathroom door stays closed and the bathroom window open until the mirror is clear. I also leave the bathroom open a crack pretty much all the time.

I'd rather a cold bathroom than a mouldy one.

AngryLips

https://www.boards.ie/discussion/comment/118536719#Comment_118536719

This is not true. I have a small window in my bathroom but was also having damp issues. The bathroom fan I got in made a massive difference, the problem is gone (that said, it was done as part of vents throughout the whole house and a vent in one location might just move the damp to another part of the house).

Sleeper12

https://www.boards.ie/discussion/comment/118543910#Comment_118543910

You are sort of proving my point. Apart from windows, every room in the home should have a vent to the outside of the building. Obviously modern airtight homes are the exception. If you didn't have vents then this totally explains why you would have mold. Insulation also plays a major part in this too. I'm in 1000s of bathrooms every year. From 100 year old homes to modern homes. In insulated homes you get much less or no mold at all. If you do get it you will see it in corners where insulation might not be installed correctly. In non insulated homes moud will form everywhere on ceilings & walls. A fan won't have anywhere near as good an effect as an open window. A fan doesn't suck or blow steam outside. An extractor fan moves air around but doesn't remove steam.

In a house, with a vent & an open window, an extractor fan will have little or no effect.

mickdw

An extractor fan moves air around but not out. I don't get ya.

I find the extractors as required by regs very efficient at preventing steam build up.

Sleeper12

https://www.boards.ie/discussion/comment/118544890#Comment_118544890

If an extractor moved steam out then you would see condensation on the fan & ducting. If you open a window you can steam actually moving outside. I have never in my life seen steam being blown out of a bathroom. You would need a much more powerful fan to actually remove steam. Even something as big as a kitchen fan wouldn't blow steam from inside a bathroom to the outside. A bathroom fan is like a circulation pump on your heating system. A circulation pump gently creates a flow for your heating. It isn't like a booster pump that gives you a power shower. Likewise a bathroom fan slightly moves air around the bathroom. That's all they are designed to do. It doesn't suck out steam or anything like it.

Sleeper12

You got to love boards.ie. Where else would you get someone with no professional experience telling the tradesman that he's wrong. 🤣🤣🤣

mickdw

Im a Civil Engineer with 20 years experience in building and house construction.

I don't agree with your theory whatsoever.

Extractors work very well.

Garlinge

Best to open windows before putting on shower so vapour keeps moving as it is created and not allowed to settle on surfaces/walls. An extractor could be position directly over the shower and vent thru the attic to the outside. Having a south facing bathroom is a bonus too.

10-10-20

And I'm a few bags of fertiliser short of pallet - but I know that you also can't see humidity in an airflow unless it's saturated to the point where it condenses into a vapour mist. That doesn't happen with room vented air as the exhausted air isn't sufficiently loaded with humidity. But look at the exhaust output of a standard non-condensing boiler on a cold day - you have vapour mist there for sure. That's carrying moisture.

So I'd refine that theory of yours with help from the learnings on boards.ie. ;)