Steamy bathroom

[Doug71]

My tenant has reported that now the weather is colder the bathroom gets "ridiculously steamy" when they have a shower even with the window open and have requested a more powerful extractor fan.

The shower is over the bath and the extractor is more or less directly above it (I presume the extractor is working properly but will check).

Now I know ventilation is generally thought to be a good thing but the open window is quite close to the extractor and I'm wondering if the extractor is just sucking in cold air from outside and pushing it straight back out again rather than actually clearing the room? The bathroom door is the opposite side of the room so I wondered if they would be better shutting the window while showering and leaving the door slightly ajar so that there would be air movement right across the room?

I guess the answer is to try it and see but thought I would ask to see if people think my theory makes any sense or if they have any other ideas?

I know the tenants have not put the heating on yet and will be suggesting that it would help if they did.

 

[Stigmorgan]

I would agree that having the window open is probably the issue, our bathroom set up has the window between the shower and extractor fan, same issue, I quite often have to reset the smoke detector in the hallway outside the bathroom

 

[duke]

I would agree that having the window open is probably the issue, our bathroom set up has the window between the shower and extractor fan, same issue, I quite often have to reset the smoke detector in the hallway outside the bathroom

Also agree Doug, Now that we here are running the wood stove regularly the RH drops a lot and the extra steam, moisture from showing is welcomed.

 

[RobinBHM]

Is it the title of a Tina Turner song…..

 

[duke]

Possible the extractor grill is clogged , I clean ours every few months.

 

[RobinBHM]

I know the tenants have not put the heating on yet

There’s the problem

 

[JoeS]

My experience is that tenants who have lived with **** landlords in the past - have always been told that they should open the windows to let fresh air in. The problem with that is that when they end up in a place with suitable airflow and venting and extractor fans - they continue to let cold air pour into the house and it creates lots of condensation issues.

Lastly not using the heating is a classic - it is a total false economy if it's your house in terms of damp and cold...the problem is that It isn't their house!

 

[pgrbff]

The fan needs to give 8 changes of air per hour. Calculate the volume of the room and choose the fan to suit. The fans installed in most bathrooms are too small. Better if it has a timer, better still if it has a humidity sensor but both of these will need an extra live at the fan.

 

[Ollie78]

We recently had an inspection done regarding damp issues at our house ( a long and annoying saga ) and the guy tested our bathroom extractor with a sort of box thing he put over it with what I presume was an anemometer in it.
Our fan was working at about half its original rating, possibly due to fluff build up in the pipe etc and just the age of the fan. I am going to get a new one or try to upgrade it to a higher flow version. The only issue is mine is a low volt type because its near the shower in zone 2 or whatever.

I always think the method of the bathroom fan is wrong. It would be better to open a foot square hole and use a really powerful fan for 30 seconds to just purge the steam really fast than a very weak little fan running for hours and doing very little.

 

[Cabinetman]

I fitted an in line large motor fan in the attic at my old house, might help. But I would think the reason they are complaining about the steam is the warm damp air hitting the cold air from the window- fogbank time.

 

[woodieallen]

The fan needs to give 8 changes of air per hour. Calculate the volume of the room and choose the fan to suit. The fans installed in most bathrooms are too small. Better if it has a timer, better still if it has a humidity sensor but both of these will need an extra live at the fan.

But if they have the window open then all your calculations go out ......etc

 

[XTiffy]

I have just finished a new build and two of the bathroom fans failed the (required Building Regs.) air test. Both had new fans which the sparks specified over the required extraction rate. I had to replace the low voltage 100mm one with a 150mm fan. The figures given by the company are extremely suspect. This low voltage one extracted only through a straight 350mm pipe through the wall. The second bathroom extracted through a roof tile vent and because the loft area was sealed, my only solution (without cutting holes in the ceiling or removing roof tiles) was to put a second (large) fan venting through the outside wall. These mods then passed the test.
Incidentally the calculation is based on 10 air changes per hour not 8.

 

[XTiffy]

The relevant Building Regs. is Part F. For a bathroom the minimum figure is 15 Lt/second. The calculation used is:
How to calculate the extraction rate
The fan size should consider the room size and not necessarily the minimum required by Part F of the Building Regulations.
The extraction rate is the air moved from the room in 1 hour. It is measured in metres cubed per hour (m³/h).
Installing a smaller fan will not do the job efficiently, leading to the fan failing its test.
First, calculate the area of the room to calculate the extraction rate. (a typical bathroom) Width 2.7m x length 2.55m x height 2.25m = 15.49m³
ACH required = 6 -10 (6 to 10 ACH based on Vent-Axia’s guidelines 10 ACH). 10 x 15.49 = 154.9m³/h
Usually, when purchasing a fan, you will find the specification in m3/h. However, there are times when the specification is in l/s, so a quick conversation is needed.
1l/s is equal to 3.6m3³h. Divide 154.9m³/h by 3.6 = 43.0l/s Therefore, the fan size required for this bathroom is 43 l/s, not as per Building Regulations, 15 l/s.
One other point is that Bldg.Regs. require a 10mm gap under doors. Which was new to me, having previously built four houses without that requirement.

All of the deluge of paperwork and tests will mean (unless skipped) there is no way this goverments house building targets are possible.

 

[Agent_zed]

My experience is that tenants who have lived with dung landlords in the past - have always been told that they should open the windows to let fresh air in. The problem with that is that when they end up in a place with suitable airflow and venting and extractor fans - they continue to let cold air pour into the house and it creates lots of condensation issues.

Lastly not using the heating is a classic - it is a total false economy if it's your house in terms of damp and cold...the problem is that It isn't their house!

My experience is that a lot of Tenants dry their clothes indoors and wonder why it is damp.

One of the things that seems to be missing from a lot of people's thinking is that if you are sucking 8+ times the room's worth of air out every hour, it has to be coming in from somewhere.

If your house has nicely sealed doors and windows, then any fan, no matter how big, will be fighting to suck air out of the room. If you look at proper whole house ventilation systems they have air inlets to allow fresh air in as well as vents to suck air out.

Opening the window or trickle vents a little is going to be necessary to allow the air to be changed. The problem is when the outside air is higher humidity than the inside air, at which point a dehumidifier is really the only way around it.

 

[Ollie78]

One other point is that Bldg.Regs. require a 10mm gap under doors. Which was new to me, having previously built four houses without that requirement.

This is crazy, I wonder how this works with other regs like fire spread prevention, intumescent strips etc.
I swear they are just randomly generating regulations to confuse us and be as awkward as possible.

 

[XTiffy]

This is for a door where an extractor is fitted. In my case en-suite bedroom/shower room. Then bathroom/landing.
Read up on Part F (if you get really bored!)

 

[John Brown]

My experience is that tenants who have lived with dung landlords in the past - have always been told that they should open the windows to let fresh air in. The problem with that is that when they end up in a place with suitable airflow and venting and extractor fans - they continue to let cold air pour into the house and it creates lots of condensation issues.

Lastly not using the heating is a classic - it is a total false economy if it's your house in terms of damp and cold...the problem is that It isn't their house!

Is that right? I thought that cold air carried less moisture, and lowered the humidity in your house, but the tradeoff was that you had to work the heating harder.

 

[Ollie78]

This is for a door where an extractor is fitted. In my case en-suite bedroom/shower room. Then bathroom/landing.
Read up on Part F (if you get really bored!)

Ok, makes a bit more sense in that context, is it because there is no window with accompanying trickle vent in there ?

 

[Gez1007]

Someone mentioned fitting higher powered fans. These are available (in 100mm size) and I fitted one about 3 years ago. What I have found though is that their higher efficiency rotor is more aerodynamically sensitive to the build up of crud. After one year of use, these things keep stalling (aerodynamically) every time a door is opened or a gust of wind outside tries to blow against the fan. Once stalled it wont recover normal flow until you force air through it by pushing a door in the opposite direction or the wind changes direction. (One knows when they fan is stalled as the fan speed rises and the flow reduces to almost nothing.)

My solution is to have two of these units, one cleaned and ready to fit, and the other in operation and every 6 months or so I swop them over. The performance difference between a clean and dirty one is night and day. They never tell you this in the sales literature!

 

[JoeS]

Is that right? I thought that cold air carried less moisture, and lowered the humidity in your house, but the tradeoff was that you had to work the heating harder.

When the steam from the shower hits the cold air from an open window... it instantly turns the water vapor into water. It's why you end up with soaking walls if you leave the window open... a fast extractor fan pulls this moisture out and expels it outside.

In a normal setting without the steam/shower you would be correct. Heating and a trickle of circulating air air from outside will produce low humidity and dry walls... in a bathroom... not at all.