Extractor vs Window

[RizzoTheRat]

We have an extractor fan in the bathroom.

After having a shower I leave the extractor on to pull damp air from the room, which is presumably replaced with drier air leaking in around the door.

The Mrs on the other hand always opens the window after a shower. To my mind that just dumps cold air in to the room and causes all the moister to condense out.

So which is better?

[Thorodin]

I'm not a heating engineer, as demonstrated now, but I think as heat travels from hot to cold zones the air flow will be outwards through the window. Just done my bathroom that used to have only the window for venting and have fitted an extractor. The difference is amazing. No more open window in the winter and the room is moisture free with no condensation running down the tiles. Fan activates on the light switch and continues 15 mins after switching off and then the built in humidity detector will continue until normal levels reached. I'm a fan of fans.

[fido]

+1. Extractor with humidistat - removes moisture when you need to remove it.

[marshalla]

Opening the window allows the humid air from the room to vent out and mix with the drier air from the outside, so the overall humidity in the room is decreased.

[majordad]

I'm confused, do I leave the window open or closed after I shower so when fan is on?

[Martin_Hx]

I do both! Am i doing something wrong?

My missus on the other hand does none and im forever going in the bathroom after her to a room full of condensation, shes a bloody nugget no matter how many times i tell her!

[RizzoTheRat]

marshalla said:

Opening the window allows the humid air from the room to vent out and mix with the drier air from the outside, so the overall humidity in the room is decreased.

Does it, or does it let some warm damp air out and cold air dry air in, which mixes, drops the temperature of the rest of the air in the room and condenses out the moisture? The temperature certainly drops very fast with the window open, yet farts take ages to clear, so I'm not convinced that much air changes places.

[anonymous-user]

RizzoTheRat said:

temperature certainly drops very fast with the window open, yet {b}farts take ages to clear[/b], so I'm not convinced that much air changes places.

Now thats my kind of tech talk

[8-P]

Assuming the room is fairly steamy ie you can see it, then opening a window will initially let some of that steam out and make a noticeable difference. However as the room cools due to the cold air also coming in that moist air will surely condense on various hard surfaces. I always wonder how effective extractors are. We had both in my last house, the window always cleared the room faster and surely moisture in the air would condense on the inside of the extraction pipe?

My wife was told recently by a supposed building expert you should do one or another. I cant see how doing both would hurt but I read on a housing associations site that it should run for 4-5 hours with a window shut.

http://www.metropolitan.org.uk/images/CUST070_0713...

More chat here

http://forums.moneysavingexpert.com/showthread.php...

[Thorodin]

The window is not a non-return valve. The action of air turbulence in being drawn through the window creates multi-directional currents which will inevitably draw some outside air in, although in small amounts. Opening the window will initially allow a greater volume of air to be moved purely on account of the relative size of the aperture (window v. fan) but the volume will to an extent depend on the relative temperature and humidity difference between indoors and outdoors. On the other hand, an extractor fan is in effect a non-return valve as it has shutters to prevent draughts coming in. Therefore, overall, the fan will be more effective, quicker. I think.

[snobetter]

I had a structural engineer in about a separate issue, but we discussed some mould issues on an exterior lounge wall. He said we needed extractor fans in the bathroom and kitchen as it was moisture from here causing the issues.
Opening the window clears the bathroom but some / a lot of the moisture is forced into the house where it was settling on the cold (solid) wall, whereas the extractor fan pulls out the moisture and replaces with "dry" air from the house.
It made sense to me, if you open a window you can feel the draught coming in even through a closed door.