Bathroom Size: 8 feet * 8 feet * 10 feet (Height)


(1) Increase the Bathroom air freshness during use (2) Keep the Bathroom dry for the next use

Note: Intermittent Extraction of air is more preferable over Continuous Extraction

Alternative 1: Install two fans (1) Inlet fan (2) Outlet fan (Both the fans are of same air flow capacity, installation at same height side by side on a same wall)

Alternative 2: Install only one (1) Outlet fan (With the double air flow capacity the single fan in alternative 1, installation at same height on a same wall )

Which alternative will be more efficient and beneficial for Bathroom Ventilation? How?

  • I'm pretty sure if you put fans side by side with opposite airflow, the net effect will be almost no air movement at all. For Alternative 1: I would change it to be fans on opposite walls, or at least a few feet apart. – John Smith Jul 26 '13 at 16:33

Moist hot air rises. If you have a fan placed near your shower on the ceiling that can move a lot of air out you will have little to no condensation. Fan should be turned on when you get in the shower and generally speaking should stay on twice as long as the shower taken. If you buy a fan sized for a bathroom 2 times your size and keep your bathroom door or window open while showering (if you can) you would more than do it.

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Or prevent the steam from being generated in the first place.

The most effective control of bathroom condensation I've seen yet are these perspex bubbles you install on the top of enclosed showers. Basically the entire shower cubicle gets enclosed. Because it's no longer mixing with cold air, minimal steam is produced and if it is, it says in the shower.

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If you need to go with the extraction approach due to other factors like a shower over bath scenario then I'm really not so sure having an inlet fan is necessary at all. It's hard to say which one would work best for you because it depends where in the wall the fans are installed relative to where the steam is being generated among other things.

All you really need is a source of airflow to replace the air that is being forced out which will help push the steam out. Forcing cool air into the steam with an inlet fan may make it disperse and condense on the walls. It'd be best to draw it out as quickly as possible rather than potentially blow it around the room.

Get a good fan with plenty of airflow. I like larger fans as they move more air and are quieter than smaller ones. Apparently putting the fan closer to the source of steam generation is recommended too. But not right above the shower rose as condensed water can drip down on the person showering! not nice.

It's usually recommended to put the extraction fans are put on timers so that when they power on, they stay on for around 7 minutes after being switched off from the wall switch.

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  • Fan is a good idea. The bubble is the most ridiculous thing I have seen. It will cause more steam not less. It will temporarily stop warm/cold from mixing while showering which in a closed system would cause condensation. However you have to open the door and air it out or you will eventually have mold. You are just delaying the process plus putting more pressure on your shower system plus making me claustrophobic just thinking about it. – DMoore Jul 26 '13 at 5:16
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    I imagine cleaning the outside of that bubble is a nightmare... not to mention the corner against both walls. – John Smith Jul 26 '13 at 16:28

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