Bathroom Paint

[jayhawkerroy]

Just run the fan longer after the shower. Unless you saw evidence of mold or mildew while taking off wallpaper, etc, running the fan longer will do quite a bit of good. We generally run it five to ten minutes longer after we are done with the shower, and this is a 100% enclosed, small, no window bathroom. You might also want to check the exhaust fan ducts to make sure they are not clogged. Dryer vents aren't the only vents that can clog!

[Pat]

Probably too late to impact your paint job but there are scrubable paints (usually not flat) that might be important in a bath. If they didn't use green board, then consider two coats of paint, minimum.

There are inexpensive timers (mechanical twist type) that will replace a light switch and are good for bathroom fans. You can set them for 10-15 minutes after you finish a shower and that will help a lot. Think about the voolume of the room. A small bath with a tub/shower is 5x9 ft and with an 8 ft ceiling that is 630 cubic feet. The air exhausted by the fan isn't all that orderly... removed air isn't 100% stale air. Part of what is removed is recently drawn in fresh air so it takes a while to change the air in the bathroom. Lets say your fan is rated at 150 cuft per minute. Even if the aerodynamics were 100% perfect it would take over 4 minutes to change the air. In reality you'd need to run that size fan in that size room for about 20 min to do a really good job. This assumes the vent duct isn't partially collapsed by other ducts lalying on it or whatever in the attic.

To see how this ventillation thing really works, put a couple tablespoons of milk in a glass and set the glass under a faucet. Turn the faucet on to a stream sized to take 10 seconds or so to fill the glass and time the number of seconds required to fill the glass but leave the water running and time the time required before the water is realy clear (virtually all milk gone.) You will see that it takes enough water to fill the glass several times to remove the visible milk. It gets clearer and clearer but takes quite a while to get really clear. It will take at least 4-5 times as long to get fairly clear as it does to fill it.

What does this mean as regards ventilating a room? The fan has to take out at least about 4-5 times the volume of the room to get most of the moisture out (more is better). So in our hypothetical 5x9 bath with 8 ft ceiling which has 360 cuft we need to suck out about 1800 cubic feet to start to have the air mostly replaced (most excess moisture removed.) With our 150 cuft/min fan it would take 12 minutes. This assumes 100% efficiency, good air flow into the room (under the door or ...), no ductwork kinks or restrictions, etc. 15-20 minutes would not be excessive run time in this situation to allow for a little real world reality. This is 15-20 minutes after the shower is turned off.

//9th grade general science mode off//

This will not be on the quiz!

You can disagree with my assumptions and replace them with yours... fan capacity, percent eficiency, room size, ceiling height, and so forth but the general approach is pretty straight forward and in general suggests fan run times well in excess of ordinary (insufficient) practices. This is why I suggest the timer. The timer doesn't guess and doesn't forget and doesn't compromise due to convenience. I have seen bathrooms wired such that the power for the fan comes from the "light" switch so if the lights are on the fan runs. Reduces need for "disipline" but if there is a lot of lighting in the bath, especially not so energy efficient lighting, then I don't recommend that arrangement.

A real good arrangement is a humidistat in parallel with the switch in the fan circuit. This will allow you to turn on the fan and run it whenever you want irrespective of room humidity but high huidity can turn on the fan and run it till the humidity drops to your set point. No timer, automatic operation with manual override. Humidistats aren't all that expensive. Takes the guess work out of the exhaust fan situation.

[img]/forums/images/icons/smile.gif[/img] Pat [img]/forums/images/icons/smile.gif[/img]