bathroom exhaust vent

[tony voss]

Hey,guys could use some advise on bathroom fan.Im working on a 1926 two story home so putting fan in ceiling an venting it outside will take some work since there never was a fan in bathroom to begin with.seems much easier to install a remote fan below bathroom in basement run short duct up to the baseboard with a register an then wire it in.but is having the vent intake so close to the floor make it work poorly? what do think stupid idea or could it work?

[Bob Elliott]

Hey,guys could use some advise on bathroom fan.Im working on a 1926 two story home so putting fan in ceiling an venting it outside will take some work since there never was a fan in bathroom to begin with.seems much easier to install a remote fan below bathroom in basement run short duct up to the baseboard with a register an then wire it in.but is having the vent intake so close to the floor make it work poorly? what do think stupid idea or could it work?
Most humidity rises towards the ceiling but it sure would be better than nothing.
It would satisfy code.
Curious to see what others say.

[Ken Amelin]

[quote= Bob Elliott] Most humidity rises towards the ceiling but it sure would be better than nothing.
It would satisfy code.
Curious to see what others say. [quote/]

"Humidity rises at ceiling" is a bit misleading.

While the ability air to hold moisture increases with temperature, The moisture content of air migrates to areas of lower vapor pressure in any direction. Vapor pressure migration in air is very fast. (faster than temperature). As inspectors we've all witnessed moisture migration through sheet rock and other materials, So exhaust of moisture from a vent that is at a lower than ceiling level in the bathroom will work fine.

The trick is to size the fan for 10-15 air changes an hour, and allow free space under the door for make up air. As the volume of air in the bathroom is replaced with dryer make up air, the moisture will migrate to the dryer air and be exhausted.

[Bob Elliott]

[quote= Bob Elliott] Most humidity rises towards the ceiling but it sure would be better than nothing.
It would satisfy code.
Curious to see what others say. [quote/]

"Humidity rises at ceiling" is a bit misleading.

While the ability air to hold moisture increases with temperature, The moisture content of air migrates to areas of lower vapor pressure in any direction. Vapor pressure migration in air is very fast. (faster than temperature). As inspectors we've all witnessed moisture migration through sheet rock and other materials, So exhaust of moisture from a vent that is at a lower than ceiling level in the bathroom will work fine.

The trick is to size the fan for 10-15 air changes an hour, and allow free space under the door for make up air. As the volume of air in the bathroom is replaced with dryer make up air, the moisture will migrate to the dryer air and be exhausted.
Must be a tough trick judging by the weak exhaust fans I see most of the time.I especially hate the passive vents in old high rises since there is no way to upgrade due to location but thanks for the detailed rundown.
I agree.

[Rick Cantrell]

Tony

There are fans that mount and exhaust through an exterior wall. That is if you have an exterior wall.

[Ken Amelin]

[quote=Bob Elliott]Must be a tough trick judging by the weak exhaust fans I see most of the time.I especially hate the passive vents in old high rises since there is no way to upgrade due to location but thanks for the detailed rundown.
I agree.[quote/]

Not that difficult to achieve. A 6ft X 10ft bath with 8 ft ceiling has 480 cu.ft. @ 10 air changes per hour = 4800 cu.ft./60 mins per hr = 80CFM fan.

[Bob Elliott]

[quote=Bob Elliott]Must be a tough trick judging by the weak exhaust fans I see most of the time.I especially hate the passive vents in old high rises since there is no way to upgrade due to location but thanks for the detailed rundown.
I agree.[quote/]

Not that difficult to achieve. A 6ft X 10ft bath with 8 ft ceiling has 480 cu.ft. @ 10 air changes per hour = 4800 cu.ft./60 mins per hr = 80CFM fan.

Personally with the amount of growth I see(mold in grout joints) what may look good on paper(your specs) is not enough and I would like to see exhausts that pull your hair straight up.:)

[Rick Cantrell]

"I would like to see exhausts that pull your hair straight up.:)"

You mean like this

YouTube - Broan combover commercial (http://www.youtube.com/watch?v=qO9r8WgsB3Y)

[Michael Thomas]

The problem is often not the general humidity level within the bathroom, it's the condensation on the ceiling immediately above the shower/tub.

In my experience a ceiling fan is required to deal with that condensation, and the placement of the fan is critical to its effectiveness - its not unusual for me to be asked to discover the cause of a "ceiling" leak in a large bathroom that is in fact just condensation at the ceiling even though there is a operational ceiling fan just a few feet from the shower/tub footprint.

This may seem like a common-sense observation, but I'm occasionally paid to make it to homeowners, and sometimes even have to persuade them to discontinue the use of the shower for a few days so I can come back and demonstrate with IR and /or moisture meter readings that moisture levels at the ceiling have in fact returned to ambient.

[Markus Keller]

Having done this install more times than I can count, I'm not understanding how you think it would be so difficult or more difficult than the basement duct version. I used to know a developer who loved putting one right by the back of the toilet. After a few years, he came to see that for some reason they rusted out like crazy.
Install the ceiling model or a wall model. Forget the low install, it won't save you anything. If you do go with a low model, provide GFCI protection for it.

[Bob Elliott]

"I would like to see exhausts that pull your hair straight up.:)"

You mean like this

YouTube - Broan combover commercial (http://www.youtube.com/watch?v=qO9r8WgsB3Y)
Good one.:)

[Rick Cantrell]

Good one.:)

I have my moments :cool:

[Michael Derrick]

Hey,guys could use some advise on bathroom fan.Im working on a 1926 two story home so putting fan in ceiling an venting it outside will take some work since there never was a fan in bathroom to begin with.seems much easier to install a remote fan below bathroom in basement run short duct up to the baseboard with a register an then wire it in.but is having the vent intake so close to the floor make it work poorly? what do think stupid idea or could it work?

If the bathroom is on an outside wall, why not put a wall vent in? or if you open up the ceiling you can run duct to the outside wall that way.

Mike

[tony voss]

Thanks for all the input,we decided on putting it high on wall an exit outside its a little extra work but worth it thanks again