I have a little bathroom, I want to have the most powerful fan in there
that I can, without obviously overdoing it - like having a lot of wind in
there! I'd put an inline fan in the attic. I'm not sure how much would
be too much. I'd like it to double as house ventilation, to empty the hot
air out of my house overnight, that's why I want a fan more powerful than
the minimum.

If you have a powerful bathroom fan, and it's too powerful, can you tell
me its CFM and what the square footage of your bathroom is?

Or, if you have a powerful bathroom fan, and it's NOT too powerful, same
thing? So I can get a ballpark idea of how much power is too much.

I could put a variable speed control on the fan, Fantech's inline fans
take a variable speed control that goes from 0-100% - so I
could put in a bathroom fan that's too powerful for the bathroom, and
use it dialed down when it's being used just for bathroom
ventilation. I guess - I don't know if there are hitches in that idea.

Thanks.
Laura

If you try to use the bath fan for whole house ventilation, you will have a
problem in the winter when you want to get rid of steam and smell cause the
window is closed and you end up exhausting all that air in the rest of the
house you just paid to heat up.

I think a timer and thermostat would result in more efficiency than a
thermostatic control only. Consider the thermal mass of the house and
contents. If you wait for a thermostat to demand the fan, the whole house
will be hot when it comes on and it will take longer to cool as the
furnature and walls are hot as well as the air.

With a timer, you can set it to run into the evening pulling in cool night
air and cooling the contents, then turn it off in the morning to keep that
cool ari inside as the air outside warms up, then at the right time, turn
the fan on to prevent the inside air from warming above the outside air temp




"Lacustral" wrote in message
...
I have a little bathroom, I want to have the most powerful fan in there
that I can, without obviously overdoing it - like having a lot of wind in
there! I'd put an inline fan in the attic. I'm not sure how much would
be too much. I'd like it to double as house ventilation, to empty the hot
air out of my house overnight, that's why I want a fan more powerful than
the minimum.

If you have a powerful bathroom fan, and it's too powerful, can you tell
me its CFM and what the square footage of your bathroom is?

Or, if you have a powerful bathroom fan, and it's NOT too powerful, same
thing? So I can get a ballpark idea of how much power is too much.

I could put a variable speed control on the fan, Fantech's inline fans
take a variable speed control that goes from 0-100% - so I
could put in a bathroom fan that's too powerful for the bathroom, and
use it dialed down when it's being used just for bathroom
ventilation. I guess - I don't know if there are hitches in that idea.

Thanks.
Laura

Lacustral wrote:
I have a little bathroom, I want to have the most powerful fan in there
that I can, without obviously overdoing it - like having a lot of wind in
there! I'd put an inline fan in the attic. I'm not sure how much would
be too much. I'd like it to double as house ventilation, to empty the hot
air out of my house overnight, that's why I want a fan more powerful than
the minimum.

If you have a powerful bathroom fan, and it's too powerful, can you tell
me its CFM and what the square footage of your bathroom is?

Or, if you have a powerful bathroom fan, and it's NOT too powerful, same
thing? So I can get a ballpark idea of how much power is too much.

I could put a variable speed control on the fan, Fantech's inline fans
take a variable speed control that goes from 0-100% - so I
could put in a bathroom fan that's too powerful for the bathroom, and
use it dialed down when it's being used just for bathroom
ventilation. I guess - I don't know if there are hitches in that idea.

Thanks.
Laura


Laura-

Bathroom fans serve the purpose of odor & mositure control. The
suggestion of 1 CFM per square foot of bathroom area is a good one.

Sizing an attic fan / whole house ventilator uses the same rule of
thumb but results is a whole different animal!

Even a small house (1500 sq ft) would suggest a 12,000 CFM fan
..........about 100 times the capacity of the fan for a large
bathroom.

I have "cheated" & used a 20" box fan jammed in a window as a "poor
man's" whole house fan......not the "correct" solution but if you get
good night time temperature drop where you live, it will do the job and
cost peanuts.


A 20" box has about 2000 cfm......now you're only off by a factor of 6
or so not 100! Use two 20" fans & your even closer.


cheers
Bob

Bobk207 wrote:

Even a small house (1500 sq ft) would suggest a 12,000 CFM fan...

"Hello. I am your small house. I suggest a 12,000 CFM fan."

Nick

wrote:
Bobk207 wrote:

Even a small house (1500 sq ft) would suggest a 12,000 CFM fan...

"Hello. I am your small house. I suggest a 12,000 CFM fan."

Nick

Nick-

I'll bet you crack yourself up.

cheers
Bob


BTW both small houses were wrong with their suggestions :

a whole house fan for a 1500 sq ft house sound have ~ 4500 CFM capacity

which is apporx 20 air changes per hour

(Lacustral) wrote:

If you have a powerful bathroom fan, and it's too powerful, can you tell
me its CFM and what the square footage of your bathroom is?

I installed Panasonic fans in my baths, at ~150cfm they are meant for
much larger baths, but are quiet enough not to be objectionable. With
an approx bath size of 500cu ft, that is a turnover of once every 3-4
minutes.

I wear eyeglasses, and now I can see when I get out of the shower, since
the glasses don't get fogged up, so it works great.



--
If I had something witty to say, this is where I'd say it.

Even a small house (1500 sq ft) would suggest a 12,000 CFM fan...

"Hello. I am your small house. I suggest a 12,000 CFM fan."

I'll bet you crack yourself up.

cheers


Well, he cracked -me- up completely! Thanks!

Bonita

Can you tell what model you installed? We need a more powerful
one, I think--we have a huge mildew problem, probably because one
member of our family takes extremely long showers.

And this would be a good time to change, as the motor from our
old one died.

Anyone know if a powerful fan helps discourage birds from nesting
in the duct?

Bonita





John Hines wrote:
(Lacustral) wrote:


If you have a powerful bathroom fan, and it's too powerful, can you tell
me its CFM and what the square footage of your bathroom is?


I installed Panasonic fans in my baths, at ~150cfm they are meant for
much larger baths, but are quiet enough not to be objectionable. With
an approx bath size of 500cu ft, that is a turnover of once every 3-4
minutes.

I wear eyeglasses, and now I can see when I get out of the shower, since
the glasses don't get fogged up, so it works great.



--
If I had something witty to say, this is where I'd say it.

wrote:
Bonita Kale wrote:

Can you tell what model you installed? We need a more powerful
one, I think--we have a huge mildew problem, probably because one
member of our family takes extremely long showers.

And this would be a good time to change, as the motor from our
old one died.

Anyone know if a powerful fan helps discourage birds from nesting
in the duct?

Bonita



Birds are kept out of ducts by a proper vent cap. If the std vent flap
type is insufficient, they also make covers with smaller holes that fit
over existing vent caps.

As for sizing the bath fan, you could see what model you have now and
figure out it's rating, then adjust accordingly. Or figure about 1
CFM per Sq Ft for typical bathroom. Since you are having problems, you
may want to go a little higher. You'd also want to go larger if it's a
bigger bath due to vaulted ceilings, super large shower, etc.

I'd also check and make sure yours is actually working and air is
coming out outside. Sometimes the vent pipe just dead ends against
insulation at the soffits, for example. Or in your case that it's not
blocked by a bird's nest.

Thanks. Our vent cap closes, but the birds pry it open,
apparently. You mean something that stays closed all the time?

Bonita

Had to reply to the "whole house fan size" questions above here because
older replies above won't accept comments, at least through GOOGLE
groups.

--------

Keep in mind in that it's definitely possible to oversize a whole
house fan to the point where you create negative pressure and back
draft appliances pulling their combustion air from inside the house, or
do the same with a properly sized fan if sufficient replacement air is
not available.

A classic example, which I've actually seen, is a cool evening with the
windows closed and the fireplace going when someone turns the whole
house fan to clear smoke from guests smoking at a party - the
fireplace back drafted so badly you could watch the tendrils of smoke
enter the stairwell and travel two stories up to the fan intake.

The real danger in such cases is not a visible back draft, but
backdrafting invisible carbon monoxide from a combustion vent back into
the house.

There are also efficiency issues - place your hand at an undercut on
the bottom of a bedroom being cooled by a window air conditioner when a
whole house fan is on, and unless there is sufficient replacement air
being supplied from openings elsewhere you will feel cold air being
sucked out of the cooled room. The same is true of attic ventilation
fans - if they are oversize, or attic vents are blocked, and you go
up into the attic and close the hatch, if central or window AC is
cooling rooms below you will usually be able to find many places (for
example, the openings around ceiling "can" lights) were conditioned
air is being sucked into the hot attic - often, a *lot* of conditioned
air.

Why are such fans missized? Unusually, they are an "afterthought",
or their size is "guesstimated", or the installed just assumes
"bigger is better", or HD only has one size on the shelf - about
the only time I see their size actually specified is when the HVAC was
designed by a mechanical engineer or a really competent HVAC
contractor.

Michael Thomas
Paragon Home Inspection, LLC
Chicago, IL
mdtATparagoninspectsDOTcom
eight47-475-5668