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Old 01-21-2010, 06:27 PM  
AeR0
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Default Bathoom Fan

bathroom currently does not have a fan... ive found one that i would like to put in.. my only problem is where should i put it? in the middle of the ceiling? right above the shower? or closer to the toilet??



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Old 01-21-2010, 07:22 PM  
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Default well

If it a small bath, just put it in the center of the room. Unless you have a bath over 200 sq feet, I would put it where it is best accessed in the attic, and where it will be easiest to install between the joists., and vent to the exterior, not the soffit vents.



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Old 01-21-2010, 07:44 PM  
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Quote:
Originally Posted by inspectorD View Post
If it a small bath, just put it in the center of the room. Unless you have a bath over 200 sq feet, I would put it where it is best accessed in the attic, and where it will be easiest to install between the joists., and vent to the exterior, not the soffit vents.


so you say vent it up through the roof and not out through the soffit?

can i ask why?
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Old 01-21-2010, 08:49 PM  
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That's why we'ar all here.
In the winter when your home has heat escape into the attic space, you create a convection. You draw cold air from the soffits and hot air tries to ecape at the highest point.By introducing your warm water vapor into the mix, you create a peitri dish for mold to grow. And it gets even worse in the summer months. I see it all the time, and just want you to avoid further work, and damage.
You can vent through the roof easy enough, they sell vents or you can make one with a 3 inch plumbing boot and some pvc pipe and elbows.
Hope this helps to explain.

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Old 01-21-2010, 11:58 PM  
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Believe it or not, if it were me, I would try to put it close to the ENDS of the ceiling joists in your bathroom rather than in the middle of the room. And, I'd try to locate it furthest away from the bathroom door.

The reason why I wouldn't locate it in the middle of the bathroom ceiling is that when I've installed fans there I've found that any vibration in the fan tends to cause the whole ceiling to vibrate, and that creates a loud and almost unbearable HUMMMM in the bathroom whenever the fan is on. I think you're less likely to come across that problem if you locate the fan away from the middle of the ceiling. The ceiling closer to the walls can't move as far when the ceiling joists vibrate, and therefore the noise of the vibrating ceiling won't be as loud. It's the middle of the ceiling joists that can move the furthest, so having a vibrating fan located there seems to be a bad idea. The further the middle of those joists move up and down when they vibrate, the louder the noise created by a vibrating ceiling will be.
(Also, vibrations caused by ceiling fans is usually due to dirty impellers. The heavier the spinning impeller, the more shaking force it imparts to the fan housing and hence the ceiling.)

I'd locate the fan further from the door to increase the "sweep efficiency". That is, make up air is primarily going to come into the bathroom through or under the bathroom door. The closer the fan is to the door, the lower the volume percent of the bathroom that's swept out by fresh incoming air.

Keep your bathroom fan exhaust duct as short and straight as possible to get the highest airflow through the ducting, and use RIGID galvanized or aluminum ducting. Plastic ducts with wires to keep them round or metal ducts with ridges along their length induce severe drag on the air flow through the duct, and that results in less air flow through the duct.

Ceiling fans come in two duct sizes; 3" and 4" inch. I install NuTone Model 8832 ceiling fans in the bathrooms of my apartments because they have the highest CFM rating I could find in a 3 inch duct fan without having to pay extra for special sound quieting features.

Also, just cuz the fan duct size is 3 or 4 inches, doesn't mean you have to stick with a 3 or 4 inch duct all the way to the roof vent. If you go with a larger duct between the fan and the roof, (say 4 inch instead of 3 inch, or 6 inch instead of 4 inch diameter) you'll have more airflow because of less resistance to flow through the duct. The smaller, longer and more elbows or bends in the duct, the higher the resistance to flow.

And, heavily insulate your duct and above your fan. Otherwise condensation can form on the inside of the duct and you'll have water dripping out your duct onto your bathroom ceiling and causing the paint on the ceiling to crack and peel. Ditto for the fan housing. You want as much insulation over the top of the fan housing as there is over the rest of the ceiling drywall.

Insulate

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Old 01-22-2010, 08:01 AM  
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Speakinawhich, anybody know the Total Equivalent Length [TEL] for a 4" to 3" reducer?

It would be like, this reducer is equal to
X feet of 4"
or Y feet of 3" pipe,
[with Y > X since 3" pipe offers more resistance than 4" pipe].

I couldn't find this anywhere for pipes this small.

And if your config. allows it, don't forget to pitch the exhaust pipe downward, probably 1" in 10', so any condensate drains to the outside.

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Old 01-22-2010, 08:40 PM  
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Quote:
Originally Posted by inspectorD View Post
That's why we'ar all here.
In the winter when your home has heat escape into the attic space, you create a convection. You draw cold air from the soffits and hot air tries to ecape at the highest point.By introducing your warm water vapor into the mix, you create a peitri dish for mold to grow. And it gets even worse in the summer months. I see it all the time, and just want you to avoid further work, and damage.
You can vent through the roof easy enough, they sell vents or you can make one with a 3 inch plumbing boot and some pvc pipe and elbows.
Hope this helps to explain.

thanks for that info... i could understand that using the soffit vents for venting the bathoom wouldnt be a good idea...

as the soffit vents are designed for the attic to breathe.


what if though i went and put something like this in?

http://www.nachi.org/forum/attachments/f16/26596d1233421565-exterior-vent-covers-img_1811.jpg

my house is not brick its siding.

im not really a fan of venting up through the top of the roof as its just another way you could ask for a leak...
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Old 01-22-2010, 08:46 PM  
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Quote:
Originally Posted by Nestor_Kelebay View Post
Believe it or not, if it were me, I would try to put it close to the ENDS of the ceiling joists in your bathroom rather than in the middle of the room. And, I'd try to locate it furthest away from the bathroom door.

The reason why I wouldn't locate it in the middle of the bathroom ceiling is that when I've installed fans there I've found that any vibration in the fan tends to cause the whole ceiling to vibrate, and that creates a loud and almost unbearable HUMMMM in the bathroom whenever the fan is on. I think you're less likely to come across that problem if you locate the fan away from the middle of the ceiling. The ceiling closer to the walls can't move as far when the ceiling joists vibrate, and therefore the noise of the vibrating ceiling won't be as loud. It's the middle of the ceiling joists that can move the furthest, so having a vibrating fan located there seems to be a bad idea. The further the middle of those joists move up and down when they vibrate, the louder the noise created by a vibrating ceiling will be.
(Also, vibrations caused by ceiling fans is usually due to dirty impellers. The heavier the spinning impeller, the more shaking force it imparts to the fan housing and hence the ceiling.)

I'd locate the fan further from the door to increase the "sweep efficiency". That is, make up air is primarily going to come into the bathroom through or under the bathroom door. The closer the fan is to the door, the lower the volume percent of the bathroom that's swept out by fresh incoming air.

Keep your bathroom fan exhaust duct as short and straight as possible to get the highest airflow through the ducting, and use RIGID galvanized or aluminum ducting. Plastic ducts with wires to keep them round or metal ducts with ridges along their length induce severe drag on the air flow through the duct, and that results in less air flow through the duct.

Ceiling fans come in two duct sizes; 3" and 4" inch. I install NuTone Model 8832 ceiling fans in the bathrooms of my apartments because they have the highest CFM rating I could find in a 3 inch duct fan without having to pay extra for special sound quieting features.

Also, just cuz the fan duct size is 3 or 4 inches, doesn't mean you have to stick with a 3 or 4 inch duct all the way to the roof vent. If you go with a larger duct between the fan and the roof, (say 4 inch instead of 3 inch, or 6 inch instead of 4 inch diameter) you'll have more airflow because of less resistance to flow through the duct. The smaller, longer and more elbows or bends in the duct, the higher the resistance to flow.

And, heavily insulate your duct and above your fan. Otherwise condensation can form on the inside of the duct and you'll have water dripping out your duct onto your bathroom ceiling and causing the paint on the ceiling to crack and peel. Ditto for the fan housing. You want as much insulation over the top of the fan housing as there is over the rest of the ceiling drywall.

Insulate

thanks for taking the timet to type all that out.

my bathroom is very small 8'x5' lol

so a small CFM fan will work well for me.. im thinking in the middle of the bathroom b/c its 1/2 way from the shower and 1/2 way from the toilet.

the toilet is on one side and the shower is on the other.

i plan on venting this way:



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