Exhaust Fan Mystery??!!


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Old 10-14-05, 11:50 AM
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Exhaust Fan Mystery??!!

We decided to gut and renovate the bathrooms in our house. The house is twenty years old, and the bathrooms appear to be the original. The main bath is 95% done. I'm just waiting on the granite to be cut so we can install it on top of the vanity.
In the meantime, I figure I'll pop in a new exhaust fan. The old one is nasty, dusty, crusty, and a heath hazard. So I pull out the old one and I see this and this. Am I seeing things, or did some dolt stick an exhaust fan in the ceiling 20 years ago without ever venting it anywhere? There you can see the fan housing, but it doesn't lead to anywhere. Nary a hole or opening or exhaust of any kind. WTF? Who built this house, and what were they thinking? Can't wait to see what surprises I'll find in the other bathroom.
 
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Old 10-14-05, 11:55 AM
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Pretty nasty photos

Appears from your pictures that you're about to install new ceiling fans and ductwork for same.

Your permit inspections will require that the fans be vented to the outside. I see some ceiling removal/reinstallation in your future.....
 
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Old 10-14-05, 12:30 PM
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I just can't believe this! The renovation was going like clockwork, and now this. I'll have to look further and see if any ductwork is already in place. Otherwise, do you see any alternatives for some type of bathroom venting? I shudder to think what the ductwork installation might cost me.
 
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Old 10-14-05, 12:36 PM
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I don't know about where you live, but here, I am required by code to have a vent in the bathroom that exhausts to the outside of the house.
 
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Old 10-14-05, 12:59 PM
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I'm in south Florida, Broward County. And I cannot imagine that the code would be any different than your's.
BTW, how is that fan housing held in place? I want to yank it out to see what, if anything, lies behind it.
 
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Old 10-14-05, 02:07 PM
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hard to say without being there... check for screws/nails holding it to the ceiling joists... Possibly a metal span between the joists - or nailed to blocking between joists...

Don't just yank it out.... it's possible there is venting behind the unit... no point is ruining your ceiling if you don't have to....
 
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Old 10-16-05, 10:56 AM
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not exhausted outside

Here is a good one. I was told by a plumber that I do not need to cut any holes. Just vent it into the attic. My brothers place was built in 1958 and is vented into the attic. No issues with his ceiling or anything else. The guy that told me this told me his has been that way for years as well with no problems. If you really think about it, in the heat of the summer this same condition exists naturally in the attic area of everyones homes unless you have a fan system to disburse it and keep the air moving. I think the little bit of humidity that comes out of a bathroom is not going to hurt anything. Not the same however for those with saunas and hot tubs etc...That's just my opinion and god knows I have a lot to learn.
 
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Old 10-16-05, 12:26 PM
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It is important to remove excess humidity inside the home to the outdoors. Bathroom vents are suppose to be vented to the outdoors. Excess humidity can cause moisture and mold and mildew problems. Humidity level inside the home should be between 53-55%. Bathrooms and kitchens tend to be more humid than other areas of the home. Today's homes are built much tighter than in the past and the need for ventilation is greater.

http://doityourself.com/mold/moldresources.htm

Some recommend that for bathrooms up to 100 square feet, an exhaust fan should provide 1 cfm (cubic feet/minute) per square foot. Say, your bathroom is 8x5'x8' ceiling, you need a minimum of 40 cfm fan. For bathrooms larger than 100 square feet, cfms can be calculated based on number and type of fixtures--toilet (50 cfm), shower (50 cfm), tub (50 cfm), and jetted tub (100 cfm). Calculate the number of cubic feet (Length x width x height), and this will tell you the number of cubic feet of air the vent needs to move. Divide by 8 air exchanges, and this will tell you the number of cfm required for your vent. Bathroom vent/fan units should be allowed to run for at least 20 minutes after bathing to completely exhaust humidity out of bathroom.

4" vent pipe is recommended. Any turns should be gradual, avoiding 90 degree turns in order to reduce air noise. Vent pipe should have no leaks that would allow humidity to enter the attic.

For a well-ventilated attic space, venting into attic may never cause a serious problem. Sending warm, moist air to attic, however, sets a homeowner up for potential problems. Mold and mildew spores are everywhere, including in the attic. Once the right conditions and humidity levels, mold and mildew can be a problem. Health issues, wet insulation, dry rot, and other moisture related issues are of concern. Venting to the outdoors prevents condensation and wet ceilings. During winter, when warm, moist air enters attic, condensation forms when it encounters cold air. Worst case scenario is icicles hanging down in the attic. When they melt, the water damages insulation, wood, and possibly ceilings below.

To check to see if attic is adequately ventilated, calculate attic square footage (length x width). Apply the One in 300 rule: 1 square foot of attic ventilation (both intake and exhaust) for every 300 square feet of attic space for Net Free Area of ventilation needed. Divide square feet of attic by 300. Convert the square feet to inches by multiplying by 144" (number of square inches in a square foot). Then, divide by 2 because the number of square inches of ventilation has to be divided between intake and exhaust. Intake ventilation must be at least equal to exhaust ventilation, and exhaust ventilation should not exceed intake ventilation. Adequate, balanced ventilation in the attic is important.
 
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Old 10-16-05, 01:20 PM
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Exhaust Fan Mystery??!!

Venting into an attic is a no-no!!!

Even if you have a well ventilated attic under normal conditions, a sudden burst of moisture and heat (in the cooler months) will cause big problems in terms of moisture accumulation.

Any decent DIYer can vent a bathroom. That is one of the reason for all the handly fittings to do it properly.

Also, keep in mind typical bathroom fans really are designed to vent air and not be true moisture-laden air. If you get a powerful fan you will just dump more moisture into your attic.

Dick
 
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Old 10-18-05, 05:19 AM
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Ok I got the point and pretty much new we couldn't vent into the attic. But we put a new exhaust fan in and attached a flexable vent pipe about 5 feet long leading to an existing roof vent. Just stapping it below so the air would go directly out the roof. Could this cause any problems?
 
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Old 10-18-05, 08:51 AM
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Venting in that matter here would casue the inspector to slap your wrist and make you fix it right, but still MANY shadey guys do it that way for fact of ease.

proper way is to either get a dedicated roof vent just for exahust fans-whole $17 and maybe 25 minutes of your time to install it.

Or if you have a gable end or access to an outside wall installing a typical "dryer" type vent is the other approved method.

We're required by code here to use 4" insulated ducting, and are allowed the use of 4" insulated flexible ducting, so that's what i use.

Needed to add this also: Our town follows what's going on nationally and updates codes very often (wihtout telling us till we're dont and need ot fix it) anyways, last year whenever we did anything interior wise $1K or more we have to install smoke detectors throughout the house, this year if ANYTHING is done inside the house needs to have smoke detectors installed. As of now we're allowed to just put up battery powered units costing about $5/ea, but was told in the near future they're going to change it to code of new houses requiring the smoke alarms be hard wired....and just when people thought that standard bathroom remodle was pricey before....LOL, you aint seen nuthin yet boys and girls...figure another $1K on top of normal bid for added electrician work.
 
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Old 10-19-05, 02:18 PM
spirit
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Thank-you for the reply. Allthough I was looking for the possibillitys of us doing damage by strapping the vent under an existing vent from ice, snow or whatever!
 
 

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