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all. I live in an old Edwardian home where the attic above is a finished loft space so I can't run any ducts upward. I have a second floor bathroom below that needs to be vented correctly. Right now it's only venting directly between the joists. What's really unfortunate is that the current exhaust in the ceiling is literally less than two feet away from an outside wall. But the joists run the wrong way. I don't know a lot but I know not to cut a four inch hole into a joist.

Since the joists run the wrong way there is a bedroom next to the bathroom. I think it'll be around thirteen feet, including the bathroom area to run a duct from that point above the ceiling along the adjacent bedroom to get to an outside wall. My question is, will this be too long to run a duct or will I encounter problems of some sort?

Here is the model that I'd like to get. It has good reviews and appears to be the quietest:

[https://www.amazon.com/dp/B003U9TNG0/_encoding=UTF8?coliid=I1FB73YAR81YX4&colid=3CARMNY93861P&psc=1][1]

Unless anyone has any ideas for a wall mounted exhaust that is of similar quality and as quiet I feel like doing a ceiling mounted exhaust is my best option.

Hope to receive some suggestions.

Thanks.

Adrien
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The Panasonic product you listed supports 4" or 6" round duct, according to the installation manual. 13 feet should not be too far at all, especially if it is a relatively straight run. And to be extra safe, use 6" round duct. The rigid kind, not the cheap flex stuff! The increased size will allow less restricted airflow.

Also, try to avoid using any 90 degree turns. The model you referenced has a side port, which means if you install it between joists you should be able to take the duct straight out of the side of the fan and straight through the exterior wall to the vent cap.

In reality, you should be fine with a straight run of 4" rigid duct. But 6" would give you some peace of mind.

Doug Hill
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Typically in all bath fans I seen go in, a 30' run was allowed IF there was no elbows used. If elbows are used, which will be pretty much the case in any install, you need to deduct 5' for each elbow added. For example, if a given run needs 3 elbows, your total length of run cannot exceed 15' and still have an effective draw. The static pressure will be too great and the rated CFM of the fan will not be realized.

Jack
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