Bathroom Ventilation

CHARLES_4

Follow local codes for bathroom venting. Yeah, the job's being done w/o permit and it will never be inspected, but follow the code anyway. If there's no time/money to do it right, will there be time/money to do it over?

MagicJS

Turbine Ventilators

Hi, I'm working on a five story residential building. For bathroom exhaust, the client asked me to use ceiling mounted exhaust fans in bathrooms and a wind powered turbine ventilator on the roof instead of a roof fan. The shaft are straight runs, a few offsets on top floor.

Has anyone else done something like this. Will the ceiling fan and ventilator be enough or should I insist on installing roof fans

Thanks.

Brad White_80

My view...

I think that if the common duct is large enough (constant area all the way up) that will go a long way toward balancing.

It will work much better than if all of the fans had long ducts (4-inch? Huh?) running twenty feet. Most fans spin, make noise and move pathetically little air when so ducted. Avoid flex if you can.

Sometimes this is done without a wind turbine and they can work well enough, so having the turbine is helpful. All you want to do is maintain a negative pressure in that shaft. (The shaft duct I would size for a net free area velocity not over 500 FPM in my experience. See below for comment on up-turned duct obstructions.)

Yes, check your local codes for air volumes to be moved. Our code here in MA requires one value if constant and a higher one if sproradic. My rule for sporadic use is the greater of 75 cfm per water closet fixture or 100 cfm with toilet and shower, or two cfm per SF.

One point to make abundantly clear: Fire protection. What you are doing is combining several exhausts from different tenancies. You have to check the spread of fire and smoke from one unit to another. Unless you have fire dampers, the ducts entering the common shaft have to up-turn 22 inches. Why 22 inches? Heck if I know. Fire does not like to go down and I guess it carries a measuring tape. See NFPA-90A for more information. Duct penetrations without dampers should be sleaved and sealed with firestopping compound.

Your code may require smoke detectors if not at each level than at the top of the shaftway. Every jurisdiction has it's quirks and issues; thes are some I have run across.