Apartment Building Dryer Exhaust
Apartment Building Dryer Exhaust
(OP)
I have a three story apartment building wih drayers in each apartment. I want to have a dryer exhaust shaft with a booster fan on the roof.
I think it is fairly typical but I have some questions.
It will be a sheet metal vertical duct in a shaft with a constant speed fan at the top. The 4" individual dryer vents will penetrate the vertical duct and extend up 22". There will be a cleanout at the bottom.
Should I have a drain at the bottom (I do not want one)?
I have a vent at the bottom to allow constant up air flow and air flow when no dryers are operating, but, I am thinking of reducing this vent or eleiminating it as the rooffan should draw a reduced air flow through the dryers which are not operating.
I had to guess on the dryer CFM based on a max. pressure drop requirement I found in one installation manual. Does anyone have better info on residential dryer air flow?
In my case there will be 5 dryers per floor for three floors.
I think it is fairly typical but I have some questions.
It will be a sheet metal vertical duct in a shaft with a constant speed fan at the top. The 4" individual dryer vents will penetrate the vertical duct and extend up 22". There will be a cleanout at the bottom.
Should I have a drain at the bottom (I do not want one)?
I have a vent at the bottom to allow constant up air flow and air flow when no dryers are operating, but, I am thinking of reducing this vent or eleiminating it as the rooffan should draw a reduced air flow through the dryers which are not operating.
I had to guess on the dryer CFM based on a max. pressure drop requirement I found in one installation manual. Does anyone have better info on residential dryer air flow?
In my case there will be 5 dryers per floor for three floors.





RE: Apartment Building Dryer Exhaust
Steve
RE: Apartment Building Dryer Exhaust
RE: Apartment Building Dryer Exhaust
I know what dryer they are using but it, like any other dryer info I have found, does not list the CFM.
One hour shaft. I do not need fire dampers with the 22" projections of the duct into the shaft.
The shaft is actually a sheet metal duct in the 1 hour shaft.
The fan motor is not in the air stream and the fan is aluminum (standard rooftop fan).
I am expecting an air flow when the dryers are all off, but a reduced air flow (hopefully very reduced).
RE: Apartment Building Dryer Exhaust
RE: Apartment Building Dryer Exhaust
The IMC and NFPA limit you to 25 feet of ducting unless you can prove the dryer has “extended” capacity. A few dryers do have extended capacity but most dryers are owner provided. The codes vary upon year.
We have done a few 3 story buildings that use separate 4” runs to a roof mounted vent hood. I like this design except you run out of fan capacity on the lower floor.
I try to vent each unit via a separate vent to sidewall. When all venting is in the unit it forces the unit’s occupant to maintain (clean) the vent system. Remember dryer fires are one of the leading causes of residential fires. Make sure building ownership cleans the lint traps.