Finishing off the basement...How many ducts?

Old 09-04-02, 11:00 PM
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Finishing off the basement...How many ducts?

Ok, a couple of questions here...

I am finishing off my basement (approx 450 sq feet). I am planning on adding four 6 in. ducts (taking them off from the main trunk) Plus, I am planning on leaving the small vent that is already cut into the main trunk (for a total of 5 vents). I am adding a bathroom and was going to run one of the 4 new vents in there.

I was also planning on cutting into the 'cold air return' and running a 6 in. duct about 4 feet to an interior basement wall for an air return in the basement.

Am I on the right track here or way off base? Also, how can I find out if my furnace/A.C. can handle these new ducts? I don't have any documentation on the furnace/A.C.

One last question. By cutting into the cold air return so near to the furnace/A.C. and running a 6 in. pipe, will I be "sucking" too much air from the basement and not enough from up stairs?

I live in Missouri where the winters are cold and the summers are hot....

Thanks for the help...I kinda rambled on there....
Old 09-09-02, 12:35 AM
lynn comstock
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basement duct recommendations.

1) at least 1 per occupied room
2) the maximum distance the air can spread is typically 8 t0 10 feet from the grille to get good coverage of the space.
3) locate the grilles to cover the area with airflow.
4) put a damper at the start of each branch so you can adust the volume of air. The basement doesn't really need much air.
5) 5-inch branch ducts to each grille should be ample but 6-inch is OK. Don't forget the dampers.
6) if the grilles are ceiling mounted, I would recommend 8-inch by 8-inch size, 4-way centrally located in the room space.

The return duct in the basement (containing the furnace) is a possible code and safety violation. The furnace area needs to be separate from the conditioned areas and it needs to have ducted combustion air to the furnace space. You probably need a permit to be legal. I strongly recommend that you have the building and safety people inspect the installation and approve it. Live is short enough without CO poisoning. A CO detector is no substitute for a safe installation.

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