installing a makeup air vent

Old 01-06-10, 07:37 AM
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Join Date: Jan 2010
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installing a makeup air vent

Hi. I'm finishing my basement, where the finished area will be completely enclosed and the 2 windows are in the unfinished area adjacent to the furnace. According to the inspector (we got permits to make sure I do it all correctly), because of the layout I need to put in a makeup air vent. I've read here and elsewhere 2 ways of doing it: A) direct vent from outside to the return air plenum B) direct vent from outside then pointing straight down to the floor.

Couple questions:
1. Is (A) going to lower the temperature of my furnace's heat output (like today the temp outside is the then teens), and is there a gravity controlled flap that I can install in the duct to minimize cold air going in when the furnace isn't running

2. Is (B) going to make my unfinished area cold because of the outside cold air

3. Which is the optimum way of doing it A or B

4. Can I just use regular HVAC 6" duct for the above

5. I've seen (B) terminate inside a box- what's the purpose of this

Thanks for your expert advice. I just want to do it all correctly
Old 01-06-10, 08:08 AM
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Join Date: Dec 2009
Location: Louisiana
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Consult yuor inspector as to what your code requirements are

Every area is different but as a general rule follow the international mechanical code and you should be ok.

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