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Old 01-15-2008, 03:16 PM   #1
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Basement ducting size???

Just have a quick questions. I am currently finishing my basement, it is about 700 sqft (basement of a townhome). I need to run two heat runs, one to go straight off the furnace about 14 feet (no bends) and then the other one goes about 16 feet, makes a 90 degree turn and runs an additional 12 feet.

My question is: What size ducting do I need. I'm not using the flexible stuff. I think I would be ok with just 6 inch. The HVAC guy that came out mentioned 8 inch. What size would be best. I would prefer the smaller if I could. Also, the townhome is in the middle of 2 other ones so I only have 2 insulated exterior walls in the basement(Not as cold).



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Old 01-15-2008, 05:04 PM   #2
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Not too sure what the industry math formula is. For me, I compare the same amount of "floor space" to my main floor area. For example, Rec room, eating room and kitchen. For these 3 rooms on the main floor, we have 6 x 4x10 heat discharge vents connected to standard 5" round air ducts - off the main air duct. With this in mind, my basement (of equal floor space) needs the same amount of heat discharge vents.

In my Northern colder home where heating is used more then AC, I want my basement "heat vents" discharging on the basement floor. And I want 2 x cold air intakes on the basement floor level - on opposite side of the basement of where the majority of floor level heat discharge vents air installed.

To force heat down the basement heat discharge vents, I close some of main floor heat vents. Thus, forcing more heat into the basement rooms. Since heat naturally rises, it keeps the main floor "floor" warm. And, indirectly heats the main floor as well.

Where possible in your basement, heat and cold air vents are installed within your inner basement walls. The outer basement walls are insulated. Use 5" round Flex pipe between 2x6 inner walls. To reduce possible fire, NO air intake or heat vents within your basement furance room. Having a cold air intake near the outside of furance room that has a shut-able door is ok.

Off topic but related.... If you are thinking of installing tile on your basement floor, one might install Tile with infloor heating. Heating strips where majority of folks might walk or where a fixed postion sofa might be installed. Thus, folks have toasty toes when putting their feet on these tile positions. If you use infloor tile heating, one can reduce their heat vents by 1/3. Thus, less heat discharge vents but same number of cold air intake vents. Having cold air intake vents at floor level (for northern colder houses like mine) is a good thing to do. In hotter sourthern homes, having basement ceiling height "cold air" intake vents is better.

Hope this helps...



Last edited by Spike99; 01-15-2008 at 05:56 PM.
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