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I would like to install my own ducting after I remove the old radiators in a three story small (1,000 square foot) row home. First floor has four rooms; second floor has three rooms and third floor is a finished attic space (bedroom). Heating system will be gas fired in the basement. I have some interior walls out and could frame out for just about any size ducting or configuration. Anticipate using insulated 8 inch, 10 inch or 12 inch flexible with a 60,000 BTU heater. My question is which size ducting to the various rooms and why. Any/all input appreciated. Thanks.
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There is an excellent article on the subject in the newest edition of Journal of Light Construction, with a table and formulas for making this determination. Good Luck!
Tom
*I just installed all new ducts in my house. I found that the local plumbing supply was willing to design the ductwork in order to earn my business. Of courese their prices are slightly higher than Home Depot but the materials are better and there is much less risk of having an imbalanced system with some rooms hot and some cold.
*I agree wtih Greg - spend a couple of bucks at the local plumbing store and get the ducts properly sized. I've lived in houses that have rooms that are too hot and cold -- coldest ones seem to be right on top of the furnace room and the warmest are the longest run.
*I use to size ducts when designing a home based on heat loss and gain calcs for each room and a cfm air flow of between 500 and 750 . Your local plumbing or HVAC store may help but their sizing may be based on what has worked before. Have them also calc return air grille and duct size and get clues on air circulation.
*Thank you all. I have followed up based on your suggestions. A local HVAC dealer loaned me his copy of Trane's Air Conditioning Manual - they're in La Crosse, WI. Chapter 9 is the chapter of interest. Also, I have a catalogue of The Journal of Light Construction publications on its way. They are at 800-784-0290 ; jlconline.com; 932 W. Main Street, Richmond, VT 05477.
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I would like to install my own ducting after I remove the old radiators in a three story small (1,000 square foot) row home. First floor has four rooms; second floor has three rooms and third floor is a finished attic space (bedroom). Heating system will be gas fired in the basement. I have some interior walls out and could frame out for just about any size ducting or configuration. Anticipate using insulated 8 inch, 10 inch or 12 inch flexible with a 60,000 BTU heater. My question is which size ducting to the various rooms and why. Any/all input appreciated. Thanks.
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You mentioned fexible duct work. While much easier to install, it creates more frictional losses in the air flow than rigid duct work, requiring a blower that puts out more pressure.
Consider balancing valves between floors to make adjustments in the future. Some rooms want more or less of the air in different seasons. Some of that can be addressed at the grates, but a balancing valve is a better way, if you got a way to access it.
Consider your return air paths carefully. All the air you put into each room has to leave somehow (or no more will flow in). Where do you want to be the warmest, where is it okay to be drafty (near the vents). Do you want hot air stratified high at the ceiling, simulating radiant ceilings (and have cold floors)? Or do you want to try to stir the air around by introducting the hot air down low which creates more vertical air currents and moves even more dust around the house? Draw diagrams of where the air will go and look at other houses and offices for what works and what doesn't.
-David