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AllGoNoShow 01-16-2007 09:45 PM

How many heating vents needed per room?
I have an 80 year old house and am redoing the floors so i figure this is the best time to make the heating vents (forced air system) in the right places. The guys who converted the house to HVAC 50 years ago also hacked the main beam to get ductwork up so i doubt much thinking went into the design and placement of heating vents.

On the first floor I have three rooms and a kitchen-if you were to place an imaginary line down the center of the house I have 4 heating vents in the front half....and only 1 in the back half! Needless to say the back living room is always 2 degrees cooler (or hotter depending on season) then the rest of the house. The front room is only 12x19 yet has three heating vents. Can i cut these down to two so i can move a vent to the back of the house? What is the general rule for how many vents are needed per room?

Thanks for the help!

#CARRIERMAN 01-17-2007 01:41 PM

Hi AllGoNoShow

Get your tape measure, your calculator, pencil and paper. Do a cubic footage of the room, devide that by four. That is going to be the required air exchange per hour for that room. Once you have done that you will need to post that number and one of us can give you the equivelent duct size to achieve this, and how many registers it will take. We will also need to know if its in the ceiling, floor, wall.

Good luck

AllGoNoShow 01-18-2007 10:41 AM

Exact Cubic footage of the front living room is 1720. 1720/4= 430 Right now there are 3 heating vents (duct is 6 inches wide and the registers are 2 1/4 inches by 12 inches).

Then attached to that room (behind if you were looking at a floorplan layout) is my dining room which has cubic footage of 1028 and has 1 heating register. 1028/4= 257 This dining room is in the middle of my front living room and rear family room.

The family room which is in the back (again as if you were looking at a floorplan layout) is the room that is always 2 degrees cooler or hotter depending on season-This room has a cubic footage of 1950 yet only has 1 heating vent! 1950/4= 487.5 Ultimately I want to see if I can move one of those heating vents out of the front living room and put it in the back family room to balance the system more.

Can you share the information/calculations on duct sizing for rooms (and also for central return sizing) so that i can do these calculations for myself in the future? Any website/info/book to read you can provide would be very helpful! Thanks! PS- All the heating registers are in the floor except the one in the rear family room which is placed 4 feet offcentered, about 1 foot off the floor in the wall.


AllGoNoShow 01-23-2007 02:16 PM


#CARRIERMAN 01-23-2007 04:06 PM

Hi AllGoNoShow

I haven't forgot about you, I have been busy getting ready for a new carrer. I will post back a little later with the spec to help you.


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