Located in Ontario Canada, so winter tend to be cold and summer mild.

We are finishing basement, the finished area is about 900 square feet.

We have came up with the following locations and numbers for the supply and return vents. The supply vents all uses 5" round metal ducts, and are located in the ceiling. I will need to add some return vents after framing is done, and planning to put them at the floor level. The return vents will use 6" round metal ducts where needed (Very hard to find 7" or 8" round metal ducts here in homedepot Canada).

Please see layout of the basement and locations of the ducts below:




Now few questions.
1. Do I have too many supply ducts in the living room? Is supply vent D really needed?
2. For the living room return duct A, can I get away with a 6" duct? Or do I need a either a second return vent, or somehow use 8" ducts?
3. Is return duct A location okay? My concern is that it is bit far from the bathroom and majority of the living room. It is the most convenient location though due to existing ductwork.

Any help is appreciated. Thanks.

 

You need to know the size of your furnace and whether or not the existing ductwork will handle the additional outlets. I don't get involved in that as I don't consider it Diy work.

Someone may be able to help you.

 

What you will find in a basement is that in the summer everything gets closed because it's cold down there anyway, so your really only putting heat down there in the winter.

But that means the rest of the house will now be lacking that volume of supply!

 

You have about 98 square inches of outlet size with five 5" ducts and only about 56 square inches of return area with two 6" ducts. You want there to be more return duct area than supply. Even more important since one of your returns is located in a room that can have a closed door.