Duct work placement

Cylindersticks

Hi there I am doing a complete renovation of my basement and I am looking for some advice on the placement of the heat supplies and cold air returns.

Specs on the basement-1700 sq/ft, Forced air high efficiency propane furnace, 10ft high ceilings, 2 large rooms (20 X15) to medium rooms(10x12) to small rooms(8x8)-

For the supplies I would like to bring them down to floor level, as it will make your feet warmer and the hot air can travel up ten feet not down ten feet. For the smaller and medium size rooms I would like to put in one supply low on the floor near the outside walls and a return on the opposite wall about a foot off the ceiling. The larger rooms I would like to use two supplies on opposite ends of the room with the return up high in the center. I would like to use 5 inch round ducts that would travel about 20ft off the main trunk down to the floor.(10ft over 10ft down), I am not sure how big the cold air returns need to be or if what I have proposed will work. Thoughts??

beenthere

Doing that with your supplies will make you very uncomfortable when the furnace shuts off.

Better to have the supplies in the ceiling at the outside wall blowing down to the floor so it mixes the room air that way. Returns can be high or low.

You may want to consider zoning, if you really want the basement to be warm, and not cold most of the time.

Cylindersticks

Why are the supplies on the main level at floor level, but in the basement I want them at ceiling?

beenthere

With a furnace is in the basement, it was much easier, and cheaper to use floor supplies.

Cylindersticks

so I do want to put them in the ceiling in the basement? the opposite of the main floor? and how do I zone?

beenthere

Heat blowing from an outside wall toward the inside never works good. So yes, you want them in the ceiling at or near the outside wall. Blowing down to the floor.

You'll need a zoning panel, and another thermostat for the basement. Along with a new supply trunk for the basement. Although you can use zone dampers in every supply instead of a separate supply trunk, it gets very expensive doing it that way.

Cylindersticks

By the way when I move the supplies up and the returns down how big do the returns need to be? do I need one for each room? and should they all tie into the systems or some just into the furnace room for combustible air?

Jackofall1

Hello and welcome Cylindersticks, to the best DIY'r site on the web.

RA size should be at least 110% of the supply in equivalent area. Combustion air should really come from the outside.

Zoning will be expensive either way you attack it, (dampers in ducting or dampers in branch runs), it will make things more comfortable, but the payback is just not there.

If you basement is subgrade and insulated, the amount of heat you will need is minimal by comparison to the upstairs, this being, there is far less heat loss/heat gain.

Mark

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Cylindersticks

hey mark,
Thanks for the welcome and reply. I looked into the cost of zoning and it is very expensive. Would I be able to get away with manual dampers just inside the runs? I am planning on having all the exterior walls done with spray foam, will this help with what I am planning to put in?

Jackofall1

You should have manual dampers in your branch ducts regardless of zoning or not. Once your basement is insulated I believe you will find a big difference in the temperature stability. Set the dampers and walk away.

I did find that once insulated, my basement was quite comfortable as long as the door to the upstairs was closed.

I had about 900 sqft finished and used 4 x 5" supplies of which they were about 1/2 open in the winter and even less in the summer.

Mark

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beenthere

Combustion air should come from outside. The returns should all tie into the return trunk.