Duct Work


Old 01-23-03, 10:28 PM
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Duct Work

I am in the process of knocking out my plaster walls to do extensive wiring, insulation and duct work. I plan on replacing all the existing duct work for the heating and air. When it was done originally it was done poorly and it is also inadequate. Since it was first installed there has been additions, dormers and an attic converted into living space. The entire upper level has NO duct work at all, brrrrrr! Anyway, when planning the route a duct should take how should I go about it? As I said I am knocking out the plaster in the 1st floor and the furnace is in the basement. My question is, are the ducts most effective running up the outer walls or inner walls of a home? Also, is it recommended to have more than one duct per room? Reason I ask is because it seems no matter how you place furniture in a room it always seems to cover a heating vent. I figure with two, on opposite walls I would have a choice. Once more question, as far as the cold air returns go. Is it recommended to have them high up on the wall or close to the floor? I have seen it both ways and never knew which was correct. Thanks in advance!
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Old 01-24-03, 06:10 PM
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I was stalling off answering your question in hopes of a tin wizzard showing up, but I'll have to do I guess.

If you are planning to divert a fairly large volume of air from the furnace you would have to originate this supply directly from the plenum, which is the section of duct that is right at the furnace.

The route you use to feed the upstairs really doesn't matter.

The supply grills should be on the outside walls and the returns on the inside walls.
Depending on the difficulty in accessing this area you likely could get away with a return in the hallway and just undercut the bedroom doors a bit.

It would not be necessary or adviseable to have two grills/room in the smaller rooms. Sizing and balancing would be a pain as well as trying to fit it all in.
Living room, kitchen and dining room would have more than one grill and would be spaced to distribute the air evenly.

There could be a lot of discussion on return grill location but at the floor works and is easy to install.

Are you planning to DIY?

It might be an idea to get a few quotes from a sheet metal shop to see if it's worth doing yourself, or find a shop that will build the ductwork and offer advice on its installation.

Here is some misc reading on the subject:


Some slightly technical stuff:


Cmon back if you need more info.

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