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-   -   Air return vents (http://www.houserepairtalk.com/f8/air-return-vents-8295/)

jkinder 01-04-2010 01:42 PM

Air return vents
 
We bought a house that does not have any cold air returns. Basically the furnace just sucks air from the utility room in the basement, obviously not a very good setup.

We have a great room that dominates the majority of the upstairs including a living room, breakfast area and kitchen....no interior walls. There are also 2 bedrooms and a hallway.

Right now we have no AC unit, but will be installing one either this year or next.

Obviously I want to get the air returns setup so that we have a much more comfortable house. The bedrooms will not be a problem, I can use the walls as ducts to the basement, and since the room below them is unfinished right now, I can easily route a new main duct over to the furnance for those.

We have a coat closet pretty close to directly above the furnace that I can put a cold air return duct into.

Also, I have a straight shot in the basement that runs through under the middle of the great room where I can put an air return vent .

The question is for the great room.

Can I install the cold air returns in the ceiling, then put duct work in the attic from the vents over to the trunk in the closet? Are there any issues doing this? I have only seen air return vents in walls, never in a floor or ceiling, so is there a reason for this, or just that most houses have interior walls to put the vents in?

Also, I would put cold air returns in the floor, one in front of the island opposite side of the kitchen in the living room and one near an exterior wall farthest away from the furnace, but on the same duct that the vent in front of the island would be on.

In the summer I would shut off the floor vents and close the ceiling vents, and vice versa in the winter.

Thoughts? Also, I tried to explain the best I can, if you have more questions feel free to ask.

GregC 01-24-2010 11:27 AM

Hello, Cold air returns are best in high area. Remember this..."Low feed" and "High" returns. Feeds to outside walls if all possible. Yes, you can place returns in the high part of wall or in ceiling. This works best because heat raises which will recirculate back to furnace and cold air will stay low but with a high return it will bring it up to more comfortable level then circulate back.
Be careful with returns, NO return close or IN a bathroom or Kitchen!! This will suck and bring all odors back to furnace and recirculate them through entire home! You will be smelling your morning bacon or your last B.M. everywhere! :cool: Hope this helps GregC

Wuzzat? 01-24-2010 12:17 PM

Seems like you first need to

"calculate heat loss . . .using a Manual J workbook and
spreadsheet.
Information from the spreadsheet. . .used to
calculate the heat loss for each room, and the entire house.

Duct design [to] incorporate information from the heat loss
spreadsheet to design a duct system to distribute the correct
amount of air to each room to satisfy the load.
"

HVAC design is more complicated than electrical circuit design; everything is non-linear, interdependent and 3 dimensional, and what equations you can find work only over a limited range [so they use look-up tables or graphs].

ASHRAE is the ultimate authority but they don't lend their books to libraries; ACCA is another source.

duct cfm - Google Search

Ducts - Noise Generation

http://www.engineeringtoolbox.com/fan-noise-d_61.html

Heating & Cooling Degree Days - Free Worldwide Data Calculation

http://www.google.com/search?client=safari&rls=en&q=%22outside+design+temperature%22&ie=UTF-8&oe=UTF-8


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