Adding A/C Vents this way Reasonable?

[Mike]

My house is 55-years old and all the outlet and return vents are positioned near floor level in the walls. Central A/C and a furnace share the ductwork, and the A/C doesn't work well in the upstairs bedrooms. I'd like to have additional outlet vents in those rooms positioned near the ceiling so that I could open them when using A/C (furnace vents closed) and close them when using the furnace (furnace vents open). It looks to me like a reasonable way to add an outlet in my house would be to open up the wall above the existing ductwork, extend the ductwork to near the ceiling, install a vent there and close up the wall. Has anyone tried this either via contracting or as a DIY project? Any thoughts or recommendations?

Thanks, Mike

[PrecisionMachinisT]

No shit, man.....

Nobody ever seems to thing about how there gonna draw the air into the unit.....

Thats the point where it all starts......

[CBhVAC:)]

As a suggestion, since not a soul on the internet can tell you what YOU need, since the duct design, and static pressure of the existing machine is dictating what you can, and cant do, would be to think about returns, not supplys and get an evaluation by a licenced and insured contractor that is familiar with manual D, and J.

[Joseph Meehan]

This is not really a do it yourself thing. To get everything working right means taking the proper measurements, doing the calculations and then determining the best solution. This take knowledge to take the measurements and do the calculations and experience to determine the best/possible solution(s). Experience counts.

[barry martin]

Mike:

M > My house is 55-years old and all the outlet and return vents are M > positioned near floor level in the walls. Central A/C and a furnace M > share the ductwork, and the A/C doesn't work well in the upstairs M > bedrooms. I'd like to have additional outlet vents in those rooms M > positioned near the ceiling so that I could open them when using A/C M > (furnace vents closed) and close them when using the furnace (furnace M > vents open). It looks to me like a reasonable way to add an outlet in M > my house would be to open up the wall above the existing ductwork, M > extend the ductwork to near the ceiling, install a vent there and M > close up the wall. Has anyone tried this either via contracting or as M > a DIY project? Any thoughts or recommendations?

Seems like it should work though can't be sure for the reasons the others gave (Manual J, etc.)

The office my father works in has the heat and a/c through ceiling vents, the returns are in the walls. Close the upper one or lower one depening on the season. Seems to work fine, though was designed this way.

One thing you might want to consider before adding vents is to change your vent covers where the heated/cooled air exhausts into the room. Possibly spraying the cool air up (towards the ceiling) may help.

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[Mike]

Thanks for the advice, gentlemen.

Mike

[Stormin Mormon]

It may provide some relief. The different duct sizes provide different flow rates of air, so you might not do any more good. Worth a try in one room, maybe?

I've often seen undersized air returns, that's very often a problem.