A/C Return Air Transfer Grills between rooms?

I live in S. Florida and want install transfer grills above the doors of our bedrooms to increase the return air flow back to the main return grill in the livingroom. Currently the doors are slightly cut on the bottom but I don't believe it provides the proper amount of return air.
I would like to know how these are typically installed. I will be cutting a how in the sheetrock on each side of the wall above the door and will place about a 6"X12" grill on each side.
I need to know a few things:
If there is a stud which obstructs air flow; is it cut and braced horizontally or just left in place and ignored.
To keep air from flowing from the insides of the wall, should I frame it out with wood or just try to seal it off with pieces of duct board and foil tape?
Will I need a baffle between the grills to reduce noise and retain privacy between rooms? If so, can I buy these pre-made or is the an easy way to make them myself.
I have not seen a home yet with a return duct system in South florida; is this common practice?
Do you think adding the transfer grills is overkill and I should just undercut the doors more? I hasd a quote from an AC Duct company and they said that the new code requires these transfer grills.
Thanks for all opinions and advice, Doug
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snipped-for-privacy@keithandschnars.com wrote:

NO
Are your ducts properly sized according to manual D? Some info to print, but follow Manual D http://www.udarrell.com/proper_cfm_btuh_duct_sizing_air_conditioning_systems.html
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http://www.udarrell.com/air-conditioner-capacity-seer.html
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Cutting holes in your home is not the solution to your problem if there is one.
Before cutting the doors how about pinning the door open and see what difference it makes.
Udarrell sends good information.
Best bet is to call a licensed pro and ask them to evaluate your system in person.
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Just curious - who would be the licensed pro in this case? I am interested because I, too, live in FL and the only air return vent in my house is in the great room. Unless we leave the doors to the bedrooms open, there is no air flow.
Have wondered how to correct this problem and have no idea where to start. I think all houses down here built in last 20 years have same problem.
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The proper way is to provide eneough return air through jumper ducts, tranfer grills or a return air duct system back to the handler so the air circulates BUT it is too expensive and builders do not want to spend the $$$ to do it right. They just cut the door bottom which does not provide enough return air and looks ridiculus if you cut it too high.
I'm just a homeowner not a "pro"; although I do seem to be more knowledgable than most A/C installallers that come to give me quotes and answer questions...which is pretty sad. Installers down here never use Manual J or Ds they seem to be mostly hacks, even the big companies. The installers that read the groups here seem like real professionals (except for the same few w/smartass comments) and take their trade seriuosly; I wish I could find a guy like that down here in South FLA.
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DougD wrote:

I feel sorry for you in that situation, especially with maybe 2600 to 2800 cooling hours a year. That is where the best techs ought to be! - udarrell - Darrell
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I like living where i don't have 9 months of winter sports
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reminder
I live in S. Florida and want install transfer grills above the doors of our bedrooms to increase the return air flow back to the main return grill in the livingroom. Currently the doors are slightly cut on the bottom but I don't believe it provides the proper amount of return air.
snipped

KB homes is doing that exact thing now days here in Phoenix. I closed the master door and had the sales man turn the unit on. Grills were about 20x20 above the door. As soon as the system was pressurized there was a nice whistling sound. Not loud mind you, but annoying to me.
I learned long ago that closed doors and air conditioning in the desert were not compatible.
Keep looking for a pro that will help.
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Couldn't you use a transom?
snipped-for-privacy@keithandschnars.com wrote:

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wrote:

Lets just cut to the chase scene then, and simply remove all of the doors.....
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If it were my home, I would do as you're suggesting as far from opposite the supply vent as you can get it. Don't cut studs, just position the registers in between. For privacy, the louvers should provide enough. If sound transmission is a concern, you might want to vertically offset the vents on either side and use the wall cavity as a short duct, lining the interior of the drywall (between your two cuts) with a duct liner such as : http://www.knaufinsulation.co.uk/output/products/page_394.html to keep the sound from bouncing between.
I don't think you have to create a frame inside your cut outs since each stud cavity is likely sealed off. It certainly wouldn't hurt, but is probably more work than is necessary.
I very much dislike doors that are undercut. For one thing, hot air rises and an undercut door is sucking cool air out and leaving the hot air in the room. Besides, it just looks bad.
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Doug,
You are on the right track. You can't blow air into a coke bottle.
The return air duct your talking about doesn't have to be over the door. But further away from the supply duct to the room is a good idea.
Commercial sites use 'cross-talk silencers' I think is the phrase. A duct that goes up, over to the next room and then back down into the ceiling again. Any decorative grill would work that allows the air to flow through freely. Remember that a fan is pushing the air into the rooms and that same fan must suck it out. So make it bigger than the supply duct. For sound isolation, the metal duct is coated internally with this black fibreglass insulation. It keeps the sound down a lot between the spaces.
You can make them up yourself or get a sheet metal shop to make them for you. They do the insulation very neatly as well. Shape them to suit your construction needs. As long as the over all shape is a big letter C, then it should work fine.
Dave
snipped-for-privacy@keithandschnars.com wrote:

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