New AC return feasibility

[rbacu]

The bedroom above our garage is at least 4 or 5 degrees higher than the rest of the house. An AC guy came out and said that we should add a return from the hot bedroom. The bedroom already has 2 vents for cool air, and has dimensions of about 12x12 ft. Does anybody have experience in how much adding a return my benefit. I want the room to be comfortable because a newborn baby will be staying there soon, but I don't want to spend $275 unless I have to. I don't know if the garage ceiling is insulated because it is drywalled, but I assume that it is.

Would replacing the vents with 8 inch diffusers help us out, or should I replace the vents with diffusers and also add a return.

Any help is appreciated.

Thanks,
RB

[LazyPup]

You HVAc guy is absolutely correct. An Air Conditioner does not cool the ir in the room, it displaces the air in the room with cooler air.

In order to displace the hot air in the room with cooler air there must be a provision for a volume of air equal to the CFM of the supply air to exit the room. This could be acheived by leaving the door open, but that only forces the hot air into the next room. The proper solution is to install a return duct in each room which can move a volume of air equal to the supply volume back to the HVAC unit for cooling.

Given that supply ducting is under postive pressure while return ducts work by negative pressure the actual size of the return ducts needs to be slightly larger than the actual supply ducts to the room.

[imeduc]

like to tell people to think of a room as a big balloon. So when the heat or AC come on It can only blow so much air into it if it dont have a return. Do you keep the door open to it??? some time we have to cut the bottom of the door off so air can get out. Like when the blower comes on if you just crack the door open does the blower pull it shut? this will tell you a lot.

ED

My mistakes dont define me they inform me.

[rbacu]

quote:Originally posted by imeduc

like to tell people to think of a room as a big balloon. So when the heat or AC come on It can only blow so much air into it if it dont have a return. Do you keep the door open to it??? some time we have to cut the bottom of the door off so air can get out. Like when the blower comes on if you just crack the door open does the blower pull it shut? this will tell you a lot.

ED

My mistakes dont define me they inform me.

I used to keep the door open, and the room would be a couple of degrees warmer, but since I thought this warm room may be affecting the comfort of other rooms, I closed the door which leaves the room a few degrees too warm.

Would it also make sense to replace the existing 2 vents with diffusers. He mentioned it might help the bonus room in the attic, but he did not say one way or the other about the baby's room.

[lonestarheir]

The only thing that "diffusers" help to do is spread the air out. The same is true with "grills," either one will do the job. You would be wise to bite the bullet and add the return duct


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Brandon
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