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Where is return supply air coming from?

669 Views 7 Replies 4 Participants Last post by  beenthere
I just installed 12x6 air return grill above the bedroom door. Since my doors only have 1/2 inch opening om the bottom, I thought the 12x6 grill will increase air flow from the bedroom and it will make it cooler when doors are closed. Well, the draft through the grill is barely noticeable, I was expecting a bit more.
So, I assume the return air is coming from other rooms, but they have same 1/2 inch space on the bottom door. Checking by hand I only feel faint draft at the bottom, when doors are closed.

My AC is new 3T with 20x20x1 filter, in family room with windows and 3 bedroom doors. There is no return duct system, the return air supply is directly below the AC drawing ari from family room.

Is there way to discover where is the return air coming from? Garage doors and front doors seem to be working very well as nothing is coming through the sides, cracks, same for windows, I don't feel any wind coming in.

Is there way to discover where is the return air coming from?

John D.
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The only way to find out where outside air is leaking in, conditioned/heated air is leaking out, is to have a Blower Door test done.

Majority of homes do not have proper returns and also do not have proper return in those spaces that doors are closed to. The best solution if done right from the beginning is that every room should have a return to help better exchange the air. You do not want returns in the Laundry area, utility room, Bath's or Kitchen.
Most utilities charge around $25-50 for it and charge your bill. Once you fix the problems that they list, they will come back and do another one and if you got them to pass, they will then credit it back.

I went around and pulled the stops on all of my windows, which are Retro-fits and used the DAP foam in a can to fill all gaps. When I put the stops back on, I ran a small bead of Clear Silicone to help seal them at the window and at the edge of the stop that faces you.

My doors I used the Aluminum Weather Strip that has the same type of Nylon with foam core that is used on newer doors. Attic I made sure that all huge gaps were filled with insulation and sealed those wire openings in the top plate.

Also went around to outlets and sealed between the box and the wall with the DAP foam, placed the Foam gaskets they sell on the outlet while the foam was still wet, so that it made a seal, then put the cover plate back on.

I actually got my house to the point that you do not feel any drafts when our furnace runs, but it still has just enough leak that it is able to still pull in a little fresh air.

The other item is that on the Bath vent fan, if there is not a damper to close it when off, put one in or the double door type on the outside of the house.

As for the airflow issue. You can get the CFM/Temp testers pretty cheap for under $40 nowdays. I just use a standard -20 to 200 probe thermometer when I check my air temps. Difference between my Supply and return is around 15 degrees. I am seeing around 34 for supply and maybe 45 at returns on a warm day or after the oven is on.

I have a single floor Bungalow that originally had a old Octopus furnace in it. It had one Return in the front of the house in the Living room and one towards the rear at the Back Bedroom door. I went a step further and added two returns in my basement and two supplies, which has helped me out really well.
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