Routing Additional Return Duct

robert.juric

I have a two story house with the master on the 1st floor. We've had problems year-round trying to keep the room comfortable since we have to keep the door closed constantly. After some research I believe adding a return will help.

I started my project this weekend and ran into a problem routing the new duct work. The bedroom and the air handler are on opposite sides of the house, separated by 2nd floor bedrooms. My plan was to run the duct between the 1st and 2nd floors through some engineered i-beam space. This is how the current main supply duct is ran. However, when I began to run the new duct I realized that the new space I was going to use has some blocking in the middle of it and I won't be able to run new duct between the floors. My next thought was to run the duct up and over the 2nd floor bedrooms over the the 1st floor master. The 2nd floor bedrooms currently have their ducts on top of the rooms already so I figured this might be an acceptable solution. This also turns the duct length into about 60'.

Would this be acceptable, or do I have any other options?

TarheelTerp

How about putting a register in the bedroom door?

robert.juric

The master is on the opposite side of the house from the only 1st floor return. Even when we leave the door open, we have problems keeping the room comfortable. I've seen room-to-room type fans, but I'm not sure if that would get the job done?

TarheelTerp

Your first statement said something else.

As to your return duct run plan to cut a good sized hole in the floor/ceiling at some point. Ideally... in a closet or other odd out of the way corner.

robert.juric

I apologize for any confusion, we've always had temperature problems in our master bedroom.

I don't have a problem cutting a hole in the ceiling drywall, but I'm concerned that I can't remove the blocking between the i-beams.

TarheelTerp

Forget the Ibeam route altogether.

I'm going to assume that the furnace and AC is in the basement...
look for a spot down there that is 1) on the same side of the basement as the equipment and 2) will give you a clear shot up to the second floor.

THAT is where you need to cut a hole in the floor for your duct.
Once in place you can then extend it horizontally to the equipment.

robert.juric

It's a 2 story house on a slab. The 1st floor hvac equipment sits in space above the 1st floor ceilings, and the 2nd floor hvac equipment sits above the 2nd floor ceilings.

My plan was to go from 1st floor ceiling where hvac equipment is, over the 2nd floor ceiling where the 2nd floor ductwork is and then back down to the 1st floor ceiling of the master bedroom.

My concerns were running the return duct vertically to hop over the 2nd floor ceiling and the length of the duct (about 60').

beenthere

You will need to increase the duct size due to the length.

hvac5646

Yep...long way to run a return...

robert.juric

I had planned on running 8", would 10" be a better choice then?

Evstarr

Isn't there a closer one you can tie into? Then if needed increase the size on the one you piggybacked into.
Or is this not allowed like it is on supplies?

robert.juric

There is only a single return of rigid duct directly connected to the ac/furnace.

The problem is how the HVAC system is split from most of the supply by the 2nd floor bedrooms. I talked to an installer who said that the system should probably be flipped, but we can't do that until it's time to replace the whole shebang.

beenthere

What size is the supply to the room?

robert.juric

Two 12"x5.5" registers fed by 6" flex duct.

beenthere

A 10" will get you close to what you need. Probably won't make the room perfect. Since the installer probably figure he was going to get 100 to 110 CFM out of each of those 6" supplies, instead of the 80 CFM they are really doing.