Return Air

[lkaufman]

Hello, I had a new house built about 3 years ago. FHA with A/C, 2 Zone. For the most part the FHA works well. All of the bedrooms have their own floor mounted RA. The way it was designed is the installed paned the stud cavity between the basement and the second floor instead of hard duct.
Once of the smaller bedrooms 10x10 has a 6" supply to a floor register but no return was installed. In the past we did not use the room much so we did not notice that it was uncomfortable due to the lack of return. The adjacent room has an 8" supply and a return. As I do not want to cut open walls to put in a new retun, can I tie the two rooms together as the return would be thru a ceiling joist? Will this mess up the larger room?

thanks

[dash]

With a 6" supply you may or may not need a return ,it may be a lack of supply air to the room.


Test It:Feel the volume of supply air coming in with the door to the room open,then with it closed,if the volume is noticabley reduced with the door closed,you need a return or a "return path",supply could still be too small(can't tell from here) ,but return would be needed.If the room temperature is fine when the door is left open,that strongly indicates you need more supply air.

A 12X6 opening in the wall ,with a grille on each side will provide a return path to the living area where the main return(s) are.If privacy(noise transmission) is a concern a 12X can be installed in the ceiling and connected by a duct to another 12X6 in the hall or living area .

[lkaufman]

HI Dash,

The room warms up too much with the door closed leading me to believe that there is no return path. With the door open, it is comfortable.

The reason that I wanted to tie the smaller room return in with the return of the larger adjacent room is to avoid having to put in new ductwork for a return. The larger room return is on the other side of the wall of the smaller room. I could cut a hole in the floor and tie the two in via the ceiling joists or do as you suggest with a transfer louver from one room to another. My only conern is that with the two rooms on 1 return I would reduce the return in the larger room and affect its balance? The larger room is about 12x14 and has a paned return (3.5"x14") and a 8" supply.

Thoughts?

Thanks

[dash]

I'd do the tranfer grill or transfer duct,but connecting it to a room with a small return as you have described may not be a good idea.

Can't you duct it to the main living area?

Without seeing it ,my gues is the 8" return wouldn't be large enough for both rooms.

[lkaufman]

Hi Dash,

Unfortunately I could only do either a transfer grill or underfloor connection to the adjacent room with a single 3.5x14 (paned) return. The room is on the second floor on one side of the hall. Only other option would be to the hallway that does not have a return. This would result in a 12x14 and a 10x10 room being on a 3.5x14 return. According to my calcs the 3.5x14 return is just large enough for the 12x14 room. Any other ideas? If I did use a xfer grill would this mess up the larger room?

Thanks

[dash]

Isn't the hallway open to the main living area with a large return?The distance to a main return doesn't matter ,as long as there's no door inbetween.

[lkaufman]

Unfortunately Not, there is no main return in the 2nd floor hallway. Just in each individual room (less the room we are talking about).

[dash]

How many returns and rooms on the upstairs system and what size if you know?

Is your zoning two systems or one ,with zone dampers?

If the room is comfortable with the door open,it has a return path somehow.It could be going into another room ,passing under the doorway ,or to one with a door open.

[lkaufman]

Hi Dash

There are 4 bedrooms, each has a panned return 3.5x14 down to the main trunk in the basement, with the exception of the one room in question. Each has a 6x12 floor register.

The system is 2 zones with zone dampers.

I agree, with the door open it is finding its way to another return. When people sleep in the room with the door closed they say it is like a sauna. With the door open it is ok. I am afraid to install the transfer grill as it may mess up the balance of the room it is going into?

Thanks

[dash]

Are you saying the hallway is not open to any other room in the home ?
I'd think it's open to the stairs,living are etc.

Is your home ,basement with two floors above,and the problem is on the top floor?

[lkaufman]

Hi Dash,

The upstrairs hall connects all of the bedrooms as well as the stairs leading to the first floor.

Yes, basement with first and second floor. Problem bedrooms is on second floor with furnace in basement.