Adding return ducts

[Bushum]

First I'll explain my current setup as best as I can. I live in a two story house, kitchen/dining, living and 2 bedrooms downstairs; bedroom and bonus room upstairs. The furnace is located in a closet within the living space right in the middle of the downstairs area. There are currently four return ducts one in each wall of the furnace closet so they are fairly close together. There is one in one of the downstairs bedrooms, one in the living room, one in the dining/kitchen, and one in the stairwell to the upstairs about halfway up. So downstairs every room has a return but one bedroom. Here is the problem or at least I'm hoping if you can tell me if it's a problem. Neither upstairs room has a return and they both have doors so are sealed off from the house most of the time.

First question is do the upstairs rooms need returns in them? I'm replacing the furnace and getting A/C which wasn't in the equation before.

Next are the two options I can think of:

First is obviously cheapest and easiest. If I cut holes in the walls of both rooms upstairs and add a register cover the air from both rooms will be directly connected to the air in the stairwell where there is a return currently. I don't know if the returns create a negative pressure and this will pull air where it needs to go or not.

Second option is to run new returns with ductwork through the attic and then down into the closet and attached to the existing return box. Obviously much more expensive.

Option 2 will probably work better but will option 1 be functional and circulate air as it needs to? If it matters I'm having a 2 stage variable speed furnace installed with a split system a/c. Before anyone gets mad this is NOT a DIY question. I already chose a contractor and I'd like to have a plan before talking about the new ductwork. Thanks!!

[beenthere]

Although going through the wall will work. Be carefull. Sound travels easy that way.
If you go throough the wall, offset the holes. high in the room, and low in the hall.

[DanW13]

As beenthere suggest make the return separate for each room, I would also put 1 vent high and 1 low for heating and cooling so you can suck the hot air from the ceiling in the summer and cold air in the winter off the floor. Make sure you get the proper grilles for the returns.

[Bushum]

Make sure you get the proper grilles for the returns.

Can you please elaborate on this. I thought there was only one kind of return grill. :confused:

[Bushum]

If you go throough the wall, offset the holes. high in the room, and low in the hall.

Do you mean inside the room put a register high and in the hallway on the same wall put a low register? The air would be traveling through the stud cavity this way. Am I misunderstanding you?

[beenthere]

No, you got it right.
If the grilles are straight across from each other, sound will go right through them.
I would prefer jumper duct in the attic.(flex)

[cem-bsee]

I installed return vents hi in hall, lower in clothes closets of 3 bdrm with clos adjacent to hall -- offset horizontally over 4th door
-- uniformly 2inches down from ceiling.

the size needs to be 20+ % more than amount of air needed per loss | gain calculations [ normally for a/c= gain air flow ] since lots of bdrm upstairs.

[dash]

Although going through the wall will work. Be carefull. Sound travels easy that way.
If you go throough the wall, offset the holes. high in the room, and low in the hall.

The wall space,turns and length ,may not allow enough air flow ,as there's very little static pressure to move the air.

[Bushum]

I would prefer jumper duct in the attic.(flex)

This would be having a vent in the room and another in the hallway connected by duct in the attic but NOT connected to the return plenum? That could be done with minimal work too!

Are these ideas far inferior to connecting directly to the return plenum or is it worth saving some time/money?

Thanks everyone for the help so far!

[adrianf]

Air egress passage way should be sized based on supply cfm for Thru the wall or transfer duct. Someone needs to measure the delivered airflow first.

[Coolmaniac]

Don't know where you're at, but out here in the wild west, just about all houses here have 1 reurn in a central area. Leave the doors open in the rooms that don't have one when unoccupied and don't worry about it.

[jcameron]

As you probably already have found out - return air is essential for proper heating and cooling of any space. As everyone has told you - Either way will work.... But, if it were my home or you were my customer, This is how I would advise you - for best results, direct ducting to your return air system is the "most correct way" to properly provide air movement to your 2nd floor bedrooms. If $$ is the problem, tranfering air through the wall or through a transfer duct in the attic to the hallway, will work too. (Commercially you see alot of "transfer" ducting of return air from smaller offices to a larger common office area, at least in Ohio you do.)
I don't always agree with having a high and a low return opening in the same room. Yes, it is more efficient to pull the hot air from the ceiling during the cooling mode and the cool air off the floor in the heating mode, but does your system really see the 2-3 degree temperature differance - I doubt it. Plus normal homeowners forget which vent needs opened, when.
I personally would rather see my second floor returns high and my first floor returns low, for both an efficiency stand point and esstetics.
If you use the wall transfer method, staggering of the openings is definetly advisable. Sound transfer will be cut down, but not totally gone. I would suggest that you have your openings high in the bedroom and low in the hallway, with the bedroom grilles actually mounted upside down (so you can't see up into them).
Just keep in mind that "you can never have too much return air" to any system. - Good Luck

[dash]

This would be having a vent in the room and another in the hallway connected by duct in the attic but NOT connected to the return plenum? That could be done with minimal work too!

Are these ideas far inferior to connecting directly to the return plenum or is it worth saving some time/money?

Thanks everyone for the help so far!


There's nothing inferior air flow wise about a jumper duct return,other then a wall space is likely too small.

Jumper ducts are not connected to the fan powered duct system,so no fan pressure to move the air is why they need to larger then a ducted return.

Typical bedroom might be a 12X12 grilles,but with a 12" round flex duct.If going from several rooms to a hallway 12X12 in each room,if three rooms,then a 12X 36 in the hallway.

A simple test to see how large they need to be.

Turn the system fan on,in cooling or heating,whichever moves more air.

"Feel" the supply air flow with the door closed,then have someone open it slowly ,then close very slowly until the supply air flow starts to decrease,then open very slowly to feel the increase.

Measure the gap around the door,that's roughly the sq. inches of jumper duct you need,multiply by 1.25 to be safe,same sq. in. for duct and grilles.

[beenthere]

The wall space,turns and length ,may not allow enough air flow ,as there's very little static pressure to move the air.
True. Its something that has to be checked for each application.

[beenthere]

Don't know where you're at, but out here in the wild west, just about all houses here have 1 reurn in a central area. Leave the doors open in the rooms that don't have one when unoccupied and don't worry about it.
So what do you do about the room when its occupied.

[snowbunny]

Every return will need a filter, correct? (Doublechecking ahead of my new install.)

[beenthere]

Every return will need a filter, correct? (Doublechecking ahead of my new install.)
No.
One filter at the air handler/furnace will due.

Are they putting returns in every room.

[snowbunny]

No.
One filter at the air handler/furnace will due.

Are they putting returns in every room.

I'd like them to.... I thought returns were the big rectangular holes :o which require filters. There is currently one in the ceiling near where the air handler is installed, and one near the master bedroom by the thermostat (the big rectangular holes covered by a meshed grille). Most of the rooms have a single duct which I assumed was out-flow only (louvered cover).

[beenthere]

If its just a swap out. And you don't have adding returns in the written contract, they aren't going to.

Do your 2 current returns have filters.
As a rule. If you have a return in every room, you don't have a filter in those returns. You use a filter at teh air handler/furnace.

[snowbunny]

If its just a swap out. And you don't have adding returns in the written contract, they aren't going to.

Do your 2 current returns have filters.
As a rule. If you have a return in every room, you don't have a filter in those returns. You use a filter at teh air handler/furnace.

Yes, the two current returns have filters. And of course, when the AC kicks in, the filter is sucked against the return (which is noisy). (I'm guessing there are tricks to weighting the filter(s) so that that does not happen.)

The return work is not written into the contract, but agreed orally, and it will be written before work starts or they lose the work. I haven't signed anything nor put a deposit down, either.

[dash]

Yes, the two current returns have filters. And of course, when the AC kicks in, the filter is sucked against the return (which is noisy). (I'm guessing there are tricks to weighting the filter(s) so that that does not happen.)

The return work is not written into the contract, but agreed orally, and it will be written before work starts or they lose the work. I haven't signed anything nor put a deposit down, either.

If the filters are doing that,likely the filters and grilles,maybe the return duct ,are undersized.

Post filter sizes and equipment model numbers to find out.

[Bushum]

Thanks everyone for the help! Unless the costs are very close I think I'm going to go with the jumper ducting through the attic.

[sneezer]

The disadvantages of jump ducts vs. using the stud cavity are that you are putting more holes into the unconditioned space and the ducts and air will pick up some heat in that space. Yes, you can seal the openings and insulate the ducts, but nothing is perfect.

Assuming that the stud cavity is sealed, you will have no losses with offset grills. The conventional way to install this kind of return path is to put a grill near the floor in the hallway and one near the ceiling in the bedroom or other room. In addition, there are commercially-available baffled return air pathways that can be inserted through walls. They are reasonably priced and won’t leak into the stud cavity. I have not experienced them in use so I can’t give a first-hand review.

[hangfirew8]

I don't always agree with having a high and a low return opening in the same room. Yes, it is more efficient to pull the hot air from the ceiling during the cooling mode and the cool air off the floor in the heating mode, but does your system really see the 2-3 degree temperature differance - I doubt it.

I don't understand this statement. I see a high return vent as a way to get the hottest air out of a room in A/C season, not as a way to increase efficiency. If anything, it will make the A/C work harder because it is cooling hotter air. In other words, it makes the A/C more effective, not efficient.

As a homeowner how can trace his bedroom ceiling duct cool air flow right down to the return, I can really coming around to the idea of having high and low returns in the same room.



Plus normal homeowners forget which vent needs opened, when.


If the homeowner is asking for the solution, they may forget to swap on any given Spring or Autumn day, but you better believe if they pay extra $$$ they're going to use the feature during the hot and cold seasons.

-HF

[hangfirew8]

As beenthere suggest make the return separate for each room, I would also put 1 vent high and 1 low for heating and cooling so you can suck the hot air from the ceiling in the summer and cold air in the winter off the floor. Make sure you get the proper grilles for the returns.

I too am also curious as to what return grilles you recommend- or perhaps you mean registers?

-HF