Our small slab house had a "tv" room addition when we bought it. Approx 24 feet by 18 feet.

The tv room had two ceiling registers. One 16 X 8 inches, about two feet into the room as you enter it from the main house. One 14 X 14 inches, in the middle of the ceiling.


We had a major HVAC, all new ducts, improve insulation, etc., redo. Everything is great, but the new duct work is only connected to the smaller 16 X 8 register. There is no duct connected to the larger register in the middle of the ceiling.

To long to explain but part of the duct register confusion/mess is my own fault.

The companies last message to me was they can connect the unconnected register (and would have to "touch up" some of the attic insulation in that area) if I felt there was not enough cool air coming to the room via the small register that is connected.

I think "duh, of course I want the bigger register right over the couch connected, of course it will make the room cooler." But I may be making a wrong assumption.

I want message board input before I get myself into another duct mess and tell them yes connect the HVAC to the register in the middle of the room.

It is not a matter of money. Just want to be sure connecting the central ceiling register makes sense.

Where not there to see it but that whole set up to me sounds wrong.
A room that size would have needed a return, and registers are almost never installed so the blow in the middle of a room.
The air should have washed over the windows,and any door openings, not just dump into the middle of the room. I highly doubt just one register would have been enough in that room.

I'll second what Joe says except for the requirement of a return. Many systems use open doorways as the return to a central return duct.

With or without a return, your supply duct(s) sound too large in size and located wrong. It's most efficient to put multiple supplies around the perimeter of the room near load areas like doors or windows. Supplies are placed around the perimeter so that the conditioned air moves completely through the room as it heads for the return.

Do you have attic access above this room? If so, you may be able to run several smaller supplies (6" to 8") and forget the 14 x 14 completely. While it will vary depending on things like windows and insulation, a 24 x 18 room will have 3 to 4 supply runs of that size.

it is my amateur DIY NON-certified-professional belief that if you want airflow in a room, predictable and dependable, you put a return duct in that room.

ADNCP with modern construction and insulation, you would pressurize the room under windows, long walls to the outside, etc. and depressurize the room near where the people spend most of their time, so the room is most evenly heated and cooled.

it was wrong to start with, and is now wronger, ADNCP.

so what access do you have above/under/beside the room to make that work? the contractor missed the boat here. I would not expect it all to get fixed gratis, but they need to come back and fix it correctly with some sort of good discount for the time spent making it wrong.

This message has been edited. Last edited by: swschrad,

Thanks, now I am even MORE CONFUSED, ha ha.

The house has a return, approx 2 feet by 1 foot, in the hallway of the original house. Does the room addition need its own separate return? How many returns does one 1500 square foot house need?

The original house is about 1000 sq feet. The house has registers in all bedrooms, front room, bathrooms, etc. they are near doorways, walls, etc.

The smaller register in the addition had never been connected to anything. We realized this a year or two after moving into the house. I (not knowing any better) asked a different company to connect the "phony" register to the HVAC.

I had always "assumed" the larger register in the addition was a register, not a return? I honestly don't know if it was a return all along and I assumed it was a register? But it has a lever on it like regular register, you could open and close if desired? I ?think? once in a while I stuck my hand up there and didn't feel much air movement, but I thought, think, I felt a little air blowing out, and assumed the whole system just didn't work very well? Some rooms got a good flow of air from the HVAC, some didn't.

I know the current company kept saying something about the ducts in the addition and "it is a return" but I just nodded "yeah" assuming I don't know what? That there was some confusion about the phony register I had had another company connect? Never dreaming there would be a need for two returns?

Does the addition really need its own return? The addition attic crawl space is tiny and very hard to get into, it that makes any difference?

My "I know nothing about HVAC" mind still thinks why not a register blowing cool air in the middle of the tv room that gets so hot?

I've been living with a room that it pretty similar to the room you described. I have the same scenario where there is a single supply in the middle of the room. I agree with Joe. "The whole setup to me sounds wrong." It just doesn't do the job.

When we had an energy assessment recently, one of the observations was consistent with what Jaybee advised; "supplies should be placed around the perimeter of the room".

And my family's experience is consistent with what swschrad said "if you want airflow in a room, predictable and dependable, you put a return duct in that room". When my "problem" room's door is closed (for example, when someone is sleeping in there), it gets extremely cold in winter and extremely hot in summer.

My plan is to have three different HVAC companies come in to give an assessment of what they would do. I want to know if my furnace and central air have the power to handle that room. I'm also going to run an idea by them. I want to put in a tray ceiling that will contain the duct-work to carry the conditioned air to supplies positioned above the windows. On the opposite side of the room, the tray ceiling will contain the returns. I'm also going to ask them about adding returns at the floor level. The thought being that the upper returns would be open in the summer (to catch the hot air that rises) and the floor level returns would be open in the winter (to catch the cold air at floor level).

But, the main thing is that I want the opinions of three reputable pros before I decide what to do.

Please share with us how things progress with your HVAC problem. I know that I'd be very interested in hearing what you learn.

This message has been edited. Last edited by: SturdyNail,

Sturdy Nail. Since I haven't heard back from our DIY crew I just kind of threw up my hands and went with connecting the HVAC duct to the register in the middle of the ceiling.

I realize, as I have learned here, that is not the way it is supposed to be, but I can live with it. I don't see how it can hurt? It has to make the room a little cooler?

We live in mild weather area. Only a few really really hot days, our cold days are mild compared to many parts of the country. So I can live with it being done "wrong."

Good luck with your project.

There are many ways of setting up a forced air duct system. It can be correct to have multiple returns - one in each room and it also is correct to have only one main return on each floor. More older systems use the multiple returns while most modern systems use one central return point. The thing is, both are correct - which one depends on the layout of your house. If there have been many remodels then there is a greater chance that you will have multiple returns as the system was modified as the remodels progressed.

Simple way to see what you have is to place a piece of toilet paper in front of the vent. If it blows out it's a supply, if it sucks up against the vent then it's a return.

You may have solved your problem just by adding a duct to that central vent. It may not be the most efficient but you are adding more cooling air to the room, which is what you needed.