Ask Me Help Desk - Uneven vent flow in townhouse

I checked the basement and currently all dampers are open from the air handler. There's three main "exits" from the handler, one w/ damper to the basement vents, one w/ damper to main floor, and then a direct feed straight up for the upstairs. The house is a townhouse build in the mid 80s. The one set of vents that's excessively powerful is the master bedroom and master bathroom vent. They're overly powerful and I have to close the vents often. The other two bedrooms upstairs are weak. I would think the whole upstairs would perform similarly but those two bedrooms are frozen... and I feel basically nothing coming out of them when the other rooms can be used to heat the dryer. The main floor is marginally better than the two bedrooms, but about 1/4 the strength of the master bedroom. The basement one... I haven't checked carefully since we're rarely down there. Why is it so uneven? What can I do? Thanks in advance.

When a system is installed it should be balanced after it is heating or cooling to make sure that all of the system is getting the air that is needed in a certain spot. This is done by closing some vent dampers slightly and opening others more.

The only two dampers in my system. One that controls the basement, and one that controls the main floor. Currently, they're both completely open. I can't imagine closing one or both completely or partially would decrease the flow upstairs right?

What you could do is buy sheets of insulation board or some other rigid material, cut them to the size of the register, then stick them in tightly. The amount of air coming out is controlled by the size of the hole you cut in it.

I put those in in my house, and it works very well. You have so much control over where the air goes.

Quote:

Originally Posted by mtnbkr

I checked the basement and currently all dampers are open from the air handler. There's three main "exits" from the handler, one w/ damper to the basement vents, one w/ damper to main floor, and then a direct feed straight up for the upstairs. The house is a townhouse build in the mid 80s. The one set of vents that's excessively powerful is the master bedroom and master bathroom vent. They're overly powerful and I have to close the vents often. The other two bedrooms upstairs are weak. I would think the whole upstairs would perform similarly but those two bedrooms are frozen...and I feel basically nothing coming out of them when the other rooms can be used to heat the dryer. The main floor is marginally better than the two bedrooms, but about 1/4 the strength of the master bedroom. The basement one...I haven't checked carefully since we're rarely down there. Why is it so uneven? What can I do? Thanks in advance.

Can you see the smaller ducts that branch off the main upstairs duct to feed each of the individual rooms? Each of those branch ducts should have its own damper to individually control the flow to each upstairs room. I can't imagine that the branch ducts leave the main upstairs duct behind a wall, so this should either be happening in the basement, a utility closet, or the attic. Look where the supply registers are located in each of the bedrooms and also look inside of the registers to see the direction from which the duct is coming. That should give you a clue as to the branch duct connections may be located.

If you can find them, and there are dampers there, make sure that the dampers to the cold rooms are fully open (the handle of the damper should point in the direction the air should be flowing). Let the system temperature re-equilibrate. Then close the damper to the hottest bedroom by a small amount (ca. 1/8 of a rotation of the handle in a dirction towards the handle being oriented perpendicular to the air flow). Re-equilibrate the temperature and repeat until that room's temperature is in an OK range. Then do it over with any other rooms that are too hot until all are in an OK range. Note that you may need to go back and re-adjust some of the earlier rooms if you cut off a lot of airflow to a later room.

I've looked all over the upstairs for an access point, in hopes of finding another damper. I have not gone to the attic. Since all of the upstairs vents are on the floor, I can't see why the ducts would go to the attic first, and then break apart. Is it worth going up there?

To my understanding, there's just those two dampers. Should all dampers be relatively easily accessible? I went all over the place trying to trace down all the vents, and from the basement utility room where the air handler is, I only see the two. The main duct that goes straight up has no control. Maybe I'll open the panel on the air handler and see what the looks like. I'll try to brainstorm some more. Thanks.

*EDIT
Ok, went to the basement and opened up one of the panels on the air handler. Turns out, there's a damper for the upstairs run... just no way to access it from the outside. You need to stick your arm inside of the unit to change this one. I was able to close it so that maybe 1/4 was left open still. Hopefully, this will redirect some air over to the main floor and basement. It still won't solve my upstair's uneven flow problem. Right now, like I've said, I just closed the vents in the MBR. Seems somewhat better already.