An air conditioning question

[dennis thompson]

My home office is on the second floor of our house and it is considerably warmer than other rooms at this level. Two of the rooms are bedrooms which we do not use. If I close the a/c vents in those two rooms would that push more air into my office and cool it down?
Thanks

[George Yetka]

Yes. i typically flip my vents summer/winter. I like them closed upstairs in the winter as heat rises and vice versa. But if a room is unused closing its vents will direct more air to you.

[Bill Howatt]

Also, close any unnecessary vents in every part of the house.

[Malcolm McLeod]

My home office is on the second floor of our house and it is considerably warmer than other rooms at this level. Two of the rooms are bedrooms which we do not use. If I close the a/c vents in those two rooms would that push more air into my office and cool it down?
Thanks

Moderation in all things...
A great deal depends on the overall airflow and AC design/capacity. You can close too many vents and degrade your system efficiency (maybe even freeze the evaporator coil?). If you close one vent and don't get the equivalent increase through others, you are probably at the pressure limit of the blower and likely your efforts won't end as you hope.

One local jurisdiction requires return air in all BRs. Obviously more work to accomplish this in existing homes, and your office, but will throw it over the 'idea' fence.

Also, take a look at solar heat gain. Better curtains can sometimes solve AC issues.

[Jim Koepke]

My home office is on the second floor of our house and it is considerably warmer than other rooms at this level. Two of the rooms are bedrooms which we do not use. If I close the a/c vents in those two rooms would that push more air into my office and cool it down?
Thanks

My honest answer would be, "I don't know." After all, the vent in your home office might be a return. It could be blocked. Could it be your office is facing south with large windows letting in a lot of sun all day to warm the room faster than the air conditioning can cool it?

My second part of the not knowing would be, "why not try it and find out?"

jtk

[Jim Becker]

While you can certainly help your situation by turning down or turning off outlets in unused rooms (as long as you keep them closed), you may also be able to rebalance air flow at the ductwork level...a properly installed air system will be tunable so that air flow to each branch can be governed with a "valve" you can turn in the duct. You will see little metal handles on the duct for these and they operate kinda like ball valves on plumbing...turn the handle. You may want to have the system balanced by the HVAC company you use for maintenance.

We do have one room here in this relatively new to use house that has failed to respond to any kind of system manipulation. We call it the "red room" 'cause it's painted that color and it's the fourth bedroom that was likely just storage space when the house was built. There is almost no air flow to the two registers in that room. In this particular case, if we decide to use the room for anything other than Professor Dr SWMBO's shoe collection and other storage, I'll likely install a small minisplit dedicated to the room.

[Jack Frederick]

If it is accessible I would suggest looking at the supply and return ductwork and see if there is a disconnect or crushed duct. We just installed some Bali Solar shades. I just asked my wife if she felt the shades improved the temp/comfort in the room and she said definitely.

[Stan Calow]

We have an upstairs room that we have been unable to manage well. Builders who make home with upstairs bedrooms with cathedral ceilings should be punished.

Unfortunately our HVAC ductwork has no dampers or means to control flow from the basement level. Closing other upstairs vents hasn't helped. Our only solution has been adding a small window AC unit to that room, but unfortunately that is against HOA rules, and I agree it is aesthetically ugly and noisy. We'll see how long we can get away with it.

[Doug Garson]

We have an upstairs room that we have been unable to manage well. Builders who make home with upstairs bedrooms with cathedral ceilings should be punished.

Unfortunately our HVAC ductwork has no dampers or means to control flow from the basement level. Closing other upstairs vents hasn't helped. Our only solution has been adding a small window AC unit to that room, but unfortunately that is against HOA rules, and I agree it is aesthetically ugly and noisy. We'll see how long we can get away with it.

Why not add the missing dampers? There is no way to properly balance the system without them. Builders who don't install proper dampers are the ones who need to be punished.

[Alan Rutherford]

Stan - I agree about cathedral ceilings in bedrooms. 2-story-high great rooms also have their problems. You might try a register booster fan. Example: https://www.amazon.com/Howeall-Super-Quiet-Register-Booster/dp/B0BZ3FP759/ You can also get fans that go inside the duct.

In our house we found the airflow to one bedroom completely shut off by a valve in the ductwork, hidden in the attic. We also find that since there are no returns in the bedrooms, closing the door restricts the airflow.

[Stan Calow]

Why not add the missing dampers? There is no way to properly balance the system without them. Builders who don't install proper dampers are the ones who need to be punished.

Yep I agree. In my case the main plenum (coils inside, up to basement ceiling) goes straight up from the furnace/ac , and then all the way up to the attic, then down to vents in the walls. So there is no place to insert a damper to control the second floor air. I've had three different companies look at it and they agree there's no way to retrofit. Opening and closing downstairs vents has minimal effect.

But Dennis if your duct work goes up there, its worth taking a look at what's going on in your attic,. I found the duct to one of the bedrooms was disconnected (plastic tube) from the distribution point, so one room was getting no air at all.

[Bill Howatt]

Where are the outlets in the office room? In many houses, especially older ones, they are in the floor and the cold air just stays at the floor level since heating was the reason (at least in a lot of places) for the ducts.
We have some south facing windows up high in a cathedral ceiling design and put heat blocking film on them for the summer months. Have used it for years (Lee Valley sold it way back to put on patio doors, IIRC). Spritz a bit of water on it and the windows, put it on and then squeegee out the bubbles. In the fall, peel it off and put it away, repeat as necessary each year. It certainly makes a difference.
What about one of the indoor AC units that you pipe to a window with flex hose?

[George Yetka]

Most home systems are sized to be used 100% open at every outlet/register. They are also low static units so closing a damper or 2 should not matter to the system. If you have dead rooms its probably undersized/blocked/kinked ductwork or an undersized AHU. Standard practice is not to put balancing dampers in a home. I, being in the business, would if it were me designing/laying out the HVAC. And it is 100% what we do on all our work which is commercial and balanced by a 3rd party.

Your registers should be on the supply side but even if it was installed on the return side it will cut flow to that room if closed(and the door is closed).

Dennis did it work?

[Doug Garson]

Yep I agree. In my case the main plenum (coils inside, up to basement ceiling) goes straight up from the furnace/ac , and then all the way up to the attic, then down to vents in the walls. So there is no place to insert a damper to control the second floor air. I've had three different companies look at it and they agree there's no way to retrofit. Opening and closing downstairs vents has minimal effect.

But Dennis if your duct work goes up there, its worth taking a look at what's going on in your attic,. I found the duct to one of the bedrooms was disconnected (plastic tube) from the distribution point, so one room was getting no air at all.
My bet is the installer didn't follow the design to save a few buck at the home owners expense. My first job out of university was commissioning the AC and ventilation system for a hospital. We found numerous cases where the installer didn't understand why the duct runs were designed the way they were (primarily to self balance the system ) and ran them to save a few feet of sheet metal. Made it almost impossible to properly balance the system like your case.

[Bruce Wrenn]

Stan -. We also find that since there are no returns in the bedrooms, closing the door restricts the airflow. That's why bottoms of doors are raised about an inch off floor finishes.

[Lee Schierer]

To get good air flow into a room, you need an inlet and an outlet. I would locate one of those cell phone bore scopes and snake it down the supply duct and the return air duct. Look for collapsed duct work, dirt, leaks, closed dampers in inaccessible areas. Duct runs in outside walls are prone to having very poor insulation. Adding dampers in duct work involves buying the right size damper from a big box store, taking apart a section of duct and drilling one hole. I've added several in my house. Get a hand held anemometer and record the air flow from each register, then when you make any changes you need to add up the total to make sure it didn't decrease significantly. The other bit factors in cooling a room are the location of the room relative to the sun, the amount of insulation in the walls and ceiling. As noted above, warm air rises so a second floor should be getting equal or slightly more air than the lower floors. The amount of air should be roughly proportional to the size of the room.

[glenn bradley]

This is one of those things that is not inherently obvious. Talk to an HVAC engineer, not just an installer :). I have never come across a system designer that recommends closing off any registers in a system. Google "closing unused AC vents in the home?" or something like that and you will see what I mean. A couple of old-timer friends in the HVAC field have great stories about the moment they realized they had to stop trying to explain this sort of thing to customers. It runs contrary to one's knee-jerk reaction, takes a long time to explain, and the customer will end up closing off "unused" rooms anyway :D.

[Alan Rutherford]

... Get a hand held anemometer and record the air flow from each register....


So that's how you do it!! I was having a somewhat-contentious discussion with the installer of our system and trying to compare the airflow in 2 rooms by holding up a hand to the registers. He told me "You ain't doing it right. Use 2 hands."

[Tom M King]

Sometimes in poorly designed and built systems, which are very common, a duct booster fan might solve the problem.

https://www.supplyhouse.com/Field-Controls-AB-8-8-Air-Boosters-for-Round-Metal-Duct-or-Flex-Duct-up-to-425-CFM?utm_source=google_ad&utm_medium=shopping_neutral&utm_campaign=Shopping_Neutral_Returning_users&gclid=Cj0KCQjwz8emBhDrARIsANNJjS7cNuKOXvt4xZLfNhqR ACQ2ME0TVKaQRduhnF9c0_wSkABV2d1UETsaAuu_EALw_wcB

[Bill George]

Having worked in the Trade for over 30 years, yes its acceptable to turn off a supply register in a close by room to help balance air flow, but not All in the building unless you have someone who knows how to do a test and balance.

Done the right way all supply runs should have balance dampers installed when the system went in.

They should have done a ACCA Manual J heat loss , heat gain room by room and then designed and sized
the duct work with the Manual D.

But most residential jobs are absolute lowest cheapest one the Builder can get.

[Jim Koepke]

So that's how you do it!! I was having a somewhat-contentious discussion with the installer of our system and trying to compare the airflow in 2 rooms by holding up a hand to the registers. He told me "You ain't doing it right. Use 2 hands."

LOL!


Get a hand held anemometer and record the air flow from each register, then when you make any changes you need to add up the total to make sure it didn't decrease significantly.

I've used those for adjusting dual carburetors, old blue print machines and was issued one to keep an eye on lung function after my heart surgery.

jtk

[Tom Bender]

You can satisfy some customers all the time, others none of the time, some in summer, others in winter.

In our house making any adjustment to a window shade or the thermostat will get unmade in minutes. I am not told how to dress so a hat and fleece in the house is allowed. Pick your battles.

[George Yetka]

Sometimes in poorly designed and built systems, which are very common, a duct booster fan might solve the problem.

https://www.supplyhouse.com/Field-Controls-AB-8-8-Air-Boosters-for-Round-Metal-Duct-or-Flex-Duct-up-to-425-CFM?utm_source=google_ad&utm_medium=shopping_neutral&utm_campaign=Shopping_Neutral_Returning_users&gclid=Cj0KCQjwz8emBhDrARIsANNJjS7cNuKOXvt4xZLfNhqR ACQ2ME0TVKaQRduhnF9c0_wSkABV2d1UETsaAuu_EALw_wcB

Boosters are not a good fix. I work a lot of hospital critical rooms(Imaging/OR) and we have come across a lot of situations where the room has to have "x" air changes an hour to be used for X function. The systems cant always support that so inevitably a booster fan is brought up and usually shot down by the engineer. I believe the issue is that if the inlet air is not there to begin with the booster cant make it be there. It will cavitate like a pump without water. What it can do is create a lower static and draw a small amount of air to it. The few times when they were OK'd, they didnt get us the air we needed and we had to redo ductwork( shorter more direct runs with less hard turns)

[Tom M King]

I'm glad I've never needed one of these.

https://www.supplyhouse.com/Fieldpiece-STA2-STA2-In-Duct-Hot-wire-Anemometer

but this thing is surprisingly sensitive and has been fun to play with when the wind is blowing stronger than I can gauge by experience.
https://www.amazon.com/gp/product/B07J64TCBQ/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&th=1