Unused Rooms....Should I Close The Vents Or Leave Them Open - HVAC - DIY Chatroom Home Improvement Forum

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Old 05-15-2014, 05:51 AM   #1
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Unused rooms....Should I close the vents or leave them open

I have a two story house. I do not use the upstairs at all. There are 4 rooms up there.. Should i close the room vents? Close the vents and doors?? Close the doors and open the vents?? Should I open the vents. Open them just a little bit???............ If I ask 10 HVAC guys, 5 will say open / 5 will say close???. Any thoughts out there??


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Old 05-15-2014, 06:07 AM   #2
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Leave them open.

You can control flow if there is a damper at the main supply trunk but that will affect all the distribution on that line.

I would leave them open and just close them slightly if you would like to.


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Old 05-15-2014, 06:13 AM   #3
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There "is" a damper at the main supply trunk that supplies the upstairs. Well, that would lead me to asking ,,, should I close the that main damper that controls the upstairs air
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Old 05-15-2014, 06:29 AM   #4
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this is more of an hvac question, but my to my understanding, by closing some rooms off you are throwing off the balance of the system and causing it to operate less efficiently.
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Old 05-15-2014, 07:32 AM   #5
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I say close the vents of the rooms you are not using --- but with some stipulations:

1. Before closing too many (say more than one out of five) you need to reduce the system fan speed. See the system instructions; this typically requires re-arranging of a few wires on screw terminals.

2. You also need to close the return vents in the affected rooms but you need enough return vents still open for the system to operate properly.

3. What stays open should be at least half of the vents fully open (mid-duct damper also fully open), or the equivalent.
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Old 05-15-2014, 08:45 AM   #6
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Move into a smaller house.

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Old 05-16-2014, 06:14 PM   #7
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I have a similar question, since my wife believes that closing the doors of unused bedrooms will somehow conserve heat (we have a gas-fired hot air system) or cooled air. I believe this is a waste of time and, in fact, it reduces the necessary air flow in the house by preventing enough air from making it back to the returns.

Perhaps a professional could weigh in on this. Thanks.
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Old 05-16-2014, 08:44 PM   #8
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Air conditioning needs 350-400 cfm of air moving across the a coil and your heat needs enough air flow to keep the temperature rise from going to high. If this is a old system that has duct work over sized you will be okay, If it is sized correctly you will not be running the a/c at its designed flow, And the temp rise on heat may be to high

The dampers in the basement are for adjusting airflow in the house to balance it
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Old 05-17-2014, 12:09 AM   #9
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one system for whole house? Zoned or not?
I'd leave all vents open and leave doors to all rooms upstairs open fully.
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Old 05-17-2014, 09:53 AM   #10
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Close them and see if anything bad happens.


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