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Old 11-15-2011, 12:15 AM   #1
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will tapping into a 10" supply for second vent help?


My son's room is 12x12 but has a vaulted ceiling. There is only one 10-inch supply coming to this room. The room is temp is hard to control - too cold in winter and too hot in summer.

If I just tap into the current 10-inch supply duct and run an additional vent to this room, will this improve anything? Reason tells me that with an additional vent, it will be easier for air to flow into that duct - sort of like a path of least resistance - and I will get increased flow to that room - perhaps even 2X the current.

Thoughts?

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Old 11-15-2011, 06:08 AM   #2
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will tapping into a 10" supply for second vent help?


If your duct work is installed right then tapping into it can cause you more problems you should be running 400 CFMs per ton. Is there any space at the bottom of the door? If that room is sealed off then you are not getting a proper return and you could have neg. presure in there which will cause infiltration in that room. If you can cut the bottom of that door off 1 1/2- 2" and you may see a big difference in that room.

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Old 11-15-2011, 10:31 AM   #3
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will tapping into a 10" supply for second vent help?


There is probably an inch under the door now - I'd be hesitant to put in a door vent or cut the door more for privacy and noise issues in that room.

There is no return in that room.

Down the hall in another smaller room (further away from the HVAC) - it actually has a 12"x12" return in the ceiling...hmmmmm.

How about instead of adding the second supply vent in the room in question like I described, I add a return vent?

Could I tap into that return run from that other room and run a 10-inch return vent to the problem room?

The problem room has vaulted ceilings that are easy to get to. I don't know if the ceiling is the ideal place for a return (like the othe room).

I suppose I might be able to drill holes in the top of the wall plate and attach the return there - then in that same wall stud cell lower in that room on the wall, put a wall vent.
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Old 11-15-2011, 11:16 AM   #4
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will tapping into a 10" supply for second vent help?


Quote:
Originally Posted by jkv View Post
If your duct work is installed right then tapping into it can cause you more problems you should be running 400 CFMs per ton. Is there any space at the bottom of the door? If that room is sealed off then you are not getting a proper return and you could have neg. presure in there which will cause infiltration in that room. If you can cut the bottom of that door off 1 1/2- 2" and you may see a big difference in that room.
Shouldn't that be positive pressure?
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Old 11-15-2011, 12:22 PM   #5
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will tapping into a 10" supply for second vent help?


A pos. pressure will cause the conditioned air to be pushed out, a neg. pressure will pull the outside air into the house.If you can feel the air from the outside of the door then you have a pos. pressure in that room. You should be able to add a return in that room it is best to have a double return one on top and one on bottom that way you can close the one on top off in the winter and the bottom off in the summer.
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Old 11-15-2011, 12:29 PM   #6
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will tapping into a 10" supply for second vent help?


What you are wanting to do is correct, allow air to dispense from not just one but two spots.

They make a 10 x 8 x 8 'Y' . Same air flow out and through the original 10" feed but splits into two 8" duct runs from said 10".

Put one a few feet in from the outter walls each and it's done, easy monkeys. granted you will need new register boxes as now it's 8" at the registers.

You can probably even upsize that to a 12 x 10 x 10 without much concern to harming anything. It's done all the time and while we do do it without any scientific cfm formula, the homes never seem to suffer anywhere else. If they did, we wouldn't continually do it.
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Old 11-15-2011, 12:35 PM   #7
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will tapping into a 10" supply for second vent help?


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Old 11-15-2011, 12:46 PM   #8
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will tapping into a 10" supply for second vent help?


Quote:
Originally Posted by denemante View Post
There is probably an inch under the door now - I'd be hesitant to put in a door vent or cut the door more for privacy and noise issues in that room.

There is no return in that room.

Down the hall in another smaller room (further away from the HVAC) - it actually has a 12"x12" return in the ceiling...hmmmmm.

How about instead of adding the second supply vent in the room in question like I described, I add a return vent?

Could I tap into that return run from that other room and run a 10-inch return vent to the problem room?

The problem room has vaulted ceilings that are easy to get to. I don't know if the ceiling is the ideal place for a return (like the othe room).

I suppose I might be able to drill holes in the top of the wall plate and attach the return there - then in that same wall stud cell lower in that room on the wall, put a wall vent.

On vaulted ceilings a return up in the vaulted area is a good idea to accompany the 10 x 8 x 8. Air circulation is the key. The one inch under the door is fine.
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Old 11-15-2011, 07:02 PM   #9
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will tapping into a 10" supply for second vent help?


IMO your money would be better spent finding the cause like leaking windows or missing insulation.
A ten inch supply in a 144 square foot room is insane overkill as it is. That sized room should be 60 degrees all summer and 85 all winter with that much air. No need to add more and spitting into 2 8's will be the same amount you have now.
No return could be an issue. Try leaving the door open for a while. If the room is still not the same temp as the others then you know a return will not help. Bottom line...find out what the problem really is before doing a lot of work for nothing.
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Old 11-15-2011, 07:16 PM   #10
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will tapping into a 10" supply for second vent help?


Quote:
Originally Posted by Marty S. View Post
IMO your money would be better spent finding the cause like leaking windows or missing insulation.
A ten inch supply in a 144 square foot room is insane overkill as it is. That sized room should be 60 degrees all summer and 85 all winter with that much air. No need to add more and spitting into 2 8's will be the same amount you have now.
No return could be an issue. Try leaving the door open for a while. If the room is still not the same temp as the others then you know a return will not help. Bottom line...find out what the problem really is before doing a lot of work for nothing.

no retun...........no work, heating and cooling is all about air flow.......you hit the nail on the head Marty. People want to make or trade like being a brain surgoen...........its not that difficult.

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