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Need To Reduce HVAC Duct - Building Day Bed

 
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Old 12-07-2018, 06:49 PM   #1
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Need To Reduce HVAC Duct - Building Day Bed


Hello!

I'm a carpenter/cabinet maker, so I need some advice on HVAC.

I'm building a day bed in the nook you can see in the picture attached. I want to bring the air vent all the way the front of this space (flush with the entrance). The existing vent is connected to a 8" duct that connected to the furnace.

I am thinking about reducing the portion that will be under the bed to a 6" duct so it takes less space under the day bed.

Is there any problem to reduce this kind of duct from 8" to 6"? Maybe, there's too many factors to answer that question, but I'm trying...

Thank you!
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Old 12-07-2018, 07:11 PM   #2
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Re: Need To Reduce HVAC Duct - Building Day Bed


reducing and adding distance... won't be the same that for sure.
you could use some square ducts... like a 4x10.

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Old 12-07-2018, 07:14 PM   #3
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Re: Need To Reduce HVAC Duct - Building Day Bed


Are the dimensions 8x3? Maybe change to 6x4. The main issue is restricting the air flow of the HVAC and whether it will suffice to condition the space.
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Old 12-07-2018, 08:05 PM   #4
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Re: Need To Reduce HVAC Duct - Building Day Bed


The duct is placed at the window for a reason. The supply washes the wall and mitigates the heat loss/gain....but whatever..?
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Old 12-07-2018, 08:56 PM   #5
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Re: Need To Reduce HVAC Duct - Building Day Bed


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The duct is placed at the window for a reason. The supply washes the wall and mitigates the heat loss/gain....but whatever..?
Agreed this is the issue, but if I had to do it I'd go with 4x10 and put some extra blankets on the daybed.
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Old 12-08-2018, 02:02 AM   #6
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Re: Need To Reduce HVAC Duct - Building Day Bed


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Agreed this is the issue, but if I had to do it I'd go with 4x10 and put some extra blankets on the daybed.
As long as you don't need cooling/air conditioning, that would work.

But its best to keep it 8" if the room is to be at the same temp as the rest of the house.
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Old 12-08-2018, 02:42 AM   #7
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Re: Need To Reduce HVAC Duct - Building Day Bed


why run ducting at all. ac bed.

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Old 12-08-2018, 12:40 PM   #8
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Re: Need To Reduce HVAC Duct - Building Day Bed


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The duct is placed at the window for a reason. The supply washes the wall and mitigates the heat loss/gain....but whatever..?
Increasing the temperature differential between the inside of the window verses the outside which then exponentially increases the air infiltration.

They're put under windows because "that's how it was always done", "less tall furniture in front of windows" and most importantly "everybody *knows* it makes the the room warmer... maybe.

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Old 12-08-2018, 12:47 PM   #9
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Re: Need To Reduce HVAC Duct - Building Day Bed


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Increasing the temperature differential between the inside of the window verses the outside which then exponentially increases the air infiltration.

They're put under windows because "that's how it was always done", "less tall furniture in front of windows" and most importantly "everybody *knows* it makes the the room warmer... maybe.

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It does help keep the room warmer.

Back in the 40s and the 50s, supplies were put on the inside wall. Many people would complain about the sudden coolness they felt when the heat shut off. And how cold they felt sitting at the outside wall. In the 60s they started changing to supplies under the windows, and those types of complaints were reduced to almost none of that type.
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Old 12-08-2018, 04:34 PM   #10
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Re: Need To Reduce HVAC Duct - Building Day Bed


If the house was in a cold climate I would say hell no.
Unless you like frosted windows that condense and causing mold along with rot....
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Old 12-08-2018, 04:42 PM   #11
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Re: Need To Reduce HVAC Duct - Building Day Bed


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It does help keep the room warmer.

Back in the 40s and the 50s, supplies were put on the inside wall. Many people would complain about the sudden coolness they felt when the heat shut off. And how cold they felt sitting at the outside wall. In the 60s they started changing to supplies under the windows, and those types of complaints were reduced to almost none of that type.
That's not an appropriate comparison. You're comparing floor supplies to wall supplies, and the floor supply is almost always superior to a mid-wall supply due to a decrease in stratification, regardless of its location around the perimeter.

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Old 12-08-2018, 05:12 PM   #12
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Re: Need To Reduce HVAC Duct - Building Day Bed


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That's not an appropriate comparison. You're comparing floor supplies to wall supplies, and the floor supply is almost always superior to a mid-wall supply due to a decrease in stratification, regardless of its location around the perimeter.

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When on an inside wall, a floor supply doesn't make the outside wall area feel anywhere near as comfortable as a floor supply on an outside wall does.

But either way, it doesn't matter, as the OP has a wall supply.
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Old 01-01-2019, 03:53 PM   #13
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Re: Need To Reduce HVAC Duct - Building Day Bed


Thank you, Sorry for my late reply. It's a 10" flexible duct attached to a 10 x 4 vent. I'm thinking extending the 10" duct underneath the bed for 3 feet. I guess it's not going to restrain the air flow much. House is in Oakland so not much frost in the windows anyway.

Last edited by guilamontagne; 01-01-2019 at 03:56 PM.
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Old 01-01-2019, 05:24 PM   #14
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Re: Need To Reduce HVAC Duct - Building Day Bed


Have the bumpout surveyed with a thermal camera. Fix the heat leaks...

Upgrade the windows to R-6 or better with a storm window and maybe thermal shades?....

Check for appliances that use internal instead of outside air for combustion, like fireplaces, old style furnaces,hot water heaters and ovens, They worsen the situation by 'Sucking' in Cold air.

Make sure your duct work is to code BEFORE changing it..

DO the math on the current setup, you might need MORE ducts, not fewer.

If your furnace is oversized, and never runs nearly full time at Max delta Ts, a smaller output furnace could run a lower CFMs fan speed, that would make the existing ducting/plenums "larger"...

If you so re-size your furnace, don't forget the effects of wind at Max cold.

I've used remote wireless thermometers that are part a cheap "weather station" to collect data on cold/ hots that record highs and low temps.

I'd consider installing the bed/furniture a few inches higher to leave ample room for air out or in, A space to collect the "wild" dust bunnies.
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Old 01-01-2019, 07:23 PM   #15
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Re: Need To Reduce HVAC Duct - Building Day Bed


Quote:
Originally Posted by guilamontagne View Post
Thank you, Sorry for my late reply. It's a 10" flexible duct attached to a 10 x 4 vent. I'm thinking extending the 10" duct underneath the bed for 3 feet. I guess it's not going to restrain the air flow much. House is in Oakland so not much frost in the windows anyway.
3 foot won't hurt anything.

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