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Returns at ceiling. Why or why not?

1280 Views 27 Replies 9 Participants Last post by  57TinkerMan
I am in Texas. It is hot most of year. I seldom use (gas) heater.
I have designed new home build (2 story duplex, concrete slab) with AC and all ducts within air conditioned space.
Because heat rises seems to me that return ducts make more sense to be near ceiling rather than near floor. (All return air is usually installed near floor.)
In my design, hvac closet is centrally located in the living space and most return vents can directly be installed into hvac closet therefore total return vent duct is 8 feet. Total supply duct is 48 feet.
Is it better to put return ducts near ceiling in order to facilitate returning hot air at ceiling?
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I wonder if this may be of interest to you.

I live in Wisconsin
I have several friends with new homes.

In each of their homes, every supply and return has 2 vents.
One at ceiling level and the other at floor level.

It was explained to me by my friends that ...

In winter
Close the ceiling return vents and open the floor return vents. (Cuz the cooler air is on floor level and needs to be drawn in to be reheated.)
Close the ceiling supply vents and open the floor supply vents. (Cuz warm air will rise.)

In summer
Close the floor supply vents and open the ceiling supply vents. (Cuz the cool air is heavier and will drop.)
Close the floor return vents and open the ceiling return vents. (So the warm air is pulled in and re-cooled.)
 

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I wonder if this may be of interest to you.

I live in Wisconsin
I have several friends with new homes.

In each of their homes, every supply and return has 2 vents.
One at ceiling level and the other at floor level.

It was explained to me by my friends that ...

In winter
Close the ceiling return vents and open the floor return vents. (Cuz the cooler air is on floor level and needs to be drawn in to be reheated.)
Close the ceiling supply vents and open the floor supply vents. (Cuz warm air will rise.)

In summer
Close the floor supply vents and open the ceiling supply vents. (Cuz the cool air is heavier and will drop.)
Close the floor return vents and open the ceiling return vents. (So the warm air is pulled in and re-cooled.)
I did the same thing in the house I built in Connecticut. Makes sense, seemed to work well with my geothermal heat pump - total cost to keep the house at 72° all year was around $550, course there other "tricks" and design decisions that also helped.
 

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In winter
Close the ceiling return vents and open the floor return vents. (Cuz the cooler air is on floor level and needs to be drawn in to be reheated.)
Close the ceiling supply vents and open the floor supply vents. (Cuz warm air will rise.)

In summer
Close the floor supply vents and open the ceiling supply vents. (Cuz the cool air is heavier and will drop.)
Close the floor return vents and open the ceiling return vents. (So the warm air is pulled in and re-cooled.)
Not necessary for supply vents. You size them so they have good throw and mix the air anyways. Having double returns can help, but it's not done very often due to cost.
 

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If i were to have another house built , unless i determined to have all duct in conditioned space like the O P , it would have PVC supply duct under the concrete slab with returns in the ceiling just as the one we built nearly 40 years ago . The old 2.5 ton GE must like it because it's never failed heating or cooling for those 40 years .
 

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I am in Texas. It is hot most of year. I seldom use (gas) heater.
I have designed new home build (2 story duplex, concrete slab) with AC and all ducts within air conditioned space.
Because heat rises seems to me that return ducts make more sense to be near ceiling rather than near floor. (All return air is usually installed near floor.)
In my design, hvac closet is centrally located in the living space and most return vents can directly be installed into hvac closet therefore total return vent duct is 8 feet. Total supply duct is 28 feet.
Is it better to put return ducts near ceiling in order to facilitate returning hot air at ceiling?
I am in Houston, and would kill to be able to get my ceiling return moved or re-located lower down a wall. Why? because in the winter time, the large den stays cold because hot air does not get pulled down to the floor and the room stays cold.

The best of both worlds would be my recommendation to you: both locations one in the ceiling and one lower down the wall especially if you have high ceilings. DO yourself a favor!
 

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I am in Houston, and would kill to be able to get my ceiling return moved or re-located lower down a wall. Why? because in the winter time, the large den stays cold because hot air does not get pulled down to the floor and the room stays cold.

The best of both worlds would be my recommendation to you: both locations one in the ceiling and one lower down the wall especially if you have high ceilings. DO yourself a favor!
That's a good example why our house is comfortable at -20F . It's difficult to believe the HVAC industry is still attempting to force cold air up and hot air down .
 

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Discussion Starter · #9 ·
If i were to have another house built , unless i determined to have all duct in conditioned space like the O P , it would have PVC supply duct under the concrete slab with returns in the ceiling just as the one we built nearly 40 years ago . The old 2.5 ton GE must like it because it's never failed heating or cooling for those 40 years .
I considered PVC but it is extremely expensive in 8" 10" and 12" diameter. And it appears "code" does not allow PVC for heat.
 

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Discussion Starter · #10 ·
I wonder if this may be of interest to you.

I live in Wisconsin
I have several friends with new homes.

In each of their homes, every supply and return has 2 vents.
One at ceiling level and the other at floor level.

It was explained to me by my friends that ...

In winter
Close the ceiling return vents and open the floor return vents. (Cuz the cooler air is on floor level and needs to be drawn in to be reheated.)
Close the ceiling supply vents and open the floor supply vents. (Cuz warm air will rise.)

In summer
Close the floor supply vents and open the ceiling supply vents. (Cuz the cool air is heavier and will drop.)
Close the floor return vents and open the ceiling return vents. (So the warm air is pulled in and re-cooled.)
I will consider this. However for me, winter each year lasts less than total 20 days with each episode being less than 4 days. With good insulation, the inside temperature of house changes very little.
 

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I will consider this. However for me, winter each year lasts less than total 20 days with each episode being less than 4 days. With good insulation, the inside temperature of house changes very little.
If you have a high and low, it will give you a better return mix. I would have all ceiling returns in all other rooms. You want a return down low in the wall if you have high ceilings. JMO
 

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If you have a high and low, it will give you a better return mix. I would have all ceiling returns in all other rooms. You want a return down low in the wall if you have high ceilings. JMO
For a cooling dominated climate like the OP, high returns only, are my recommendation. Low returns in cooling come with an efficiency penalty. In a place like Texas, that'll add up quick.
 

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For a cooling dominated climate like the OP, high returns only, are my recommendation. Low returns in cooling come with an efficiency penalty. In a place like Texas, that'll add up quick.
We are both in the same climates, if anything him being North of Houston, he gets more snow than us! High returns in a room with high ceilings, wont cut it in our winter, we are living it and have done so since 1998! Obviously summer is a non issue.
 

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FYI, Texas isn't very familiar with -20°f.what works in your house isn't going to do nearly as well for the OP.
That house has had its share of 105°F - 112°F days with that same 2.5 ton. How about 100°F - 110°F for 35 consecutive days with over night lows of 85 and 100° by 11:00 AM . I'm tellen ya that duct under concrete works . Warm air rising with cooler air staying at a level where most people live , with the excepition of those that are 6' -12" tall , feels good
 

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I will consider this. However for me, winter each year lasts less than total 20 days with each episode being less than 4 days. With good insulation, the inside temperature of house changes very little.
Different people's situations are just that... different. The OP has already established the above. I concur with supers05, in the OP's specific situation, the cost of both high and low returns isn't justified. Therefore, if you're going to do one set of returns then they should be optimized for the predominant conditioning mode... which is cooling.
 

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The one thing the OP has ignored is every manufacture builds 2 basic kinds of air handlers, Up and down flow. Which ever you use one side has to go further and more 90's to get to the unit using a closet. Bad for return air unless over sized.

I find 90% of the returns, ducted or not are on the very edge of min requirements. My systems are usually 50% above the min and are a lot quieter when running. Costs a bit more.

There is a Manual D calculation which helps figure out the duct work. Returns are complicated in my experience. Just adding a new one is a good way to destroy the system. So I usually just go bigger.
 

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We are both in the same climates, if anything him being North of Houston, he gets more snow than us! High returns in a room with high ceilings, wont cut it in our winter, we are living it and have done so since 1998! Obviously summer is a non issue.
A low return that has a damper is probably the best option. In your case, you need to maintain velocity at the register to maintain its throw down. If you a standard register that you find in any big box store, they are only good for about 6-8ft in height.
 

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That house has had its share of 105°F - 112°F days with that same 2.5 ton. How about 100°F - 110°F for 35 consecutive days with over night lows of 85 and 100° by 11:00 AM . I'm tellen ya that duct under concrete works . Warm air rising with cooler air staying at a level where most people live , with the excepition of those that are 6' -12" tall , feels good
I'm not saying it doesn't work, I'm just saying that what works in one climate doesn't work always work in another without a bit of redesign.
 
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