# Return duct code requirements



## Richard Buckingham (May 28, 2020)

I am in a situation where we are re-constructing my mother-in-laws 1900 era home that burned.  The heater has been replaced and we upgraded to central AC.  One thing I have discussed with the mechanical contractor is the absence of any return ducts on the 2nd or 3rd floor. The only returns on the 1st floor.  I thought halls and stairs were not to be used as returns.  Should there be a return duct, at least one, on both of the upper floors?  This is a relatively small house in an older part of the city, so about 2500 sq. ft. total.  The last heating system only had returns on the 1st floor but it was installed decades ago.


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## cda (May 28, 2020)

Not an ac person 

But for better circulation and comfort I am thinking should be there.

As far as required will let others answer 

Is it to late??


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## classicT (May 28, 2020)

Not a code requirement that I am aware of...

But as I like to remind folks of, the code is a minimum standard, not best practice.


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## Keystone (May 28, 2020)

2015 Residential Code, the code does not specify exact locations of return air it states,
M1602.2 Return Air Openings, Return air openings for heating, ventilation and air conditioning systems shall comply with all of the following: 
2. The amount of return air taken from any room or space shall be not greater than the flow rate of supply air delivered to such room.
3. Return and transfer openings shall be sized in accordance with the appliance or equipment manufactures installation instructions. Manual D or the design of the registered design professional.  

In my experience unless you have open concept floor levels and even then it will be very difficult to meet return air requirements without at a minimum hallway returns on each floor level and either undercut doors or wall transfer openings into each conditioned space.


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## Paul Sweet (May 28, 2020)

High returns, to capture hot air that rises, are a good design practice but are not a code requirement.


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## north star (May 28, 2020)

*$ > $ > $*

Richard Buckingham,

On your new Central AC unit, does it have a Return
Air opening on it, that is supposed to receive Return
Air ?.......Is the unit designed to have Return Air ducted
back in to it ?

What did the Mech. Contractor say about the absence
of Return Air Ducting ?

Where is the new Central AC located ?........Can you
provide the Brand Model Number of your New Central
AC ?........What does your Owner's Manual require for
Return Air ?

*$ < $ < $*


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## klarenbeek (Jun 2, 2020)

The prohibition of using corridors for return air movement applies to egress corridors in larger commercial buildings, not residences. One central return for a house is not a code violation.

That being said, having returns on just one level of a multistory home is a poor design and you will have airflow problems.  Best design would be to have a return in each bedroom and family room/living area.  Not always easy to do, especially in an older home without opening up a lot of drywall.  I would at least try to get one on each level and provide a way for the air to get out of every bedroom either with a gap under the door or a transfer opening through the wall.  Think of trying to blow air into a room without any way for the air to get out like blowing into a pop bottle.  Once its full you can't get any more air in unless there's a way for the old air to get out.


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## VillageInspector (Jun 9, 2020)

Absent any specific language in your codes I would refer to the manufacturers installation manual but I think best practice would be to have at least one return per level at a minimum


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## ADAguy (Jul 6, 2020)

All good comments


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## Kelaris (May 5, 2021)

Perhaps you should contact the mechanical contractor and other specialists because this problem looks severe, from my perspective. If I were you, I'd start with a major overhaul and redesign the rooms' layout and all the air ducts, if you had any. If you want to keep the location of the rooms, of course, it will be more difficult, because before the concept of an air duct was a maximum of "open a window to ventilate the room", and now the technology is completely different, right? Would you consider doing a heating duct repair to make it easier for everyone in the house to breathe after recovery?


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## eruca_clb (Sep 11, 2021)

Does the prohibit return-air inlet on top of wall?


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