Cold Air Return

[Steve in UT]

On a conventional forced air furnace w/AC in a tall garage, Would it not be a good idea to have a high and a low return? The high return for returning warmer air during the summer to be cooled and the low to return the cold air during the winter. You would obviously close one or the other. Anyone done this or seen it done?

 

[The Cobbler]

I've done it on 2 houses that I have owned . I think it makes sense & works well. others will say there's no difference & it's all hype.

 

[yeldogt]

How high ?---- with AC the goal is to keep the lower part of the space cool .. you don't want to pull the hottest air from the top and try and cool it .. your not trying to cool all the air.

The supplies make a difference.

For heat -- the goal is to take the cold air from the floor and be pulling the hot air around -- in a tall space this can be a problem. Again supplies are important -- flow direction. There can be situations where having a duct that pulls heat off a tall ceiling can aid .. but this depends on overall gain.

 

[tab2]

As a commercial GC, I think residences typically don't have enough return air pathways, but we think about return air just as much as supply.

With only return air up high in the heating season, you stratify your hot air up high, you want a return low to pick up that cool air to try to have a consistent temperature through the space.

I think it would be beneficial. You could also damper them and flip them seasonally or try to balance them so it would be more comfortable.

 

[dcg9381]

Interesting, never considered high versus low return.. but I'm in a "hot" state.
I've run into the under-sized return. Not so much about HVAC performance, but an undersized return can generate a ton of noise...

 

[bored350]

I'm also curious if there is any advantage/disadvantage to multiple returns on opposite sides of the room in? For example, on a garage that is 46' deep, if the unit is at one end with it's return, would it be advantageous to duct a return that runs to the far end of the building?

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[Jking24]

I am also interested in this

 

[DC73]

What about the potential for explosive vapors to be drawn into the furnace? Most vapors from flammable liquids like those present in typical garage workshops are heavier than air and tend to sink.

DC

 

[Steve in UT]

What about the potential for explosive vapors to be drawn into the furnace? Most vapors from flammable liquids like those present in typical garage workshops are heavier than air and tend to sink.

DC

Yeah, I could see why you might not want it right next to the floor. Seems like I've read others refer to code requiring a certain height off the floor.