Low or high for HVAC return vent?
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| Posted in Mechanicals on
In Minneapolis Zone 6 my general contractor and his HVAC sub insist that the proper return vent location is high on the wall near the ceiling. This seems counterintuitive as heat rises wouldn’t I want the returns low to circulate. As the supply heat enter to room and rises the return vent would draw that warm air back down. The opposite would be true when running our AC but we only run the AC for about 1 month and the furnace runs from at least October through March.
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Replies
David,
This question was recently discussed in another thread. Why don't you read the responses to that thread -- then if you still have questions, post them here.
Here's a link to the earlier thread:
https://www.greenbuildingadvisor.com/community/forum/mechanicals/19510/return-air-vents-high-or-low
Martin,
Thank you I had already read that thread. Your first response in the linked thread was that:
“In cold climates that are heating-dominated, it is usual for both supply registers and return grilles to be located near the floor”
Is the usual location also the best location? I didn’t get a consensus opinion form the other thread.
David,
If you are only running your AC for one month of the year, I would be inclined to install my return-air grilles in the usual location for cold-climate systems: near the floor.
Martin
Wouldn't the placement of the vents be affected by how air tight and how well insulated a home is? The link you provided talked about R31 walls and R50 ceiling. I am assuming pretty air tight. A home such as that would have a lower rate of stratification that a drafty poorly insulated home.
I would think a number of factors would affect the placement. My thoughts are a multi-stage furnace that runs longer would have more stirring and less affected by placement of returns. The same for heat pumps which would run longer.
Many of our rules for duct placement has been formulated for poorly insulated homes that leak a lot of air. I had heard Joe L and others state that as homes become more efficient that it is not longer necessary to place the supplies along an outside wall.
As we change to more energy efficient homes are we going to see a change in duct placement and size.