Return Ducts are absent, Help!

8 years ago

Home is under construction, extremely tight build, geothermal unit housed in walk out basement, 6500 sf of conditioned space, located in North TX. Truss design between basement & main floor elicited a "field decision" to use an open air design for return air instead of ducted returns. Homeowner was not aware until mostly completed. At this late stage it is possible to cannibalize a closet and use attic to duct a return duct for the upstairs . However, the basement would cost many thousands to now to fur down a meandering soffit for a return duct. Question: Is it possible to use a ducted return for the upper floor and the "open" air return design on the basement floor using jump ducts, grates, grills, louvered doors, or what have you as long as there is a clear path back to the geo unit for the air? We nixed this "open" air design for the entire home because there are no double height rooms, over looking balconies, or any opening to the upstairs other than a single doorway which does have a door on it. If it is possible to have return ducting for upstairs but open air in basement, what would it look like going back to the geo unit? (Is it possible to divide the return intake on the unit to fit both a duct but also permit open air to be sucked right in?

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Comments (2)

klem1
8 years ago
Yes,,,,No,,,,,maybe so,certainly. Mentioning basement in N Tx is enough to scatter the herd. Less than .05% of N Tx contractors know straight up from down about geothermal,much less how to design one. 6.5k sq ft start's at over 1mm before any extras like geo and fancy floors. Any thing is possible but it's foolish not hiring engineers for projects like this.
David Cary
8 years ago
From your description, I would say it is hard to say.

My one thought is that basements typically need very little conditioning. I had a 2000 sqft walkout that I put a single 14x20 in and honestly could have skipped. As long as the door to upstairs was open, there would be enough air flow.

I am not a HVAC engineer. The designs I see are often terrible to this engineer minded person. But a big open basement (not sure if that is what you have) with an open stairwell and the unit in the basement with louvered doors etc is not a big deal. At all.

I don't know what the rule of thumb is but a non walkout basement will typically use no a/c and heating will be 20% of the upstairs. Now typical is really really hard since you said "extremely tight". But those walls and floors exposed to 60 combined with a ceiling exposed to 70 doesn't really represent a heating or a/c load.

Why why does an "extremely tight" build in N. Texas call for Geo? It is my pet peeve. What you have is a mild climate based on temperature. Geo helps with temp extremes - ie over 110 or under 20. Temps seen certainly less than 10 days a year - although North Texas is probably variable. And you have extremely low electric costs (generally). But you didn't ask and you can't change so sorry for that rant. And you do save some outdoor space.
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