Hello everyone and Happy Holidays!
Attic ductwork is ubiquitous in extant, single floor, single family housing and we are all too aware of the numerous shortcomings. A number of years ago, I decided to address the issue of a single, central ceiling return in my 1750 sq. ft,, 2002 home (10' ceilings) and the subsequent problems with cold hardwood floors and interminable recovery from setback.
I won't review my crawl space encapsulation or the fact that I have limited setback to just one degree (it makes my wife happy to "force" heating upon our typical wake-up time), both of which have improved comfort at no measurable difference in heating cost. After reading Dr. Bailes recent tretis on HDD, I suspect savings would be difficult to estimate anyway. The home has been blower door tested (precise numbers escape me, but were excellent) and insulation heavied in the attic.
Back to that single, central ceiling return.
Being a rocket surgeon in my spare time, it occurred to me that pulling cooler air from floor level in the heating season could only help the previously described problems and I found a place in the corner of a hall closet, very near the central ceiling return, where I could install an 8" flex duct. Much larger, and the duct took more space than my wife would approve. At the bottom of the duct, I installed a 90* adapter with a section of 5" X 14" filter media.
In the closet ceiling, a suitably sized, very tight clearance hole permitted entrance of the flex into the attic, where the duct is connected to an adapter on the single, enormous flex duct that leads back to the furnace.
An appropriately sized grill on each side of the bottom of the closet door ensured air movement.
I appreciate overall return air has not increased, but my calibrated, wet finger indicates considerable air flow. Also, the added duct is closed during the cooling season.
My questions to the group are, what unintended consequences may I have introduced into my system and does anyone have any thoughts on potential cost savings? My DIY efforts came in at around $50 and two band-aids.
All the best.