I very recently had a new system installed in my apartment. I had the old duct board replaced with metal and when I went into the attic I was surprised to see that all the new ducting was circular rather than retangular. The contractor explained that round is better as there is less air resistance and this seems to make sense. Is there any reason why rectangulr would be better?
Separately, I was also surprised to see that the ducting (which is in the attic) was all elevated about 20 inches or so above the joists, whereas the old ductboard was attached flush ontop of the joists. Is that ok? What are the pros and cons of such an approach?
(BTW, title should read Rectangular v. ROUND Metal duct)