I've heard people who swear by curved supply registers, and others who say that they make no difference at all vs. "normal" stamped registers. A town nearby requires them in their building code, but the county (where I'm building) does not.

The only thing I could find giving an opinion online was here, but even that doesn't seem to do a genuine scientific rundown of airflow dynamics, just a description of what they think the airflow will do.

Has anyone done a more thorough study? What are the opinions of the green building talkers?

I don't think you will see an appreciable difference with either one

Air movement in typical A/C systems is about 10% of the energy of the whole system. This varies a lot based on the efficiency of the cooling portion. You can reduce the energy for air movement by 70% by having very efficient variable speed fan systems and efficient low restriction ductwork. This is at best a 7% improvement in overall efficiency and is attacking the smaller side of the equation. The register is an even smaller part of the overall system efficiency.

If you are using more efficient cooling system that use less cooling energy than the air movement portion of the equation can be more significant. If the goal of the system is to be part of a zero energy building it becomes significant. In a standard building the registers are in the mud and would be hard to quantify. I would guess that a curved register representative visited their group with a dog and pony talking only about the registers and only about the difference in loss on one versus the other.

Brian

I have been working in industrial ventilation for 30 years, and I am amazed how home duct work is run. They break about every rule of efficient air movement!

Tee intersections, right angle turns, s turns etc, all add to raising static pressure. Now I would assume they are just upsizing fans to evercome it, but the efficiency and balance are still affected.

Most commercial systems with exposed round ducts,( restaurants etc) do a pretty nice job. Large radius turns, decreasing size main ducts etc.

Personally I am hoping to install correct ducts in my new home, but realize there will be an added cost and design difference.

Good information for CORRECT systems can be found in:

Industrial Ventilation, A manual of recommended practice
American Council Of Govermental Industrial Hygenists.

This is geared to Industrial but Air movement is air movement.