John Ingle Yellott (October 25, 1908 – December 30, 1986) was an American engineer recognized as a pioneer in passive solar energy, and an inventor with many patents to his credit.

Yellott said the change resulted from "the realization that the entire world, and the United States in particular, was running out of fluid fuels, and that we must find a way to gain economic access to the limitless energy of the sun.

He served as Headmaster and then Director of Development for Phoenix Country Day School, and taught environmental control systems at the College of Architecture at Arizona State University.

[5][10] Soon after the oil crisis, Arizona State's College of Architecture instituted a solar program and chose Yellott as its head; he continued to teach there until his retirement at age 70.

According to his Illinois Institute of Technology Hall of Fame entry,[11] Yellott's work resulted in more than fifty patents, such as an electric locomotive with a coal fired gas turbine using pulverized coal directly injected into a combustion chamber;[12] a film-type solar water heater [13] and a transparent cover to heat swimming pools by trapping solar radiation[14] Yellott's pool cover idea remains in commercial use to this day.

[10] The experiments at Yellott's laboratory encountered obstacles such as the unexpected "healthy growth of 'wrigglers' within plastic-enclosed water" from the city mains; then "a pair of nesting birds was attracted to the comfort of a projecting portion of the roofpond.

The researchers eliminated the unwelcome 'wrigglers' as well as a prolific growth of algae with chemical treatment; they considered the “cheerfulness of the birds a pleasant relief from the drudgery of data-collection,” but recommended “preventive measures for those not wanting such company.”[10] Yellott's and Hay's experiments did prove the roofpond concept technically feasible, later confirmed with expanded testing on dormitory roofs at Trinity University[16] in Texas.

According to Dr. Jeffrey Cook, College of Architecture and Design, Arizona State University, writing the introduction to the Passive Solar Journal's John I. Yellott Memorial issue, "he made major contributions in areas of basic research, instrumentation, analytic methods, applications, collaboration, education, and demonstration.

"[10] Cook also wrote: "[h]e published no definitive book," but "[a]rticles bearing Yellott's name will remain classics in solar energy literature;" he "developed no distinctive demonstration, no outrageous solar machine, and no landmark building or award winning engineering system," yet "as a consultant he influenced such major architectural feats as the St. Louis Arch and the new Hong Kong and Shanghai Bank;” his analysis “contributed to the industry development of architectural glasses .

that have gained worldwide use.”[10] His pervasive influence in solar science is largely found in the ongoing work of others, as “he was a mentor to architects, inventors, and students.” "Thus,” Cook concluded, “as gentle and persuasive as the sun, Yellott touched many people and places.".