John I. Yellott — Wikipedia article and supporting sources (fetched 2026-07-19)

Primary URL: https://en.wikipedia.org/wiki/John_I._Yellott Fetched: 2026-07-19 Reliability: mixed — Wikipedia biographical claims (esp. family/death details) are unsourced in the article itself; cross-checked against ASU News and ASES where possible.

Biography

John Ingle Yellott, born October 25, 1908, Bel Air, Maryland; died December 30, 1986, Phoenix, Arizona (heart attack), age 78. Survived by second wife Barbara, a son, a daughter, two stepsons, six grandchildren.

Education: Bel Air High School and Episcopal High School (Alexandria, VA); Johns Hopkins University, M.E. (1931), M.M.E. with distinction (1933).

Pre-solar career

Stevens Institute of Technology, then Illinois Institute of Technology: chairman of Mechanical Engineering (1940-1943), director of the Institute of Gas Technology (1943-1945).
WWII: consultant to the Metallurgical Laboratory, University of Chicago (Manhattan Project) — corroborated independently by ASU News, which describes him as “an internationally recognized scientist who contributed to the Manhattan Project during World War II.”
1945-1955: Director of Research, Locomotive Development Committee, Bituminous Coal Research Inc. — developed a coal-fired gas-turbine locomotive (pulverized coal injection), one of 50+ patents he held.

Switch to solar energy (1955)

Cited motive: “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.” Moved to Arizona in 1951. Helped found the Association for Applied Solar Energy in Phoenix (1954). Founded John Yellott Engineering Laboratories and the Yellott Solar Energy Laboratory, Phoenix (June 1958).

Arizona State University

Sources give somewhat different framings: ASU News states he was hired as a lecturer in ASU’s College of Architecture in 1963, became visiting professor in 1973, emeritus in 1979. Wikipedia frames it more broadly — taught environmental control systems in the College of Architecture, became head of ASU’s solar program after the 1973 oil crisis, taught until retiring around age 70 (~1978). Received an honorary doctorate from ASU (1985). Co-founded ASU’s Master of Science in the Built Environment program.

Skytherm / Harold Hay collaboration

Yellott’s belief in Hay’s roofpond concept gave Hay the opportunity to build the full-scale 1967 Phoenix prototype in the Sonoran Desert. Yellott donated the property, instrumentation, and thermal-comfort engineering advice. Testing surfaced practical issues (mosquito larvae, nesting birds) addressed with chemical treatment; the concept was later extended to a Trinity University (TX) dormitory-roof test.

Other contributions

First chairman, ASME Solar Energy Applications Group (later Solar Energy Division). Developed the solar heat gain factor (SHGF) method for glass, now an ASHRAE standard; consulted for Corning, PPG, Libbey-Owens-Ford, Pilkington. Organized the 1957 “Living with the Sun” competition. Invented a transparent solar pool cover still in commercial use. The “Yellott Number” (thermosiphon solar water heater characterization) is named for him.

Publications

Energy for Our Future (1957); Solar Energy Utilization in North America (1958); Solar Radiation and the Atmosphere (1976); The Fundamentals of Solar Technology (1979); hundreds of articles and papers. Papers archived at the American Heritage Center, University of Wyoming.

Honors

Member, Order of the British Empire (civil division); inaugural inductee, Solar Hall of Fame (1976); Associate Commander, Order of St John of Jerusalem; IIT Hall of Fame; Fellow of ASME, ASHRAE, AAAS, Arizona Academy of Science; Benjamin Franklin Fellow, Royal Society of Arts (London); ASME “John I. Yellott Award” (biennial, named for him); ASES “John and Barbara Yellott Award for Graduate Solar Research,” funded by a Yellott philanthropic gift.

Flags / uncertainties

ASU hire-year framing differs slightly across sources (1963 lecturer per ASU News vs. Wikipedia’s broader 1973 solar-program-head narrative) — not necessarily contradictory, but unreconciled against a single primary ASU source.
No independent newspaper obituary located; Wikipedia’s family/death details are unsourced in the article itself.
American Heritage Center finding aid PDF (uwyo.edu) could not be parsed as text — likely the most authoritative biographical document, flagged for future manual review.

Supporting URLs

Source: web research compiled 2026-07-19 for wiki article expansion.