Day Chahroudi

Name correction: Earlier versions of this wiki used “Gary Chahroudi.” All patent records, publications, and professional sources consistently identify him as Day Chahroudi. No source uses the name “Gary.”

Physicist, chemist, and inventor. University of Rochester (undergraduate), Brandeis University (graduate). Currently Founder/Owner of Suntek, Inc. in Tijeras, New Mexico.

Career

Designed equipment for manufacturing early integrated circuits. Worked as a physicist at Lawrence Livermore National Laboratory. Joined Zomeworks after reading Steve Baer’s Dome Cookbook — reportedly walked up the road with a rucksack. Baer was “so impressed by his approach to engineering problems that he persuaded him to stay.” Worked alongside Baer, Dave Harrison, and Dick Henry. Developed a passive solar tracker mechanism and taught Baer “some principles of physics.”

Taught architecture at MIT; with Sean Wellesley-Miller and the New Alchemy Institute, coined the term “bioshelter.”

Inventions

Low-E coatings and Heat Mirror

Founded Suntek Research Associates with a group of MIT students; in 1976 moved to Silicon Valley. With DOE funding, developed the first Low-E coating for glass (1976), adapting airplane windshield coating technology for building glazing. Collaborated with John Brooks and Sean Wellesley-Miller to form Southwall Corporation, commercializing the technology as Heat Mirror (~1981) — a transparent coated plastic film reflecting radiant infrared heat while transmitting visible light, roughly doubling window R-value from R-2 to R-4.

Cloud Gel

Chahroudi’s signature invention, trademarked by Suntek, Inc. A thermotropic (temperature-responsive) optical shutter material: poly(methyl vinyl ether) dissolved in water, crosslinked with methylene-bis-acrylamide. At cool temperatures it is transparent (92% visible transmittance at 25°C); when heated, polymers shed their water coating and clump together, turning translucent white (6% transmittance at 50°C, up to 90% reflective). Switching temperature is adjustable (10–65°C). Fully reversible, requires no mechanical parts or energy input. Limited commercial availability from 1995.

Chahroudi envisioned Heat Mirror and Cloud Gel working together as a complete passive solar glazing strategy in the “Bioshelter House.”

Key patents

US 4,307,942 — Solar Control System (1981)
US 4,389,452 — Transparent Infrared Radiation Absorption System (1983)
US 4,259,401 — Methods for Storing Heat (phase change materials, 1981)
US 5,404,245 — Automatic Light Valves with Polymeric Layer (1995)
US 5,524,381 — Solar Heated Building Designs for Cloudy Winters (1996)
US 5,755,216 — Building Products Incorporating Phase Change Materials (1998)