In his capacity as professor and department head, Jordan modernized the experimental laboratories and broadened the curriculum to include studies focused on new technologies. He encouraged engineering innovation and recruited faculty members with worldwide reputations in engineering science. Under his leadership, the department became a center of excellence in a number of areas, including heat-transfer studies, particularly the generation of solar power through the use of solar collectors, and rose in the rankings to fourth in the country. He also oversaw the creation of a particle-transfer laboratory and took part in its research projects.

Jordan, whose work in heating and refrigeration was internationally recognized, wrote more than 200 technical publications, including Refrigeration and Air-Conditioning, with G.B. Priester, (Prentice-Hall, 1949, revised 1956), a key textbook in the field for many years.

Aware of diminishing world-energy resources, Jordan advocated solar energy as an alternative to fossil fuels. “Any home in the United States may be heated entirely by a solar energy heat pump system,” he wrote, “if a sufficiently large collector, heat pump, and heat storage facilities are provided.” He established a solar-energy research program at the University of Minnesota in the mid-1950s; it focused on solar energy as a way to control energy consumption in buildings. He and his students made pioneering contributions to fundamental research on solar radiation that are still widely regarded.

Jordan began studying sustainable, cost-effective ways of collecting solar energy early in his career. His papers “Solar-Energy Heating” (1954), “Heat Pumps and Solar Energy” (1955), and “Solar Energy Utilization” (1956) are as relevant today as they were when they were published. “Direct Solar Radiation Available on Clear Days” (1958) and “The Interrelationship and Characteristic Distribution of Direct, Diffuse and Total Solar Radiation” (1960) provided fundamental data on solar radiation that have remained substantially unchanged over the years.

Recognizing the importance of air quality in the building sciences and the need for energy conservation, Jordan began a program of study on air filtration and building insulation.