Carl, through collaboration with John Tandberg, also developed foam plastic (known by the Dow Chemical trademark as Styrofoam). Foam plastic was made to expand by introducing soluble gas under pressure into the melted substance. When the pressure was quickly lowered, the substance bubbled and hardened into a highly porous structure that turned out to have excellent insulating properties. Although Carl envisioned its use for insulating refrigerators, the product was used in life vests and rafts during World War II. Today we encounter it in numerous forms as insulating and packaging material. Though foamed plastic is not often used in HVAC applications, it is likely the most widely used of Carl's inventions.
In 1953, Carl and his associates made their big breakthrough in developing efficient heat and mass transfer surfaces. They developed structures using thin, tightly bound corrugated sheets that provided enormously higher efficiency in a heat transfer device of any given size. The new structures were dramatically smaller. Carl and his colleagues immediately started to pursue innovative uses for these structures such as compact heat exchangers, cooling towers, dehumidifiers, humidifiers, and heat recovery units. Today these inventions are known as Heat Recovery Wheels, Evaporative Air Cooling, and Humidification Media. One year later his team started to develop a compact but highly efficient fill for cooling towers. Carl was actively promoting indoor environmental quality and sustainability in the 1950s!