The triframe modular design is used in several of haertlings projects. It first appeared in the design of the Fredrick House of 1965. It was again used in the design of the Solarcrest Condominiums. Other examples are a house in Cleveland, and Faith Court in Albuquerque.
Proven to be very economical and quickly constructed, Haertling realized the potential, and applied for a patent.
A Photograph of Linda Haertling and the Triframe modular design in July 1963 indicates that Haertling had developed the concept even before 1965.