Building Physics started in the 1930s in Soviet Union with publishing the book “Stroitielna Tieplofysika”. With a focus on thermal performance in moist, field applications, Russian literature the 1950s and 1960s exploded. During this time, work of J.S. Cammerer in Germany and H. Johansson in Sweden, brought “Baufysik” and “Byggnadsfysik” to limelight’s respectively. These trends merged with the Architectural Science from UK and Australia and in the late 1960s, the academic discipline of Building Physics was firmly established in Central and Northern Europe. The academic version of Building Physics was a simplified introduction to heat, air, water and water vapor transfers and their effects on materials and assemblies, introduction to acoustics, noise and vibration, and fire protection.In 1971, Canadian Professor Neil B. Hutcheon, in the keynote at 25th anniversary of Indian Building Research Institute highlighted predictability of field performance as the focus in Building Physics and called it Building Science [1]. As the limiting condition of performance (failure), is also known, the distance to failure becomes the measure of performance. He said:“Knowledge about building, called, for convenience, building science, is valuable largely because it is useful in predicting the outcome of the result of some building situation…. Reliance upon direct experience as a basis of prediction is highly restrictive. Only with knowledge is it possible to assess the relevance of experience and thus to draw upon broader and more varied experience to develop predictability.”The term “building science” became a substitute for “building engineering” because the merger of theory and practice is the essence of engineering. While the first two generations of engineers had to accept that science is the basis of building technology, as this paper explains, the emergence of IDP (integrated design protocol) in the 1990s and ongoing 4th industrial revolution created a new thinking paradigm.