Our buildings are designed to isolate the interior climate from the exterior climate, which means we need to consider every way energy moves between the interior and exterior, including the roofs, walls, floors, doors, windows... literally every square inch of the places where heated or cooled spaces encounter the outside world. Most of these 'boundary conditions' consist of a variety of materials assembled in fairly complex ways. One of the least obvious and more complex of these places where energy constantly flows between the inside and outside environments is the building foundation.
There are many possible ways to go about creating foundations. Evaluating which is the optimal choice requires a full understanding of the performance, price, and environmental implications of the various alternatives. The detail drawing of the footing seen here could be constructed in many different ways, using various combinations of materials.
Thermal imaging reveals graphically what is not visible to the eye - how heat moves through complex combinations and configurations of materials. The ability to accurately simulate and understand the actual performance of different options eliminates speculation and guesswork. With this clarity, we can then evaluate the matrix of related financial and environmental costs and benefits.
The lowest quality solution allowed by law - the 'built to code' option - establishes something of a baseline for how heat will move from the warmer condition to the colder one. This image is what is known as a 'Flux Diagram'. It shows the areas where energy is moving from higher heat energy to lower heat energy (hot to cold). It is clear to see that at the edges of the floors, where they will meet the base of outside walls, there is a high amount of energy movement.
Compare this with one of our high performance foundation assemblies, which does a much better job of isolating the interior thermal climate from the exterior. The area where the base of walls meets the edges of floors shows just a small amount of energy activity. Energy is still moving from the warm interior climate to the cold exterior climate, but it is doing so very slowly.
Author: Sam Rodell
Sam has been practicing as an award winning architect for over thirty years, and has also built many of his clients' projects. He is currently licensed to practice architecture throughout most of the western United States and Canada, and is certified by the National Council of Architectural Registration Boards (NCARB) which expedites registration in other states and provinces. He was the first Certified Passive House Consultant (CPHC) architect in eastern Washington and northern Idaho.