What is a building envelope?

This is a question that nobody asks. Frustratingly, they don’t ask it because they have never heard the term, ‘building envelope.’

This is a reflection on how little we have been educated in the field of building science over the last 20 years, and the main reason we are doing a poor job with energy efficiency. As building scientist Joe Lstiburek says, “If you don’t get this concept, nothing else really matters.”

Here’s a clue. The red line in the provided image represents the building envelope. The concept of addressing Water, Air, Vapour and Thermal applies to this line.

A building envelope is the physical separator between the conditioned and unconditioned environment of a building including the resistance to water, air, heat, light, and noise transfer.