The Only Engineering Rules You Will Ever Need

Having recently moved to Boston, I was rummaging through some old boxes at work and come across a small little notebook from my first year of Engineering Science at the University of Toronto. It was from CIV102 – Structures and Materials, my first introduction to engineering and still my favorite course. It was taught by Professor Michael P. Collins. Those who know him and have attended his class will likely fondly remember his lectures (and his brutal problem sets). For those who don’t, I encourage you to watch his introductory lecture “In Search of Elegance” – a truly inspiring talk.

I’m sure I learned a great deal at University, and I can probably even recall an equation or two, but I will never forget Professor Collins’ 3 Principles of Engineering:

1. F = ma
2. You can’t push on a rope
3. To get the answer, you must know the answer

At the time, I found these principles cheeky and elegant – much like Professor Collins himself. It wouldn’t be until after I graduated and found myself neck deep in learning the ropes of building performance simulation, that I truly appreciated the beauty of their universality. These three simple concepts have helped me on my journey into sustainable design and building performance analysis. Whenever I approach a new problem, I turn to them for guidance

F = ma. Just like Newton’s Second Law governs classical motion (in the world of bricks and mortar that I work in we can usually ignore Einstein and Quantum Mechanics…for now), so too Fourier’s Law governs conductive heat transfer in building assemblies. Specifically, Q = UAΔT. Heat flow is proportional to the difference in temperature and dependent on the heat transfer coefficient (specific to each material) and the cross-sectional area. The take-away is this: you can’t ignore physics when designing buildings. Doubling the amount of insulation will halve the heat load and adding thermal bridging will significantly increase it. To understand how to make buildings perform better requires a deep understanding in building physics and the fundamental equations of heat, moisture and energy.

You can’t push on a rope. Ropes and cables can only take tension. Concrete (for the most part) can only handle compression. You can’t ignore the reality of your experiences just because the math says so – chances are the math is wrong. Heat flows from high temperatures to low temperatures. Moisture moves through building materials along a vapor gradient. Reducing the lighting load will increase the heating load. You can’t get more energy than you put in. With the increasing complexity of building materials, envelope and HVAC systems, it is critical that we keep in mind the fundamentals – if the simulation runs counter to our expectations, we need to dig deeper.

To get the answer, you must know the answer. At first a seeming paradox, but on closer inspection, an endorsement for intuition and experience. I rarely start a new energy model without doing some paper math first to develop a sense of the solution so that when the sophisticated computer simulation finally spits out a number, I already know that it’s in the right ballpark. A recent trend in simplified energy analysis tools geared towards architects or automated continuous commissioning and fault diagnostics aimed at facility operators promises to make data-driven design and management easier and more ubiquitous. Press the “simulate” button and you’re on your way to a great low-energy design. Without a fundamental understanding of the physics, we run the risk of training a generation of designers that know how to “model” buildings without actually understanding what is going on “under the hood” – and that is incredibly dangerous. Without knowing the answer before running the simulation, designers will be left blindly stumbling around and grasping at the first answer that comes from the software, without having the experience and expertise to critically evaluate and interpret the data.

Despite all the advances in modern architecture and engineering, including the development and proliferation of computer modelling and analysis programs, I find it really fascinating and comforting that underneath all of that is a rather beautiful simplicity. An elegance of problem solving and understanding that has stood the test of time. As we turn to more and more sophisticated software to aid our more and more complex designs, we should keep in mind these 3 simple golden rules.