Sep 1, 2023

Building Physics vs. Perception: Dispelling "magic arrows" and other misconceptions through teaching

Updated: Sep 8, 2023

Just finished my 6th year of teaching the M.Sc. course of Integrated Sustainable Design (link) and it is always a real pleasure to engage with the students during the lectures and ask for their opinion. And to see their surprised faces when what they perceived to be true is actually not the case. Springing these surprises on the students is a great way of grapping their attention, challenging their preconceived notions and conveying new knowledge.

Here are three of the engagement exercises that I usually will incorporate in the lectures, which have to do with sustainable building design including the principles behind passive and active building design:

Question no. 1) Where can you find the coolest surface temperature in this image taken at noon in Kuala Lumpur, Malaysia?

So far, I have not had any people, who could give me the right answer. Most people will guess the obvious places like in at the shaded are at the entrance of the building. But this is not correct. Believe it or not, there's a place that has a temperature below zero degrees Celsius? Can you guess where it is?

Question no. 2) Design an Energy Efficient and Comfortable Central Atrium for tropical Office Building

In this atrium design exercise, the students are put in groups and asked how to make the most energy efficient and thermally comfortable design for this atrium placed centrally inside an office building. The students are allowed to design the roof in any way they like, as well as propose what openings to have to the atrium, including introducing naturally ventilated ground floor openings. And the students are asked to use arrows to show how the air moves in the atrium. And to state what kind of temperature and humidity they believe that they can achieve in the atrium at 2 pm on a sunny afternoon with a outdoor temperature of 32°C.

Interestingly, most of the student design suggestions will have the ventilation arrows going in the wrong direction, what I often call the "magical arrows". It might look convincing that the air will flow in a certain way, but once applying the laws of building physics (e.g. the principle that hot air rises) reality might be different.

Question no. 3) What surface is cooler, the wooden table top or the metal table legs?

This exercise can easily be done in all class rooms, where you ask the students to touch two different surfaces and ask them which one is cooler? The students will usually say that the metal surface is cooler, but is it really the case? And could the perceived temperature of the material have something to do with its thermal conductivity? For example, the thermal conductivity of metal is about 100 time higher than for wood.

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I hope that the above questions, which have surprising answers to most students, have sparked your interest? And that it gives you cause to question your preconceived notions as well. As green building designers, it is important that we have a firm grasp of the building physics principles, so we can use them to our advantage during the building design process in order to create buildings that work and are truly high performing.