The Minergie Weather Disconnect

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When winters were long and cold Minergie seemed like a fantastic idea. They would turn a home into a thermos, blocking all heat loss to save on energy costs and more. Minergie does work extremely well in capturing and holding on to heat, from the sun, washing machine, dish washer and more. You might think “But those aren’t heaters” and you’d be right.

During a heatwave the Minergie thermos has a serious flaw and that is that it requires open windows. Open windows in theory, and practice are easy. Wake up, open the windows, and once outside is warmer than inside close them. Then you keep the ambient temperature low and comfortable.

With a traditional building when you open and ventilate walls and other surfaces lose heat so when you close windows, doors and veluxes it takes a while for heat to radiate back out.

With Minergie heat lingers. You open a window, and you need a high flow of air to cool the air within a room, and you need a huge volume of air to cool the structure itself.

In the last two or three days temperatures have gone down which is fantastic. If you open windows you get 22°c air to cool the environment, or at least the medium of air. Cement and other mediums store heat for varying amounts of time.

Yesterday I was out for the entire day so I didn’t aerate at all. It was interesting to see how flat the temperature graph was. It was around 28.9 for the entire day with .01 of a degree or two variance.

When I mess around with open windows, and ventilation the volume of air changes by two or three degrees, but as soon as I close windows the temperature shoots back up to the base 30°c depending on which sensor I look at.

The hallway that I believe heats all the top floor apartments in winter, also heats them in summer. Overnight I forgot the Aranet sensor in the hallway and saw that it displayed 29°c. Any heat from the hallway radiates upwards into the duplex apartments. That’s why, when I have the opportunity, I ventilate the hallway as well as my apartment.

In scuba diving we learn of the dead air space and why it is important to take deep breaths, rather than shallow ones. The concept is simple. By opening my hallway door, and the balcony door I allow the building to take a deep continuous breath and to expel all of the hot air.

It doesn’t flush the heat from the walls, tiles and concrete, but it does flush the air, and that’s better than not doing anything. It has a psychological benefit, if nothing else.

My frustration with Minergie is that it gets to 30°c and stays at that heat, whether it’s 22°c or 36°c, which, if it’s warm outside is a relief, to some degree, but if it’s 22°C then it acclimates us to tropic heat that is not local. I don’t like that my apartment is 8°c warmer than the outside air in the morning, and that I can’t ventilate in the afternoon, due to my desire not to add yet more heat.

Minergie is forgiving of open windows in winter, for ventilation, but not at the hottest time of day during a heat wave.

It’s important to highlight that I love the heat, and that I can cope comfortably with the heat, as long as I have a hat and a water bottle. The issue with heat waves, and minergie, is that I’m in a building with no natural air flow and where various forms of noise pollution make open windows unpleasant.

In 2003 I was perfectly happy with windows open all day long, and at night I felt fine. In 2026 I can’t keep windows open for the entire day, so heat accumulates.

I theorise that in April and May, when some people spent eight weeks re-building a roof the noise pollution was so great that I kept the windows closed. That’s when I captured the heat, and with three or four heat waves (canicules) in a row it was impossible to release it back into nature.

In a quiet place a Minergie building can breath, but in a noisy village the heat gets trapped and fans are required, to provide the draft that open windows would provide without a carbon footprint.

I suspect that summers, from now on, will be a challenge, for many, in modern buildings that were built for a winter that no longer exists whilst forgetting that cooling is just as important, in summer.