The world is getting hotter. But if we need AC, we have to use it sparingly.
For many years I took the position that air conditioning was evil and there were many ways to avoid it, including all kinds of "lessons from grandma" and old buildings.
It's one reason I have become a big fan of Passive House or Passivhaus design; it takes summer comfort seriously. Insulation keeps heat out, as well as in, and careful window sizing and placement can minimize internal heat gain. It's all carefully calculated in the big PHPP spreadsheet.
Which is all very nice, except if you design your passive house based on a set of climate data. Then what happens if the climate changes? That's what Jessica Grove-Smith of the Passivhaus Institute tried to find out. She explained at the Passivhaus Portugal conference how she studied both climate change and the urban heat island effect, which can also skew the data. Then she and the Passivhaus Institute developed a tool for the big Passivhaus spreadsheet where you can now plug in estimates of the temperature rise due to the climate crisis and see how it affects your design.
At 1.5 degrees of increase, you can design around it. At 3 degrees, it gets scary, and even in temperate Munich people are going to be seriously uncomfortable. This is yet another reason that we all have to work hard to build a 1.5-degree world. If everyone in Munich needs AC, imagine what it will be like in warmer climates.
It is an unfortunate reality that in many climates, even temperate ones, we have to get used to air conditioning. The nights don't cool down like they used to, and the days are going to be a lot hotter. Grove-Smith says we should be realistic and not rule out what she calls "active cooling." But she also notes that if it is in a Passivhaus, then you get "significant increased comfort with minimum energy input and it's not a climate sin."
Some have said that Passivhaus was designed for temperate Germany and doesn't work in hot climates. In fact they do work very well, and control of solar gain has become a priority.
Theoretically. But does #Passivhaus actually have an open-up-and-breathe standard for hot and humid places? I haven't seen that, but would like to if it exists.— Steve Mouzon (@stevemouzon) November 14, 2019
Others, like architect Steve Mouzon, claim that those Original Green ideas still work and that natural ventilation can do the job in warm climates, but we can't keep pretending that we can just open up all the windows and bask in the cool evening breezes, especially in cities with heat islands, pollution, noise and a warming climate.
Air conditioning has become pretty much essential and will become even more so. At least with Passivhaus, it uses as little as possible. And at least with Passivhaus, they are acknowledging that the world is changing, and are trying to plan for it.