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How To Design Or Renovate Your House For Comfort During Heatwaves

Updated: May 13, 2023

SPOILER ALERT: throwing a central air-conditioning system or even portable air conditioners at the problem won't fix the issue of overheating in your home, and I'll explain why.


The frequency and duration of heatwaves has been increasing for at least a couple decades. Certainly the mention of "La Niña" and "La Niño" has increased. Now we've even added an extreme new term to our vocabulary: "heat dome".

photo of a man laying in bed at night, sweating

At some point this summer, you'll be living in exile - maybe outside in the back yard trying to be productive, or at a nearby pool/beach/park. Maybe you're hiding out in the garage because it's the only place at home where you can keep cool. Worse, more people are taken to the hospital or even dying as a result of the heat. Not only is the daily high temperature higher than typical for several days in a row, but it doesn't cool down enough at night to bring your house down from the day's heat. (Note - that's how a heat dome differs from a heatwave; it doesn't cool down at night.). This is assuming that a wildfire doesn't destroy your house.


I discuss this trend and explain the concepts below in much greater detail in my article Passive Cooling Strategies for Heatwaves.

When the outdoor temperature may be close to 30°C, the temperature inside your home can easily be as high as 35°C depending on a number of things. Windows are an obvious culprit since they let in infrared (heat-generating) radiation from the sun, and visible light that enters also is converted to infrared radiation. Blinds, curtains, blackout drapes, and even an interior foil covering are of limited benefit because they're inside the window; once the heat energy has passed through the window glass into your home, it's trapped, bouncing off the glass instead of escaping.

photo of a young Asian woman tangled in yellow horizontal blinds

Only an exterior shading device - brise-soleil, movable shade, or exterior shutter - can effectively block the heat energy from entering in the first place. Add exterior shading FIRST to cut down on the amount of the sun's heat energy ("solar heat gain") getting into your house.




Exterior shading will make a big difference, but when the outdoor air temperature is stupidly high, you'll still feel sweltering indoors. Opening the window and running the fans is just blowing hot air around your home. "That's why I'm biting the bullet and investing in central air for my home, silly!" I hear you mutter. 30-second technical time-out here: all cooling equipment - including air conditioning systems and units, refrigerators, freezers, grocery store display - are all designed to remove a certain amount of heat, at a given ambient temperature. Effectively, they take air in and cool it down a given amount. When it's 27°C outside, they might be spitting out air at 17°C and therefore are able to keep your home a pleasant 23°C. HOWEVER, if it's 33°C outside, the air coming out of the aircon might be 25°C. I won't go into the math (it's more than just simple averaging), but your home might be 30°C inside. You might think that "the AC is on the fritz", but it's still doing its job. You spent $20-30k on air conditioning and are sweating indoors. Who's silly now?


Buying a higher-capacity system (like residential systems in Dubai, for example) will cost more to install (double or so), cost more for maintenance and cost increasingly more to operate (since a warming climate causes you to run the AC for more hours of the year). In addition, it's going to last only 15-20 years at most before you need to buy a replacement.

funny personification of a tired, old portable air conditioning unit

You know how during a particularly nasty winter cold spell, your home's heating system isn't able to keep up with the heat loss through the walls and roof and by warm air leaking out (and letting in cold air)? EXACTLY THE SAME THING HAPPENS WITH AIR-CONDITIONING DURING A HEATWAVE: the cooling system isn't able to keep up with the heat gain through the walls and roof and by warm air leaking in (and letting out cooled air). I explain this more in my other article, "Don't Install Air Conditioning In Your House - You're Wasting Your Money".


illustration of money blowing out the door

#1: Make your house more airtight: seal the gaps around doors and windows, invest in better windows, seal around penetrations and gaps in the air barrier.

#2: Then add more insulation in the walls and roof - not only to keep you warmer in the winter but to keep you cooler in the summer.


house in a glass bubble

Once you've taken care of the bigger problems, then you can investigate active methods to cool your home. People in hot, humid climates have been using heat pump products for decades, and these products are beginning to be more available and understood in North America. In my article, "How Does A Heat Pump System Work?", I explain heat pumps in simple terms, and I show you in my other article, "What Is The Cheapest Way To Heat And Cool Your Home?", a variety of ways in which heat pumps can be incorporated into your home's heating and cooling system. If you don't want to read the article to find what's the most appropriate and cost-effective solution for you, you can instead download my free "Heating and Cooling Systems Guide" using the button below.


So the question is: which costs more - a renovation to improve shading, window performance, airtightness, and insulation; or a big, expensive, noisy system blowing (hopefully) cool air through the house and right out through the walls and roof? An ultra high-performance house is more affordable than you may think especially when compared to your current, costly home.


If you're curious how well your current home performs, you can download my free Home Performance Assessment HERE.


I'm a Vancouver-based architect specializing in modern, ultra high-performance homes. Over the past several years, I've developed the UltraHome™ concept -- the most comfortable, healthy, climate-resilient optimized home design.


If you're considering changing the house but don't know that there's an affordable way to get a much better one, I offer my Tuning Report™. In this exercise, I will prepare a simple cost comparison of keeping your house the way it is for another 30-40 years versus overhauling your current house or building new.


Book a 'Diagnostic Session' with me where I will compare the cost of running your current house to the cost of an overhaul or replacement to get you a far more comfortable home that will last twice as long. You'll get what I call "Pre-Design Diagnostic Scan™” within about a week. The longer you wait, the more time you'll be spending down in the garage like a dog escaping the heat; and/or the more money your AC system will be blowing money right out the door (...and walls and roof).


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