This is a temperature reading of South facing stucco heating up to more than 140˚ in the sun

Strategies for making existing homes more comfortable in a heatwave

My last post was about how well the super-insulated, high-mass, natural homes we build perform in heatwaves and power outages, but few of us currently live in such homes.  Most of us live in homes that were built with minimal insulation or consideration for solar orientation.  Short of knocking these houses down and starting over, what can be done to make them more comfortable and efficient this summer?


Here are some reasonably achievable strategies to make the best of your existing home during the hottest days of the year.

Bank the cool – Open windows at night to capture cooler night air then close them before the outdoor temperature rises again.  This will start you off on good thermal footing for the day, though how long the cool will last depends.

Keep the sun out – Sunlight coming through glass = heat gain.  To stop more of the heat, the sunlight needs to be stopped before it gets inside.  If you have East facing windows that get direct sun in the morning, South facing windows that get sun any time of day, or West facing windows that get afternoon sun, create shade on the outside of those windows to prevent heat gain.  Installing exterior shades that can be lowered and raised as needed is one solution.  A longer-term solution would be building awnings, pergolas, or planting trees.

Lighten the load – Turn off or unplug any appliances that you do not need.  Some appliances shed heat that will add to the problem.  If you have a gas wall furnace with a pilot light that is always lit, consider shutting it down for the summer to eliminate a significant source of unwanted heat.  Also, making cold meals or cooking outdoors on the grill will help prevent extra heat buildup. 

Move the air – Although they do not change the air temperature, ceiling and floor fans can be cooling.  They cause perspiration on the skin to evaporate, creating evaporative cooling.  Make sure ceiling fans are set to draw air upwards during the summer for maximum effect.

Direct the airflow – When opening windows or doors for ventilation, try to direct the airflow in from as low as possible on the North side of the house then exhaust it out as high as possible, ideally through a skylight.  This will help create a stack effect that will draw in the coolest air and get rid of the hottest air.   Avoid opening windows and doors on the South side of the house as this is typically the hottest area.

These strategies will make some difference but to really address the issue, consider what might be possible for your home from the following list:

Get a good hat for your house – We tend to think of insulation as keeping us warm but it can also keep us cool.  Insulation slows the movement of heat from one place to another, such as from the blazing outdoors into your comfortable home. If you have an attic space with no insulation or old, inadequate insulation, have an insulation company give you an estimate to clean out the old insulation, seal air leaks, and install new installation to at least R-30. Insulating the attic/roof is the single most effective place to insulate as 40-60% of heat loss or gain happens through the roof.  If possible, also have them add a radiant barrier in the attic to help bounce radiant heat back out.

Get a good coat for your house – If you don’t have insulation in your walls, consider getting an insulation company to blow insulation into your wall cavities.  This involves them making small holes in each stud bay and then forcing chopped insulation into the wall.  It is not a perfect solution as some areas may not get completely filled, but it is much better than nothing.

Stop air leaks – Air leaks undermine all of these other strategies because they cause the cool air you have to be lost and diluted with hot outside air.  They are uncontrolled, unintentional air movement: air could be coming in from the attic or the South side.  If your windows or doors are old and ill-fitting, consider adding weather stripping or possibly replacing them.  Have an energy consultant do an audit of your home to determine the sources of air leakage and possible solutions.

Consider internal thermal mass – This one is trickier but worth thinking about.  If you have any dense, heavy surfaces or objects that receive direct sunlight, they will act as a heat battery, absorbing, storing, and emitting lots of unwanted heat.  Find ways to prevent them from receiving direct sunlight.  On the other hand, if these same dense, heavy surfaces or objects can be cooled, they will act as a battery for cool, effectively creating heat sinks to suck heat out of the air.   

Consider external thermal mass – As you can see in the photo above, stucco is a high-mass surface and can get extremely hot sitting in the sun.  That means long after the sun goes down and the air temperature cools, this stucco will be radiating heat.  Without good insulation, much of that heat will be transferred indoors.  If this wall was shaded, it would not become as hot.

Make your surroundings cooler – The materials we put next to and around our houses have an effect on how hot our immediate microclimates are.  Unshaded paving, gravel, and other high-mass materials absorb heat, making our surroundings hotter.  Plants, shrubs, and trees do not heat up and also shade the soil, lowering the ambient temperature.  Do consider wildfire safety guidelines when adding plantings around your home.


I hope these tips for making existing homes more bearable in the heat are helpful in the short term.  I will keep dreaming of a future when we all live happily ever after in well-built, super-insulated, high-mass homes that stay 72˚  all year round.