Keeping the house cool during the dog days of summer

Keeping the house cool
​during the dog days of summer

Ninety degree weather is hot, even with low humidity. But if you don’t have air conditioning in your home, how can you make the house more comfortable? Our old farmhouse was built in the 1850’s, at a time without electricity and therefore without air conditioning. So how did the homesteaders who built it  keep cool during those sweltering days of summer?

They did what a lot of people do, they opened all the windows during the night when the temperatures were cooler, and closed them in the morning. Seems simple, right? But they were a little more clever than that. They understood the principles of Thermodynamics- specifically in this case, that hot air is less dense than cold air, and therefore expands and rises, while denser cold air, shrinks in volume  and sinks to replace it. This is why hot-air balloons can soar.(You can see more discussion of this in our gliding blog of…………).

Our house has 38 windows , i.e. on all sides of the house. When I open all the windows before going to bed and there is a slight breeze, I have cross ventilation and the warm air that accumulated during the day will rise out and the cool night air settles in. I have an indoor/outdoor thermometer installed by one of the downstairs windows. In the morning when I see that the temperatures inside and outside have equalized, I close all the windows to keep the cool air inside. As our house is shaded by mature trees for most of the day, the cool night air will last most of the next day.

With a little attention to detail, you can use the heat of the sun against one side of your house to enhance a ‘chimney effect’ to increase a drafting effect to move fresh air through the house. If the sun is baking one side of your house, open the top floor windows on that side, and open the downstairs windows on the shady side. The heated air in the upper floor rooms will expand and rise out of the open windows, pulling air inside the house behind it. The denser, cooler air near the ground on the shady side will be pulled in to replace the air moving up to the hotter floors. Of course, it might be a negligible draft, and the temperature gradient in the shade may not be much better, but it will help at least a bit.​

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Any air movement will make a huge difference in comfort! That is why ceiling fans can be so important, both in summer and winter! A slowly turning ceiling fan doesn’t seem to be doing much, but the volume of air it moves is actually quite surprising. In a square room, it will create a rolling donut of air, the ‘hole in the donut’ being a column of cooler air at floor level, which is being pulled up by the fan, then radiating across the ceiling and sinking back down the walls. By mixing the air in the room, it becomes much more comfortable, with a more even temperature and not layers of hotter and cooler air.

​Most people don’t realize that by flicking a switch on the fan body to reverse the spin of the fan, they will save lots of money on heating and be much warmer in the winter as well! Just as the fan pulls cooler air up from the floor in the summer and mixes it with the rest of the room, by reversing the fan in the winter, all the hot air that is trapped up by the ceiling (that you paid for with your radiators), will be pushed down into the room and mix for a more even, comfortable feeling.

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Another strategy is window awnings.  Before modern air conditioning, the huge appeal of big window glass was the view and light of the outside world! The downside was the tremendous heat gain. If you only had south facing windows, you may have great light streaming into your space, but the glass trapped the inside air and the lack of circulation quickly heated the space to intolerable levels. Window awnings shaded the glass and dampened the heat gain inside. If you look at pictures of city buildings in the late 1800’s, most windows with southern exposure had awnings.They fell out of favor with the advent of modern air conditioning, but our newer, greener approach to energy is seeing a resurgence of awnings on houses.

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I sometimes think that people equate air speed (velocity) with cooling! This is why they ignore a slowly turning ceiling fan as possibly creating a more comfortable space than a high speed box fan placed in a window. But think about this.

​I have a friend who has a house that was built with a deck off his kitchen/living room with a southern exposure. It is a beautiful, expansive deck and is bathed- as they wanted, in sun most of the day. When we visited it was a very hot day, they have no air conditioning and the deck-side portion of the house was sweltering. My friend was laying on a couch inside with a box fan, bungee corded into an open deck window blasting a high speed stream of air from the outside deck into the house. He apologised that it was so hot but that was as fast as the fan could could run, but it was still unbearable.

Although the outside temperature was in the high 90’s, the temperature over the bare deck was over 105 degrees! So although he was blasting air from the outside quickly into the house, it was much hotter than the air that he could have drafted from opening windows in the back (shaded) portions of the house- which were as much as 5- 10 degrees cooler, and therefore much more comfortable.

Of course all of our windows have fly screens, making sure that all the critters swarming around during the night, don’t find their way into the house. Sometimes I hear one of those big moths ramming its head against the flyscreen trying to get in.

We are lucky, because we have so many windows and more than that, we are surrounded by trees that protect us in the wintertime from the fierce winds from the north and provide us with lots of oxygen and shade the rest of the year. ​

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Now that summer is here, everything looks so lush and green and  you are happy to be outside enjoying what nature is offering.

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