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How Passive Solar Heating (& Cooling) Works

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Jonathon Engels, a long-time vegetarian turned vegan, is currently on a trip from Guatemala to... Read More

For those looking to make their homes more energy-efficient, using passive solar heating and cooling techniques is a major step to getting there. Air conditioning and heating are huge and inefficient power sucks. Maintaining a specific temperature requires the HVAC to run constantly, so developing a larger range of comfortable temperatures (try between 60 and 80 degrees Fahrenheit) drastically reduces how often we run the HVAC.

There are tons of other factors that come into play as well. The way the sun shines through windows will adjust the inside temperature. If the oven or the dryer is on, that’ll move the thermostat. Curtains and blinds can be a factor. The type of flooring in the house. All sorts of stuff matters when the goal is to heat and cool with as little (or no) power as possible.

Once you understand the basics of how passive solar heating and cooling works, it is really simple and can massively decrease your carbon footprint, as well as save you some money.

The Simple Explanation of How It Works

Essentially, passive solar heating and cooling take advantage of (heating) or block out (cooling) sunshine. When using solar power to passively heat a house, the goal is to let in as much direct sunshine as possible. Contrastingly, when passively cooling, the goal is to minimize the amount of direct sunshine that gets into the house.

In other words, direct sunshine creates warmth. Thus, when we want things to be warmer, more sunshine is good, and when we want things to be cooler, less direct sunshine is better, such as sitting under a shade tree.

How to Passively Heat Your House

There are lots of tips for designing homes to maximize passive solar heating, but most of us aren’t in the situation to design our homes from scratch. For those who aren’t designing homes but rather already living in them, there are ways to get some benefit from the sun.

Use the curtains/blinds to your advantage. Curtains are going to block the sunshine out of the house, but they’ll also block some of the cold that transmits through the windows. Open the curtains on the south-facing side of the house to invite the sunshine in, and close the curtains on the north-facing side of the house where the sun never shines in. Open them to the east in the morning then open them to the west in the afternoon.
Make the most of the right spaces. The places where the sun shines are going to be the warmest, and those where the sun doesn’t shine will be the coolest. Be sure to close the doors to rooms that are coolest and adjust to spending time in the spaces that are naturally warmed by the sun.

Utilize thermal mass heat traps. Objects and materials with dense thermal mass are good at capturing and retaining heat while the sun is shining on them. Then, when the sun goes down and the air starts to cool, these heat traps begin to release the heat within them similar to radiators. Stone or tile floors are great, as are brick or stone fireplaces. Tanks of water, like aquariums, also have good thermal mass.

How to Passively Cool Your House

Most people stop at passively heating the house, but equally so, there are things we can do to cleverly thwart the sun from warming our homes during the summertime. The idea behind passively cooling is to block the sun from shining in and take advantage of times when it’s cooler (and warmer) outside.

Open and close windows wisely. Though it may seem to be sensible to open windows if the house gets too hot, that isn’t necessarily the case. If it’s hotter outside than inside, opening the windows isn’t going to make it any cooler, is it? Instead, keep the windows closed during the day. Then, open them at night when temperatures dip.
Shut the curtains when it’s sunny. Sunlit rooms are often our favorite rooms in the house, but they are also the hottest. Opposite to passively solar heating a space, to passively cool it, closing the curtains during the day on the south-facing windows will prevent the sun from shining in and making the place hotter.
Take advantage of the sunny weather. Instead of running heat-creating appliances like a clothes dryer, find ways to do tasks outside like hanging clothes on a clothesline. Similarly, get outside, enjoy the warm weather, and cook on the grill (or even outside stove) so that the kitchen range isn’t heating the house to make dinner.