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Keeping Cool Using the Sun?

Heating with the sun is a popular topic on this blog site, and any reliable sustainable-living resource usually covers this topic. Most everyone can get their head around using the warmth of the sun to heat our homes passively. But when I talk about passive cooling with the sun, I get more confused expressions.

We can keep our homes cool, even during the warm summer days, by working with the sun.

We designed our homes to bring in the heat of the sun in the winter by placing the long side of the house facing south and placing most of our windows on that side. This arrangement of the house and windows also allows us to block the summer sun with an eave or overhang. The very first step of efficient cooling is to prevent the sun from heating the room in the first place.

This Illustration is taken from the book Twisted Oak: A Journey to Create A Self-Sustaining Life and Home by Kristina Munroe PE


If you have a large, unprotected east-facing window, you have likely felt how the house begins to heat up during summer mornings and remains hot throughout the day. Also, if you have a sizeable unprotected window facing the setting sun, you have likely experienced the intense heat build-up in those western rooms. If your bedroom resides in one of those spaces, sleeping is probably very uncomfortable.

Rooms with large windows placed on the east or west can make summer slumber nearly impossible.

The first important step in designing an affordable, comfortable, and sustainable home, is to pay attention to the placement of all windows. Then, understand how the sun will interact with those rooms during the heating and cooling seasons.

One of the most powerful design features of a comfortable home is the use of materials that store and regulate temperature. These materials are dense and act as thermal mass. Using thermal mass is like having a heating and cooling battery in your home.

Click here to learn more about thermal mass.

The building code does not require builders to incorporate any thermal mass into new buildings. But using these materials can make the difference between living in a cool and comfortable house, or suffering in an unbearably hot home.

It also makes the difference between having zero cooling costs or needing to use electricity to run an air conditioner or swamp cooler to keep a building comfortable.

Here at Twisted Oak, we have zero cooling costs. We have thick thermal mass walls, and the house and eaves are designed to block out the summer sun. The summer days here in the Southwest can heat up into the ninety's. Here's a photo taken on a recent summer afternoon, but our house stays in the cool 70's.


I sometimes forget how comfortable our home is until I travel or stay in a conventionally built building. I have forgotten what it is like to lay awake in a room where it is too hot to sleep. Or listen to the loud whirring of an air conditioner or the constant hum of a fan. These inconveniences don't exist in my world. And I am grateful.

I wonder why we continue to build homes that are so uncomfortable when it is so easy and affordable to create homes that are more pleasant to live in without the use of fossil fuels to cool them.

I worry about people living in homes that rely on the ever-increasing cost of power to stay habitable. We can build houses from affordable, safe materials. We can build homes that will take care of us, the planet, and our wallets.

I know this because I've done it, and I know that anyone who wants to build a more comfortable home can too. But, you must take it upon yourself to learn about the sustainable options so that you can work with a professional or build a house yourself that is safe, comfortable, and affordable.

Learn more at

Learn more about how I designed and build our home at





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