Sun energy. There are many ways you can capture sun energy and use it in your home. It is a significant sector to take into consideration in home design. Installing solar panels is an obvious way to use it, but there are many ways to passively heat your home with the sun too. As well, you can block the sun to cool your home.
Sun energy is blocked in summer by roof overhangs and roof insulation. In winter, it’s allowed into the home and the heat is captured in stone floors or adobe walls, which release the heat slowly back into the home at night.
Thermal mass is the capacity of some substances such as water, the earth or rocks, to slowly absorb heat, hold and release it. This can be used in numerous ways to help passively heat your home. The following are different ways of capturing thermal mass using sun energy.
Trombe wall. This is a dark wall facing the sun behind glass. It collects heat and sends it where it is wanted. Because heating air can move it, it can set up a passive air flow throughout your home.
This wall is used to heat air and send it back into the house/
In this version, the hot air is released through a vent in summertime. Sun energy is used to create a “draw” through the home that sucks in cool air from another location and releases the hot air outside the home.
There are many ways one can control how much sun hits the wall and thus the temperature. This could be done with any material, such as stone or adobe, that has enough mass to release heat slowly. There are also a number of ways to create the passive “flow” effect of moving air of differing temperatures to where you want them. We’ll cover more examples in the section on cooling.
I used this principle to heat a home I had by placing black barrels of water in front of a large wall of south facing windows. They would heat up during the day and release heat at night. This didn’t fully heat my home, but kept the main great room warmer than it would have been.
On hotter days, I threw some white blankets over the barrels, preventing the sun from hitting them and keeping them cool. In the summer, an overhang protected the barrels from the sun and they would cool off at night, releasing cool temperatures in the morning and delaying heat gain in the house.
Adobe wall. One of the best examples of use of an adobe wall I’ve seen was at veteran permaculture designer Scott Pittman’s previous home in Santa Fe, New Mexico, a combination straw bale/adobe house that he very thoughtfully designed.
The large enclosed courtyard had a terrarium and a greenhouse roof in it. The terrarium had tropical fruit trees, a small fish pond, and even tropical birds flying freely in it.
All the water used in the house flowed into the system as greywater, keeping plants watered and fertilized. In the summer, the sunlight would hit the terrarium, which would absorb the heat. In winter, the sun, at a lower angle, would hit the back adobe wall, about 18” thick, and gradiently heat it up.
Behind the wall were the bedrooms, and the wall would radiate that heat into those rooms during the night, keeping them around 65-68F.
It was an inspiring design. A great example of integrating the natural world, and the sunlight sector, into the home.
Scott Pittman’s terrarium living room. The adobe wall that heats from winter sun is in the background.
Think of the ways you may be able to use thermal mass to capture sun energy. There are numerous inspiring examples online, and see our resource section for more info.
Earth berm.
Have you ever visited a silver mine or any other type of mine? Even in the desert at 110F, the mine stays at a comfortable 68F. Earth is a great insulator. Six feet down or more, it is a constant temperature year round. There are many ways to create earth bermed structures, limited only by imagination.
Australia, Nigel Kirkwood. This man is using quonset hut type metal to build his house, which has plenty of light inside.
An earthship is a self-contained home that uses a greenhouse plus tire walls that are earth-bermed to create a self heating and cooling home. We shared some examples of earthships in the introduction to this course.
This is an earthship style greenhouse we built on the Pine Ridge reservation.
We went six feet into the ground which created some temperature regulation. Tires provided structural support (this model was later used to create root cellars, a major need on the reservation which greatly enhanced food security as well as safety in tornadoes. Wood is sustainably harvested and was milled on site with a hand-made wood mill. Bryan Deans, the Lakota who initiated this project, designed a number of improvements that reduced labor and increased regenerative elements.
Tin roof was repurposed. North end and sides were further earth bermed. Most of the builders were inexperienced.
In a climate that reaches 110 F in summer and -30F (-50 wind chill) in winter, the greenhouse protected plants throughout the winter with no supplementary heat. It enabled an extension of the usual 3-4 month growing season to year-round growing, and cost almost nothing to build.
There are many advantages to earth bermed homes:
Protected from damaging winds, hurricanes/tornadoes.
Protection from fires depending on how they are built.
Great temperature control even in extremes.
The home becomes part of the land, providing ecosystem services instead of harming ecosystems.