Passive Heating and Cooling Off-Grid

Living off-grid can mean unreliable energy sources, and unreliable energy sources can lead to unreliable comfort control. Passive heating and cooling techniques harness the energy of the elements, through design, to maximize control you have over the interior environment. This is an introduction to some of the concepts that might help you design your home, so that it does not have to rely on modern, and consumptive forms of heating and cooling. There are many ways to passively heat and cool a home in even the most extreme climates, but here is a rundown of some of the main driving forces in passive heating and cooling.

Orientation

One of the first steps you should take in designing for the environment you’re in is understanding the sun. The path of the sun can dictate the form your building takes, whether it is trying to capture as much of it as possible or avoid its rays. If you are in a cold climate you can orient your windows toward the sun at its highest point to heat the interior space. Reverse that logic if you are trying to keep things cool, shield openings from the sun at its highest point and you will be able to keep things cool.

Wind and Orientation is one of the most important things to consider when building an alternative habitat in a hot or humid climate. Orienting points of ventilation points toward the wind is key to keeping air flowing. In the case of climates with high winds, the form of the building should act to funnel the wind around it. If you imagine a house of cards with a fan in front of it where would you want to put it? You would want to put it at the front so that the thin edge of each card could allow the wind to pass by it; rather than on the side where the wind would meet a face and blow it over. Apply that same thought process to your home. What form can the building take so that it does not blow over? Domes forms are good at shaping the wind around it, or uniquely formed tiny homes that are thinner in toward the strongest winds.

Color

It’s pretty unpleasant to wear a black shirt on a hot day, that is because black absorbs heat energy. The colors that you use on different parts of your building will impact the temperature, by either absorbing or reflecting the sun. In warm climates, light exterior colors will help keep the inside cool. In a cold climate, dark exterior colors will absorb the sun’s heat and transfer it to the interior space.

Ventilation

Ventilation is probably the biggest factor in comfort for the majority of people. Ventilation means less humidity and more fresh air. If you have an idea about the term “ventilation” adapt it to “cross ventilation”. Cross ventilation means that fresh air is constantly passing through the space. Positioning windows directly opposite from each other allows the wind to flow into one window and out the other. The constant air flow keeps things cool and the humidity tolerable.

Apart from the opposite direction of ventilation, there are other locations, that you might not think of, that allow airflow. In addition to the primary ventilation, openings toward the top of the building of the structure will allow the heat, that travels up, to flow out. It can also be very effective to elevate your structure off the ground so that air can flow underneath it in higher wind areas.

Solar gain

In a hot climate with intense sun, rays shading can be extremely effective. This can b done with landscaping around the home, or with operable shades. To minimize the amount of solar gain during the day, you could shade the windows. At night you could detract the shades, to allow airflow through your points of ventilation. Pergolas and full shade structures are another good options that might allow you to spend more time outdoors on hot days.

Using the sun to heat your home can be done using a series of techniques. As I mentioned, placing large windows in the path of the sun will allow for the primary solar gain. To maximize this, the use of reflective interior materials, particularly floors, can help distribute the sun’s energy around the interior space. The structure of your roof and the materials you use can also help transfer heat absorption to the interior space.

Thermal mass

Thermal mass allows a material to absorb, store and release heat. These dense materials, like earth or concrete, can help keep your home comfortable in both warm and cool climates and is particularly effective in places where temperatures vary by season or time of day. Examples of the use of thermal mass include adobe homes, where they absorb the heat of the sun during the day and slowly release it at night when the temperature drops. Dugout earth homes are typically useful in a colder climate, where the thermal mass of the earth helps to store energy from the sun for long periods of time and insulate the home.

Adding a water component to a design with a hot climate can greatly improve the indoor temperatures. As water evaporates, it is using up heat energy, and cooling the air. In dry climates, water features can be used to bring cool air in, especially when strategically placed to capitalize on wind flow. Roof ponds are also an option to absorb the heat of the sun and use that energy in the evaporation process.