The earth is solar-powered, and passive solar design makes it possible to make the most out of one of the most sustainable resources in the world: sunlight. Of course, passive solar design is not a new concept whatsoever, although officially calling it as such may be a more recent development.
What many people don’t know is that passive solar design can go much deeper than simply installing a few windows and skylights in a home. Instead, today’s best passive solar design is the result of centuries of testing different layouts, materials, and systems for optimizing the way sunlight is used to heat and illuminate a living space.
In this complete guide, we will explore the concepts and intricate details of every kind of passive solar design in order to provide a larger understanding of the concept as a whole. In doing so, we will also showcase some examples of passive solar design from around the world, in hopes to illustrate real-world examples and inspire the adoption of this timeless, sustainable practice.
What is Passive Solar Design?
Okay first things first, what is passive solar design anyway? Well in the collaborative powers of Wikipedia, passive solar design (or passive solar building design) can be defined as purposeful construction of “windows, walls, and floors… to collect, store, reflect, and distribute solar energy in the form of heat in the winter and reject solar heat in the summer.”
Passive solar design is a continuously evolving technology with scientific concepts borrowed from fields such as climatology, thermodynamics, and building design. Unfortunately, there is rarely ever a one-size-fits all solution for global passive solar design. Instead, adapting to local climates and geographic sun conditions through a proper site audit is usually the most important step in a successful passive solar building.
The Goal of Passive Solar Design
The goal of a passive solar design is to convert sunlight into ambient heat in a building or home. This is known as solar gain, which can be used to heat a building’s internal air, water supply, or thermal mass. Most commonly, this is achieved by letting sunlight hit the proposed area through windows, skylights, and open concepts.
Although providing heat is passive solar design’s primary principle, keeping air, water, or thermal mass cool is also an important part of smart thermal solar design. Specifically, many buildings are specifically designed to block the sunlight during periods of intense summer heat.
Passive Solar Design vs. Active Solar Design
Passive solar design refers to smart systems built without any moving parts or electrical components (i.e. passive systems). With this in mind, buildings with intentional passive solar systems are meant to work incredibly simply, without much effort or upkeep required from building owners.
On the other hand, active solar design refers to the installation of either gas or electric solar energy components such as photovoltaic solar panels or thermal solar heating systems. Although active solar systems also require very little attention from home and building owners, they are given the “active” moniker because gas and electric systems have many working parts with heat, electricity, or water constantly being fed from one place to another.
In many instances, passive and active solar design work hand in hand. While passive solar can heat the interior of a space, active solar designs are generally more efficient for heating water and can be used to generate renewable, off-grid electricity.
The Benefits of Passive Solar Design
Buildings that incorporate passive solar design come with many benefits both for the system owner and the environment. The following are some of good passive solar design’s most distinct advantages:
- Free solar gain from sunlight
- Utilization of a renewable, unlimited resource
- Adaptability to nearly everywhere in the world
- Designed to minimize energy use and lower utility costs
- Bring heat and light into a home
- Can be used to block harsh sunlight
- Increased aesthetics and easy design integration
- And more
Essentially, passive solar design can be used to lower the utility costs of a building while adding light and heat to living spaces all over the world. Many different materials and designs can be incorporated in order to meet the passive solar advantages of any specific geographical area, so long as the sun is shining.
How Does Passive Solar Design Work?
It doesn’t take a scientist to understand that the sun is both bright and warm, and its light and heat can be used in our daily lives. With that said, there is one underlying scientific principle that is responsible for the majority of how passive solar design works.
Passive solar designs are purposefully built to create a radiative heat transfer from the sun’s radiant energy. Here, a passive solar home’s components are specifically designed to allow solar radiation to enter the home during the winters month, while shielding its entry with a insulated roof against overhead sunlight in the summer.
Once the radiant heat enters a home, such as in the image above, it can be captured and absorbed through heat collecting materials such as thermal mass. The thermal mass retains the heat and is able to increase the room’s ambient temperature for long periods of time, much like a stone or brick fireplace.
While this concept has been used for thousands of years, today’s technologies make it easier than ever to implement passive solar design for the best possible results.
Typical Components of Passive Solar Building Design
As mentioned above, location is one of the most important, variable factors when considering the construction of a specific passive solar building. While purposefully laid-out communities can be built for symmetric passive solar design, the materials and blueprints of passive solar buildings vary greatly around the world.
With that said, the chief principles of passive solar buildings are the same no matter the location.
To start, where and how you place your building is the first thing to consider with passive solar design. Unfortunately, building orientation is typically only applicable when considering new construction, as existing homes cannot be easily picked up and replaced.
For optimal sun conditions, passive solar buildings are designed to be facing the equator. This allows for sunlight to hit the “front” of the house directly, all year long. The building is then built square along on the East-West line, typically using the same heat transferring materials and orientations throughout.
Windows are the second most important element of passive solar building design, as this is where the most direct and indirect sunlight will be entering the living space. Windows must be placed in a way so that they receive direct sunlight in the winter, but are protected from direct sunlight in the summer. Typically, this is done with shades or overhanging fixtures.
Beyond their placement, the insulation of a home’s windows is also very important for passive solar design to work effectively. Around the house, windows should be affixed with movable or permanent window coverings or glazings to prevent radiant heat from escaping from the building. This is critical for windows on the equator facing wall, the sides of the homes, as well as northern facing skylights.
This may surprise you, but heavy insulation is NOT always recommended for equator facing windows, as this could prevent maximum radiant heat from entering in the first place. Heavy glazings should be avoided here if they inhibit solar gain. The same principle is used for east and west facing skylights that can capture the morning and afternoon sun, respectively.
Thermal mass is one of the principal components of good passive solar design, as it is used for the majority of the heat capture. Here, large portions of the home’s floor and walls are covered with materials that can not only absorb the heat, but continue to radiate the sun’s heat throughout the home.
Thermal mass can come in the form of many different materials. For one, a nice concrete slab and nothing else actually does a very good job. Beyond this, common building materials such as tile and brick are also great for retaining heat from the sun.
Here, surface area means everything. As more and more square feet of thermal material capture direct sunlight, the quicker a home will typically heat and stay heated. Extra thermal lawyers may be required in climates with particularly cold temperatures.
Landscape and Garden
As a true part of the environment around them, passive solar homes are also optimized by proper landscaping and gardening. Optically, deciduous trees can be placed around a house to shade the summer sun from the home, while shedding winter leaves and allowing direct light to hit the building in colder temperatures.
How to Install Passive Solar Design
If you’d like to know how to incorporate passive solar into your home, there are a few different kinds of systems that you can install. Here, we will give a brief overview of the three different configurations of passive solar design.
Direct Solar Systems
Direct solar systems are the most common configurations of passive solar design, which we have been outlining throughout this article. In a direct system, direct sunlight enters the home seasonally through windows and skylights. The heat is absorbed by the building’s interior thermal mass, and it is stored and distributed throughout the evenings and non-sunlight hours.
Indirect Solar Systems
While indirect solar systems use the same primary principals of passive solar design as direct systems, there is one key difference here. An indirect solar system does not use direct sunlight. Instead, the south facing windows are replaced by a solar thermal wall. Oftentimes, glass is also placed outside of the wall so that it can trap and absorb even more of the sun’s heat.
Here, the interior/exterior, equator-facing thermal solar wall, sometimes known as a “Trombe Wall” radiates heat through the building. This is often a very thick wall, which sometimes incorporates water heating systems for pipes within the insulation.
Isolated Solar Systems
Lastly, “microclimates” on properties can be created with isolated solar systems near and attached to regular homes. Isolated solar systems, sometimes known as sunrooms, solariums, and sunspaces often look like a greenhouse or simply a room with a lot of natural light.
Isolated solar systems use both direct and indirect passive solar design elements to properly heat and beautify an interior living space.
Passive Solar Energy Examples From Around the World
Okay, that’s enough conceptualizing now isn’t it? One of the best parts about passive solar design is that it has been used for thousands of years and is currently experiencing a renaissance as sustainable building is at the forefront of most city planning. Here, we will take some time to showcase interesting examples of passive solar design from around the world.
1. Taos, New Mexico Earthship
First, let’s head to Taos, New Mexico, where you will find some of the most interesting looking buildings in the world. In this photo above, you can see one of Taos’s very own “earthships,” which is a specially designed net zero home incorporating many interesting sustainable practices.
Although the green curved walls can be hard to look past, this photo actually showcases both passive and active solar design. Here, the south facing side of the building is purposefully angled to allow direct sunlight to hit both the glazed windows and PV solar panels. At the same time, the sun is able to provide heat and electricity for this unique home.
Beyond this, an insulated window on the west side of this building create’s the “dragon’s eye,” which is beautifully surrounded with recycled bottles that allow indirect sunlight to shine through all year round. The building is constructed east-to-west and also uses indirect passive solar heating throughout the concrete walls.
2. Expansive Domed Glazing
Next, here is an image from GreenPassiveSolar.com which shows passive solar design being utilized by a more traditional looking home. With that said, the domed exterior makes it continuously apparent that passive solar design can be incorporated to fit within many unique styles and applications.
Here, the south facing glazed windows are expertly designed to fit within the building’s unique shape. Like in geodesic designs and yurts, the curved walls of this structure make it possible for heat to be continuously circulated within without getting stuck in isolated corners of the room.
Apart from the building itself, this home also incorporates the landscape design elements that can easily be incorporated to optimize passive solar heating. As you can tell from the photo, trees around the property help shade the roof form the summer sun, while the overhanging awning shades the large windows. In the winter, these trees will shed their leaves so that the maximum amount of light can hit the building.
3. Denver’s Wellington Webb Office Building
Okay, now it is time to think even bigger. Passive solar design is not only reserved for small residential homes. Instead, this image of the Wellington Webb Municipal Office Building in Denver, Colorado takes passive solar design principles and extroplates them to the next level.
When most people hear the words “municipal office building,” this image is usually the last thing that would come to anyone’s mind. However, this massive multi-unit working space has been specifically designed to maximize the amount of direct and indirect sunlight that reaches the building’s interior.
Here, offices lining the spacious atrium get the benefit of passive solar lighting and heating, even from within the direct center of the large building. The concrete floor, insulation, and smart designs throughout this space also make it possible to retain as much heat in the building as possible.
4. Cleveland Museum of Art
Moving right along with massive, naturally lit spaces, passive solar design is one of the chief principles behind the beautiful Cleveland Museum of Art. That’s right, Cleveland! Other than perhaps Buffalo, New York, Cleveland has a reputation as one of the colder, darker cities that can be found in the United States. However, this has not stopped passive solar design from prevailing once again.
In this large atrium, museum visitors can bask in the warmth of direct sunlight and radiant heat, even during Cleveland’s notoriously harsh winters. The building also incorporates a smart shading system (which can be seen partially on the right side of the roof) that can be released if direct sunlight should be blocked during the hot summer months.
Of course, this passive solar design also helps the museum save on electricity costs! Look at all of those people enjoying a well lit, temperature controlled environment, without a single light bulb in sight!
5. Bradford, Missouri Passive Solar Greenhouse
Lastly, we’d like to remind you that people are not the only ones that can benefit from the powers of passive solar design. For instance, this greenhouse has been designed and installed using many of the principles of passive solar design, all for the purpose of growing plants!
Here, direct sunlight all year round can infiltrate this insulated space’s interior, allowing for high radiant air temperatures regardless of the climate outside. With this in mind, many non-native plants can be grown in climates throughout the world as high temperatures can be maintained constantly within. Although this greenhouse is found in Missouri, chances are it may even be capable of growing high-sunlight species like banana trees!
Considerations With Passive Solar Design
Passive solar design makes it easy for well-designed homes to become a part of their local environments, rather than exist as isolated living spaces. With this in mind, passive solar designs can provide some benefits to a home, but will rarely be a building’s lone source of light or heat.
Here are some of the limiting issues to keep in mind with most passive solar buildings:
- Often needing supplementary energy for heat (gas, electricity, etc.) in cold climates
- May be difficult to retrofit current buildings for passive design
- Not applicable to apartments or crowded living spaces without direct sunlight
So naturally, passive solar design is not going to work for every living situation. Even in climates where sunlight is readily available in the winter, passive solar design is often not quite enough to keep interior living spaces warm enough for comfort.
In off-grid cabins, this is usually supplemented with a wood-burning stove. In cities and towns, grid tie ins for electric or natural gas heaters are much more common.
In conclusion, passive solar design is one of the easiest building principles to implement and use in sustainable homes and buildings throughout the world. As a tried and true science with rapid advancements in planning technology, more and more sustainably minded developments are merging with passive solar design as a totally necessary component.