The interior of a passive solar home with the sun shining in brightly through a floor-to-ceiling set of windows

Now more than ever, people are becoming dedicated to green living. This lifestyle means harnessing nature instead of human-made resources, and one of these green methods includes passive solar home design. 

Passive solar design is a fascinating topic with dozens of advantages, both for convenience and environmental impact. Continue reading to learn why you should consider this lifestyle. 

What Is Passive Solar Home Design?

Passive solar home design uses a home’s structure and layout to collect, store, and distribute heat with minimal reliance on electricity to warm or cool the interior. This method uses a building’s exposure to the sun to warm and cool the building through predicted air movement—with minimal energy consumption.

Passive solar doesn’t need the installation of active solar panels. Instead, it’s a way to reduce the need for robust heating or cooling systems. 

Why You Should Implement Passive Solar Design

The simple answer to why you should implement passive solar design is that it maximizes heat absorption, minimizes heat loss, and distributes warmth where it’s needed the most. 

This natural heating and cooling method combo means that you’ll never find yourself freezing in the winter or boiling in the summer. Instead, your house regulates itself to achieve that with minimal input from inhabitants. 

Passive solar design is a rising trend for two reasons:

  • Firstly, it’s economical, especially in the long term. 
  • Secondly, it’s sustainable, which is a big deal in a world where finite resources are slowly dwindling, and climate change is a reality. 

Now, let’s look at these reasons in more detail.

Passive Homes Are Economical 

Passive design allows us to be comfortable in our homes while reducing heating and cooling expenses.

Instead of depending on a giant AC or noisy heater to make your home comfortable and relaxing, you rely on the house’s design to do the work. 

The interactions between such factors help cool and warm the space according to the season and temperature. It may not permanently remove the need for heating and cooling appliances, but it will significantly reduce it. 

While you’ll sometimes need significant investment to achieve an efficient passive solar home, the long-term savings from low energy bills make up for it—these homes are exceptionally energy-efficient

Your savings may increase even more when fuel and electricity prices rise, making you less dependent on the economy and more self-sufficient. 

Passive Solar Cuts Costs But Keeps Comfort

It may sound impossible, but building a passive solar home out of high-quality materials is cheaper than building a traditional house. 

Building a structure that relies on renewable energy for heating and cooling means spending far less on installing costly electrical systems to do the same job, with less sturdy building materials for the home itself. 

Front yard view on an all-electric net-zero home with an EV charging in the driveway and solar panel array on the roof

You’ll also save a considerable chunk of money on your electric bill. The US has hit record prices for electricity, with residents spending hundreds of dollars per month, with a large part of this going towards heating and cooling. 

By reducing your reliance on the grid, you’ll save money on ever-growing utility prices, which worsen with every heat wave or cold front. 

Sustainability doesn’t mean sacrificing basic comforts like proper insulation—it can afford a better standard of living if executed correctly. 

Passive solar designers build their structures to optimize natural airflow and heat distribution. This harnessing of natural sources means that your home will maintain a consistent temperature and is unlikely to overheat or become too cold. Thus, ensuring your comfort level without you having to monitor temperature and energy use constantly. 

Many who live in these structures still use fans to circulate air better when they feel it’s necessary. In addition, most keep a thermostat and can adjust room elements to increase or decrease the temperature. 

A homeowner adjusts a smart thermostat connected to a mini-split system on the wall of her home

Though the home’s entire heating and cooling systems are relatively natural and automatic, you still have significant control over the temperature. 

Passive Homes Are Sustainable 

The demand for more environmentally-friendly and sustainable practices is rising, including in architecture and construction.

Climate change and global warming are becoming a frightening reality, and it will be exacerbated if we keep up with our traditional, energy-inefficient practices. Conventional energy sources, like fossil fuels, are diminishing. 

We’re rapidly going through our traditional fuel supply, yet the use of renewable energy sources is still minimal.

While not everyone can own green buildings with wind turbines on the roof, a passive solar design is easy to incorporate. You can retrofit your existing home to give it passive solar power. If you’re about to build your home, including such a design is much easier. 

The Attainable Home Net Zero renovation, with solar panels on the roof and the Tesla parked in the driveway.
The net-zero renovation we did in Florida proves that it is possible for an existing home to be made net-zero. You can read all about how we did this in our net-zero case study.

Passive solar design uses minimal mechanical elements, like fans, so traditional fuel isn’t used much. But when you also use active solar energy to power those mechanical elements, it becomes even more sustainable. 

Working Towards Net-Zero Home Status

A net-zero home operates entirely through renewable energy rather than electricity from the grid. Solar panels are taking over the energy market at an astonishing pace, with solar installations in the US growing by 43% from 2019 to 2020 alone. 

Solar panels provide active solar design, which converts energy from the sun’s heat into electricity. This conversion is a significant move toward net-zero status. However, passive solar design – albeit a minor move towards net-zero – is still a move.

A worker installing solar panels on the roof of a home

By optimizing your home to produce and control your heating, you cut energy consumption by electrical appliances like fans and heaters by an estimated 90% while still having all the comforts and advantages of a regular home. 

Shifting your reliance off of grid electricity to natural heat and cooling, even in small ways, is beneficial to the environment. These small sacrifices build up over time and contribute to a greener lifestyle while saving you a fortune on electricity. 

Check out our Attainable Home blog for more information on solar alternatives and how we can create more solar-friendly households. 

How Passive Solar Design Works

Home building plans always take environmental aspects into account. As a basic example, the spots that get the most sunlight dictate where the garden and windows go. 

Passive solar design has similar aspects to traditional home design, but designers base all considerations on sun exposure. 

Passive solar design works on four fundamental principles:

  • Aperture – windows and other solar collectors should face within 30 degrees of true south and should be fully exposed to the sun from 9 am to 3 pm in the summer. 
  • Absorbers – the surfaces exposed to direct or indirect sunlight and heat.
  • Thermal mass – passive design incorporates materials that absorb sunlight in the warm season and warm air from within the house during the cooling season. This process is most effective with brick, stone, tiled, or concrete masonry. 
  • Distribution – methods by which stored heat is distributed to areas in the house using conduction, convection, and radiation. 
  • Regulation – structures that shade the aperture during summer, ensuring the house doesn’t overheat. Awnings and roof overhangs are popular choices. 
Solar panels installed as a window awning to create a more eco-friendly plastic window
A solar panel awning provides a passive and active solar double whammy.

Each of these elements is customized to serve the purpose of a particular passive solar design. For example, consider the aperture in the context of exposure to sunlight, which factors in both altitude and latitude.

Due to the sun entering south-facing windows, the entire house floor plan needs to consider where to place particular rooms for exposure to the sun in summer and winter. 

It makes sense that a house in Montana requires a much larger aperture than a Florida or Texas home due to the sun’s position in the sky and the solar incidence angle on the ground. Likewise, every passive solar design has to choose the other elements based on the solar radiation available in that area.

The floors, walls, window panes, and roof have thermal qualities that absorb and distribute heat to various parts of the house during cooler periods, such as at night or on cold fronts. 

Passive Solar Design Absorption Methods 

How one utilizes thermal mass is paramount to how much heat is absorbed, into which areas, and how to prevent heat loss.

Direct Gain

Passive solar designers incorporate the thermal mass to absorb heat directly into the living space. An example could be tiled flooring or a polished concrete kitchen island. 

This heat collects through the day until night, when the thermal mass releases the heat into the room. 

Direct gain utilizes upwards of 60% of the sun’s energy, making it the most potent and effective form of absorption. 

Indirect Gain

The sun filters in through windows, but thermal mass in the living space doesn’t absorb it directly. Instead, it collects at the window and transfers into the area through conduction. 

A standard method of indirect absorption is a Trombe wall. A Trombe wall is a massive masonry wall situated south of the house. This darkly-colored wall absorbs the bulk of the sun’s heat and radiates it into the living space when there’s a drop in temperature. 

Closeup on the gap between a Trombe wall and exterior south-facing windows in a passive solar home
Courtesy of Mr Bim Architects

Indirect gain is a more subtle form of absorption, utilizing upwards of 30% of the sun’s energy. You will inevitably lose some of this energy during its transfer from the Trombe wall into the living space. 

Isolated Gain

One achieves isolated gain through dedicated rooms, called sunspaces, which can be shut off from the rest of the house when needed. They provide an auxiliary living area built especially for warmth to share with the rest of the house.

Residents of these homes often use these sunspaces to grow plants, though they’re not as ideal for that purpose as greenhouses are. However, the warmth and abundance of the sun make sunspaces great for plants that thrive in direct sunlight. 

These all work through one of three particular heat distribution methods—convection, conduction, or radiation.

Passive Solar Design Heat Distribution Methods

Heat distribution occurs through three methods:

  • Convection – heat transfer through air and water. Solar homes use air to carry heat from heat-concentrated areas to the rest of the house, 
  • Conduction – heat transfer through objects in direct contact with each other. Many solar homes use their flooring as thermal mass, becoming naturally heated floors. 
  • Radiation – heat radiating outwards from a source, such as what you would feel standing next to a window filtering through direct sunlight. 

Regarding convection, water is the best source of heat convection. As you can imagine, it’s not always simple to include water sources in a home design.

Some choose to construct a tank of water in their living space, allowing it to absorb the bulk of the sun’s energy through the windows. This technique is a simple and cost-effective way to incorporate convection, but it isn’t always attainable. 

It could be a great feature if your flooring can support a heavy container of water and you have the space for it. However, those with smaller floors and less stable flooring will want to avoid this method. 

Passive Solar Design Cooling Distribution Methods

A passive solar design can facilitate cooling using one or more of the following methods:

  • Shades
  • Heat absorption
  • Ventilation

A passive solar design in the north with a lower angle of incidence needs a larger aperture and little to no shade to heat a house. However, the opposite is true for cooling, especially in the south. 

Cooling requires a thermal mass outside a property and the insulation under it toward the interior. Heating requires the opposite. A thermal mass is inside to warm the interior when the sun is down, and the insulation is toward the exterior wall to prevent heat loss.

Planning a Passive Solar Home Design

Designing a house to utilize the sun’s energy requires forethought and planning. 

Some crucial considerations include:

  • Checking your local zoning laws to ensure no construction will block sunlight from your home in the future. 
  • Ensuring there are no south-facing trees that obstruct sunlight.
  • Deciding on the material you want to use to construct your home. Experts recommend stone, brick, tiling, and concrete. 
  • Taking note of the sun’s position in summer and winter. You want the winter sun to line up directly with your living space and the summer sun to avoid direct contact to prevent overheating. 
A south-facing window in a net-zero house..

The overall design is entirely up to personal preference. However, using darker colors for thermal mass objects is strongly recommended. For example, direct gain works best with dark tiles and countertops. 

Passive Solar Floorplanning

Designing a solar home requires detailed planning of where every room needs to go according to the sunlight it needs.

Draw up a floor plan, and put each room in its block. Ensure you place the rooms you want to have the most summer sun closest to the south (in the northern hemisphere) where the most sun filters through. 

Also, it would be best to take the movement of the sun into consideration.

Factors to consider include:

  • In the summer, the sun is higher – therefore, it would be best to place eaves, awnings, or other shading mechanisms at a level that shields the windows from direct sunlight. Then, while the heat from the sun still absorbs into the masonry, the house stays cool.
  • In the winter, the sun is lower in the sky – ensure that eaves or awnings don’t obstruct winter sun; otherwise, remove them and implement other shading tools like blinds. This direct sunlight keeps the home’s interior warm.

The video below provides a visual explanation of how orientation and shading devices play a role in heating and cooling during summer and winter:

Screenshot from a video of how orientation and shading devices play a role in heating and cooling during summer and winter
Courtesy of Master Builders Victoria

The Plan Collection has pre-made, customizable floor plans for those eager to get started on their passive solar homes. These plans also provide insight into planning your design and what factors to consider. 

There is no uniform passive solar design. There are standard features, like south-facing glass apertures, but no two passive solar plans will be identical.  

To truly maximize your passive home, the design must be holistic, considering the home, environment, and climate to make the most out of it. For instance, passive cooling should be a priority if you live in an area where the climate is constantly hot. Overhangs and glass sizes should control passive heating in these places, or the home may overheat.

Disadvantages of Passive Solar Home Design

Though the sustainable lifestyle has many advantages, passive solar design has a few significant drawbacks.

Passive home disadvantages include the following:

Climate Dependence

A design that relies wholly on the sun’s light to generate a heating and cooling system works best in climates with a lot of sun and environments with limited tree and architecture coverage. 

Unfortunately, this type of design would be highly challenging, if not impossible, to implement in a cold climate or an environment with heavy and frequent cloud coverage and rainfall. 

Limited Design Choices

Putting a passive solar design into action means your home is also a conduit for solar energy, meaning every architectural and design choice has to work in favor of the sun’s reach and position. 

This limitation gives you less freedom to play around with the design and instead pivots on set features you can design around. For example, you may want your main bedroom to get the most sun, which would mean placing a large window in this private living space. 

A bedroom with full glass panel exterior doors

These limitations extend to the exterior of the house too. For example, certain areas must remain clear of foliage and other potential obstructions, perhaps leading to a more sparse garden than you’d like.

Complex and Time-Consuming Planning

This design requires meticulous planning and building; the process can take months, if not years. The house is built according to exact measurements and relies heavily on features like the right kind of glass in the windows and pergolas angled—so they don’t cast heavy shadows.

You may also spend a fair amount during the construction process, as the construction is precise and particular. 

Limited Energy Capabilities 

Passive solar homes work differently than active solar homes because the energy stored doesn’t go towards electricity. So you save money on power by not using electric heating and cooling systems, but you won’t be able to generate electricity this way. 

Living fully self-powered takes much more planning, preparation, and equipment, such as solar panels and water heaters. Learn more about active solar-powered homes at Energy.gov.

Final Thoughts

The drawbacks of passive solar home design mean it isn’t necessarily a good option for everyone, but it’s an incredibly accessible and sustainable living choice for the most part.

Passive solar homes save money and energy, making them more environmentally friendly while not compromising on basic comforts. 

Sources

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