A passive solar winter lake home on the edge of a forest

With modern homes designed with enhanced energy efficiency, passive solar homes are becoming more popular in cold climates. Houses with pass solar design have better building form and retain more of the sun’s natural heat. 

So, how are passive solar homes designed? 

This article will discuss how passive solar homes are designed and provide real examples to outline the benefits of these design strategies in colder climates.

How are Passive Solar Homes Designed?

Passive solar homes are designed with better building orientation and form and use ventilation, daylighting, shading, and other techniques to improve the house’s energy efficiency. Passive solar homes also use thermal mass and effective distribution mechanisms to retain more heat. 

Best Passive Solar Home Designs for Cold Climates

If your house is in a cold climate (between climate zones 4-7 in the US), you’ll likely spend a lot of heating in the winter. 

According to the Energy Department, designing your home with passive solar design strategies can improve the building’s efficiency and reduce energy costs. The ultimate goal is to get a net-zero solar home

However, passive solar design differs for houses in cold and warm climates. In cold regions, the goal is to maximize solar heat retention. On the other hand, you should focus on improving heat dissipation in warmer temperatures to keep the house cooler. 

In this article, we’ll discuss some passive solar design strategies for houses in colder climates. Of course, you can also use some of these strategies for homes in warmer temperatures, but most of them are designed to retain heat and will be more effective in climate zones 4-7. 

Here are some passive solar design strategies for homes in colder climates: 

1.) Optimize the Building’s Orientation

Before looking at other design strategies, always try to optimize the building design and form. For example, the building’s orientation should maximize heat retention and minimize direct cold air flow toward the house. 

The most critical factor of building orientation in passive solar houses is the direction of the front and sides of your home. The windows should be positioned to maximize the amount of winter sun intake, meaning facing south in cold, northern areas. 

A south-facing window in a net-zero house..

Windows in passive solar houses in cold climates will generally be lower than those in warm temperatures due to the lower position of the winter sun. This design will often have the garden and trees located in the part of the house facing north so they don’t block the winter sunlight. 

2.) Use Heat Absorptive Materials in Building Design

Passive solar houses in colder areas will use heat-absorbent materials in the building design to maximize natural heat retention. On the other hand, dwellings in warmer climates should use reflective materials to keep the house cool in the summer. 

These materials are referred to as “thermal mass” and are effective at retaining more heat. For example, masonry materials are ideal for maintaining solar heat as they don’t dissipate it as quickly as other materials. This feature is why houses in colder climates often have exteriors made from stone or brick instead of wood. 

When building a house in a colder climate, always use denser building materials that retain heat for longer. They will warm up during the day and release heat as the temperature drops at night, keeping your house warm for longer.  

This passive solar house utilizes dense thermal mass in the exterior design to maximize heat retention. Notice the stone walls and dense structure with low-hanging windows to maximize the amount of winter sunlight entering the house.

Front view of a passive solar house utilizing dense thermal mass in the exterior design
Courtesy of Brickworks

3.) Large Windows and Sunroofs To Maximize Daylight Heat Absorption

Passive solar homes will always have larger windows and transparent glass doors to maximize heat absorption. Sunroofs are another feature of these houses. These glass windows should be double-glazed to reduce heat dissipation. 

In the passive solar house below, the large glass sunroof faces south at a 30-degree angle to allow more sunlight to warm the building in the daytime. Since daylight hours are reduced in the winter, more windows help the house heat up faster, like a greenhouse. 

Exterior rear view of a passive solar house with large glass sunroof
Courtesy of Build It

4.) Darker-Colored Exterior Paint

While the type of material is more critical in determining how much natural heat a house retains, the house’s exterior color is also important. Darker colors absorb more heat and are more effective in colder climates. 

If your house in a cold climate has a thermal mass of a darker color, its heat retention will also improve, and the home will stay warmer at night. One reason for this is the ability of darker materials to absorb more sunlight since they are less reflective. 

This example of a dark-colored house for passive solar design in colder climates is perfect, but you don’t have to opt for black or dark brown paint. Slightly darker stones, bricks, and even light brown paint will absorb more heat than white paint. 

A dark-colored passive solar home and patio
Courtesy of Sanctuary

5.) Using a Trombe Wall for Indirect Gains

While most passive solar houses are designed to maximize direct heat gains, indirect gain designs can actually retain heat for longer. 

For example, instead of maximizing the windows’ size to allow more sunlight to strike the floors and walls, these buildings use a Trombe wall, which has a glass panel in front of the masonry, to maximize heat absorption. 

A Trombe wall is much thicker than a regular wall (usually around 8-16 inches) and is made from stone or brick to maximize heat retention. As a result, when the sunlight goes through the glass, the heat is amplified as it hits the wall. This amplified heat is then absorbed by the dense thermal mass of the wall. 

The wall will start dissipating heat into the house’s interior in the evening when the temperature drops. This is an effective way to keep a home warmer at night without using additional heating. The thick wall is also beneficial in keeping the house cool in the warm summer months. 

This is an example of a simple Trombe wall designed to transfer solar energy into your house.

Closeup on the gap between a Trombe wall and exterior south-facing windows in a passive solar home

6.) Using Windows With High Solar Heat Gain Coefficient

A window glaze’s solar heat gain coefficient (SHGC) rating can significantly affect how much heat it lets in. Windows with a higher SHGC rating will retain more interior heat in the winter, sometimes as high as 2x the heat retained by simple windows, making them ideal for passive solar homes in colder climates. 

Windows with Low-e coatings are more likely to retain indoor heat and will reduce the amount of solar radiation entering your house. Experts recommend installing windows with an SHGC rating of 0.45-0.57 in colder climates to maximize the amount of solar heat transfer. 

While this may seem like a simple factor, it can significantly affect a house’s heat retention capacity. Not all windows are designed for the same type of climate, and “energy-saving” windows designed for hot climates won’t be as effective in a cold environment since the goal is to maximize heat absorption. 

What Else To Look at in Passive Solar Homes

Home design can do wonders for passive solar houses, and slight changes in the design can significantly impact how hot or cold your house stays in the winter.

While we’ve covered most of the major design factors for passive solar homes above, here are some additional ones to consider: 

  • Planting trees and bushes in the direction of cold winter breezes can prevent your house from bearing the full effect of these icy winds. In most cases, these winds will come from the north, so try to have the garden located in the northern-facing part of the house. 
  • Building a sunroom in the front of your property can help absorb more direct sunlight during the day, which will then radiate throughout the house as the sun recedes. 
  • Using timber-paneled walls will provide an extra layer of insulation and reduce the rate of heat loss in the winter. 
  • Rock gardens are effective at retaining heat, especially if they’re located near the walls. You can also use earth berms to keep the heat around the house. 
  • This example of an earth berm in a passive solar house shows how rock and earth can be used as additional insulators. 
Arial view of the back yard and patio of an earth berm home
Courtesy of The Spruce

Final Thoughts 

Passive solar home design is a great way to save on winter heating costs and reduce the need for expensive heating systems. It’s also an eco-friendly and energy-efficient way to build your home. 

Building design and orientation are essential for passive solar houses, but there are other ways to convert an existing home to a passive one without altering the structure. 

These include landscaping designs, using heat-absorptive materials in building design, and replacing windows with ones that retain more heat.

Sources 

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