If you’re reading this right now, chances are you’re more or less pretty familiar with solar energy. But just what exactly is passive solar energy?

By definition, passive solar energy is low-tech solar with only one moving part: the sun/earth.

Comparatively, active solar energy is high-tech with more moving parts used to capture heat or electricity.

Passive solar energy is how a structure is designed to take full advantage of the sun’s free heat and light.

It is the concept of using the sun to help make your house as energy-efficient as possible.

In fact, according to Mother Earth News: a certified passive house can use up to 90-95% less energy on heating and cooling!

Overall, a passive solar house will use 60-70% less energy compared to a standard grade home.

Unfortunately, to fully optimize you really need to build your house efficient from the ground up. It can be hard to retrofit after the fact, but it definitely can be done!

How it works

When the sun shines it emits photons that travel at their respective wavelengths such as infrared, ultra-violet, and visible light.

The shorter high wave light works best for producing electricity and heat for our purposes.

This high wave light easily penetrates glass and windows.

But as soon as it hits a solid material it bounces off as low wave heat.

This is essentially how a greenhouse works. It absorbs light photons and traps them as heat energy. Some of the heat is absorbed into the material, while the rest dissipates into the surrounding space.

Think of your car on a hot sunny day.

Sunlight shines in and starts bouncing around the interior as heat.

Knowing this, we can properly align windows to allow light in, and with the right materials, you can efficiently trap this heat energy for your home.

With basic principles, any house can be built more efficient with a few methods such as:

South Facing efficient windows

Angled roof overhang

Thermal mass

South Facing Windows

The way the earth is angled at 23.5 degrees, here in the northern hemisphere to take full advantage of the sun, you need to face your windows south towards the equator.

This way you fully receive the sun’s rays where you can use them for heat and light.

When the sun shines during the winter you can get the full benefit of much-needed heat and light, reducing other expensive heating costs.

This heat is free!

And in the summer, your optimized roof overhang blocks the rays to prevent overheating, minimizing cooling costs!

Angled Roof Overhang

For the summer, heat retention is not the goal at all. As shown above, depending on your home’s latitude you can design the overhang of your house to block the direct rays into your windows.

The angle is very important, as each latitude differs as far as how the sun hits your home.

Use a solar calculator to find your correct measurements.

With this setup, and if you have solar panels on your roof, you can really maximize making the sun work for you instead of against you!

Once you’ve determined when and how to let the sun in, its time to use good materials to attract and trap this heat appropriately.

Thermal Mass

Thanks to thermodynamics, we have a concept called thermal mass.

Thermal mass is a material’s ability to absorb and store energy.

By building your home or structure with the right materials, like concrete and brick, you can optimize the amount of heat stored and maintained inside.

This includes using high-performance windows and doors.

In fact, windows can be a make or break for absorbing and retaining heat. As such, become familiar with terms like solar glazing which is how windows are sustainably rated.

Why not use Passive Solar Heating?

Every house to some degree receives passive solar energy.

But it’s not really until they implement a correct passive solar design that they are really able to take advantage of it.

In the winter, the standard house retains little to no solar heat. So much is wasted or poorly retained.

Much is either absorbed into the attic, bounces off the sides of the house, or escapes through inefficient ventilation, etc.

And in the summer, the greenhouse effect can work against you, forcing higher electricity and a/c bills.

If you properly use the sun, you can have serious heating and cooling savings.

If more homeowners knew the substantial benefits of better design and materials, they would save more money, time, and energy.

The sun would do it all for them!

Our Past and Future

Mesa Verde in Colorado, credit: National Park Service

Passive solar energy isn’t new.

In fact, if you look at ancient cliff dwellers like Mesa Verde, their windows faced south as well. Other cultures to like the Greeks and Romans knew to face their windows south.

People have been utilizing the sun since the beginning of time.

However, in the modern-day, we grew distant from being sustainable and using what was free and already at hand.

We use quick energy like coal, oil, and gas. We build houses rapidly and forget many of the basic tenents that our ancestors knew.

But now, Solar is becoming cheaper, more efficient, and easier to implement every year.

It’s time we start educating people to start taking this FREE energy seriously! Not only will other forms of energy like fossil fuels run out they have their own slew of problems.

Thank YOU for helping continue this movement forward.

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