passive solar home, windows, trees
Donald Dust
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I write from experience, as I am currently living in a passive solar home and have been for the past five years. As home utility expenses continually increase throughout the U.S., people are rethinking their approach to home buying and home design. After many hours of research, we thought a passive solar home would provide the balance we needed. It has pretty much eliminated heating and cooling bills. We don’t even have an air-conditioner. We utilize a woodburning fireplace during snowy days with little sunlight. Our passive solar “envelope” home is half underground with the exposed half made of glass and wood situated at an elevation approximately 8,000 feet above sea level. We do get our gas, water and electricity from the grid. But if it went down, we would be just fine.

An Ancient Concept

Our home is unique, but the features stem from its passive solar home design, which is not a new concept. Most notably, Mesa Verde, created by the Anasazi Indians of North America in Southwestern Colorado, is the quintessential passive solar design structure. Prior to the Anasazi, Paleo Indians used the cavern where Mesa Verde is located and its orientation to the sun to their advantage.

Passive Solar Home: Mesa Verde, cliff dwellersAs time progressed and hunter-gatherer cultures became more permanent, Mesa Verde was “settled” and high thermal density materials like clay and stone were utilized to build solid, permanent structures in the cavern, which is naturally south-facing with a large protruding cliff above, much like a modern roof overhang or awning. The cliff provides protection from the intense summer sun, while the southern exposure lets in more direct sunlight during the winter months. The structures at Mesa Verde also faced south and made use of thermal blockers.

A Simple Idea

Passive solar home design is starting to take hold and confirm its place in today’s real estate and construction markets. For the family looking to keep one foot in the grid and the other slightly out, it is a great money saving option that offers freedom in many ways. The basic idea is that walls, windows, floor and the overall building materials collect, store and transfer heat from the sun to the home during winter months. They also block heat during the summer months. Sounds simple, right?

Homes face south when in the northern hemisphere, and north in the southern hemisphere. These use thermal material to capture the sun’s heat in winter and reduce its heat with thermal blockers in summer. The “passive” action of passive solar design means that it has no mechanical or electrical components. Instead, it relies on materials of high thermal density. These include concrete, bricks, tiling and cinder blocks. Also, those with low thermal density, such as wood and synthetic building materials, for the storage and transfer of heat. The transfer from the stored thermal material occurs mostly at night when temperatures begin to shift from daytime to nighttime temperatures.

Best in Winter

When a home is made of thermal materials, the sun’s heat penetrates through its south-facing windows. It is stored through thermal conduction in higher density thermal materials. This works best during winter months as the sun moves lower across the daytime sky, providing direct light and heat from the sun. During the summer months when the sun’s path through the sky is much higher compared to winter months, thermal blockers like large deciduous trees block the sun’s heat. This creates shade, lowering home temperatures and eliminating the possibility of thermal material absorbing the sun’s heat.

When building a passive solar home you must address some key considerations.

Let There Be Light

The building location or the geographic region, like mine in Colorado, must maximize the days of sunshine with thermal collection. Bottom-line, rule number one, you must live in a region that has well over 300 days of sun a year. You might be able to get away with less, but will need secondary heating options. These will cost in the long run, and if your objective is to go low or no cost, other home design options might be worth exploring. A passive solar home will not work effectively in a region that does not enable the design to harness the sun’s rays. The solar orientation or the alignment of the home along the sun’s natural path through the sky to maximize thermal collection is the number one rule in passive solar home design.

Material Matters

Second rule, you must use high-density thermal materials to collect, store and transfer heat during colder hours and months. If you don’t use the proper materials, you are going to do more harm than good. For example, if you have windows that allow thermal heat to pass and enter the home with no high-density thermal materials to collect the heat, you are essentially going to live in a giant oven. The heat must have a place to be stored.

If not, whatever room the sun’s rays enter will increase in temperature and continue to do so, reaching well over 100 degrees. Think of your car on a hot summer day when you close the windows and doors and leave for a few hours. You come back and it is hot, extremely hot. So hot that plastics can melt and pets and people could die. Why? Your car is made of extremely low-density thermal materials and the heat has nowhere to go and be stored.

This same effect can occur in a passive solar home that does not properly utilize high-density thermal materials to collect the heat. The crazy part is that this is more likely to occur during the winter months. This is because thermal blockers like deciduous tree have no leaves and the sun is lower in the sky, allowing direct sunlight into the home, thus creating the temperature increase. My home is built so efficiently that if I have too many sunny winter days, I must lower large fabric blinds to reduce the amount of sunlight coming through the windows.

Sunblockers

Thermal blockers must be in play during summer months. We can’t forget that the sun is higher in the sky during the summer. The best thermal blockers are deciduous trees. Evergreens are not ideal thermal blockers. Yes, they will block the summer sun when it is not needed; however, they will also block the winter sun, when it is a must- have. Deciduous trees are natural, aesthetically pleasing and, for the most part, maintenance free. Manmade thermal blockers, such as permanent roof overhangs or awnings that are built into the home, help block the sun’s rays when it is high in the sky as well. These are not a bad secondary option to have in the event of trees dying or falling over from a storm.

Do Your Homework

I have talked with many people about their passive solar homes and the positive and negative experiences of living in one. One reason for the negatives is that the home was not designed or constructed with full passive solar design in mind. Unless you find people who have extensive knowledge of passive solar design, you will find yourself quickly adding a heating and cooling system to compensate for the poor design. If you think passive solar design is a course of action and lifestyle you are going to take, talk to people who live in passive solar homes. Research contractors and construction companies that understand and can fully implement passive solar design. Shop around, talk, interview, find resources and do it right the first time.

A passive solar home is not for everyone. It works well for my family and me. I can live more freely and still offer modern conveniences to my wife. The heating and cooling bills are zero…nothing. Even my electric bill is extremely low as the design utilizes roof-based passive solar lighting to capture natural light and intensify it. The back of my house is mostly glass, which provides natural light. Additionally, my roof is constructed to collect and store water in a natural roof reservoir for use in gardens and other tasks. Bottom line, my home’s design saves money, gives me self-reliance, freedom from stuff, a happy life and a happy wife.

passive solar home design, illustrationTop 10 Passive Solar Home Pointers

  1. The Heat is On

During winter months, a secondary heat source is a must. Woodburning stoves or a centrally located fireplace that emit radiant heat will make days with no sun livable.

  1. Location, Location, Location!

You have to live in a geographic location that offers numerous sunny days. A good rule of thumb is, “300 Days of sun makes my passive solar home fun.”

  1. Stay Cool

Shade is a must. Use thermal blockers like deciduous trees to create shade during hot summer months.

  1. Good Bones

Passive solar homes are highly insulated and are air and watertight. This makes construction strong, sturdy and solid.

  1. Time to Eat

Growing fruits and vegetables year-round in planters and pots in a passive solar home is a viable option; however, this method of gardening is different than other growing methods and you may need to learn the required techniques.

  1. Show Me the Money

Your heating and cooling expenses will be lower if not almost non-existent when compared to those for a traditional home.

  1. Feeling Good

Living in a passive solar home just makes you feel better. Maybe it is the natural construction materials, or the lower energy costs or the fact that you are harnessing the natural properties of the sun the same way our early ancestors did. It makes you feel free!

  1. Going Green

Passive solar homes foster a green way of living. You are now part of the solution in preserving our planet and reducing the impact we place on it. You will be the example of green living to your friends, family and colleagues!

  1. Be Smart

To live in a passive solar home, you must know your home, how it works, how to maximize its capability. There is no point in having a passive solar home if you are not going to live a passive solar lifestyle.

  1. One of a Kind

Passive solar homes are for a unique type of person and family. They’re a little rough round the edges and are funky at best, but a home is what you make of it.

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