An Optimally Efficient Off-Grid Passive and Active Solar Home

This off-grid, owner-designed and built house is one of the most impressive passive and active solar combinations I’ve seen. Located at an elevation of 9,000 feet in the Colorado mountains, on a windy, snowy January day, after entering the home, I experienced a quiet confidence and a solid feel of warmth and comfort.

Solar panels, greenhouse, and southern facing windows make an efficient house.

This passive solar house is located off the grid and makes its own solar-based electricity and hot water.

You may be thinking, “Right. Aren’t homes off-the-grid efficient?”

They should be, but actually aren’t because they are designed and built by different people.  There are a few traits that work together to make a passive solar home efficient: windows (glazing) facing the south with some sort of control, thermal mass, insulation, along with the ability to harness naturally occurring convective air currents for cooling the house in the summer.  Not only the passive aspects of this house are impressive, but its active systems are something that others interested in off-grid solar should take notes from.


living room in a passive solar home

The living room beams of quiet luxury as the concrete floor absorbs the solar heat. This view is looking toward the double entry.

Because this house is located off the electricity grid, this house creates all its electricity from the sun.

In order to have the modern convenience of continual electricity, off grid homes necessitate systems of backup.  Yet this home is so efficient that the backup systems are not often utilized.

The home was built 10 years ago when a couple relocated to Gunnison, Colorado. The husband was a former manufacturing engineer and was attracted to the ideas of passive solar design and the freedoms of living “off the grid”.

At the time, not fully familiar with the design and engineering principals of passive and active solar building, he took a two week class with SEI in Carbondale, CO.  He then combined his engineering background with the newly  learned to design and build an extraordinary efficient and comfortable off-grid home.

This article will discuss the design and passive solar building elements of the home, then continue on to the solar thermal and electric systems.


Passive Solar Design Elements

Off-grid homes can be comfortable, spacious and because this one is passive solar, it’s also quiet.  It is warm in the winter and cool in the summer.

It was in the middle of winter when I first visited the home.  After entering through a double door entry, the open configuration of the home was welcoming, sunny and warm.

Upon entry, one sees a living/entertainment room, and beyond the stairs there is a greenhouse, seating area and kitchen.

Since the sun was out,  the home absorbed the sun’s heat within the polished concrete floor (a material with thermal mass).

The floor throughout the lower level of the home is comprised of 8 inches of concrete with radiant in-floor heat tubes throughout it. Underneath the concrete, is a layer radiant heat film made out of double insulated aluminum.

Because the house is well-built and incredibly efficient, while the house has been plumbed with radiant in the floor heat, it is not used.

Attached Greenhouse / Heat Sink

greenhouse attached to the main house for solar heat

The greenhouse is attached to the main house and used to capture solar heat.

The greenhouse has an angled roof that allows it to efficiently capture solar heat.

The space can be used to draw heat into the house, while it can also easily be shut off from the rest of the house.

It is important to note that the greenhouse is not used to grow plants throughout the year.  While it is not that much of an issue for them, using the greenhouse space throughout the year can cause issues with humidity. In her words, this is how she uses the space:

I do start seedlings, but I also grow tomatoes, green beans, peppers and herbs such as basil and marjoram during the summer as it is too cold outdoors for those crops. Also, although I could grow cold weather crops like lettuce, spinach, and mache, I do not grow in the winter because I want a break! Also, any other plants would require more heat at night for optimal growth than the passive heat would provide. Humidity is not an issue – I wish it were since it’s so darn dry here.

The greenhouse is also instrumental in adding solar heat to the house in the winter and is referred to as a ‘heat sink’.


passive solar greenhouse

The buckets were painted black and filled with water to increase the heat storage capacity in the house.

How the heat sink works: Two feet of gravel (a dense material that has thermal mass that absorbs heat) make up the floor of the greenhouse.

As the greenhouse absorbs solar heat throughout the day and become warmer, the hot air rises.  Because the roof rises in an angle, hot air will collect near the top of the angle.

Two fans located on each side of the door on the top of the turquoise colored tubes pull hot air from the top of the greenhouse to a manifold located 2 feet under the rock.

As the hot air flows from the top of the hot greenhouse to the very bottom of the two feet of rock, it warms the rock from the bottom so that the mass later radiates the absorbed heat for a longer amount of time.  (Notice that there’s a lot of thermal mass throughout this home.  This is part of what helps this house to be very efficient.)



a fan pulls hot air 2 feet under the rock

Detail of the fan.

The fans are controlled by a temperature gauge that is set to automatically turn on when the room reaches a certain temperature.

Buckets have been painted black, filled with water and stacked near the building.  This also increases the building’s thermal mass.  Water is one of the best mediums that can absorb and radiate solar heat.  It also stabilizes the building’s temperature swings by absorbing solar heat, then slowly releases it through the cooler evening.

Masonry Heater

large masonry heater

The Canadian-made masonry heater sends the heat through tubes run within the mass of the stove to increase the surface area of radiated heat.

After returning to the home from the greenhouse, one can’t help but notice a beautiful masonry heater. Notice the size and mass of this stove.

This was the first time I’ve seen a masonry heater inside a home, but after learning about more about how it works, I realize that it makes brilliant sense!

It is a wood fired stove that has a flume that snakes through the masonry to add more heat to its thermal mass allowing for greater potential to capture and radiate heat before it escapes out the top of the home.

Most wood fired stove-heaters have a fire contained within the stove, while the stove radiates the heat while a massive amount of the heat is quickly lost through the chimney.

The masonry heater is UL- listed and made by the Canadian company Tempcast.


I visited the home at a time close to the winter solstice.  Notice how deep the sun’s rays reach within the home.  Also notice the the amount of thermal mass throughout the home that is absorbing the heat.

In contrast, during the summer when the sun travels a higher path in the sky, the sun does not enter the home and the thermal mass (because it helps to stabilize temperatures and absorbs heat) helps to keep the house cool.


Kitchen, Master Bedroom, the Walls and Roof

Passive solar kitchen

The kitchen is located in the northern-most section of the home, yet receives solar heat from the 2nd story windows.

Located behind the masonry stove, the kitchen is located in the northern-most section of the home.

Because the home is situated on an east-west axis, (the long direction of the home) it allows the sun to warm the northern sections of the home.

The open configuration on the southern side of the home allows sunlight from the 2nd story windows to warm the northern sections.  Once again, we see passive solar winter heating at work in the kitchen.  The tile in the kitchen absorbs the solar heat and slowly radiates it through the cooler evening and night.

The house is so well built that while the home has hot water radiant heat tubes installed throughout the floor, because the house is built efficiently, the radiant floor tubes that run throughout the home are not used. (I realize that I just repeated myself, but the utilization of thermal mass throughout a passive solar building can not be understated.)




A well insulated home

This home is so well insulated that the heat loss through the windows is not an issue.

The master bedroom and bathroom are located above the kitchen area.

The home has a combination of fixed and operable windows. All the windows in the house are 1 inch, double pane, low-e windows. The operable windows are triple gusseted to help create a better seal when they are closed.

Regardless of how efficient windows are, windows tend to be an area within homes where a lot of heat is lost.  Glass is a material that is simply not a good insulator.

The owners said they they had created the valance above the curtains with plans to create insulated window coverings, but because the house is so well insulated, they are still using the flimsy small bamboo reed privacy shades.  They simply haven’t felt the need to make insulated window shades.  This is a testament to how well the house has been built.

Around the perimeter of the home, they utilized double studded walls to cut down on thermal bridging.   Within a double studded wall, the studs are offset, thus creating a thicker or wider wall allowing the insulation to be continuous and woven between the alternating studs on each side of the wall.   Wood is another material that is not a great insulator and allows some thermal bridging as cold or heat travels through the wood.

From the inside to the outside, the perimeter walls consist of: drywall, followed by a foil barrier, metal studs, blue board insulation, a vapor barrier, fiberglass insulation, plywood, Tyvek and cement, followed by siding.


bedroom in a mountain home

The master bedroom and bathroom are located on the second floor.

In looking at the photo, some builders may be scoffing at the tongue-and-groove vaulted ceiling – as these types of vaulted ceilings are notorious for leaking heat, but don’t let that fool you.  This roof has also been well-insulated.

This roof is referred to as an ‘Idaho’ double roof. It is a roof with two separate roof systems comprising 20 inches.



A solar tube allows like to enter back rooms

Solar tubes are a great way to allow light into rooms located in the northern sections of the home. (It’s located just past the stove pipe.)

Beyond the tongue-and-groove wood paneling is a high density fiberglass insulation, followed by a layer of aluminum foil. Beyond that is a 4 inch urethane SIP (structured insulated panel) that is then covered by a metallic roof.

The roof also has solar light tubes that increases the amount of solar light in the house. This eliminates the need to turn on the light during the day and thus saves electricity.

The house is also bermed into the hillside and built on ICFs (insulated concrete forms).  ICFs are essentially Styrofoam blocks made out of extruded polystyrene and filled with cement.

While the home is warm in the winter, it is also cool in the summer because they harness natural convective air currents throughout the home.  By simultaneously opening windows on the ground and second floor, warm air is pulled out the top of the house while cool air enters on the ground floor.

Yes, the penchant for efficient building continues with the electrical systems.

An article about the electrical systems along with a peak inside the utility rooms will be posted next.

Click on a picture below to enter the gallery to see more aspects of this amazing passive/active solar home.

Passive / Active Solar Photo Gallery


An article on the electrical systems has also been published.  ‘Like’ the Facebook page and you’ll receive passive solar tidbits.


Square footage: 2700 square feet

Time to build: One long summer

Owner/builders: Kris and Ken Kilz




Keya Lea

Keya Lea likes to spend time outside, enjoying the sun.

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15 Responses

  1. Diane Belanger says:

    Hello, love everything about your home. Are you selling bluepblueprints or more detailed information about building a similar home. In Maine.

    • Keya Lea says:

      Hi Diane, this was a truly impressive home and build. I don’t have blueprints for the house, and I’ve been informed that the owner/builders of the house have since moved. Because of this, it’s best to take ideas from the build and incorporate them into your own. Best of luck!

  2. David Oyler says:

    Any tips or ideas for “retrofitting” a house to be more energy efficient? My house is already pretty decent, our usage is pretty low, and we have solar panels that help us break about even with our usage, but we wouldn’t have enough to go off-grid, although it’s desirable.

  3. Anonymous says:

    Wow, that’s what I was looking for, what a information! present here at this
    weblog, thanks admin of this website.

  4. Jolie says:

    I am interested in any house plans Ken/Kris may have or be willing to share and guidance. We are in the North GA mountains and we are planning on doing something just like this, maybe a little smaller but I’ve been overwhelmed with where to begin.

    • Keya Lea says:

      I’ll let them know. Something to keep in mind is that the mountain environments of Georgia and Colorado are very different. Their house was built for a mountain elevation of 9,000 feet.

      It can be a bit overwhelming when first embarking on building a home because the options are endless. Also try to take a look at passive solar homes located around you.

      Best of luck to you!

  5. rob jones says:

    trying to build a passive solar home . my builder says design it , he will build it . I am at a loss . is there a passive solar book for dummies ? any help would be greatly appreciated . thanks , rob jones .

    • Keya Lea says:

      Luckily, passive solar design is pretty simple because the Earth orbits the sun on a predicable pattern. There’re just a few guidelines to follow. If you’re in Texas, depending on your local climate, you may want to maximize for cooling in the summer. Along with different searches for book resources, finding different building-styles online, you may want to talk to other other passive solar owner-builders to see what have done in your area.

      Here are some basic guidelines, but make sure you make considerations for your own tastes, local climate and weather.

  6. W Ben Keel III says:

    Hello…wow…that is just what we would like to do except we are on the hot humid gulf coast and the other caveat is that we have five kids that we need to make room for….we are planning on building ourselves an off the grid passive solar using the sun to both cool and heat the house…I have several books and a friend here that has already done just that and is very happy….we are leaning toward SIPs just for the efficiency here outside of Houston TX what other advise can anyone share? Neither one of us (my wife or I) have ever been in the building industry we just have big goals and dreams and the willingness to work hard and study the process then do it…any and all advise is appreciated! Thanks, Ben

    • Keya Lea says:

      Hi Ben,

      It most definitely can be done. Most, if not all of the homes featured in GreenPassiveSolar were built by owner-builders. Many of them also did a majority of the work on the home.

      You’re on the right track. SIPs would aid in home efficiency depending on how the home is situated. There are many homes built in warmer areas that rely on building a tight envelope along with building with mass and overhangs to block the sun’s heat. Passive solar and efficient homes can be large, built to comfortably house large families. As for the specifics, it’s recommended that you get in touch with architects that live and work in your area that design homes that are responsive to the sun. (Many owner builders also designed their own homes, but I write about the ones that have done it correctly. Sometimes it doesn’t go well and building a home is complicated because it brings together many different systems – that you really need to have work correctly and to code.)

      Best of luck and let us know how it goes.

  7. Kris Kilz says:

    Happy to help you with advise, etc. Let us know if you are still interested.

  8. Jess says:

    I love this. Thanks for the article. Are there associated plans for this house that Ken and Kris have/would share? It’s perfect!

  9. Richard says:

    I want to buy a prefab cabin that incorporates all of the things you have in your home….the best of active and passive solar heating etc. Do you have any suggestions? Richard

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