Keya Lea

A Concrete Modern Passive Solar Home

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The building style is modern, exhibiting a state of simple grace and elegance.  This owner-built passive solar home utilizes concrete as its priniciple building material.

Modern concrete passive solar home

The southern side of this concrete home is dominated by windows.

Concrete is a dense material that can absorb, store and radiate heat.  Concrete is a material with thermal mass.  The thicker the material with thermal mass, the more potential mass can be utilized to act as a temperature stabilizer.
 

 

Concrete, Thermal Mass and Passive Solar Design

A close up that shows the cement around a core of blue insulation. The sliding door is to the right side of the picture. The sliding door can be seen in the picture above.

The home is built with concrete that is sandwiched around a core of insulation.

The owner-builder believes that this is the best wall system to keep a constant and stable temperature.

A typical building will use insulation as a means to prevent temperature exchange.   As an example, a stick frame house uses layers of insulation between the 2 x 4s.

Within this concrete wall system, the insulation is also located in the middle of the concrete wall and functions to slow the transfer of heat.  Sandwiched between the outer layers of concrete is 4 inches of extruded polysterene (blue board) insulation.

A diagram showing basic passive solar design. Source: energysavers.gov

Along with other technologies that work together, passive solar houses are engineered to be cool in the summer and warm in the winter.

 
Here’s how basic passive solar design works.

On a cold, but sunny winter day, because the windows are situated on the southern side of the home, the house absorbs the sun’s heat energy throughout the day and stores the heat within the thermal mass of its floor and walls.

After the sun goes down, the structure will naturally radiate the heat that it stored throughout the evening and night.
 

 

A poured cement floor gleams in the front room, while it also absorbs solar heat.

Inside the windows, the living room has a seating area on a gleaming, concrete floor.

Notice the concrete floor in the living room.  The room sits just inside of the southern windows.  Both the floor and the walls are made of poured concrete and have the potential to store solar heat.

During the summer, because the sun travels a higher arc in the sky (photo comparison of the sun during the winter and summer solstice) the sun’s heat is blocked from entering the home.  As a result, the density in the thermal mass stays cool.  In the evening, the home can be opened up to the cooler night air.

This house does not have a mechanical cooling system.

The home is built in Montrose, Colorado, where the temperature in the summer regularly reaches into the 90s, yet on the hottest summer day, the house warms only to about 75 degrees Fahrenheit.  In the winter, while the temperatures can dip below zero, the average temperature on the coldest days is around 65 degrees. The owner’s highest heating bill was $84.

 

The north side of the house is typically the coldest as it is in the shade.

The house is heated exclusively with electricity.    Built on a 5 inch concrete slab, the house also has in-floor radiant heat with an electric flash, on-demand water heater.

Because it is a passive solar house, the north facing side of the house has only two windows and a door.

 

Concrete forms the Walls, Floor, and Counters

Objects with a high amount of thermal mass, such as concrete, inherently work to slow the rate of heat transfer.  The dwelling resists rapid temperature swings because of its mass.

Here are a few other pictures that show the use of concrete and other details of the house.

 

 

Continue on to Page 2 – See the SIPs roof, more of the Interior and the Radiant Heat Hot Water System

 

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12 Responses to A Concrete Modern Passive Solar Home

  1. barb krebs July 24, 2011 at 1:01 pm

    Keya–What a great article! I especially enjoyed all the photos. They really help illustrate what you are saying and they make the house look good. Thanks a lot.

  2. Ana July 25, 2011 at 10:16 am

    What did you use to make concrete floor in living rooms to look shiny? Great home!!!

  3. Keya Lea July 25, 2011 at 12:27 pm

    I asked the builder and he said that a combination of things made the concrete floor look shiny and so striking. When the floor was poured, it was hand troweled to give it that ultra smooth finish. After it dried, they used a high gloss sealer to finish and protect the floor. It was also cleaned just prior to the pictures being taken.

    Thanks for your comments!

  4. Matthew August 2, 2011 at 1:38 pm

    I want this house!

  5. Keya Lea August 2, 2011 at 7:23 pm

    Matthew – the builder would be happy to build you one.

  6. Kuhn Oberholtzer August 24, 2011 at 5:00 am

    Keya,

    I Really love the use of concrete in the construction, it’s such an underrated material.

    Where can I get more info on the water/glycol system you guys used for the solar heating system?

  7. Keya Lea August 24, 2011 at 10:53 pm

    Kuhn,
    Here is a link to another solar hot water heating / glycol system that explains this type of system in better detail:
    http://greenpassivesolar.com/2011/01/active-solar-thin-film-evacuated-tubes

    The link is to an article on a grid-tied house that integrates both solar photovoltaic film and solar evacuated tubes – that use glycol to tranport the solar heat into a water tank / heat exchanger. It is similar to the system that is used in the concrete house, but goes more indepth in the explanation of how the glycol and heat exchange takes place within the water tank.

  8. Suzanne January 16, 2013 at 1:25 pm

    Now that you have lived in the home a few years I’m wondering how often the radiant heat floors are used? I hope to build a passive solar home this summer. I wanted radiant heat tubing put in the concrete floors, but have been reading that radiant heat can over heat the house. That it is better to use that money on other things such as more insulation, etc. How would you respond to that?

  9. Keya Lea January 17, 2013 at 12:02 pm

    Suzanne,

    I emailed the owner of this house and asked him to follow up with your question. In the meantime, here are two houses that have radiant in-floor heat.

    They both are located in cold, mountain climates, in sunny Colorado. This one is grid tied – http://greenpassivesolar.com/2011/01/net-zero-pv-log-home/. It uses solar thermal to both heat hot water for domestic use and for heating the home. In the case that the system gets too hot, for example, in the summertime, the heat sink (heat dump) was plumbed to the garage and not to the living areas. This might be something to consider.

    This house was built really efficiently (double studded wall, double roof, triple gusseted windows, etc.) and while it was plumbed for in-floor radiant heat, is not used because the house doesn’t need the extra heat. This one is off-grid. http://greenpassivesolar.com/2012/03/optimally-efficient-off-grid-passive-active-solar-home/

    Best of luck to you and your build! Keep in touch.

  10. Sven January 24, 2013 at 9:15 am

    Susanne, the cost of installing tubing in the floor is minimal and gives you an easy and flexible way to control it’s temperature. It’s also a simple way to prove a back-up heating source to satisfy a mortgage lender’s requirements if you (or a future buyer) need financing.

  11. Roger June 4, 2013 at 2:31 am

    Does Sven sell plans of this great house?

  12. Keya Lea June 5, 2013 at 11:20 am

    I think so. I asked him to get back to you, but not sure if he emailed you directly, or thought he would post here…

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