A Modular Solar Envelope House

Old Dominion University and Hampton University joined forces to build a Solar Decathlon house called Unit 6 for the 2011 competition. Their goal was to create a solar net-zero energy house that would contribute to the formation of walkable city neighborhoods.

The Virginia team designed a home called Unit 6 for the 2011 Solar Decathlon.  Photo credit: Jim Tetro/U.S. DOE – Solar Decathlon

Team Tidewater created a modular home made from four main sections and featured passive and active solar design.

The roof had solar photovoltaic (PV) panels to generate electricity.  Seen above, they were arranged in a square pattern.  Located in the middle of the PV, a solar thermal panel collected solar heat to generate hot water for the home.

The panels were mounted on racks to allow air flow behind them to help keep them cool as solar PV operates more efficiently within a lower temperature.   The panels were integrated into the roof.

Passive Solar Aspects

A diagram shows how the sun does not enter the home during the summer, but  does enter during the winter months to utilize its heat energy.

The home was designed to be passive solar so that the summer sun would not heat up the house.

Its overhang and window placement block the summer sun’s heat, while they allow the winter sun to enter the house.  Its design and materials enable the house to collect solar heat and later releases it to warm the home through the cooler evening and night.  It does this passively, without motors or fans, and instead by the construction, design and orientation of the home.

A passive solar home works with the natural laws of physics, leveraging home design, materials utilized for thermal mass, along with the natural cycles of the seasons.

While this may sound complicated, it’s actually really simple and can be achieved by following a few passive solar guidelines.

Passive solar building was frequently utilized by civilizations that observed the movement of the Earth and sun, and used solar principles to their advantage.  The ancient Anasazi builders built their homes in southern facing cliffs, while the Greeks utilized the sun to help heat their bath houses and designed accordingly.

Thermal Mass and Phase Change Materials

The porch area could be enclosed or opened. Photo credit: Jim Tetro/U.S. DOE – Solar Decathlon

The same basic principles are still being used, albeit with different types of products.

The home featured a southern facing porch space that could be utilized throughout the year. The porch was lined with a dark colored, tile floor.

Tile is a material that has thermal mass, but the house had additional thermal mass with the utilization of a phase change material installed below the tile.

A phase change material is one that changes from a liquid to solid matter at specific temperatures having a high heat of fusion.  With these capabilities, it can store and release large amounts of heat.

The phase change material was contained within plastic ‘dimples’ located directly under the tile floor. It liquefies when it is warm and forms into a gelatinous material after cooling. The material is similar to having water’s superior ability to store and release heat.


This is a phase change material used in passive solar building, encased in plastic.

The phase change material placed under the tiles increases the amount of thermal mass.


How this works:  During the winter when the sun shines on the tile, it warms it, allowing the solar heat to be stored both with in the tile and the phase change material.  Because these materials can store large amounts of heat, after the sun goes down, the heat is slowly released from the material, transferred through the tile, and helps to keep the home warm through the cooler evening and night.

Using Air Flow to Heat and Cool

The window to the left hand side of the kitchen opens to the porch. Photo credit: Jim Tetro/U.S. DOE – Solar Decathlon

The Unit 6 home could be categorized as an envelope house because it uses air currents to cool the home.

The motorized window in the front porch area seen above allows air to be pulled through the porch and into the kitchen.

The home is naturally ventilated as the warmer air is pulled out the windows located at the top of the home, as warm air naturally rises.

The air flow takes place from the left to right side of the picture.  An open window can be seen on the upper right hand side of the kitchen where it will exit the home.

In order to save energy, the HVAC that was installed can sense when any windows are open and will not operate.  This is a function that can be overridden, but over time, it is also one that saves enormous amounts of energy.

The kitchen and bathroom were located in close proximity to keep the water lines short and energy efficient.


 The Windows

The windows open in different ways.

Windows, sometimes referred to as ‘glazing’, are another important aspect of an efficient passive solar home.

The windows that Unit 6 utilized in the southern facing living room had the ability swing open on the side, or from the bottom.

The team used double paned windows on the southern side of the building and triple paned windows throughout the rest of home.

Outside the windows, wooden overhangs block the summer sun’s heat, while they allow the winter sun to warm the home.

Windows are often the culprit of energy loss, however, these windows have mechanical gaskets that can be seen in the gallery below.


Other Features of Unit 6


Instead of a swinging door, a sliding bookshelf closed off the room. Photo credit: Jim Tetro/U.S. DOE – Solar Decathlon


Instead of a door, the home had a moving bookshelf to close the bedroom off from the living room.  See the shelf with the TV on it?  That section of the shelf can slide to the right to meet the other bookshelf and provide a partition between the separate areas.

Other facets of this Solar Decathlon home include a water cistern located in the back of the home.  Water could be collected from the roof, stored in the cistern and reused as irrigation water in the yard.

The utility room was located outside the home. It was accessible under a southwest facing awning that was also helpful in shading the area from the afternoon sun.

The Tidewater team worked with a modular home contractor to build the home, yet integrated local materials such as the Cyprus wood from neighboring North Carolina used for the bands of natural wood surrounding the home.

Take a look at the photo gallery and video to learn more about the Unit 6 Solar Decathlon home from Old Dominion and Hampton University.


The Photo Gallery

Team Tidewater scored the highest in the categories of Comfort Zone and Appliances with a 4th and 5th place finish, respectively.   The Unit 6 house was estimated to cost  $325,613.44  and the team finished 14th overall in the 2011 Solar Decathlon.

Scores for the team from Old Dominion and Hampton University

A screenshot of the final scores from solardecathlon.gov.


To learn more about the Unit 6 Solar Decathlon house take a look at the video below.



See the original model that was submitted to the Solar Decathlon.

Page on Solar Decathlon Website: solardecathlon.gov/past/2011/team_tidewater_virginia.html

The 2011 Solar Decathlon Main Website: solardecathlon.gov



Keya Lea

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

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5 Responses

  1. Esther Fillmore says:

    Great would love to have a home in the country just like this

  2. Carol Benally says:

    Do you have any plans for the house #6 and where can I get phase change material. I am in Arizona,
    I have a lot that I want to put this plan on. Any ideas or help you can give me, I would appreciate. Winter heating here in Northern Arizona is extremely expensive. Thanks Carol Benally

  3. Excellent description of Unit 6 by Team Tidewater Virginia. The team is competing again in Solar Decathlon 2013 with its Canopy House. The Canopy House harmonizes two of Team Tidewater’s most important values: design in response to the environment and design for all. Drawing from the principles of Universal Design, the Canopy House strives to make sustainable living accessible to all people, regardless of physical impairments and limitations.

    The design harnesses the power of the sun, both as an energy-efficient method for providing heat and electricity, and as an integral foundation for the home’s innovative technology. Through this technology, the house aims to instruct the user about living sustainably as well as to provide the tools to lead a safe and independent lifestyle.

    Visit our website http://www.canopyhouse.org for more information and links to like us on facebook and follow us on Twitter.

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