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The Solar Pop-Top Residence in
Boulder doubled the size of an existing home by adding a second
story while reducing overall utility bills. |
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Credit: Bryan Bowen |
Passive Solar Pop Top Retrofit
The passive solar pop-top is the winner of the 2005 CRES Renewable
Energy in Buildings Awards in the category of residential retrofits.
“Pop-top” is construction industry jargon that refers to removing the
roof of a one-story building and adding an additional story.
This home was originally built in the 1960s in single-story ranch style.
The owner, who is a professional musician and music teacher, wanted to
create a studio on a second story addition where he could practice and
teach. One of the interesting aspects of this project is that the second
floor is acoustically isolated from the first. The owner can teach
students and play his instruments without being heard on the first floor.
The owner put a lot of “sweat equity” into this project and costs per
square foot (sf) are therefore not completely known or comparable with
conventional construction. However the owner says costs were “extremely
economical” and well within his means.
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The solar fraction of the second
story is more than 50%. Tubing embedded in the floor moves heat
from the area exposed to the sun to other areas in the house. |
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Credit: Bryan Bowen |
Use of Renewable Energy
The owner also has a strong interest in solar and energy efficiency, so
the retrofit added solar features and greatly increased the energy
efficiency of entire house. He ended by more than doubling the size of
the house to 2,211 sf. After the first winter, the utility bills
declined from those of the previous year.
The second story has passive solar design, and the architect expects
more than half of the home’s heating to come from the sun based on his
experience and computer modeling. The area of south-facing glazing is
18% of the floor area. Thermal mass is provided by an area in front of
the south windows where the sun shines in winter that consists of 1.5”
of gypcrete finished with porcelain tile. There is tubing inside the
gypcrete through which fluid can distribute heat throughout the slab
when a small pump is turned on.
Solar hot water panels are fitted on the roof ready for installation
this summer, and the home obtains much of the light it needs during the
day from daylighting.
Winning Design Team
The design team was led by Bryan Bowen Architects in Boulder. Other
partners involved in the project include:
- Mike Marsh, owner & builder
- Jim Borzym, acoustical engineer
- Geri Gilman, structural engineer
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