The solar remodeling of
the author’s 1970s lake house
began with a mission:
to reduce demand to
10 kilowatt-hours per day.
By david BoLT
Over lunch five years ago, the volunteer coordinator for Habitat for Humanity
in Lenoir City, Tenn., mentioned five near-net-zero-energy houses her group
was building with the Oak Ridge National Laboratory, the Tennessee Valley
Authority and vendors. I’d been searching for ways to live more sustainably, and
the prospect of building homes that generate as much energy as their occupants
use jolted my thinking entirely. More than a year and much research later, in
mid-2005, I launched a business to help people move toward net-zero-energy houses (ZEHs). It
only made sense that the company’s first customer should be me.
My family owns a lake house in Harriman, Tenn., that we used primarily on summer weekends. It
seemed like a good place to get some experience in ZEH retrofitting. My mission: to reduce energy
demand at the house to 10 kilowatt-hours (k Wh) per day.
I set a budget of $100,000 to renovate the 30-plus-year-old, 2,400-square-foot house for net-zero
reliance on grid energy, while making it suitable
for full-time living with my wife and two children.
The budget was roughly broken into one-third for
solar electricity-generating and solar water-heating
systems, one-third for energy-efficiency upgrades
and one-third for general remodeling. We started
the remodel during fall 2005 and paid the last utility
bill in April 2006. Easy, right — draft a few checks
and wait six months?
The real story is far more complex, of course. It
involved working six months with an architect, a
builder and subcontractors to achieve major structural changes and install the photovoltaic (PV)
after increasing insulation and adding a fan
in the attic, the Bolts are able to stay comfortable through Tennessee summers without air
conditioning through old-fashioned natural
ventilation.
David Bolt is an electrical engineer and a
licensed solar and general contractor, as
well as an active member of the building
science industry. In 1996, Bolt cofounded
MarketLinx, a software development com-
pany. In 2005, after the sale of MarketLinx,
he founded Sustainable Future LLC to
educate people about sustainable liv-
ing and provide products to support this
choice. Visit sustainablefuture.biz for details
about Bolt’s ZEH retrofit, or contact him at
dwbolt@sustainablefuture.biz.
Facts: Net-Zero-Energy Home
Retrofit, Harriman, Tenn.
l
2,400-square-foot house retrofitted
to use 10 kilowatt-hours per day for a
family of four
l
$100,000 budget allocated
l
Moved to wood stove heating and
natural ventilation for cooling
l
Replaced gas water heater with four AET
28 flat-plate solar collectors
l
Installed a 3-k W photovoltaic system
grid-tied with a Sunny Boy inverter
l
Remodeling began in fall 2005; last utility
bill received April 2006
cLicK: Find steps for moving toward net-zero-energy at your home: solartoday.org/retrofitzeh
