Essay:
True Sustainability

The end result: Very little external heating or cooling is necessary to maintain an even temperature inside the building. Even without added heat, the temperature inside changes very little over night in winter months. On the coldest days when skies are overcast and there is no sunshine, a small wood stove adds supplemental heat which again is absorbed by the building’s thermal mass.

However in summer months, heat absorbed and reflected off the cement patio across the south front causes the building to take on too much heat.

To combat this, a pergola has been built across the front to support a vine which in summer months provides shade. Air conditioning supplements the cooling in order to make work conditions more comfortable.

In order to serve as a more complete model of alternative construction and technology, Alan has also installed a 4.2 KW solar photovoltaic system to supply virtually all of the building’s electrical needs.

State and federal incentives and rebates took care of up to three quarters of the total investment for the installation of solar panels and other hardware.

The electricity generated by the panels does not charge batteries but connects or interfaces with the main electrical lines, otherwise known as a “grid-tie” system.

An inverter converts the DC electricity from the panels into the AC voltage compatible with the grid.

The building has two meters, one that shows the amount of electricity that has been used and a second which shows the amount which has been generated. A monitoring system also calculates the total amount of generated power and other statistics.

Monitor the system's statistics and power generation online.

During winter months when daylight hours are short and there is often little sun for days at a time, the cost for electricity powering the building’s lights and equipment will run on average from $10 to $15 a month, still a substantial reduction from his pre-array electric bill.

As the days increase in length even when powering supplemental air conditioning the panels generate more power than is consumed, with the excess feeding directly into the grid, in essence producing a financial credit.

The amount of financial incentive is enhanced because, at the time of this writing, TVA (the source of electricity from the grid) actually pays quite a bit more for the electricity that is produced than it charges for the power that is consumed.

Going one step further as a model of sustainability, a solar water heating system was installed to supply a small kitchen and bathroom. A radiator style collector heats a fluid similar to antifreeze which transfers the heat though indirect contact to water which is then stored in a large tank on the roof.

The solar water heater works well, but the amount of that water needed or used in the building is relatively small and dollar for dollar, Alan feels additional solar electric panels would have been a better investment.

Reflecting on what might have been done differently to improve the energy efficiency or “green” aspects of the building, one option would have been to choose a different color for the roof. The roof is sheathed with a dark green enamel coated tin which has a 40 year warranty and never needs painting. The color green was chosen to allow the building to better blend in with the environment, important since the structure is located only a short distance below the owner’s home. However a white or lighter color would have reflected rather than absorbed heat and could have helped keep the building cooler during Tennessee’s long, hot summers.

There’s one other aspect of sustainability around this site that is worth mentioning. Directly adjacent to the office is a fenced in garden. Periodically throughout the day, as a break from working at computers, time can be spent in the garden, planting, weeding, and harvesting, all following the permaculture model that sees home, work and food production as an integrated system.  All in all it is a powerful example of the sustainable lifestyle.