Renewable Retrofit

When you think of the word “office,” what usually comes to mind is a sterile cubicle in a large boxy building surrounded by a parking lot, totally dependent on fossil fuel infrastructure for its existence. But when you’re a nonprofit organization like The Abundance Foundation (TAF) in Pittsboro, North Carolina educating people about sustainability through workshops, green tours, and local food and renewable energy events—residing in such sterile surroundings goes against your mission. You want to create an “office of the future.”

The group was starting to feel cramped in the existing space, an office shared with Piedmont Biofuels—a local biodiesel cooperative (see HP122 and HP132) that was expanding and needed to occupy more of the converted warehouse for its own employees. TAF employees imagined an office that would help showcase the organization’s commitment to sustainability—something beautifully crafted using locally sourced lumber, powered by renewable energy, and situated on the edge of the organic farm that surrounded the property.

As luck would have it, a 10- by 12-foot screened-in sleeping shed, intended to house summer interns for the organic farm, was sitting unused. TAF moved the building close to the existing quarters so the staff of three could use the kitchen and bathrooms in the adjacent structure. The small building was large enough for an office, yet small enough to make heating and cooling relatively easy. TAF hired local designer-builder Green Door Designs (GDD) to retrofit the small structure for year-round occupancy. GDD built the block foundation, and used local, Forest Stewardship Council-certified lumber to build out the frame.

The small office was wired for AC, then spray foam insulation was added to the beefed-up frame (2 by 4 walls; 2 by 6 roof rafters) to create a tight building envelope with a higher insulation value than conventional fiberglass insulation (about R-6 per inch). The floor received a few inches of spray foam and was also covered in reflective foil. Recycled doors and windows, purchased from a Habitat for Humanity reuse store, were installed. Unfortunately, the energy labels on these windows were missing, which led to incorrect assumptions about their passive solar capabilities (see “Window Shopping” sidebar). The interior was finished with locally milled pine bead-board, making the structure drywall-free. GDD also built an accessibility ramp and a loft for storage. They then protected the structure with a colorful paint job using zero-VOC paints purchased from the local building supply store. 

Energy Retrofit: PV System

The group wanted to use solar electricity and as much supplemental solar heating as possible. They drafted board member and PV expert Rebekah Hren to help design and install the solar-electric system, and asked me to help with a solar air heater for space heating. Keeping to their educational mission, the staff turned the installation of both systems into workshops.

One decision TAF faced was whether to tie the PV system to the grid or to go with an off-grid battery-based system. If the staff wanted to create an “office of the future,” then tying into the grid would make sense. Grid-tied systems are less expensive, require less maintenance, and send any excess renewable electricity out to the grid. But grid-tied systems require access to the grid and extra paperwork that can make their implementation more onerous initially. Running the additional wiring from the existing building to tie it to the grid proved too expensive for such a small space. Since there were few examples of off-grid systems in the area, and learning about off-grid solar has more appeal to the DIY crowd that routinely signs up for TAF workshops, the staff decided on an off-grid system.

The office has only a few loads, so sizing the system was straightforward. A few laptop computers, a ceiling fan, lights, printer, and a wireless router are the primary loads. Rebekah interviewed the office staff about what loads they needed and expected to run (how many laptops, printer, router, etc.), and sized the system accordingly with a system sizing spreadsheet.  

On a weekend in November 2009, Rebekah and I ran simultaneous workshops to install the off-grid PV system and the solar air heater. With almost 30 people attending, it was a little crowded around the small cabin, but we managed to get everything done.