The Alice Ferguson Foundation recently cut the ribbon on its new “Grass” education center, a net-zero energy, net-zero water, carbon-neutral structure that’s designed to meet the strict requirements of the Living Building Challenge. Located on the shore of the Potomac River just a few miles south of Washington DC, the building will support the Foundation’s mission of promoting sustainability through STEM education.
Image courtesy of the Alice Ferguson Foundation
Energy
A 47 kW rooftop photovoltaic array generates more electricity than the building uses. The array is grid-tied, so it sells excess energy during the day and buys energy at night, using the grid as “virtual storage.” Electricity consumption is reduced through efficient LED lights and ample daylighting. (The picture above shows the south-facing roof. The north side features clerestory windows for daylighting.) Energy consumption and distribution are regulated by an advanced Building Management System.
Five vertical loop geothermal wells, each 450 feet (137 m) deep, take care of the building’s heating and cooling needs. The geothermal system’s total capacity is 8.8 tons, which is more than enough to handle the 3800 square foot (353 sq meter) facility. Although horizontal wells would have been less expensive to install, vertical wells have a smaller footprint on the surrounding land.
Heating and cooling needs are minimized thanks to a high-performance building envelope consisting of FSC (Forest Stewardship Council) certified OSB (Oriented Strandboard) surrounding an EPS (Expanded Polystyrene) core. OSB is commonly known as “waferboard” and is often made by gluing wood chips together. FSC certified OSB is made from wood that’s been farmed with sustainable practices; the wafers are joined without formaldehyde-based glue. The building’s R-factor is about five times that of a standard building of comparable size. According to Ferguson Foundation representative Sandy Wiggins, “The walls are 2x6 studs filled with closed cell biobased foam with plywood sheathing, wrapped with 1-inch Thermax - a glass fiber reinforced foil-faced polyisocyanurate foam, and all of that wrapped with VaproShield Wrapshield - a water resistive vapor permeable barrier membrane. Windows are Alpen, triple glazed with a U value of 0.16.”
Water
The Grass building is a net-zero water facility, which means that all of its water needs are met on site. A well provides potable water, while stormwater and greywater keep the gardens green. Composting toilets turn waste into topsoil, eliminating the need for sewer and septic systems.
A solar thermal system is capable of heating 80 gallons of water every day, meeting or exceeding the facility’s typical daily hot water needs. During extended sunless periods or when hot water demand is unusually high, a thermostat controlled electric water heater supplements the solar water heating.
Waste
The Alice Ferguson Foundation published a zero-waste facilities guidebook; all of its education centers abide by those principles. For example, leftover construction materials were recycled or repurposed/reused, food waste is either fed to livestock or composted, and toilet waste is composted. Of course it’s better to reduce than to reuse/recycle, so green purchasing procedures are used to minimize waste.
Materials
Some of the wood used to build the structure was harvested from downed trees on site. Remaining wood products come from FSC certified sources. All construction materials are free of PVC, formaldehyde, and other hazardous “Red List” substances. Due to the requirements of the Living Building Challenge, many large manufacturers have changed their products and processes to more sustainable materials.
Living Building Challenge
At the time of this writing, only eight buildings in the world have achieved the full “Living Building” distinction. (One of them is the Bullitt Center in Seattle.) The Ferguson Foundation hopes that the Grass education center will become the ninth. To do so, they must provide a full year of data related to its energy and water usage. The process is currently underway and should be completed sometime in 2016.
Design for sustainability is becoming a significant factor in engineering and construction, and a few organizations, like the Alice Ferguson Foundation, have taken it upon themselves to lead the charge. By studying how these buildings operate under various conditions, engineers will learn to develop new materials and techniques that eliminate waste, improve health, and reduce energy consumption. The best teachers are the ones who set an example, and the Ferguson Foundation is giving today's architects and tomorrow's scientists, engineers, and leaders a great lesson in sustainable design.