Each year the U.S. Department of Energy sponsors a competition for the design of a home that can maximize the energy of the sun for affordable, sustainable living. This year, the team from the University of Maryland took home the competition’s top honor for their project entitled: Watershed. Rather than a visual manifesto on the rebranding of the single family home, the success of the design revolves around the integration and interconnection of a series of technologies and systems to create a compact, efficient and welcoming residence. The result can serve as a model to progressive home building in many ways–an area where our country needs no shortage of help in understanding how sustainability can be integrated into everyday living.
Merely building a small home that gathers the most solar energy would not snag you the blue ribbon in this competition. The Solar Decathlon is judged on a series of criteria including affordability, engineering, communications, comfort zone and market appeal. This is integral to the success of the challenge because despite the fact that sustainability’s public image may revolve around solar panels and wind turbines, the true meaning of the word is a holistic notion of balance that affects all aspects of living.
Simple in its parti (or spatial thesis), the form of the Watershed begins with two volumes, each with a shed roof sloping back down towards the other. One side holds the living room and kitchen while the other encloses the bedroom/office space. The two masses are slid against each other on their long axis and then pulled apart for a translucent volume to be placed between them bearing the bathroom and a small hall to circulate in between the two sides. Ultimately, this long axis is the centerpiece of the project that ties the home together.
As its namesake eludes to, the central axis of the house revolves around the use, storage and treatment of water. On the exterior, a line of plant-filled basins pierces the house from one side to the other. Though an attractive addition of foliage to the house, these aquatic containers are more than simply gardens. The combination of plants and aggregate comprise a small Constructed Wetlands—a specific series of plant life chosen and arranged in succession to naturally treat water. Each container has a different task: some that collect and treat rainwater, some that deal with runoff from the green roof and some that specifically treat graywater produced from the house. The tiered organization is not unlike the recent winning entry to the Gowanus Lowline competition.
One of the goals of the decathlon is pushing for Net-Zero homes, meaning that the house has a net meter to confirm that it produces as much power as living in it consumes over the course of a week. On one side of Watershed’s butterfly roof are 42 photovoltaic (PV) panels with a capacity of 9.24 kW to power the home and succeeded in achieving a net-zero rating for the competition period.
To help lower the net energy demand of the home, part of the competition criteria focuses on the production of hot water that is tested by a series of “15-gallon hot water draws.” The house must be able to produce 15 gallons of 110 degree water in ten minutes or less at multiple times throughout the day. The Maryland team met this goal (with a perfect score) by using a garden wall comprised of vertically oriented evacuated solar tubes to produce heated water for the residence. Even in the northeastern United States, solar thermal arrays can provide more than enough water for an average family even on cloudy days.
Energy efficiency begins with gathering more clean energy, but it ends with conserving the energy you have already used and finding ways to not use it at all in the first place. Watershed makes strides in all of these areas.
Though often overlooked, the simplest method is size. American homes have long since grown beyond the needs of their occupants They are not only inefficiently holding the spaces we use, but are wrought with outdated spaces that have little to do with modern living. Prime examples would be a formal living room or dining room that serve as great targets for improving suburban efficiency. According to its construction documents, Watershed has an interior square footage of 876 square feet, about one third of the average American home according to the D.O.E.’s 2009 energy data book. Less enclosed space not only means less energy required to build it, but also less energy needed to maintain and temper the space throughout the year.
The underneath the high side of each shed roof a line of clearstories helps utilize natural light throughout the day and decrease the need for artificial illumination (commonly responsible for 5-10% of a home’s energy usage).
The exterior envelope of the building is no small part to making the most of the energy needed to heat and cool the interior. Windows and doors have progressed to the point of many manufacturers providing dual-glazed units with Low-E coating as the standard. As a result, it comes as no surprise that Watershed employs high performance glazing throughout. The wall construction, on the other hand, moves well beyond the standard. The base of the wall begins with standard 2×6 wood framing, the cavities of which are filled with, spray polyurethane foam insulation (products such as Heatlok made from renewable natural oils and recycled plastic bottles). Unlike common fiberglass “batt” insulation, spray applications provide a much tighter seal to avoid air leaks that go unchecked in most American homes. After a layer of plywood sheathing, two layers of rigid extruded polystyrene sit beneath a layer of liquid-applied water-proofing. Lastly, a rainscreen system of cedar boards caps off the entire wall assembly with an insulating value of R-40 (a 2×4 stud wall with fiberglass insulation could be in the range of R-14).
A Plausible Home:
The design does a good job of standing as an example of something feasible for the American public. Some architects could criticize the image of the building as being unprogressive. Admittedly, the house is not trying to trailblaze into new building components or materials. For example, there are many buildings in the United States with cedar board siding, but I think this makes the project that much more appropriate. It is important for Americans to realize that building a high quality home does not require having to jettison into the bleeding edge of contemporary expression. Virtually any home in America could utilize the same wall system as Maryland’s Watershed and if every one did then the savings in energy use would be material. Watershed’s success rests on the combination of systems and orientation around a hydrologic spine.
I particularly like the fact that the bathroom and hall have picture window views to the constructed wetlands, making it impossible not to read the connection between how the water is used and how waste water is subsequently treated. Combined with other components like solar panels, solar thermal tubes and the green roof, the design succeeds in helping residents and spectators perceive the processes of sustainability and how they integrate into everyday living. The Maryland team created a great video walkthrough of the built version of the project.
The affordability component of the competition tries to add a level of realism to the exercise to avoid ending up with a bunch of tricked-out bungalows available only to the upper class. Surprisingly, of the ten judging criteria, affordability was not one of the University of Maryland’s strongest areas. The total estimated cost of construction of Watershed came in at $336,335.89, well over the target price of $250,000, which placed the team 12th in that category. On one hand, this is over twice the current average median home price in the U.S. of $156,100 according to the National Association of Realtors. Then again, it is important to remember that most of the new homes made in this country are cheaply built and bleed energy with components that can fall apart in a decade. This makes the number more of a waterline than a true benchmark.
One slightly discouraging thing about the presentation was the rendering. Not that the house does not look good—quite the contrary—but it is placed in a grassy field with trees in the background. While no doubt part of a designer’s pitch for the house’s integral link to nature, a grassland is the last place I would want to see new suburban homes. We have already lost massive amounts of natural landscape and farmland to suburban sprawl. In her book A Field Guide to Sprawl, Dolores Hayden says “the American Farmland Trust estimates that in the United States, 1.2 million acres of farmland were lost to development every year between 1992 and 1997.” I would have rather seen the house set in on a street, perhaps with an idea of how close a group of them could be to each other.
Of the things that the government spends tax payer dollars on, I have no problem with the Solar Decathlon. The competition feeds directly into our higher education system as an exercise of practical research applied to social applications that are immediately feasible. The annual repetition of the competition has helped it gain credence and anticipation in the eyes of those outside of the competitors and its high profile exhibition site helps disseminate knowledge of sustainability directly into the public that needs it most. Watershed stands as a prime example of a standard of building and living that everyone in the country should at least understand.
Image Credit: U.S. Depart of Energy Solar Decathlon