Solar Today January February 2014 : Page 22
c ase study Two views of the large, ﬂexible major space that accommodates groups of up to 50 but also as small as 10 for either seated seminar activity or active dance or workshop construction activity. Smith College Accepts the Living Building Challenge A collaborative process brought net-zero success at the Bechtel Environmental Classroom. By BRUCE COLDHAM became interested in the Living Building Challenge eight years ago. It is a straight-forward challenge with a clear energy metric based on verification-by-doing; where imperative constraints are reverse engineered from an understanding of the carrying capacity of the biosphere, rather than simply improving upon business-as-usual. Smith College purchased its 240-acre Archibald MacLeish Field Station, 10 miles north of the main campus, to site its Observa-tory. Recently the college decided to use the land in support of their environmentally themed classes and workshops — programs ranging from earth sciences and botany to poetry and dance. In support of this initiative, a gateway building was required. It was to be a 2,300-square foot multi-use classroom and environmental research building created around a large, flexible major space that I could accommodate groups of up to 50 but also as small as 10 for either seated seminar activity or active dance or workshop construction activity. This was to be supported by a second smaller laboratory-like classroom space for the science-oriented field study programs. Supplementary requirements included dis-play space, bathroom accommodations (but not in support of overnight stays), a kitchenette (but not in support of meal preparations), secure storage and a station manager’s office space. The RFP to select the designer described what seemed like an ideal Living Building can-didate: a small, manageable project requesting a “world-class” environmentally high-performing building for a long-established institutional cli-ent committed to sustainability, with a progres-sive student/alumni base. Our firm, Coldham & Hartman Architects, saw this as an important opportunity and included the Living Building Copyright © 2014 American Solar Energy Society. All rights reserved. 22 JANUARY/FEBRUARY 2014 SOLAR TODAY
Smith College Accepts the Living Building Challenge
<br /> A collaborative process brought net-zero success at the Bechtel Environmental Classroom.<br /> <br /> I became interested in the Living Building Challenge eight years ago. It is a straightforward challenge with a clear energy metric based on verification-by-doing; where imperative constraints are reverse engineered from an understanding of the carrying capacity of the biosphere, rather than simply improving upon business-as-usual.<br /> <br /> Smith College purchased its 240-acre Archibald MacLeish Field Station, 10 miles north of the main campus, to site its Observatory. Recently the college decided to use the land in support of their environmentally themed classes and workshops — programs ranging from earth sciences and botany to poetry and dance. In support of this initiative, a gateway building was required.<br /> <br /> It was to be a 2,300-square foot multi-use classroom and environmental research building created around a large, flexible major space that could accommodate groups of up to 50 but also as small as 10 for either seated seminar activity or active dance or workshop construction activity. This was to be supported by a second smaller laboratory-like classroom space for the science oriented field study programs.<br /> <br /> Supplementary requirements included display space, bathroom accommodations (but not in support of overnight stays), a kitchenette (but not in support of meal preparations), secure storage and a station manager’s office space.<br /> <br /> The RFP to select the designer described what seemed like an ideal Living Building candidate: a small, manageable project requesting a “world-class” environmentally high-performing building for a long-established institutional client committed to sustainability, with a progressive student/alumni base. Our firm, Coldham & Hartman Architects, saw this as an important opportunity and included the Living Building Challenge in our initial proposal, together with a tabulation of solution concept statements to satisfy each of the 20 imperatives of the Challenge.<br /> <br /> We wrote:<br /> “The Living Building Challenge is a considerable step above LEED Platinum. It is the very highest bar of environmental performance, essentially requiring (among other things) that all energy, water and nutrient flows are managed within the building and site boundaries. There are no points to tally, just fundamental Imperatives — all validated by measurements during a full year of occupancy.”<br /> <br /> After an interview the college chose our firm as the design team. It was clear that the client already leaned strongly toward accepting the Living Building Challenge.<br /> <br /> First we needed to know if Smith College’s original enthusiasm for the Challenge was a durable interest. Then we needed to clarify our standing with regard to the first imperative of the 20 Living Building Challenge Imperatives — Limits to Growth — that precludes green field development. The question was whether we were eligible for an “exception,” offered for projects whose primary purpose is interpretation and can demonstrate that the site’s ecological systems are not disturbed. By siting the building where once was a farmer’s boulder field that had been carelessly clear cut and revegetated with invasive species, and by siting the parking lot 1,000 feet away along an abandoned county road, we were able to satisfy the rigorous siting imperative.<br /> <br /> The Imperative Challenge<br /> It became immediately apparent to the design team that the imperatives of the Challenge are not equally demanding. Some, such as the Red List (precluding 15 chemical groups and natural elements from construction materials) and Appropriate Sourcing (establishing radii from within which materials must be sourced), loomed particularly large. Extracting formal declarations of constituent ingredients from large corporations can be difficult even though we stressed that this was an exercise in consciousness- raising rather than legal entrapment. It was daunting to go through this process for all products used in the building. We often had to reconcile tensions between Red List, sourcing and responsible harvesting imperatives, all in the course of a normal submittal review process.<br /> <br /> We designed for a mix of recessed LED lighting and soffit-valanced indirect linear fluorescent fixtures (using Phillips low-mercury T8 lamps). The recessed LEDs are very flexible — dimmable, wet-area-tolerant, cold-temperature tolerant and there is no mercury. We designed sufficient dropped-ceiling planes to enable a comprehensive lighting solution without having to push recessed fixtures into the insulated thermal envelope.<br /> <br /> Some imperatives were confounding. For us it was achieving the Net-Zero Water imperative. Our first instinct was to serve our modest load with captured rainwater, and we even established a “route” through the regulatory maze to permit such a system under the reservoir provision of the existing statute — using a cistern instead of a lake, and roof catchment instead of acres of forested land. But we concluded that holding water in a concrete cistern was not the most elegant means of containment. We reasoned that using the ground for storage was better; it is less material-intensive and the storage medium retains the water at a higher quality. It requires less energy to achieve acceptable water quality. This led to our exploration of what a “closedloop system” means, and whether using a well would be acceptable, as is routinely done in this part of the country when a project is beyond the range of a municipal water system.<br /> <br /> We used composting toilets to eliminate blackwater effluent, and initially considered using in-building planter beds designed to treat remaining graywater flow, as we had previously done for the Wampanoag building on Martha’s Vineyard (see SOLAR TODAY, January/February 1995). But the building was not well suited for this system because of its inconsistent usage pattern. There would be at least two periods each year when little or no water would flow: a four-to-five week midwinter student hiatus, and a similar decrease in activity over the summer. We considered an upper soil horizon root zone leaching field, but that would have imposed an energy penalty for a pump and dosing chamber that did not seem worthwhile given the slim nutrient return. So we elected to discharge effluent to a septic tank and from there to a leach field in a location with suitably porous soils. Graywater then percolates into the soil and down into the water table, making a complete cycle.<br /> <br /> The Net-Zero Energy imperative was more readily achievable because our office focuses on creating high performing buildings and we are accustomed to calculating energy flows as we design them. We began with an energy-use budget (see table 1, right) derived in part from what we could achieve through design, and then from what we anticipated could be achieved through a conserveruser mentality. We use an internally generated spreadsheet to do this.<br /> <br /> The assumptions upon which these use estimates are based are noted in the “Comments/ Assumptions” column, but are basically reflections of experience the firm has gained by paying attention to buildings that we have created, and others that we have taken an interest in. The goal of this tabulation was to establish the size of the photovoltaic (PV) system that we should install, and the fractional energy budget for each major load component. With the production component established, we then designed based on these load components. We did not spend a lot of time refining the crude projection of annual consumption, because we know that consumption is largely a function of behavior. Rather than try to predict behavior, this consumption projection is intended to regulate behavior by creating annual energy-use budgets in these categories. Using an Alteron Dashboard to track energy use, we would be able to identify any behavioral aberration quickly and provide timely feedback to get energy use back on budget.<br /> <br /> For mechanical components, we chose a pair of single-port air-source Mitsubishi FE 12 and 18 heat pumps with single wall-mounted indoor cassettes, one in each major space. We designed the envelope to be so tight that convective distribution of conditioned air was sufficient to keep smaller, adjacent spaces comfortable. The envelope ultimately tested at 0.7 ACH50, using 12-inch thick double-stud walls insulate with densepacked cellulose, and 16 inches of cellulose to insulate the roof. We used Serious (now Alpen) 725 Series triple glazed, krypton-filled, warmedge glazed windows.<br /> <br /> For ventilation we followed a similar path, using two Zhender ComfoAir 550 units, each serving one of the larger spaces. We balanced these with the continuous exhaust ventilation associated with the composting toilet, and controlled them using CO2-sensing demand control devices. The intermittent use and the low water temperatures (predominantly handand specimen-washing) were unsuited to a storage water heater, where standby losses from the required 140°F (60°C) storage temperature would have been a considerable fraction of the total water-heating tally. So we decided upon a Hubble instantaneous electric water heater with the temperature set at 110°F (43°C).<br /> <br /> PV panels were the obvious choice for a power source — like most sites, it was not rich in alternatives, but the sun shone brightly. Typically we would expect to size and orient a portion of the roof plane to yield a sufficient solar harvest. But here we were hard against a protected wetland tree line to the west, so pole mounts were necessary for the two 4.8-kilowatt SunPower arrays. Fortunately the site was large enough to allow this. Freed from the requirement to dedicate a large roof to solar collection, we ran a cross-gable with a large south-facing clerestory window to provide copious and controllable daylighting to the major space.<br /> <br /> A successful response to the Living Building Challenge requires demonstration — via a full year of occupancy — that the imperatives for zero net annual performance have been met. Actual annual energy use was, at 8,892 kilowatt-hours (13.2 kBtu per square foot per year), fractionally less than our projection. The actual water use, at around 5 gallons per day (150 gallons per month), was far less than our 1,500 gallons per month projection and a tiny fraction of the 30,000 gallons per month that a conventional water supply would be designed to provide. The wastewater treatment flow is similarly a tiny fraction of the 360 gallons per day, which is the design standard of the regulatory authority. The bottom line here is that water use in commercial buildings drops hugely when irrigation is eliminated and when composting toilets arrive. Then it drops off the scale when people actually pay attention.<br /> <br /> We were asked what would be the premium to build a high-performance, low-impact Living Building during the designer-selection interview. We referenced the “Living Building Financial Study” as a guide and determined that a “university classroom” building in “the Boston region” would be 16 to 21 percent more expensive. We suggested targeting the low end of the range to account for our standard practices (12-inch thick walls, 1.0-or-lower ACH50, triple-glazed fenestration). Ultimately we estimated the premium to be only in the range of plus or minus 8 percent.<br /> <br /> We found the real premium to be in design team time rather than in the cost of building materials (see table 2, left, for a summary of construction costs). The design time premium might have been reduced had we been able to engage a construction manager earlier in the design process. The conventional bid process took design team time at a critical juncture, and delayed the arrival of the construction team, reducing their important role in the materials-vetting process — a role that would have given both greater clarity to our options and avoided having to revise materials choices during the submittal process.<br /> <br /> The Value of the Challenge<br /> So is the Living Building Challenge worth accepting? Why not just do one’s best without regard to an essentially arbitrary set of targets and requirements — especially as mandatory targets can lead to sub-optimal design decisions? The answer is partly that it pushes all involved harder than would be the case if we acted solely on our own initiative.<br /> <br /> Once the stakeholders and design team decide that the underlying values and aspirations are worthy, then the Challenge is well worth accepting. Aside from doing the right thing, the brand value of the Living Building Challenge is significant. A portfolio with one or two successfully completed Living Building projects would distinguish any architectural practice.<br /> <br /> While LEED aims for change by raising the broad base of the industry by degrees, the Living Building Challenge aims at deep philosophical change. It pulls at the top, directing change to industry and regulatory environments, not by brokering broad consensus, but by excellence in example. The Living Building Challenge empowers the design team to achieve these performance standards (imperatives) with the finest creative effort it can muster. The Challenge spreads the commitment between the owner/developer, the design team, the constructors and even (and this is particularly important) the users. All parties have an integral part in striving for and achieving the Challenge. That collaboration helps make high-performance, low-impact (even restorative) buildings a reality. <br /> <br /> Bruce Coldham, AIA, graduated in architecture from the University of Melbourne and emigrated to the United States in 1982. Since 1989 he has run his architectural practice, Coldham & Hartman Architects in Amherst, Mass., and has been active in the Northeast Sustainable Energy Association (an American Solar Energy Society chapter) since 1984, including chairing its Building Energy Conference three times, and serving three terms as chair of its board of directors.