Images courtesy of Ashley McGraw Architects.

My architectural firm has long seen the importance of developing a sustainable design ethic to practice in concert with the USGBC’s LEED measurement systems. We have unique skills as architects to display both the technology of more sustainable buildings and an aesthetic that can help point the way to an as yet unrealized bright, sustainable future. Our development of this ethic can be characterized by one word: synthesis. Sustainable strategies should be part of a unified ethic: a melting pot of beauty, energy and other natural resource performance, and optimism for what the future can hold. This means challenging some of our most deeply practiced beliefs regarding the sanctity of design values in relationship to sustainability.

We saw passive design as an apt vehicle to start our synthesis journey. Passive design focuses on optimizing the building’s form and envelope to its climate, with particular emphasis on relationship to the sun. Deeply practiced passive design has the ability to speak of the synthesis of building form and energy performance. Integral to the pursuit of informed passive design was our development of an in-house specialty in energy and daylight modeling with the goal of quantifying the energy impact of our design decisions quickly enough to inform clients.
 

Test Subjects

We first applied our newly developed passive design and modeling skills to two upstate New York K-12 public school projects located in Liberty and Liverpool. Both are media center additions to large existing school buildings. Their manageable size made them easier for us to test modeling tools. Both projects were designed in roughly the same timeframe and strive for net-zero fossil fuel energy use, but their differing contexts and passive strategies resulted in two very different buildings.

The Liberty Central School District project has a compact building plan and high-performance building skin. Its shape is a figural response to the courtyard it rests in and aligns with a north-south axis to improve interior daylighting. This building reduces solar heat gain by minimizing east and west glazing and by bringing diffuse north light through rooftop monitors. Roofs are insulated to R-50 and walls to R-28. We emphasize the design of low air infiltration building skins both for energy reduction and as a vital component in creating healthy, mold-free interior environments. (Many of our new buildings, including Liberty, undergo blower door testing to check air tightness both during and at the conclusion of the project.) We incorporated automatic daylighting controls, and the addition is served by a variable air volume heating and cooling system with heat recovery. Utilizing the above strategies, Liberty is designed to consume approximately half the energy of an average school building, with the remainder offset by grid-tied photovoltaics.

The Liverpool Central School District’s design is driven by a powerful but seldom-used passive solar strategy: trombe walls. These are concrete walls separated from the outdoors by glazing and an air space. The concrete absorbs solar energy and releases it selectively toward the interior. For this project, we used energy- and daylight-modeling software to optimize the south wall of the addition, tailoring its characteristics to meet the thermal and lighting needs of the space. This resulted in a system we call the “split trombe” wall, made up of sections of trombe mass separated by glazing without trombe mass for daylighting. Exterior shading devices eliminate most of the summer solar heat gain while allowing the winter sun to penetrate the glazing to both warm the concrete trombe mass and provide direct solar heat gain. Stacked horizontal baffles inside the glazing act as mini light shelves, minimizing glare from direct sunlight and bouncing it deeper into the space. Like Liberty, Liverpool is oriented on a north-south axis, with the trombe wall facing due south. In addition to the split trombe wall, we used many of the same strategies as at Liberty: similar insulation and air tightness values, similar lighting controls and HVAC system. But the split trombe walls at Liverpool increases the school’s energy performance, and it uses just one-third the energy of an average school building. A photovoltaic system was designed to offset the remaining energy use and create a net-zero building.

Both projects are now under construction, and we are eagerly awaiting their first operational data. Both will be equipped with energy dashboard systems to track their consumption, and we will use that data to fine-tune the buildings’ systems and to improve the accuracy of our energy models for future projects.
 

Surprising Results

Unexpectedly, the logical side of passive design gave us the footing we needed for buy-in from typically conservative school boards and push these projects much further than we had thought possible - all the way to net-zero fossil fuel. Because of the strong link between building form and energy performance inherent in passive design, design decisions could be explained in common-sense terms traced back to improving the energy performance of the building. This logic was bolstered by the data provided by energy and daylight modeling.

We invested considerable energy discussing with our clients the viability of photovoltaics in our predominantly cloudy region and northern latitude. Given New York’s photovoltaic incentive program and State Education Department funding, we routinely find that payback on school photovoltaic installation is less than 10 years. This was the case for both of these projects, although Liverpool decided for budgetary reasons not to include the array in its project. The building is designed for easy addition of the system at a later date.

Our modeling work has proven to us that passive design strategies can make a large impact on fossil fuel energy consumption in commercial and institutional buildings. We also learned through these projects that we cannot assume our client’s comfort level or aspirations based on convention or our past experience. If we can learn to express our design decisions in their terms, we may be surprised at how far they wish to push the envelope. Finally and most importantly, each project is but a step on a journey toward the synthesis of sustainability, the client’s needs and character, and the continuing evolution of a philosophy that is much larger than can be manifested in any single project.
 

Liberty Central School District, N.Y. Media Center Statistics

Size: 4,428 square feet

EPA Target Finder average: 85.6

As Designed: 39.5 (kBTU)

PV System Size: 44.16 kW

Air Infiltration (LPS/SM @ 75 Pa): .02

LEED Certification: Gold (pending)

Completion Date: February, 2011

Project Teams: Ashley McGraw Architects P.C.; Appel Osborne Landscape Architecture; Robson Woese Inc.; Klepper, Hahn & Hyatt; Camroden Associates

Materials: Solon 230 Blue PV Panel, Satcon Powergate Plus PV Inverter, DPW Power-Fab PV Racking System, Lucid Building Dashboard, Blueskin air barrier, soy-based spray foam insulation, low-VOC paints, sealants, and interior finishes, rain garden stormwater system, daylighting controls and dimmable lighting fixtures, precast concrete thermal masses

Construction Cost: $260/sf (Excluding PV)
 

Liverpool Central School District, N.Y. Media Center Statistics

Size: 3,553 square feet

EPA Target Finder average: 91.3

As Designed: 31 (kBTU)

PV System Size: 25.3 kW (future)

Air Infiltration (LPS/SM @ 75 Pa): .02

LEED Certification: Certified

Completion Date: May, 2011

Project Team: Ashley McGraw Architects P.C., Appel Osborne Landscape Architecture, Sack & Associates Consulting Engineers, PLLC, Novelli Engineering

Materials: Solon 230 Blue PV Panel, Satcon Powergate Plus PV Inverter, DPW Power-Fab PV Racking System, Lucid Building Dashboard, Blueskin air barrier, soy-based spray foam insulation, low-VOC paints, sealants, and interior finishes, rain garden stormwater system, daylighting controls and dimmable lighting fixtures, precast concrete thermal masses

Construction Cost: $190/sf (Excluding PV)