Choices for the 21st Century
- By Thomas H. Rogér
- 05/01/06
With new requirements for energy efficiency, increased daylighting for educational performance and the exploding growth and cost pressures of expansion in some of the school districts across the country, owners are starting to look at some new and unique systems for the building envelope (i.e. walls, windows and roofs). For example, while the traditional brick and block masonry systems of the old“red-brick” schoolhouse still dominate the choice for wall systems for cost and durability reasons, there is a growing use of systems that have traditionally been used in the industrial and commercial markets. These types of systems include tilt-up concrete panelized systems, precast concrete, metal panels and even European-manufactured thermoset resin/wood fiber reinforced panels. Why are these types of systems being considered, and what process should your design team be using when selecting the choices for your next school project? In this article, we examine the issues that school districts face when considering the choices for the school building envelope.
What Systems Are Currently Being Used?
In a survey of current K-12 school projects across the country, masonry systems still dominate the wall system choices, primarily with a brick façade exterior coupled with a CMU block backup as the best choice based on cost and durability. Wall systems such as tilt-up concrete or prefabricated wall panels — either metal, precast, curtain wall or newer resin-based panels (i.e. Trespa Meteon panels) — are being used in more limited applications on large school spaces, such as gymnasiums, natatoriums or auditoriums. And even though these systems can have significant cost, schedule or aesthetic features, limitations on their widespread use typically occur because of the specialized needs for interior surfaces in school buildings and new requirements for energy efficiency. The exterior brick façade with an interior block surface continues to be hard to beat on durability, advantages of thermal mass and insulation opportunities in high heating or cooling climates, and also has the added benefit of allowing the contractor to concentrate work on the building exterior with one construction trade (i.e. masons), rather than with the multiple trades that can be required when using other systems.
Based on concerns with energy costs, window systems are largely insulated and specified with low-E glass. This is especially true in warmer areas of the country where reducing cooling costs is a major concern.
Roofing systems are EPDM and modified bitumen on“flat” roofs and asphalt shingles or standing seam metal on sloped roofs. Environmental problems associated with the application of traditional “built-up tar” roofs are limiting their continued use, even though they have provided very long-term performance. Roofing system selection is primarily cost based, with some consideration given to long-term performance. “Modified bit” roofs seem to outnumber EPDM in recent experience, primarily because owners and A/Es feel they are better than EPDM, while adding little to the overall cost. And the EPDM roofs are typically multi-ply for performance reasons.
Envelope’s Importance in the Design of a School
Beyond the functional necessities, there are three primary dimensions to consider in the design and construction of the building envelope. As a civic icon, the building’s exterior, particularly its enduring qualities, conveys the importance of education to all inhabitants. Secondly, as a neighborhood home for learning, the exterior can express through its materials, color and details the particular character of the community in which it resides. Lastly, the quality of construction conjures a respect and care from the entire community: a school that is beautiful to see and a pleasure to be in. If these aspects are embraced at the outset, they can be incorporated into the school’s function and find an appropriate place in the program and budget.
Some of the school buildings built quickly in the 1950s and ‘60s to provide needed space during the “baby-boom” era did not fulfill these important goals and are now being torn down. In the planning of new school facilities, it is important to learn from these mistakes and avoid creating “warehouse” types of spaces that can quickly and cheaply meet program demands, but fail as long-term community or educational facilities. Interestingly, there seems to be more to learn from the school designers from the early 1900s — as evidenced by many of the buildings that have become community landmarks and are being renovated for the 21st century. For most of these buildings, it appears there was a great deal of attention paid to envelope details that subsequently have been adopted as an important expression of the spirit of the community.
The Process of Collaboration
School projects involve a number of different constituencies, each with their own perspective, as well as the shared purpose of creating a wonderful school for students. Designing an effective process for collaboration of these constituencies is the first important, but unwritten, task for an owner and the design team. The early establishment of clear lines of communication, including the creation of advisory committees and meetings with the public, is the key to ensuring effective and timely decision making, allowing participants to contribute appropriately. Because schools are fundamentally a community resource, community involvement is particularly important.
A Continuum From Big to Small
While the choice of the envelope is critical, its place in the overall strategic planning and programming objectives of a project, including the relevant urban design goals that help integrate the new building into an existing neighborhood, need to be coordinated with other important issues. Specifically, it is critical to approach the design of the building from the perspective of a continuum from big to small, from the urban context to the smallest architectural element. A good example of how this approach can affect the design of the building envelope is the John S. Martinez School project in New Haven, CT. After conducting an extensive survey of potential sites for the school, Svigals+Partners suggested that the classrooms could be designed as curved exterior elements, reminiscent of a fleet of small sailboats, allowing the building’s scale to better relate to surrounding houses and giving the building a nautical theme reflecting its location near the city’s waterfront. Prior to dealing with the choice of envelope materials, this allowed the owner and the community to deal with the “big” issue of how the actual shape of the envelope could be designed to respond to both interior and exterior priorities.
Choosing Materials
Continuing with the Martinez example, once the envelope shape and building configuration was established, the choice of envelope materials could be pursued. For wall choices, it was determined that brick would be the best material based on considerations of cost and durability. Moving along the design continuum, brick samples were gathered and a colorful arrangement was recommended using glazed brick in different colors as an accent to the red brick facade. Further detailing of the sailboat-like forms of the school’s classrooms was developed by allowing each of the walls to extend past the corner. During this process, close coordination with the construction manager was required to avoid any significant cost premiums from this unique envelope shape and material choice. For example, with input from the contractor, it was determined that in addition to needing to specify the brick lengths for each course, the cut side of each brick needed to be inserted into mortar and a quarter-inch difference was needed between each course to develop the curve in the façade. This type of close coordination achieved a unique and high-quality façade without significant premium in cost or schedule. To further detail and enliven the façade, the architects, neighborhood schoolchildren and schoolteachers created custom relief bricks and sculptures for prominent locations around the school.
Roofing, etc.
With flat roof designs, the choice of the roofing materials usually have little to do with the building’s exterior appearance but a great deal to do with the overall weather protective requirement of the building envelope. Thus, a durable, long-lasting surface, such as an EPDM membrane roof, is typically specified for today’s school building. For the steeply-pitched and sloped roofs, the appearance is a major issue and designers are specifying both asphalt shingles and standing seam metal roofs. While more costly, the standing seam metal systems can be good choices for their better longevity. An associated but important issue with roof design is the choice of the coping system both as an architectural feature and for the long-term moisture protection of the roof and the façade. For example, on the Martinez School, precast coping was specified where the aesthetic issues were important, and lead-coated copper was able to be used in less visible areas. While the use of aluminum for this purpose can be less costly, this requires the use of sealants, which age and crack through time and are not as durable. A great deal of insight in the issues surrounding these design and material choices can be gained from talking with the installer and contractors for these systems.
Sustainability
When you take into account the total operating costs associated with the lifetime of a school building — including the salary costs that are paid for the performance of its occupants, the total construction cost of a building is only a fraction of its lifetime cost. Thus, in recent years, issues of sustainability have come into play not only in the choices of building materials, but also for the performance of the building’s systems in terms of efficiently providing occupant comfort and an improved environment for meeting overall education goals. Programs such as LEED encourage the use of green roofs, solar shading incorporated into the envelope design, building orientation with regard to solar gain, local suppliers of building materials, storm water recovery and recycling systems, and many other “green” building features that can reduce operating costs and provide long-term environmental benefits.
Construction Issues
As stated earlier, it is important to involve your CM or contractor early in these discussions of the building envelope choices, since they deal not only with cost, schedule, occupant comfort and quality, but long-term building operation and maintenance. While the initial building cost is always an important consideration in these discussions, because school buildings can be 100-plus-year-old buildings, any owner who does not consider life-cycle cost issues for the building envelope design will be “paying the piper” at a very early stage. There are so many life-cycle cost and occupancy issues associated with the building envelope, and new materials and systems have become so complex, that many large school project owners are requiring the architect and contractor to utilize specialty consultants to review their design choices, verify constructability of details and inspect critical installations.
What Do We Recommend That’s Been Successful?
As stated above, the choices for the school building envelope include many types of materials and systems. Certainly, the choice of a well-designed brick façade with CMU block backup has demonstrated itself to be an outstanding choice based on its proven longevity, as witnessed by many of the 100-plus-year-old school buildings that are currently being renovated in some of this nation’s oldest urban centers. In order to meet new educational requirements for daylighting of spaces, issues associated with energy efficiency should dictate the use of window and curtain wall systems that are both insulated and provided with low-E glass. And either metal-frame or “metal-clad” wood frame systems should be used for windows to reduce long-term maintenance costs. Roofing systems should either be multi-ply EPDM or the modified bitumen for the flat roof building or asphalt shingles or standing seam metal for the peaked roofs. Whatever your choice, don’t forget to allow for maintenance in accordance with the manufacturer’s recommendations. Even the best-designed building envelopes require maintenance or will cause leakage, mold and a number of serious problems that can require you to incur substantial costs for repair.
By Thomas H. Rogér and Philip B. (Barry) Svigals. Rogér serves as the program director for Gilbane Building Company. He can be reached at 203/946-6810 or [email protected].
Barry Svigals is the principal of Svigals +Partners Architects which is based in New Haven, CT. He can be reached at 203/786-5110 or [email protected] .