Passive Strategies for Building Healthy Schools, An AIA/CES Discovery Course

With the downturn in the economy and the crash in residential property values, school districts across the country that depend primarily on property tax revenue are struggling to make ends meet, while fulfilling the demand for classrooms and other facilities.

School boards are looking for Building Teams to deliver new buildings and reconstruction projects at the lowest reasonable cost. At the same time, most school boards want the benefits of sustainable design and construction—improved indoor environmental quality, enhanced student performance, and better student, teacher, and staff health—even if they choose not to pursue formal recognition programs, such as the U.S. Green Building Council’s LEED certification program.

How can Building Teams deliver K-12 schools that meet these demands for sustainability, while keeping projects in line with extremely tight budgets?

In recent years, the Building Team of FGM Architects, KJWW Engineering Consultants, and Turner Construction has met this challenge through a series of what might be called “passive strategies,” strategies that deliver maximum value to school districts at minimal or at most reasonable additional cost. In general, these strategies use the givens of nature—earth, water, sun, and air—to control costs while providing optimal learning environments for students.

USING MOTHER EARTH TO SHELTER THE BUILDING

One of the most cost-effective passive strategies is to use the site itself, when possible, to achieve sustainable benefits. For a project in Will County, Ill., 40 miles southwest of Chicago, the school district charged the Building Team with planning a 95,000-sf middle school in such a way that would not only minimize the impact on the site but also provide opportunities for the site features to enhance the education experience.

The site conditions:

•  A 40-foot elevation change to a 53-acre, heavily sloped site with large tree stands, a pond, and scattered archaeological sites.

•  Natural site drainage from the north to the south.

•  Practical site access limited to the northwest corner, the high point of the site.

The standard cut-and-fill approach to balancing the site would have disturbed most of the 53 acres and forced the removal of numerous trees, many of them old oaks with diameters over 36 inches. Instead, the Building Team made use of the slope to keep the impact to the site to a minimum.

This was done by positioning the structure at the mid-height of the slope with minimal disturbance to the site beyond the footprint. The building is organized along a central corridor spine that curves to follow the crest of the slope. Shared and public spaces, including the main entry, are located on the uphill side of the corridor on the upper level. Parking and drives are pitched to follow the natural slope.

Buried into the hill below these spaces along a 450-foot corridor are 21,000 sf of program areas that do not require natural light: the mechanical plant, electrical, telephone, and technology rooms, storage areas, locker rooms, toilets, music practice rooms, and storage for musical instruments, costumes, and sheet music.

On the downhill side of the central corridor are two-story classroom wings tucked close to the tree stands. With exits on the lower level, students have direct access to a sequence of outdoor science areas, environmental trails through the woods, and a stepped outdoor learning room hidden in the woods. The majestic oaks provide natural filtering of early morning to midday sunlight to the nearby classroom wings.

With a deep overhang on the uphill side and extending above the level of the classroom wings, a curved and pitched roof shelters the shared and public spaces on the uphill side from cold winter northwest winds. Winter winds enter the site at its high point and flow downhill to the building, where the roof directs the flow up and over the downhill stepping building masses below.

By shaping the building to follow the natural curving crest and locating it at the slope’s midpoint, the site’s primary water run-off swale was able to remain intact, naturally keeping water out of the building while collecting water along the drip-line of the wooded areas. The gymnasium, music and band spaces, and event commons are located on the lower-level downhill side of the central corridor and are partially buried into the hillside, further reducing the amount of exposed exterior wall. The strategies reduced the amount of exposed exterior wall by 7,800 sf over a cut-and-fill approach.

Perhaps best of all, sensitive placement and organization of the building preserved the entire stand of old oak trees.

Several lessons can be derived from the experience of this project:

 1. In general, nature—wind, water, the sun—will prevail. It is always better to take the time to understand the natural constraints of your site and work with them than to fight against them. Trying to beat nature usually turns out to be expensive and foolhardy.

2. Site Planning 101 demands that every project begin with a thorough site analysis that, along with the building program, establishes the initial design concepts. Regardless of where you think you want the building to be located and how it should be oriented, you must take into consideration how water will flow onto and off the site, the direction of the prevailing winds, and the path of the sun throughout the year.

3. Working with the natural conditions of the site can result in interesting and engaging K-12 architecture that is the most sensitive to the environment and beneficial to students, teachers, and staff.

DAYLIGHTING FOR IMPROVED CLASSROOM PERFORMANCE

Providing sufficient daylight to classrooms has become a worthwhile and commonplace strategy that is widely believed to enhance student performance and well-being. The definitive study of the performance and health benefits of daylighting in the classroom by Heschong-Mahone Group (“Daylighting in Schools: An Investigation into the Relationship Between Daylighting and Human Performance,” 20 August 1999, at: www.coe.uga.edu/sdpl/research/daylightingstudy.pdf) provides the most authoritative documentation available to Building Teams and schools officials on this subject.

Even without the scientific backing provided by Heschong-Mahone’s research, it is clear that most people prefer to work in natural light; this may be especially true for students in a classroom setting. There is also growing evidence that views to the outside provide stimulation that enhances performance (see /qa/access-views-essential-human-beings).The days of dark, dreary classrooms are, we hope, long gone.

However, getting daylighting right is not so easy, as even some of the most skilled practitioners have found. For example, green building pioneer Sandra Mendler, AIA, reported that, in a post-occupancy evaluation of several projects she had worked on, “While occupants expressed a high degree of satisfaction with having greater access to natural light, … some respondents also reported problems with light spill and glare” (“Thinking Inside the Box: The Case for Post-Occupancy Evaluation”). Failure to account for unexpected heat buildup from daylighting can also tax a school’s cooling system and throw the energy-use projections out of whack.

Fortunately, there are many more options available today in terms of controlling the kind of lighting that is desirable in classrooms. These include:

1. Vertical fins mounted on the exterior to control sunlight

2. Specialty glass to provide diffuse light

3. Integrated daylight sensors

4. Glass block and translucent wall panels

Vertical fins. For an elementary school in the Chicago suburbs, the Building Team sought to manage natural light through the use of overhangs, vertical fins, and specialty glass in the design. The design intent was to have 100% of classrooms and primary teaching spaces located on exterior walls, with wall-to-wall windows.

The design started from the assumption that the best-quality light comes from the north, providing diffused indirect light. For the east side of the building, which includes the school library and cafeteria, sun studies were conducted to determine the best angle for the installation of two-story vertical fins. These fins provide diffused light to these common spaces for the majority of the time they are in greatest use.

Floor-to-ceiling vertical fins, 48 inches wide and spaced 48 inches apart, were also used in two other Chicago-area K-12 projects to mitigate the light entering the school libraries from the west exposure and give the interiors a “northern light” feel. The large fins also became a pronounced architectural feature on the exterior curtain wall, while essentially blocking the direct west/southwest sun in the afternoon—a factor that the school librarians appreciated because direct sunlight can damage books and other library materials.

Specialty glass. For this same school, daylighting studies of a typical classroom window were conducted. One option that looked promising was the use of light shelves, which of course bounce light off their surfaces onto the white ceiling and deep into the room.

However, the team did not anticipate the response of the teachers, who were concerned that the light shelves would be hard to keep clean, and that they might even become a storage place for students’ clutter. As a result of this feedback, light shelves were dropped from the daylighting plan.

The design team then looked at specialty glass that would have penetrating qualities without the need to be bounced off a light shelf. Product research led us to an insulating glass unit in which the usual air space is filled with a honeycomb insulating core and a diffusing cloth is placed between the core and the glass.

The specified product (in this case, Solera brand from Advanced Glazing Ltd.) comes in a thickness of about three inches and has an overall u-value of 0.20, whereas the best one-inch insulating glass unit has a u-value of about 0.29. (U-value is the amount of heat in Btu that is lost through each square foot of building section (wall, ceiling, doors etc) per hour per degree of temperature difference between the warmer side and the cooler side. The lower the u-value the better.) The light transmittance varies from 22% to 73%, depending on the type of diffusing veil specified; this is comparable to the light transmittance from clear insulating glass. The translucent glass was used in the upper portion of the window assembly.

Integrated daylight sensors. Balancing natural light and artificial light has become much easier with the availability of today’s sensor technology. For ease of operation and maintenance, the Building Team has found it advisable to integrate the light sensors into the light fixtures. When daylight is available, the sensor dims the artificial lighting to maintain a set-point light level, typically 40-50 foot-candles. One of the benefits of such systems is that the dimming is so gradual that students don’t notice it, and therefore it does not interfere with classroom activity. And because the system is self-contained, the fixtures operate automatically, without any necessary interaction from teachers or staff.

Glass block and translucent wall panels. Glass block can be used to provide light transmittal in cases where initial cost is a factor, but Building Teams should be aware of its thermal properties: standard glass block has a u-value of 0.51. In its place, the team has found translucent daylighting wall panels (specifically, those from Kalwall) to have u-values of up to 0.08 with thermally broken integral I-beam support and a four-inch thick panel.

NATURAL VENTILATION – A BREATH OF FRESH AIR

The use of operable windows to provide natural ventilation in classrooms is a passive strategy that is gaining greater acceptance, particularly in climates with dramatically different seasons like the Midwest. First, however, Building Teams need to know and understand the direction of prevailing winds during various seasons for the climate zone they are building in.

For example, in typical Midwest sites, where the prevailing winds come from the northwest in winter and from the southwest in summer, classroom wings should be oriented with their long axes running in a northwest-southeast direction to minimize exposure to air seepage from winter winds and to maximize exposure to summer breezes for natural ventilation. Where possible, locating berms and non-deciduous trees on the northwest side of a site will help minimize the impact of the winter winds in the Midwest. Major entrances are best located to the east or southeast of a school in the Midwest; the building then shelters the entrances from winter winds and maximizes exposure to the sun, which can help in melting snow on sidewalks and entry plazas. Note: These recommendations apply primarily to school buildings in the Midwest; they must be adjusted to meet conditions in other climatic zones.

There seems to be a perception in the industry that mechanical engineers do not like the use of operable windows due to the impact they can have on the operation of the mechanical system. Operable windows can be successfully implemented into the design as long as several items are taken into consideration. The intent of operable windows is to provide the teachers and students a way to feel more connected to the outside, have more control over their environment, and be able to enjoy the benefits of fresh air.

Used properly under optimal outdoor conditions, natural ventilation can also reduce energy consumption in the building. For this to occur, two things must happen:

1. The size of the operable windows must comply with the applicable ventilation code. ASHRAE 62.1-2010, Section 6.4, states that the area of the opening must be a minimum of 4% of the net occupiable floor area. If a typical classroom is 900 sf, the minimum operable area of the windows must be 36 sf. Note: Since many classrooms only have windows on one wall, the maximum distance from the operable window that can be naturally ventilated is equal to two times the height of the classroom.

2. To actually save energy, control systems to turn the mechanical ventilation off when the windows have been opened, and to notify the building engineer if the temperature or humidity has drifted too far from the setpoint, must be in place.

By implementing these strategies, students and teachers will be able to enjoy the benefits of a naturally ventilated building while maintaining a comfortable environment and reducing energy consumption. 

INTERIOR DESIGN STRATEGIES TO ENHANCE STUDENT PERFORMANCE, SAFETY, AND COMFORT

Two interior design strategies that have proven effective in K-12 schools are 1) the use of translucent shade systems and 2) new flooring solutions: biobased linoleum, carpet tile, and epoxy.

Translucent window shades. Translucent shade systems, both manual and motorized, have been found to be an effective design system for use in conjunction with daylighting strategies in schools. This type of high-end roller shade (specifically, the MechoShade brand), which has been proven in corporate environments for over 20 years, utilizes a woven-mesh, vinyl-coated shade cloth that is easily wiped down, unlike the hassle of cleaning mini-blind slats. While these shades cost more than blinds, we have found their life expectancy and reliability of performance and maintenance to be unparalleled.

Translucent shades permit views through to the exterior landscape, while minimizing glare and heat gain in spaces. Note: It may seem counterintuitive, but darker toned shade cloth is easier to see through than lighter colors, which bounce light back toward the viewer. The shades are available in a variety of openness factors, depending on the sun exposure: Use a smaller openness factor on southern and western exposures and a greater openness factor on eastern and northern exposures.

Translucent shades provide a health and performance benefit to students and teachers, by allowing them to use distant viewing to “exercise” their eyes. This is especially important when students are using computers or reading intensely for extended periods. Health professionals recommend that to help prevent eyestrain, computer users should apply the 20/20 rule: Take “microbreaks” and look 20 feet away for 20 seconds to exercise the eyes.

Recommended Flooring Options for K-12 Interiors

Specialized composition tile. Vinyl composition tile (VCT) has long been popular in school settings, but it is facing competition from a biobased linoleum (manufactured by Forbo under the brand name Marmoleum Composition Tile, or MCT). MCT is made from 66% biobased materials, principally linseed oil and wood flour, and comes in 13X13-inch tiles. It is especially suited to K-12 projects because it requires less maintenance than VCT and never needs to be stripped. It also has a reasonable first cost, chiefly because it is thinner than tile or sheet linoleum (2.0 mm thick, vs. 2.5 mm for regular linoleum), and it exhibits the proven lifespan of linoleum products.

School facilities directors who prefer a shiny, wax-look floor may opt to apply protective floor finish coats, but this is not required by the manufacturer for the floor to be ready for occupancy. Recommendation: Building Teams should encourage clients to move toward low-sheen flooring materials that reduce glare in spaces and improve occupant comfort.

Carpet tile. While it is important for Building Teams to listen to clients’ preferences regarding carpet in schools, we recommend that school districts strongly consider carpet tile over broadloom. Traditional 12-foot-wide broadloom carpet used to be available only in monotone colors with no large-scale patterning; it can shows stains and develop odors over the years. In contrast, today’s generation of carpet tile offers significant benefits in education environments: 1) significant noise reduction in classrooms and corridors, 2) underfoot comfort for teachers standing for long periods, 3) ease of replacement for damaged areas, 4) slip resistance, and ) demonstrated indoor air quality benefits.

Carpet keeps airborne dust and particles from floating up into the breathing zone by temporarily catching dust at the surface until it can be properly removed by vacuuming. Carpet tile offers backing systems that are unaffected by moisture. These vastly improved backing materials do not absorb spills; common broadloom backings, once wet, never fully dry out. Stains sit on top of carpet tile, just like on other hard resilient floor materials, and rarely actually damage the nylon face fiber. Stains can be readily removed from the surface since they cannot penetrate the backing.

Recommendation: Building Teams should encourage clients to follow manufacturer-recommended cleaning methods of simply using warm water extraction and not excessively shampooing their carpets. Detergent residue is very difficult to completely remove from carpet fiber and acts like a magnet for dirt.

When carpet tile first became available, sometime in the 1970s, the goal was to make it look seamless, like broadloom. Current thinking embraces tile’s modular nature and multiplicity of patterns to accentuate its unique design capability.

Recommendation: Use more than one pattern of carpet tile within a given space so that different zones can be identified—circulation vs. main work areas—or to highlight a teaching wall or other focal point in a space. Carpet tile is unique in that multiple patterns can easily be incorporated in a design. The mix of patterns visually breaks up large expanses of floor and creates interest and clearer orientation.

Recommendation: Encourage school district clients to use larger scale patterns. This mix of patterns and colors can create interesting floorscapes that enhance architectural elements and define usage zones, while concealing dirt and traffic patterns. The more monolithic, or solid, a pattern is, the more it shows dirt.

The reality is that certain areas of carpet get walked on more than others. Even with proper maintenance, high-traffic areas like corridors may need replacement every 7-10 years; for classrooms and school office spaces, 10-15 years is a reasonable life expectancy. Tile enables you to preplan selective replacement without having to replace all of it. Selective areas that receive more wear can be easily changed out with new tile, without having to replace the product from wall to wall. Utilizing a mix of patterns can also define circulation areas and preplan for future replacement, without losing the original design intent over time.

Carpet tile can be installed without full-spread wet adhesives and with quick-release adhesives that enable tiles to be repositioned and replaced when necessary. Carpet tile has less waste (4%) than broadloom (14%); it is also much easier to recycle than broadloom. Recommendation: Check for manufacturer ship-back programs. Tile makers are eager to increase their post-consumer content and have developed programs that make it easy to send carpet back to be recycled.

One last piece of advice on carpet tile: Embrace the use of walk-off carpet tile. It’s not just for vestibules anymore. Extending walk-off carpet into lobbies and corridors vastly reduces the maintenance required for all floor types. Think about extending it for 15-20 feet into entry spaces. It’s more expensive, but it will pay for itself with reduced labor for cleaning, and it will last for decades.

Epoxy flooring. This material, once the flooring of choice in industrial settings, is an excellent flooring material for use in school restrooms, kitchens, cafeteria serveries, locker rooms, and showers—in fact, in any space that would benefit from a waterproof floor. Epoxy floors provide a seamless surface, slip resistance, and relatively easy maintenance. Installed properly, they cost far less than porcelain tile and there is no grout, which inevitably gets dirty in tile floors.

Epoxy doesn’t have to be a solid, dull color. By adding either broadcast colored quartz crystals or flakes of paint, epoxy can have as much color and pattern as is desired. Quartz crystals come in a variety of standard colors; the flakes, which can be added to the clear epoxy top coat, can be customized in any combination of paint colors. The result almost looks like terrazzo. BD+C

This completes the reading for this course. To earn 1.0 AIA/CES Discovery learning units, study the article and take the exam posted on Log In and Learn.