Shades Of Green
- By Michael Fickes
- January 1st, 2005
Maryland’s Montgomery County Public School District combines many environmentally friendly construction techniques in search of the darkest shade of green schools.
Green school construction is a cumulative concept. A building designed around an energy-efficient heating, ventilating and air conditioning (HVAC) system might, for example, be considered green. But additional green techniques can transform a building from lighter green to a darker shade of green.
According to Anja Caldwell, green schools program manager with Montgomery County Public Schools (MCPS), the combination of five key design elements can give a new school a deep shade of environmental green: site selection, building orientation, energy systems, specifications related to indoor air quality (IAQ) and water systems.
Managing energy use in a school building begins with site selection, Caldwell says. Typically, school administrators consider just about any site of acceptable size recommended by developers. In a school district focused generally on sustainable and energy-efficient building construction and operational goals, however, preferable building sites offer access to public transportation, existing roads and existing utilities.This not only cuts the cost of construction, it also eliminates the need to build new roads and lay new utilities on land you may want to conserve, Caldwell says.Another site consideration is to locate schools near students, so you can have walkers, cut fuel consumption for the school bus fleet and reduce engine emissions.
Caldwell also contends that proper building orientation can supplement an efficient HVAC system and reduce energy requirements by as much as 50 percent. Orientation decisions must be made very early, in conjunction with site selection, she says. A good site permits the architect to orient the building along an east-west axis with classrooms set on the north and south sides.
A north-south classroom orientation reduces a building’s energy requirements. In summer months, classrooms on the north side of a building will heat up slowly and require less air conditioning. Since fewer students use schools during the summer, classroom assignments can favor the north side. In the winter, classrooms on the south side of the building will benefit from solar heat and reduce a building’s overall heating requirements.
Building orientation is also about indirect daylighting, Caldwell says. Studies show that students do as much as 26 percent better if they work in classrooms exposed to indirect daylight, compared to direct daylight and artificial lighting.
Indirect daylight refers to reflected rather than direct sunlight. When sunlight comes from the west or the east, the sun’s rays come in low and penetrate glass windows, producing glare and heat build up. Classroom windows on the north and south walls of a building admit reflected or indirect light acceptable for classroom daylighting design schemes. Additional design elements, such as roof overhangs and interior and exterior light shelves placed above windows, can further reduce solar heating without hampering indirect day lighting designs.
Recent increases in electricity and natural gas prices have led to large increases in energy budgets for schools across the country. In the MCPS district, for example, facility managers have asked for a 2004-2005 school year budget increase of $3.2 million.
Rising utility costs have also generated new interest in alternative lighting and HVAC concepts. The MCPS district is switching to more efficient lighting schemes in existing and new schools — from T-12 lamps to more efficient T-8 lamps — and to daylighting designs wherever possible.
The district is also evaluating geothermal heating and cooling systems. This is our system of choice today, Caldwell says. Geothermal technology is a way to harvest the heating and cooling energy of the earth. And the energy is basically free.
Geothermal systems pump water from deep below the earth through closed-loop networks of pipes in building cooling systems. Borings or wells capture the water, which exists at a constant temperature at depths of hundreds of feet. During the summer, the temperature of deep-earth water is cooler than the temperature of the air at the surface. So it can cool the air flowing through a heat exchanger. Conversely, the earth’s water is warmer than surface temperatures in the winter and can heat the air flowing through a heat exchanger.
While geothermal systems cost more to install than conventional HVAC systems, Montgomery County schools make HVAC decisions based on lifecycle costs instead of initial costs, in accordance with state law. The state of Maryland requires that HVAC systems for new schools prevail in a lifecycle analysis comparing at least three different systems. In designing new buildings, MCPS compare geothermal, two-pipe and four-pipe HVAC systems. So far, geothermal has come out the winner. Despite a higher initial cost, savings during the life of the system makes geothermal the economical choice, Caldwell says.
Many commercial buildings don’t have the acreage to install a geothermal boring and piping system. But MCPS uses nearby athletic fields to fuel geothermal systems.
So far, the district has installed geothermal systems in two schools, with three more expected to come on line within a couple of years. The two we’ve installed work well, but we’re really just learning about geothermal systems, Caldwell says. One thing we have learned is that these systems need much less maintenance than conventional systems.
Indoor Air Quality
Dark green school construction goes beyond energy efficiency and deals with environmental issues such as IAQ. Our IAQ goals include removing formaldehyde from doors, cabinetry, shelving, desks and other plywood furnishings, Caldwell says. We also want to eliminate volatile organic compounds or VOCs from our paints, adhesives and carpeting.
The district now specifies strawboard casework and furnishings that use environmentally friendly resins instead of formaldehyde-based glue. Similarly, the district specifies wall insulation free of formaldehyde.
Caldwell adds that the district has begun to specify paints and adhesives manufactured without VOCs that create IAQ problems through off gassing. Finally, the district requires new carpets to undergo off gassing prior to installation.
Caldwell’s team is testing water conservation techniques, such as waterless urinals, double-flush toilets and storm water cisterns that provide gray water to flush toilets.
Waterless urinals dispose of urine in an oil trap. While the process may sound smelly, product manufacturers say that urine only smells when in contact with water. We’re testing these devices, and if they work, we’ll use them more widely, Caldwell says.
Double-flush toilets provide two flushing handles. One handle flushes 1.6 gallons, while the other flusheshalf of that amount. The half flush is enough most of the time and will save a lot of water, Caldwell says.
Using underground cisterns to collect storm water to flush toilets is a relatively new idea. Caldwell’s group is evaluating the cost of a system but has made no decision about building one.
The Cost of Green Construction
Doesn’t it cost more to design schools with these kinds of green features? For the past year, I’ve been telling our construction team that green buildings don’t cost appreciably more than conventional buildings, Caldwell says. They’ve taken me at my word, and we’ve jumped into some projects with no extra budget allocation for the green features.
Caldwell isn’t alone in believing that the costs for green and conventional school construction compare well. An October 2003 study entitled The Costs and Financial Benefits of Green Buildings, commissioned by California’s Sustainable Building Task Force, compared the conventional and green construction costs of 33 buildings, including eight schools. The task force found that green designs carried an average cost premium only 1.84 percent higher than conventional designs.
As the quantity and quality of green features increased in the buildings studied, the green premium tended to rise. At the lightest shade of green, the premium was 0.66 percent. At the highest deep green level, the premium totaled 6.5 percent. Caldwell is currently putting the theory of reasonably comparable green and conventional building costs to the test in bidding Northwest Number 7, an 80,000-sq.-ft. elementary school in Germantown, Md., designed as a high-performance, sustainable green school. Scheduled to open in September of 2006, the school will use nonVOC furnishings and carpet, a daylighting scheme, classrooms oriented to the north and south, energy-efficient plumbing and a geothermal heating and cooling system.
We’re also pricing a storm water collection cistern to flush the toilets, but we know that will drive the cost of the building above our average square-footage costs, Caldwell says. We may or may not build the cistern with this school. The idea is to determine what this technology will cost so that we can adjust the capital budgets of future projects.
With the bids due back soon, Caldwell is betting the overall cost for the new Germantown elementary will compare well with the MCPS average cost per sq. ft. for school construction, which currently stands at $115, plus an additional factor that related to recent increases in the prices for steel and other construction commodities.
This is an exciting time, Caldwell says. The numbers look good in the California study. Still, I’m a little nervous because costs in California may differ from costs in Maryland. When the bids come back, we’ll know for sure if the costs really match up.