Page 14 - School Planning & Management, October 2017

WHOLE DESIGN
EVERYTHING IS CONNECTED
To increase energy efficiency, designers should not simply “plug and play” vari- ous sustainable elements. Viewing whole systems and how they intersect and overlap each other provides greater results while lowering unit costs. For example, when considering a geothermal heating and cool- ing system, effective solar shading, limited east and west building exposures and increased thermal insulation of walls and roofs will reduce design loads and result in fewer wellfields and the site area required for them. The number of solar panel arrays needed to facilitate a net-zero facility can be lessened to the degree daylight harvest- ing, efficient lighting controls and high- efficiency lighting and equipment is used.
For mechanical systems, the largest loads are typically incurred by outside air requirements. Energy recovery ventila- tion, pre-treat systems, and tempered return air are strategies to consider. The use of bipolar ionizers allows for code reductions in outdoor air intake rates
by improving indoor air quality. Energy modeling at early phases of a project
can inform big picture design decisions. For renovations, it is beneficial to select energy upgrades that are a part of an energy use reduction masterplan, so that
decisions over time build upon each other. In addition to geothermal heating and
cooling systems that are effective in south- ern states, a Variable Refrigerant Flow system is an energy efficient option that
is gaining traction in school design. VRF (VRF)systems provide precise zoned con- trol that operate only at the levels needed to maintain a constant, comfortable indoor environment and have the benefit of allowing adjacent spaces to be cooled or heated at the same time. When the district and Corgan were considering an HVAC system for the four-story classroom wing addition to Grand Prairie High School, a VRF system was chosen as a more energy efficient, flexible solution than expanding the school’s chilled water system. Land was also not available for a geothermal system, and greater floor heights and large chases would have been required for the ducting of packaged roof top units.
The building envelope should also be analyzed as a complete system. Passive heat load reduction is a first line of defense. At
Hastings Elementary School for Duncan- ville ISD, horizonal overhangs and vertical fins on the building elevations minimize di- rect solar exposure. North facing light wells penetrate the main corridor at Ladybird Johnson Middle School in Irving, bringing diffused light into the building core.
Increased R-values in exterior walls have less impact without additional roof and crawlspace insulation and weather- tight building openings. For several years, Frisco ISD has incorporated Insulated Concrete Form (ICF) exterior walls and R-30 roof insulation as their district stan- dard. ICF walls are filled with concrete between two layers of rigid insulation formwork. These walls provide up to an R-40 insulation value, greatly reducing heating and cooling loads. The system has additional benefits of increased storm resistance and faster construction.
Sandy McNutt Elementary School
Ladybird Johnson Middle School
Hastings Elementary School for Duncanville ISD
14 SCHOOL PLANNING & MANAGEMENT / OCTOBER 2017
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SYSTEMS