Reference Publication: McIlvaine, J., Mallette, M., Parker, D., Callahan, M., Lapujade, P., Floyd, D., Schrum, L., Stedman, T., Cumming, B., Maxwell, L., Salamon, M., "Energy-Efficient Design for Florida Educational Facilities," Prepared for the Florida Department of Education, Tallahassee, FL., September, 2000. FSEC-CR-1682-00.
Disclaimer: The views and opinions expressed in this article are solely those of the authors and are not intended to represent the views and opinions of the Florida Solar Energy Center.
Energy-Efficient Design for Florida Educational Facilities
Janet McIlvaine, Michele Mallette, Danny Parker, Michael Callahan, Philippe Lapujade, David Floyd, Lynn Schrum,
Ted Stedman, Brian Cumming, Larry Maxwell, Milt Salamon
Florida Solar Energy Center (FSEC), R. Douglas Stone Associates, Inc.,
Spacecoast Architects, Technical Editor
Revised September 2000*
In Dena Boer Elementary School in Salida, California, electric lights can be turned on (right), but daylighting alone provides quality light (left) with sufficient illumination levels at all desk top surfaces. In a recent study, such classroom daylighting design was found to be strongly correlated with improved student testing performance and attendance. In Florida, energy reductions for the facility have been demonstrated as well (Courtesy Pacific Energy Center).
a. Cooling Systems:
Large facilities: Central chiller for facilities with total loads greater than 150 tons. Screw or centrifugal chillers should be specified with minimum kW/ton. Chiller drives can be electric or natural gas depending on relative price of fuels. The decision between air, water-cooled and evaporative condensers should consider the appropriate trade-offs between first cost and system performance. With water-cooled condensers, cooling tower size should be subjected to a careful analysis. Primary/secondary pumping with variable speed pumps should be specified for chilled water systems.
Small or medium sized facilities: Select high-efficiency packaged or split systems for educational facilities with total loads less than 100 tons. Packaged VAV systems may also be considered. Variable speed indoor air handlers can provide superior humidity control to constant speed equipment. However, pre-treatment and dehumidification of introduced outside air is a necessity with packaged equipment. Select the highest system cooling COP, EER, IPLV, or SEER. For heat sources consider using heat pumps or natural gas with straight cooling systems. Hot-gas bypass and re-heat should be avoided. Improved dehumidification can be achieved by choosing low SHR (sensible heat ratios) for equipment within a given efficiency level and never oversizing packaged or unitary equipment used to serve space conditions. Dedicated dehumidification systems may be appropriate when high classroom ventilation rates are called for.
Air Handling: Variable air volume systems, four-pipe fan coil, or constant volume systems with face and bypass dampers should be specified for projects not using packaged systems. Variable speed fans should be used with VAV systems for larger motors. Outside air should be added to such systems with a central fresh air unit, preferably with heat recovery from the exhaust air stream either using heat pipes or a heat recovery ventilation system. Fan-powered VAV boxes should be avoided or reheat will be necessary for low load operation. If reheat must be used, choose non-electric sources, either natural gas, solar or condenser heat recovery.
Duct systems should be well sealed and pressure tested prior to occupancy. The duct system should be located within the envelope insulation. Larger systems should be controlled by an energy management system (EMS) with optimal start capability. CO2 sensor ventilation control should be considered for intermittently used facilities. Air handling equipment should be balanced and commissioned prior to acceptance.
Current research suggests that ASHRAE Standard 62 recommendation of 15 cfm per person should be considered as a minimum outside air ventilation rate for classrooms (as potentially modified by average versus design occupancy). However, natural ventilation and economizer cycles were found to provide only very small savings benefits (<2% reduction in energy use) due to the high humidity levels in Florida and are likely not cost-effective. In any case, enthalpy economizers should be used in any installation considering the use of economizer cycles. The high first and maintenance costs should be carefully weighed before specifying.
However, other means of dehumidifying ventilation air is very effective: ERVs, heat pipes etc.
Operable windows should be provided in classrooms as this has been shown to decrease the frequency of complaints regarding perceived poor indoor air quality.
Dehumidification of outside ventilation air will be required if a 15 cfm/person ventilation rate is adopted for the facility. Electric or baseboard reheat must be avoided. Hot-gas bypass should also be avoided with packaged systems. A preferred alternative for packaged equipment is to choose high efficiency units with low operational sensible heat ratios (SHRs). Variable speed air handlers will improve space dehumidification in this fashion and are strongly recommended.
Optimum system design will precondition the outside air prior to its being introduced to the indoor environment. For this, a central fresh air unit is advisable using one of the following dual-path technologies: a dedicated DX system, heat pipes, run-around coils, or a total energy recovery system. Face and bypass dampers can be used with constant volume systems. Second-stage air conditioning and humidity removal of the outside air is performed prior to its introduction to the conditioned environment, using the conventional system either with chilled water or DX coils.
The project team gratefully acknowledges
the support of Suzanne Marshall and her associates at the Florida Department
of Education, Office of Educational Facilities, who funded the research
and development of this manual.
This document provides a detailed simulation analysis of a variety of energy conservation measures (ECMs) with the intent of giving design teams a basis for decision making. Designers are advised to aim for the lowest consumption building economically possible and to target the major energy users, lighting and air conditioning, to achieve that goal.
energy cost ($)
is provided for comparing relative performance of ECMs. Simple
payback of ECMs appears in a chart in each section's Overview.
Life cycle cost savings appear in the Conclusions section.
This manual addresses energy efficiency options for new educational facilities in Florida. The recommendations may not be valid when considered outside Florida's hot humid climate or for purposes other than new construction.
Construction funds spent on new construction
heavily outweigh (67%) those spent on retrofit, as reported in an annual
statistical analysis published by American School and University (September 1992). The comprehensive survey showed that construction funds
for new educational facilities nationwide have risen for eight consecutive
years, and no region has experienced more growth than the Southeast. Currently,
funds spent on energy services (excluding capital outlay, salaries, benefits,
and transportation) account for about 14% of the current expenditures (i.e.,
operating cost) in Florida schools (Eggers, 1994). Data represented in
this work shows that for a new facility, energy consumption can be reduced
by 43% compared to current construction and design practices with a cumulative
life cycle saving of over a quarter of a million dollars for a single classroom
As a matter of public responsibility, the Florida Department of Education (DOEd) encourages designers to carefully consider the potential operating savings of available ECMs.
This manual has been written for all members of the design team, including school board members, educational facilities planners, architects, and engineers. Both the expert and novice are served by this manual as it includes information on new technology and research as well as the basics of building energy use.
Understanding the "big picture" is paramount in energy efficient design. Readers are encouraged to review the section Overviews and energy Strategy summaries as a unit. With a clear understanding of how the various aspects of design affect the building as an energy using system, readers will find that the best choices become more obvious.
This manual has been written to provide
reliable, non-biased information on ECMs. Although the simulation studies
in this manual represent general building types, they offer a comprehensive
comparison of energy design options for Florida's new educational facilities.
Each new school design must satisfy a variety of requirements, with safety and education obviously having top priority. Energy conservation strategies and technology must not compromise the safety or the quality of an educational environment. Measures which compromise education to save money are a false economy.
Design teams should consider school safety issues such as evacuation, emergency shelter functions, unauthorized access, vandalism, and theft when an ECM is being assessed. Questions such as the following should be considered:
A critical priority is cost. Schools must be built, operated, and maintained within an allotted budget. Design teams must weigh the first cost of ECMs against annual or lifetime savings. While ECMs reduce energy consumption and operating costs, they often cost more than conventional practices. Furthermore, maintenance costs should be kept in mind.
Design teams should pose questions such as:
The cost effectiveness of an ECM can be evaluated in a variety of ways. Simple payback and life cycle cost analysis are two commonly used methods. Life cycle cost savings for each ECM appear in the Conclusions section, Tables 1-3.
Annual energy cost savings for each ECM
or combination of ECMs appear in the body of the manual. However, this
method of cost effectiveness evaluation does not satisfy the Department
of Education's life cycle cost analysis requirements. It only provides
a method of comparing the relative performance of different ECMs.
Energy Analysis Methodology
Likewise, the energy saving potential of an ECM can be evaluated in different ways. The method chosen for this analysis is a comprehensive computer simulation tool called DOE 2.1E, a building energy simulation software developed by the U.S. Department of Energy and Lawrence Berkeley Laboratory. The techniques used to estimate potential energy savings of the ECMs in this manual are similar to the methods used in energy efficiency research throughout the United States.
Three building types were selected for study:
These commonly appear on the campuses of elementary and secondary schools in Florida. (Larger, more complex versions of these buildings can be found on community college and university campuses.)
The physical characteristics of these three building types were modeled using DOE2.1E and are referred to as Base Case Buildings.
Next, the characteristics of the Base Case Buildings were changed to simulate the effect of each ECM on the building's energy cost.
Last, these figures for each of the ECMs were compared to the Base Case figures. Those measures that lowered energy use or energy cost were then evaluated for cost effectiveness (using life cycle cost analysis).
Two sets of input data were required to execute the simulations for each building type: one set of physical and operational characteristics for each building type and a set of characteristics for each ECM. The characteristics used to model the building types came from
Characteristics used to model the ECMs
came from laboratory or field data, engineering handbooks, discussions
with experts in building energy efficiency, or predefined options available
in DOE2.1E. Appendix A, Simulation, documents the assumptions.
Organization of the Manual
Manual: The format of the manual emphasizes that energy efficiency should be considered throughout the design process. It is divided into three sections (Figure 1).
Figure 1. The bulk of the manual is housed in three main sections:
Schematic Design, Design Development, and System Design.
Sections: Each of the Sections begins with an Overview of the energy saving strategies appropriate for that design phase. After the overview, energy conservation strategies are presented. Each strategy's objective and considerations are summarized and ECM Options (specific ways of accomplishing a strategy) are listed.
ECMs: Each ECM option is discussed separately, and simulation data on annual energy cost ($) are presented as bar charts (Figure 2). For assistance in interpreting this data, readers may contact the Building Design Assistance Center (address on page 2).
Figure 2. Simulation results are presented as bar charts for comparing performance of different ECMs.
1. Daylighting has been shown to be important not only for energy related characteristics, but also in the students abilities to learn. A recent study in Seattle, Washington, Orange County, California, and Fort Collins, Colorado quantified daylighting effects on student learning. Students with the most daylighting in the classrooms progressed faster on math and reading tests and daylighting may play a role in better student attendance, improved mood and behavior (Heschong Mahone Group, 1999).
2. Research in a pair of portable
classrooms in Volusia County has shown that T8 lamp electronic ballast
lighting systems saved 35% in energy use over the typical T12 magnetic
ballast lighting system (Callahan et al. 1999).
* Prepared for:
Florida Department of Education
Office of Educational Facilities
325 W. Gaines St.
Tallahassee, FL 32399