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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

FSEC-CR-1682-00

 

Revised September 2000*

 

 

Table of Contents

Recommendations
Introduction
Section I - Schematic Design
Overview
Energy Strategies: Optimal Orientation
Building Configuration

Section II - Design Development
Overview
Energy Strategies: Glazing Selection
Window Shading
Enhanced Envelope

Section III - Systems Design
Overview
Energy Strategies: Efficient Electrical Lighting
Efficient HVAC Systems

Conclusions

Case Studies

References and Bibliography

Glossary

Appendix A: Simulation

 

 

Recommendations

Daylighting

  • Concentrate during schematic design on properly orienting the building and laying the foundation for daylighting and determining which strategies and Energy Conservation Measures (EMS) will be incorporated during design development.
  • For the design of a low energy facility designation of daylighting zones is important. Making this effort will provide a good foundation for a daylighting scheme.
  • If optimal orientation and daylighting zones are not feasible for a given facility, it is advisable to pursue those strategies and ECMs not related to daylighting: Glazing Selection, Enhanced Envelope, Efficient Lighting System Components, Occupancy Sensors, and Efficient HVAC Systems.
  • Based on emerging research on student performance and attendance as well as energy use reduction, quality classroom daylighting should be given a very high priority within the design process. (1)

Photo comparison of empty classroom : one with skylights only, one with skylights and fluorescent lighting.

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).

  • Effective daylighting is complex, but a combination of both windows and overhead sources (skylights or monitors) seems most productive.
  • To provide energy savings, reduce the density of light fixtures along the classroom perimeter or provide an automated daylight dimming system.

Glazing Selection

  • For daylighting applications, select a double-pane solar control glazing whose visible transmittance is greater than is shading coefficient or a spectrally selective glazing (typically very high visible transmittance).
  • For any exposed east- and west-facing glazing, select an insulated glazing with a shading coefficient of 0.5 or lower. Double pane or insulated glass is important to promote even interior comfort as well as sound control
  • If low shading coefficient glazing is not selected for east, west and south exposures, plan for exterior shading from shading devices, building elements or shade trees (see Window Shading).

Window Shading

  • Provide exterior window shading, preferably with fixed covered walkways, or architectural features such as overhangs or awnings, to minimize the need for interior blinds and associated reductions in available daylight. Where interior blinds are provided use light colored materials.
  • Properly size horizontal window shades and provide them on the south side of the building to prevent glare and localized overheating.
  • Consider light shelves on south windows for daylighting applications to project light into the building interior while blocking direct solar onto areas adjacent to the glazing.
  • Use horizontal and vertical shades for any large areas of east and west glazing.

Enhanced Envelope

  • If possible use a white reflective roof finish. This will provide energy savings of 10% or more. Energy savings may be twice this level if supply air ducts or chilled water lines pass through a plenum space between the roof and insulation located on the ceiling. Reflective roofing can be accomplished at virtually no cost by choice of white colored materials. These include white metal roofing, white single-ply roofing membranes and white concrete tile.
  • Code levels of insulation for educational facilities are adequate. However, modest savings (~3%) can be produced by increasing the ceiling insulation levels R-30. Additional wall insulation beyond code levels is not effective.
  • Use light colored finishes for building walls. This is essentially a no-cost option.
  • Strategically planted shade trees may offer some energy savings at a low cost if planted as seedlings. Locate trees on east, west and south sides of the building which are otherwise difficult to shade. Allow for future growth in their location. Can promote interior visual comfort.
  • Overhangs provide energy savings and are very important to glare control if no other means of south window shading is available. Properly size the overhang length based on window height and separation from the roof line.

Efficient Lighting

  • Choose an efficient combination of lamps, ballasts, diffusers and proffers for the facility lighting system. The use of T-8 lamps with an electronic ballast and an appropriate luminaire are increasingly used and are preferred in all cases.(2)
  • Consider lower ambient interior lighting levels with task lighting for non-classroom spaces with heavy use of video display terminals (VDTs).
  • Specify fluorescent or LED type exit sign lighting.
  • Use occupancy sensors to control spaces with changing occupancy. Specify that such controls will be commissioned such that time delays are properly set and device sensitivity is adjusted. Based on two retrofit projects conducted for the Department of Education, while bathrooms and hallways are good choices, classrooms may not be. In any case, lighting energy savings from occupancy sensor use in classrooms cannot be expected to be greater than 10%. If coupled with control of HVAC systems in portable classrooms, however, saving may be very attractive.
  • Use continuously dimming electronic ballasts with photosensors to control electric lighting in daylit zones. Specify that such systems be commissioned to ensure that controls function properly and light levels are adequate during non-daylit hours.

Heating, Ventilation and Cooling

  • The many HVAC options available to schools reduce to a few options which have superior performance. These are:

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.

b. Ventilation

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.

c. Dehumidification

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.

 

Acknowledgments

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.


Introduction

Description

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.

Reductions in 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.


Mission

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 building.

As a matter of public responsibility, the Florida Department of Education (DOEd) encourages designers to carefully consider the potential operating savings of available ECMs.


Audience

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.


Priorities

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:

  • How will this ECM at this facility affect the basic functions of the school?
  • Will this ECM impede proper evacuation in an emergency?
  • If this measure or device is damaged by wind or lightning, will it disrupt normal school operation?
  • Will the ECM allow inappropriate access to any part of the facility, such as the roof, courtyards, etc.?
  • Will this strategy facilitate vandalism or provide vandals with cover?

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:

  • Can the regular operations staff maintain this ECM? If not, is reliable service available for this product or equipment?
  • How often will this ECM need service and how will that affect the normal maintenance schedule of the school?
  • If an ECM requires outside maintenance service, will the cost outweigh operating savings?
  • When will this ECM have to be replaced?


Cost Effectiveness

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:

  • a classroom building
  • an administrative building
  • a multipurpose assembly building.

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

  • Blueprints of recently built schools
  • Discussions with architects and engineers
  • Discussions with school operations staff
  • Site visits to new schools.

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
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

Figure 2. Simulation results are presented as bar charts for comparing performance of different ECMs.

 

Page 2 | Page 3 | Page 4 | Page 5

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