High Schools

General

High School Hallway

Most high schools are low-rise structures of medium size with a central core area for offices and administration, and wing-type construction for classrooms; however, some large high schools can approach the complexity of a small college. There is usually a small gym with that can typically seat a couple hundred to a couple thousand people, depending on the student body population of the high school when it was built. There may also be a number of classroom trailers required prior to and during construction of school additions, depending on the immediate growth in the area. Teaching approaches keep changing from individual classrooms to open-plan layouts and back again: open-plan schools have portable partitions that are changed frequently. Due to the ever-changing teaching approaches and layouts, the HVAC system design must be flexible in order to accommodate all of it.

The key building energy system's electrical loads are lighting and HVAC systems. Cafeteria loads - cooking, ventilation, lighting, and even water heating - can be significant in some areas depending on the availability of natural gas. With the advent of computers, office equipment is a rapidly increasing load for many schools - especially for those that administer individual laptops to their students during the school year. Nevertheless, most electricity is still consumed in the lighting and cooling systems.

Key Considerations

  • Construction materials (amount of glass areas, insulation, etc.) and orientation to the sun
  • Occupant use and maximum occupancy characteristics (especially time of day)
  • Lighting levels and lamp source efficiency (which affects the cooling and heating loads)
  • The time and seasonal value of fuel and power use in building design alternatives
  • Floor loadings for office equipment and specialized lighting
  • Availability and price of water for potential cooling system use
  • HVAC equipment should be simple to operate and require no skilled personnel

Most high schools will have large auditoriums, science labs, shops, computer labs, pools, gyms, and cafeterias. Please see the discussion of these space designs elsewhere in this library.

Schools are typically designed for a long life under difficult occupancy conditions and tend to be of high quality construction. Due to bond issues and funding with scarce tax dollars, the desire for visible amenities predominates. During original construction, energy conservation and recovery concepts that raise the first cost, but lower O&M and life cycle costs are difficult to justify. However, energy retrofits for the lighting and HVAC systems have successfully been promoted with some of the savings going towards amenity improvements - e.g. a school might get new lights and new Smart Boards with the savings from the energy retrofits. This is known as performance contracting.

HVAC

The HVAC systems will vary widely and are largely dependent on the size, age, and geographical location of the school. In past years, ventilation-only dominated; however, most new schools are air conditioned. The current trend is to use central or rooftop systems for administrative and common areas, and PTAC or geothermal heat pumps with individual controls for the classrooms. In climates with low heating loads, electric resistance heating is often used for the primary or secondary (for heat pumps) heating source. This design maximizes scheduling flexibility for the off peak uses, like PTA meetings, parent/teacher conferences, and other school meetings.

The gymnasium, cafeteria, and other large, stand-alone areas usually require their own systems, because of their unique loading characteristics. Cafeterias may have heat pump water heaters or heat recovery water heaters included in their systems.

Proper ventilation is necessary to control odors and avoid "sick building" syndrome. Provisions should be made to shut any outdoor air dampers when individual zones or rooms are unoccupied. Many areas have stringent codes regarding fire, smoke, building design, ventilation, and noise control. In many cases, noise production and protection from vandalism must also be considered. As an alternative to roof-top equipment, geothermal heat pump systems are increasing in popularity as they have no outdoor equipment to create noise or be damaged.

Energy Saving Recommendations

Energy conservation concepts should be simple: cooling interior spaces with outdoor air-using economizer cycles, night setback in individual areas, and outdoor air damper control during the system shutdown at night. Water-loop heat pump systems may also be used to conserve energy if the building has significant interior zones. In fact, it may be possible to justify upgrading to higher-efficiency equipment, or even a complete redesign to geothermal heat pumps, as existing HVAC equipment ages and must be replaced. Some designs combine thermal storage, where excess heat generated during the day is stored and used for heating at a later time

Water Heating

Service water heating is needed for janitorial work, restrooms, cafeterias, and occasionally for shower rooms and swimming pools. Cafeterias, shower rooms and swimming pools usually have their own water heating systems due to loading and temperature characteristics. Hot water used in cafeterias is about 70% of that usually required in a commercial restaurant, but can still be estimated with the same method used for restaurants. Where NSF sizing is required, follow Standard 5.

Shower and food service loads are not ordinarily concurrent. Each should be determined separately, and the larger load should determine the size of the water heater(s) and the tank whenever a single system is going to supply both loads. However, separate systems are usually required since most "field houses" are isolated from the main school. Provision must be made to supply 180°F sanitizing rinse in the kitchen, usually with electric booster heaters. The booster must be sized according to the temperature of the supply water.

A separate water heating system for swimming pools can be sized as outlined in the section on Swimming Pools\Fitness Clubs.

Requirements for high schools are based on daytime use. Recommendations do not take into account hot water usage for additional activities such as night school. In such cases, the maximum hourly demand remains the same, but the maximum daily and the average daily usage increases, usually by the number of additional people using showers and, to a lesser extent, eating and washing facilities.

Energy Saving Recommendations

Most energy conservation measures regarding water heating in schools will be about supplementing cafeteria water heaters with either heat pump water heaters - located in the cooking area - or heat recovery water heaters attached to the refrigeration systems. If a central water heater is used for restrooms or laboratories, then point-of-use water heaters will also provide good payback. Please refer to the Water Heating section for more detailed assistance.

Cooking

High School Kitchen

Food in schools is typically served Cafeteria-style and consumed by students and teachers who take their trays to indoor or outdoor tables. However, pre-planned meals with menus published in advance are becoming more prevalent.

Energy Saving Recommendations

The predominant energy source for school food service has trended toward natural gas. However, some school systems are realizing the overall benefit of electric cooking due to ventilation reductions and personal comfort of the cafeteria staff. Please refer to the Food Services section for additional assistance regarding electric cooking options.

Lighting

Clasroom Lighting

Most of the space in schools is dedicated to classrooms. A typical classroom design will accommodate class sizes of up to fifty students. There will usually be a Smart Board and/or whiteboard on one or more walls, and there may be windows to provide natural light in the room.

Adequate light levels of 50 to 100 footcandles are needed for both the horizontal work surface of desks and the vertical plane of whiteboards and computer screens. The individual school often sets the standards for the minimum acceptable number of horizontal footcandles required in a classroom.

Energy Saving Recommendations

Classrooms for special purposes like science, art, or engineering may require special task lighting. Therefore, it is imperative that uniform light levels, and lamp sources with 3500K to 4100K color temperatures and at least 70 CRI are used. T-8 fluorescent lamps, especially triphosphor types, are an ideal choice.

Classrooms with high ceilings are good candidates for a suspended direct/indirect combination fluorescent fixtures, which significantly reduce the glare on work surfaces. Lower ceilings will require either surface-mounted or recessed fixtures; however, recessed fixtures may be better in this situation, because they're less obstructive. If the classroom is a computer lab, then use high VCP fluorescent fixtures to ensure good glare-control. Providing flexible switching, such as partial fixtures or partial lamps per fixture is recommended. This allows for lower light levels while watching movies or using other audio/visual equipment.

Most lighting efficiency upgrade opportunities will range from upgrading T-12 to T-8 fluorescent and incandescent lightbulbs, to installing LED exit signs. Older gymnasiums may be lighted with incandescent or mercury vapor and thus offer upgrade potential to pulse-start metal halide. Conversion to the pulse-start metal halide can also be justified for some older metal halide systems.

Energy Management systems (EMS), especially Direct Digital Control (DDC) systems, are the most practical options for scheduling before- and after-hour events. Traditionally, HVAC systems are left running or are not available at all for special events, and lighting systems may be left on overnight if a special interest group has their meeting and walks away without switching things off. Thus, simple EMS systems should be located in the school maintenance and/or administrative office where lights and HVAC can be scheduled and controlled.

Additional Information

The trend in school electrical system designs is to place a new service and utility meter in each addition. The original school likely had at least two meters - one for the school and one for the gymnasium. It may be in the school's best interest to use a primary meter to reduce electric cost.


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