Born to Run
August 01, 2007
Appeared in American School and University
Colleges and universities need to support their basic science research and education missions. At the same time, they must be vigilant about upgrading or replacing aging infrastructure, and finding ways to attract top faculty and students. To satisfy all these demands, higher-education institutions are constructing state-of-the art science facilities. Schools expect these new facilities to last for the next 50 years, so they want reliable mechanical/electrical/plumbing (MEP) systems that can support a flexible teaching and laboratory environment.
Achieving these goals requires an integrated planning and design approach. Design of an energy-efficient mechanical system depends, in particular, on the effective orientation of the building in relation to the sun; the design of the building envelope and roof for maximum efficiency; and space planning that segregates building uses, and allows for varying cooling and ventilation requirements. Extensive energy modeling at the planning stage of a project can help ensure that materials, systems and design decisions will deliver the desired results.
A typical benchmark used in designing an air-handling system for a modern science building is to provide 2.0 cfm per square foot for a facility that will house conventional laboratories and 2.5 cfm per square foot for those that include a vivarium, although these figures will vary according to the specific program requirements. Depending upon an institution's master plan, a school should consider increasing the capacity of the MEP systems or make provisions to allow for a future expansion. It is not unusual for air-handling units to be sized up by 10 to 20 percent to accommodate expansion.
Rather than relying on a single air-handling unit to provide total capacity, the system should be designed with multiple air-handling units using manifolds or interconnections to allow shared capacity. This design provides redundancy, ensuring reliable operation in the event that scheduled maintenance or equipment breakdown takes a unit out of service.
The MEP team also should analyze the viability of a variable-air-volume (VAV) control system for the project. In a VAV system, the amount of supply air delivered to the space is regulated based on thermal requirements and operating conditions. If a facility primarily will house classrooms and teaching laboratories, it will require maximum air volume when classes are in session and minimum air volume when they are not. Alternatively, two-position controls allow for occupied and unoccupied operational conditions only. The cost of a VAV control system may be justified based on life-cycle energy savings.
A heat-recovery system is a worthwhile investment for many institutions. These systems operate by capturing energy from exhaust streams, which is returned to supply streams. Heat exchangers and heat wheels, where appropriate, can be used for this purpose. Heat-recovery systems will reduce heating costs in the winter and cooling costs in the summer.
For indoor air quality, duct-mounted and wall-mounted sensors enable a building automation system to monitor levels of carbon dioxide and carbon monoxide, and make adjustments to meet ANSI/ASHRAE standards. These systems are effective in spaces with varying occupancies, such as classrooms and auditoriums, where they will adjust the amount of outside air supplied to the space depending upon air quality in the room.
A well-designed electrical infrastructure is critical to the operation of a science facility. Planners should address three significant issues early in the project:
The size of electrical service to the building depends on requirements for laboratory equipment, lighting, HVAC systems and plumbing. Codes and engineering calculations largely drive the sizing of the electrical system for lighting, HVAC systems and plumbing. However, the specific building uses will determine the design of electrical service to power laboratory equipment. Generally, 20 watts per square foot is considered a benchmark of power service for a modern science facility. However, needs vary widely according to the type of research or teaching performed in the facility.
In particular, designers will size the electrical supply to individual laboratories and determine required sizes of distribution panels, feeders and switchboards based on the types and quantity of equipment, how the equipment uses power, and how the equipment will be used in the lab. Understanding how the equipment will be used will enable the design team to apply the right diversity factors and size the electrical equipment properly, which, in turn, reduces cost. A good design team also will determine the need for future capacity and flexibility.
The reliability of electrical service in the area is a key factor in the proper design of the electrical infrastructure. Among the issues that must be considered are the reliability of service from the local utility company, availability of feeders from two independent substations, and building users' ability to endure power outages in terms of potential effects on class schedules and research.
Thus, risk and tolerance levels will significantly affect the facility's standby power needs. It is important to understand the difference between emergency power and standby power. An emergency power system's primary function is to support life-safety functions such as emergency lighting, fire alarms and smoke evacuation. So the need for and capacity of an emergency power system largely will be driven by life-safety codes.
However, the emergency power system also will be used to provide standby power that ensures required functions and research are able to continue during a power outage. Standby power is a critical component of an academic teaching or research facility, and the system must be sized to support critical functions and equipment. The design must take into account any mechanical systems that must operate during a power outage, whether power is required for fume-hood exhaust systems, whether air conditioning is critical to research activities, and whether there is specific laboratory equipment that may require standby power.
Because standby power systems can be costly, it is important to analyze and determine what is critical. Often, designers will provide standby power outlets in strategic locations so users can selectively plug certain equipment into these outlets if a power failure occurs. This approach reduces overall standby power requirements and associated cost.
During a power failure, there is a brief delay between power loss and activation of standby power. Therefore, an uninterruptible power system (UPS) may be needed to ensure continuous equipment operation. Providing a building-wide UPS system is costly. In most instances, designers recommend local UPS systems for critical spaces or equipment only. However, as digital data collection is becoming more critical to faculty research, the demand for a larger UPS is growing.
The need for clean power generally is not a major issue for science facilities. But power quality is an issue for academic research facilities that are highly dependent on digital data collection and computer analysis, such as a proteomics research lab. In these cases, the electrical design must provide for clean power through proper grounding, prevention of harmonic distortion, clean voltage reference and proper space planning to reduce the potential for AC magnetic interference.
Category VI copper cable is still state-of-the-art for the backbone of telecommunications systems in academic science facilities, but many institutions now use fiber-optic cable for backbone. It is important to note that category VI cables are being substituted by category VI enhanced or augmented cables. This is driven by the ever-increasing need for higher data speed.
Institutions also are considering wireless and wide-area-network (WAN) data transfer as more and more research equipment is operating in the wireless environment. For the greatest flexibility, the infrastructure should provide for this evolution with adequate closets and pathways to run cables or fiber. MEP engineers recommend installing two extra sleeves for every four sleeves installed today and oversizing cable trays by using a 12×6 tray instead of 12×4 to allow for future changes. The actual sizes depend upon characteristics such as the floor and building size, and the number of data closets.
Reducing lighting costs
The United States spends about one-quarter of its electricity budget on lighting. Technologies developed during the past 10 years can cut lighting costs by 30 to 60 percent while enhancing lighting quality.
Using daylighting techniques in conjunction with automatic lighting controls, automatic shade controls, photocell daylight dimmers near windows, and occupancy sensors can help schools save even more on electric energy.
One new development is a digital addressable lighting interface (DALI), a bi-directional, digital protocol developed by lighting manufacturers to control light source levels. Because DALI gives each lighting fixture a unique Internet Protocol address, it is an ideal way to control lighting costs in new construction, including science facilities with shifting occupancies.
Most academic science facilities' laboratories have separate centrally piped systems to deliver domestic, laboratory, tempered and treated water. In some municipalities, the domestic water system also may serve laboratories. In other jurisdictions, a separate laboratory water system may be required.
Teaching and research labs also require a tempered water system to avoid temperature extremes on emergency showers and eyewashes. Designers often meet this need using thermostatic mixing valves in the domestic water system.
Proper design of a treated or pure water system requires extensive discussion in the programming phase of the project. The selected system can affect installation and operating costs significantly depending upon whether the water-quality level is Reagent Grade, United State Pharmacopoeia (USP) purified, or water for injections (WFI). Engineers will specify the types of treatment equipment, piping distribution and piping materials needed by the facility based on water-quality level.
Anticipated future needs and life-cycle cost are important considerations when selecting a system. In most cases, only a few locations require high-quality treated water. Therefore, it is not practical and cost-effective to supply high-quality water to the entire facility. Local treatment (polishing) units are recommended to raise water quality for selected users.
Compressed air and vacuum gases are the most commonly used gases in academic science facilities. Usually the highest pressure requirement determines overall system pressure. The higher the overall system pressure, the greater the installation cost and operation cost for the system. Cost-effective system design depends on an accurate determination of need. Compressed air can be distributed at pressures ranging from 15psi to 100psi or higher. Even if most of the benchwork requires only 15psi compressed air, it is wise to consider a 30psi distribution system to provide reasonable flexibility.
Modern science facilities also may use a number of special gases, including nitrogen, argon, helium, hydrogen, oxygen, steam and clean steam, in selected areas of a building. In many cases, a local supply system is an appropriate and cost-effective solution. Safety also must be considered; for example, oxygen-depletion alarms and an emergency exhaust system should be installed in lab spaces that use liquid nitrogen.
Yakren, PE, LEED AP, is a senior vice president at Syska Hennessy Group, Inc., New York City.