Consulting-Specifying Engineer - October 2008 - (Page 20)

M/E Roundtable friendly option when maintaining a sash management program. Facilities with predictable occupancy can usually benefit just as effectively with 2-state fume hood control without the initial first cost of a total VAV solution. Low-flow fume hoods are also a viable option and can be further enhanced with Efficiently planned spaces will result in less 2-state operation. square footage for a lab. This reduces the volume Collaborate with of air required to meet air change requirements. members of Environmental Health & • Pay attention to the room construc- Safety and lab directors/principal investigators tion details; a leaky room requires a much to determine if lower ACH can be used for higher offset between the supply and ventilation. They are best suited to determine exhaust airflows in order to maintain a the safety of reduced airflows based on the strong differential pressure. The extra scientific program, practices, and procedures airflow wastes energy. used within the facility. Evaluate the option • Take advantage of cascading airflows of using a continuous environmental air qualfrom clean to dirty areas to reduce the ity monitoring system as a means to reduce total amount of makeup air provided. ACH. This may be a big upfront cost, but again • Include provisions for nighttime or should be evaluated as a lifecycle cost. unoccupied airflow settings in the design. Use duct pressure reset to control the VAV Ryan Sprangers: Educating and worksupply fan serving the lab areas in lieu of ing with the owner to determine low, yet the traditional fixed static pressure setpoint. safe ACH requirements is an important Design engineers have to size the fan for first step. Next, investigate what the driv- the design pressure. The actual flow needed ing factor for the airflow in lab spaces from the fan at any other operating point is (ACH, cooling load, or fume hood make- less. By dynamically adjusting the pressure up) is and determine if it can be reduced to meet changing airflows, the fan is slowed or used to reduce the load elsewhere. For down to meet the need of the zone requirexample, labs that are governed by ACH ing the most pressure, and you have the coror fume hood makeup can be located on responding savings in fan power. For some the exposures of the building that would reason this control methodology has not otherwise have larger cooling loads due been readily implemented for laboratory to the exposure. Offices and spaces that systems, but with the requirement of meetare governed by conventional loads can ing ASHRAE Standard 90 (which requires be located on the interior or north expoduct pressure reset for DDC controlled tersure, which helps reduce initial system minals) as a prerequisite to a LEED-NC ratsizes and reduces energy consumption ing, we will probably see, and should see, over the lifetime of the building. more of this in specifications. Diane Feliciano-Welpe: Designers should There following should be considered, evaluate both initial design and long-term too: Seal ductwork and specify low leakoperating costs when evaluating energy sav- age terminal devices to minimize fan ing approaches. Labs21 is doing a good job capacity due to leakage. Use good design of obtaining benchmark data and develop- practices when laying out ductwork to ing best practices guides to help designers minimize pressure drop and its associatrethink some of the “rules of thumb” his- ed fan power. Minimize sharp bends and torically used. The following system design transitions and use low pressure drop air approaches should be considered: terminals, diffusers and grilles. Finally, size Reduce airflow: ductwork to minimize high velocities. For laboratories with a high concenJoe Brooks: A lab ventilation system, tration of fume hoods, VAV fume hood like any fan system, should be designed control still remains the most energy- to achieve its objectives using the least for the remainder of the cooling load. This does not work if the makeup air requirements exceed the airflow requirements for cooling. • Early planning can minimize the distance and number of elbows in duct runs, which reduces static pressure and, consequently, and fan energy. amount of energy. In order to minimize energy use, the system should be designed to exclude any system effects that could adversely affect the fan; the most efficient components should be selected; control systems should be designed to minimize wasted energy; and the design should attempt to operate the system near the fan’s peak efficiency point (an efficient fan will do no good if it operates in a region of low efficiency). When possible, component performance should be certified. AMCA has many certified ratings programs for equipment that is commonly used in lab ventilation systems. Inlet flow, outlet flow, power, and efficiency can be certified for all types of fans. Performance of airflow measurement stations and acoustical duct silencers can also be certified using the AMCA Certified Ratings Programs (CRP). CSE : What approaches for fume hood controls help minimize energy intensity without compromising lab safety? Tsimanis: The use of presence sensors helps to determine the presence of a person in front of the hood by detecting motion, and also commands the lab airflow control system from an in-use operating face velocity (e.g., 100 fpm) to a standby face velocity (e.g., 60 fpm) and vice versa. When the sensor detects someone’s presence and/or motion within the detection zone, it is commanding the system to the in-use face velocity within 1.0 seconds. Additionally, the use of the variable volume control for a fume hood operation is based on the position of the fume hood sash. When the fume hood sash is fully open, the fume hood exhaust will be at the maximum position; and with the fume hood sash closed, the fume hood exhaust will be at a minimum position. This strategy allows reduction in the airflow with reduction in total energy use. The most costeffective application for this concept is for a small lab with a single fume hood. Sprangers: Unless the fume hood and/or lab housing needs to operate 365/24/7, incorporate VAV controls on the hood, which will allow the amount of makeup 20 Consulting-Specifying Engineer • OCTOBER 2008

Table of Contents Feed for the Digital Edition of Consulting-Specifying Engineer - October 2008

Consulting-Specifying Engineer - October 2008 Contents Viewpoint Letters News M/E Roundtable Cities Under One Roof Eight Design Tips for Integration Is 'Green' Really New? Down the Drain Product of the Year Awards Codes & Standards Case Study New Products Equipment Lifecycles Advertiser Index Green Space

Consulting-Specifying Engineer - October 2008

For optimal viewing of this digital publication, please enable JavaScript and then refresh the page. If you would like to try to load the digital publication without using Flash Player detection, please click here.