Creating efficient, effective labs: HVAC and energy efficiency
Laboratory and research facility operators must produce precise, reliable results every time in order to stay in business—and they insist upon that same precision from the engineers working on their buildings. HVAC system design—including ventilation, indoor air quality, and sustainable systems—must be carefully considered.
H. Jay Enck, CPMP, CxAP, HBDP, BEAP, LEED Fellow, LEED AP BD+C, QxAP, Chief Technology Officer, Commissioning & Green Building Solutions Inc. (CxGBS) Duluth, Ga.
Ian Marchant, PE, CEM, LEED AP BD+C, Senior Mechanical Engineer, CDM Smith, Latham, N.Y.
Mike Walters, PE, LEED AP, Principal, Confluenc, Madison, Wis.
CSE: What unique HVAC requirements do such structures have that you wouldn't encounter on other structures?
Marchant: Laboratories typically have high exhaust requirements that dictate high makeup air loads. This results in high energy use. There are often opportunities for heat recovery from the exhaust airstream. Laboratory areas often have pressurization requirements to either prevent the spread of potentially harmful substances from within the lab or keep potential contaminants from the lab. This can result in more complex control schemes. Exhaust hood sash control systems require careful coordination and commissioning to ensure a successful installation.
CSE: How do you balance the need for high ventilation rates with the higher energy use?
Walters: A demand control ventilation system, based on air quality, is an extremely useful technology option for balancing the need for laboratory safety via appropriate ventilation and the desire to reduce energy use.
Marchant: High energy use in a laboratory setting is a fact of life. Energy reduction can be achieved by several methods. The most effective is reducing exhaust when it is not required. Hood sash controls adjust the exhaust and supply for the laboratory. The supply air must actively track the exhaust flow where space pressurization is a requirement. Heat recovery from the exhaust stream can be an effective energy-saving measure, taking care not to cross-contaminate the supply air. Heat recovery must be planned early in the design to ensure proximity of the exhaust heat source with the makeup air system.
CSE: Do you find it more challenging to retrofit HVAC systems on older buildings than installing on new?
Marchant: This question has the typical engineers' response: "It depends." If there are large portions of ductwork or piping that can be reused, it can simplify the new installation or at least save the owner first costs. A retrofit typically has space limitations. This can be a challenge and potentially limit the options available, thereby making the decision process easier. If larger equipment and ductwork are required, sacrifices may be required by all the trades involved, including the architectural aesthetics of the space.
CSE: Describe any experience you have using sustainable heating/cooling tech, such as ground source heat pumps.
Marchant: CDM Smith designed a geothermal heating and cooling system for a North Conway, N.H., treatment facility that included an environmental laboratory. The system includes 16 wells and two 15-ton water source heat pumps, and provides heating and cooling for offices in a garage building and a 3,900-sq-ft administration building comprised of offices, an environmental laboratory, and a conference room. Heating coils in the air handling unit and reheat coils in the variable air volume (VAV) boxes were replaced to allow for the lower temperature heating water from the heat pump. The balance of the plant's heating system was upgraded using an early adoption of condensing oil boilers. A plant-wide HVAC direct digital control (DDC) system upgrade was also performed, and a 167.4 kW photovoltaic system was installed. Funded via an American Recovery and Reinvestment Act grant, the project was completed in 2010. The geothermal system resulted in 192,677 lbs of CO2 reduction annually, 1213 lbs of SO2 reduction, and 210 lbs NOx reduction. The simple payback is 17 years and 23 years discounted payback.