ABORATORIES FOR THE 21ST ENTURY B EST P RACTICE G …

1 L A B O R A T O R I E S F O R T H E 2 1 S T C E N T U R Y : BEST PRACTICE guide . O PTIMIZING L ABORATORY V ENTILATION R ATES. I ntroducti o n this guide highlights best-practice strategies focused on reducing energy use, it does not specify how to set a This Best Practice guide is one in a series created by ventilation rate. Note that the terms good and better the Laboratories for the 21st Century ( Labs21 ) program, practices are used to describe options that improve stan- a joint program of the Environmental Protection dard practices. Agency and Department of Energy. Geared towards architects, engineers, and facilities managers, these guides provide information about technologies and practices to use in designing, constructing, and operating safe, sus- tainable, high-performance laboratories. Lighting 11%. Laboratories are highly energy intensive, often using Cooling four to six times more energy per square foot than a typi- 22%. Plug cal office building.

2 Most existing labs can reduce their 23%. energy use by 30 to 50% with existing technology, which is significant given their $1 2 billion annual energy costs in the Nearly half of the electrical energy use in a typical laboratory can be attributed to ventilation, and reducing a Ventilation laboratory's ventilation needs can lower the cost to build 44%. and maintain a facility (see Figure 1). The objective of this Best Practice guide is to help users optimize ventilation airflow and reduce associated Figure 1. Annual electricity use in Louis Stokes energy use while maintaining or improving safety. While Laboratory, National Institutes of Health, Bethesda, MD. Department of Energy Energy Efficiency and Renewable Energy Federal Energy Management Program 2 L A B S F O R T H E 2 1 S T C E N T U RY. In the case of building codes for hazardous classifica- .. Perspecti v e S ta n d a r d tions, ventilation rates are stipulated in terms of floor area Practi ce .. as cubic feet per minute (CFM) per square foot, while ventilation guidelines from building design standards for In standard laboratory-design practice, ventilation laboratories are based on the total volume of the space rates are usually derived from guidelines, presented as and expressed as air changes per hour (ACH), which is a range of values in design standards.

3 When using a how many times the entire air volume in the laboratory is guideline to determine a ventilation rate for a laboratory, replaced each hour. the highest value from the range is often chosen because the guidelines are highly generalized; however, design- Prevailing building codes and design standards ers should be cautious when using these wide-ranging provide a context in which best-practice strategies can recommendations. Design firms, or authorities having be implemented. Consider the ventilation guideline jurisdiction, typically use a guideline without question- provided by OSHA 29 CFR Part , which calls ing the true source and the reasoning behind its value. for a range of 4 to 12 ACH for a laboratory that often Similarly, designing by only referencing past efforts, by has an occupancy classification of B. In contrast, the what's in the drawer, limits energy efficiency and may International Building Code (IBC) (2004) calls for a rate of even compromise safety.

4 A simplified more is better 1 CFM/ft2 for an occupancy classification of H-5, which design approach is not a substitute for due diligence. is considered to be a hazardous environment (see Table 1. Ventilation guidelines should only be applied as their for this and other examples). Note that for certain quanti- authors intended as ranges, and not as absolutes. ties of flammable liquids, these must be used in a con- trol area in order for a building to have a B occupancy Standard practice also entails the blanket adoption of classification. ventilation guidelines as constant values, with the ventila- tion rate rarely being dynamically controlled or otherwise As an example of how a code's ventilation rate (or tailored to the occupancy or conditions of the site, or ambiguity) influences energy use, consider the following optimized for energy efficiency or safety. Some publica- two scenarios. One laboratory space, whose occupancy tions simply recommend 4 to 12 air changes per hour.

5 The classification is IBC H-5, has a 10-foot-high ceiling and result can be excessive (or inadequate) ventilation for the an exhaust airflow rate requirement of 1 CFM/ft2;. lab in question, causing unnecessary energy expenditures. the exhaust airflow from this lab will result in 6 ACH. Facility owners also bear the consequences of requiring an However, another laboratory space, which has the same unsubstantiated high ventilation rate, inadvertently forc- floor area but a 15-foot-high ceiling and a B occupancy ing the engineer to design a potentially wasteful HVAC classification, follows the OSHA guideline of 12 ACH and system. flows three times more air than the higher-hazard H-5 lab. Applying fan-law energy calculations, the B lab will Ven ti l a ti o n C o d e s a n d G u i d e lines consume more than three times the energy of the H-5 . lab. In addition, the first cost of the H-5 lab's smaller After reviewing the user's program, or design intent HVAC system will also be less.

6 Note that even though the document, the project architect determines the labora- airflow rate per unit floor area eliminates ceiling height tory's occupancy classification. For this resolved occu- as a determinant of air change requirements, neither the pancy classification, the ventilation rate is provided in a volumetric ACH method nor the area-based CFM method building code specified by the municipality or authority predicts the effectiveness of the ventilation. having jurisdiction. The occupancy classification has a significant impact on a building's energy use. For exam- Codes ple, for particularly hazardous occupancy classifications, the ventilation rate is legally stipulated by the applicable Laboratory designers should study code require- building code. However, for less hazardous occupancies, ments, understand each classification, be familiar with design standards with a range of rates are used only as their potential energy impacts, and relate these findings to guidelines for ventilation rates.

7 Note that a design stan- the project design team. dard may be adopted by the authority having jurisdiction as a code requirement. L A B S F O R T H E 2 1 S T C E N T U RY 3. Table 1, below, lists typical design codes that are often Standards used as ventilation-rate guidelines: .. Table 2, below, lists common design standards con- .. taining guidelines for a laboratory's ventilation rate: Table 1. Common Laboratory Ventilation Rate Codes Code Ventilation Rate Comment IBC -2004 1 CFM/ft2 for H-5 Section Sta nda r d Pr a ctice Mor e Is N ot Necessa r ily B etter IMC - 2004 1 CFM/ft2 Rate required for storage areas that While rules of thumb often dictate that more is exceed maximum allowable quantities better, , that increased ventilation rates yield increased of hazardous materials. (Section ) safety, worker comfort, and research productivity, real- UBC - 1997 1 CFM/ft2 for H-6 Uniform codes have been replaced by world experience shows that this is not the case.

8 In fact, international codes beginning in 2000. excessive ventilation can diminish safety conditions in (Section ) labs that use hazardous and odorous materials as part of their experimental studies (see sidebar on Ventilation Dilution ). Thus, best practices optimize rather than maxi- mize ventilation, and consider the mixing factor of the pollutant being removed from the lab. Table 2. Common Laboratory Ventilation Rate Standards Standard ACH Number Comment ANSI/AIHA The specific room The latest version of the American National Standards Institute and the American Industrial ventilation rate shall be Hygiene Association standard (ANSI/AIHA , Section ) states that a method established or agreed upon based on air changes per hour is not the appropriate concept for designing containment by the owner or his/her control systems. Contaminants should be controlled at the source. ANSI/AIHA also states designee. that the air changes per hour do not reflect actual mixing factors of a particular room.

9 NFPA-45-2004 Minimum 4 ACH According to the National Fire Protection Association's Standard NFPA 45, Appendix A: unoccupied; occupied (NFPA 45 2004), room air currents in the vicinity of fume hoods should be as low as typically greater than 8 possible, ideally less than 30% of the face velocity of the fume hood. Air supply diffusion ACH. devices should be as far away as possible from fume hoods and have low exit velocities. ACGIH Ind. Vent. 24th Ed. 2001 The required ventilation This standard from the American Conference of Governmental Industrial Hygienists states depends on the generation that 'Air changes per hour' or air changes per minute' is a poor basis for ventilation rate and toxicity of the criteria where environmental control of hazards, heat, and/or odors is required. The contaminant, not on the impact of the laboratory's ceiling height is identified as one reason why an air change size of the room in which approach does not adequately address the required contamination control (Section , it occurs.)

10 Air Changes). ASHRAE Lab guide 2001 4-12 The ASHRAE Laboratory Design guide includes suggestions relating to the following: Minimum supply air changes Minimum exhaust air changes Minimum outdoor air changes Recirculation considerations OSHA 29 CFR 4-12 The Occupational Safety and Health Administration specifies a room ventilation rate of 4 to Part 12 air changes per hour, which is normally adequate general ventilation if local exhaust systems such as hoods are used as the primary method of control. This range is extremely broad and provides a designer with little guidance. Studies of laboratory facilities have demonstrated hour (ACH) has a minimal effect on aerosol concentration that the room air change rate has less effect than a room of microorganisms in the first few minutes after release.. air diffusing system or other ventilation characteristic on environmental conditions. Designers need specifications Adjusting ventilation is not the only way to control that are tailored to a laboratory's air circulation arrange- environmental conditions.