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Progress Report Evaluation of Ventilation Systems Febnuary 15, 1993 APPENDIX B Rational Building Performance and Prescriptive Criteria for Improved Indoor Environmental Quality Physical Systems Tasks 2

RATIONAL BUILDING PERFORMANCE AND PRESCRIPTIVE CRITERIA FOR IMPROVED INDOOR ENVIRONMENTAL QUALITY James E.Woods, Sanjay Arora, Nisha P. Sensharma and Bjame W. Olesen Indoor Environment Program, College of Architecture and Urban Studies, Virginia Tech, U.S.A. ABSTRACT Current building codes and standards may be inadequate to meet building objectives aimed at providing occupant comfort and well-being in addition to preventing deleterious conditions. Performance criteria for building elements, derived from human response, economic, and exposure criteria, are more appropriate for addressing these objectives. This paper proposes a rational process for developing performance criteria, and transforming them to prescriptive criteria for use in design, specification, construction and operation. The proposed process can be used at each stage of the building's life. INTRODUCTION Current building codes and standards are promulgated to define minimum requirements for occupant safety and health. These documents are usually written in terms of prescriptive criteria for specific building elements (i.e. structure, envelope, enclosed spaces, and building services). They are intended to be used for project design and specification, construction, and project inspection. As a result, their usefulness during occupancy is limited. Conversely, performance criteria are usually based on evaluations of environmental and economic acceptability, and are established during the conceptual design phase to define the intended performance of the building. They include interactions among the building elements, environmental and economic factors, and are also intended to be used during occupancy. Only a few standards, such as ASHRAE 62-1989, provide both prescriptive and performance criteria which have been rationalized (1,2). The purpose of this paper is to demonstrate that a rational method can be used to transform human response criteria to exposure criteria to system performance criteria, and to further transform system performance criteria to system prescriptive criteria. RATIONALE FOR THE PROPOSED PROCESS The fundamental objectives of indoor environmental control are to provide for the comfort and well-being of the occupants and to prevent the existence of deleterious conditions. A 'healthy' building has been defined as "...not just free from building related illness and discomfort but indeed promotes well-being and health. Besides being non-hazardous, the salient features of the healthy building include thermal comfort, pleasant air quality, illumination and acoustical characteristics, support of social needs and productivity, and distinguished aesthetic qualities. These features should be maintainable over the building's life-time. The occupant should feel confidence in the building and its operation, be able to comprehend the systems and design, and be given a fair chance to control the systems (3)."

According to the constitution of the World Health Organization "Health is a state of complete physical, mental and social well-being and not merely the absence of disease or infirmity" (4). For consistency with this definition, acceptable building performance criteria must specify (a) environmental conditions below which clinical signs of disease or illness are not known to occur; and (b) conditions that provide for occupant comfort and well-being. To address the criteria for comfort and well-being, affective response criteria are preferred over perceptual response criteria, as the latter do not ensure occupant comfort (5). It is proposed here that affective response criteria are best expressed in terms of acceptability of the physical environment rather than occupant comfort because many factors affecting personal comfort are beyond physical control of the environment. From a pragmatic perspective, the relationship between human responses, exposure, systems and sources rests on a platform of economics (see Figure 1). Characterizations of human response and economics form the bases for the transformation of performance and prescriptive criteria for building systems. Human responses to indoor environmental exposures are expressed in terms of four human response domains. These responses result from exposures of the primary physiological receptors that sense environmental conditions to four primary stressors: thermal, air quality, lighting and acoustic. The role of building systems is to provide acceptable exposures by responding to loads (e.g. contaminant, thermal, illumination, acoustic) that accrue from outdoor and indoor sources. Economic implications of these interactions are critical to the acceptable design and operation of these systems. Based on these conceptual relationships, a four step procedure for establishing performance and prescriptive criteria is proposed. ~ Sourr;es Indoor and Outdoor) Th.nnal Loads Contaminant Loads flluminstlon Loads Acoustic Loads Systoma Structure Envdopa 8.rvlcas Enclosad Spacss Expoauro Th.rtnal Air Ouallty illumination Acoustic Human Reaportao Envlronm.ntal - P.reeptuN P.rsonal-P.resptual Envlronm.ntal- Atisctlv. P.rsonal - Aflactlva Economica First Costs Operating Costs En.rgy Us. Productivity Figure 1. Conceptual model relating human response to indoor environmental factors. PROPOSED PROCEDURE FOR CRITERIA TRANSFORMATION Two sets of values for performance criteria should be determined. The first set should correspond to the best quality of environment (i.e. exposure) that can be attained, given the state-of-the-art technology. For this set, the frequency of occupant acceptability should be maximized. The second set of values may relax the quality of the environment obtained,

by allowing lower frequencies of occupant acceptability (e.g. 80%). These two sets of values define the bounds within which performance criteria for specific applications should be selected. Step 1: Develop Human Response Criteria. For virtual (i.e. not yet constructed) buildings, results of previous studies of existing buildings and promulgated consensus standards should be used to determine appropriate human response criteria. As discussed above, the criteria at the upper bound of the range should correspond to maximum levels of acceptability that can be feasibly achieved. The lower bound should represent conditions that a predetermined percentage (e.g. 80%) will find acceptable. For existing buildings, a six point scale developed by Rohles, Woods and Morey (6) may be used to assess human response to the indoor environment,. If 80% of the respondents rate the environment as 5 (i.e., acceptable) or better on the scale, exposures, measured concurrently with human response, are deemed to meet the criteria defined at the lower bound of the range. Step 2: Develop Exposure Criteria. The selection of exposure parameters should be based on three considerations: (a) To assure the best practical association with the selected human response criteria, exposure parameters should be expressed in terms directly related to the relevant human sensory receptors; (b) to enable the transformation of exposure parameters to system performance parameters, the former must also be amenable to control by appropriate design and operation of building systems; and (c) existing methods to assess exposure must be capable of measuring (detecting) the concentrations specified. Exposure criteria should be derived from existing standards and guidelines as well as from empirical data consisting of human response and exposures assessed simultaneously. An example, which has been developed to design and evaluate the performance of a research and demonstration facility at Virginia Tech is shown in Table 1. Two levels of values corresponding to human response criteria are presented. Table 1. Human response and exposure criteria for the two performance levels (See References 1, 7 - 14). Continuous Exposure Criteria Human Thermal Air Quality Response Criteria Op. Temp. Relative Air Particulates C02 TVOC Nicotine2 Decipol (°C) Hum. velocity (pg/m')' (ppm) (pg/m' eq. (pg/m') (%) (m/s) toluene) Maximum 23.0±.5 45±5 < 0.15 < 30 < 400 < 0.5 <1 < 03 Accepta- bility 80% 23.0±2 45±15 < 0.25 < 75 < 1000 < 3.0 <10 < 1.5 Accepta- bility 1 For particle size less than 10 microns; 2 Derived from references 13 and 14

Step 3a: Develop System Performance Criteria. The performance of each system should be evaluated for its capability to effectively respond to the loads in the occupied space during peak and moderating conditions. System performance criteria may be expressed as: • The system should have sufficient capacity to match the design loads and maintain exposure criteria to within a specified precision. • The system should have adequate control to maintain exposure values within the same precision at partial loads (i.e. from design loads to minimum occupancy) as specified for design loads. Step 3b: Derive System Prescriptive Criteria. Prescriptive criteria can be derived from the above by using rational model(s). For air quality, a simple, steady-state expression for a one compartment model can be used to develop prescriptive criteria for design of the system and its controls. The model may be expressed as (2,12): AC=(N,-E)/V (1) where AC = Cr - C,= the difference between the uniformly mixed indoor air concentration, and the outdoor air concentration, C,; IV = the net generation rate of the contaminant; E= removal rate of the contaminant from the air, and V = volumetric flow rate of outdoor air for dilution control. Similarly, for a thermal energy balance: UA(t~ -4)+rk(h. -h)+Qme= k (h, -h.) (2) where U, = average thennal transfer coefficient of the building envelope; A,o = area of the building envelope; t, = outdoor air temperature; 4 = temperature in occupied space; m,, = mass flow rate of air (ventilation and infiltration); h,, h, and h, are enthalpy of outdoor, room and supply air, Q= = intemai heat generation rate; and rim. = mass flow rate of conditioned (i.e. supply) air. The outdoor air ranges from winter to summer design conditions, including moderate conditions when the indoor-outdoor temperature differential is negligible. These conditions define a prescriptive range. The internal loads are also variable and a range should be prescribed. These prescriptive criteria form the basis for evaluation of system operation. Enthalpy of air is a dependent variable while the mass flow of conditioned air can be controlled and therefore specified. If CP is the specific heat of air then, the "sensible" heat balance can be expressed as: UoA,(ta - 4) + rkCp(to - 4) + Q,•c = m,~ CP(4 - t.) (3) or et = t< - t. = (Q,t - kCA - t,)) / (U,A, + rillCr) (4) where At is analogous to AC; Q;, is analogous to is analogous to B; and (UA + m„Cp) is analogous to V in Equation (1). Simultaneous solutions to Equations 1 and 4 therefore allow quantification of the prescriptive criteria E, Uo, Ao, m,,, and k corresponding to the specified performance criteria C„ tt, t,, the loads N and Q,. and the range of outdoor conditions to and Co.

Step 4: Develop Energy and Economic Performance Criteria. Each system should also be evaluated for its efficiency in energy transformation and for the cost it incurs to deliver the required performance. System energy efficiency may be defined as the ratio of the energy required to maintain the environmental criteria to the energy consumed to provide the required environmental conditions (15). As a criterion we propose that: • A system energy efficiency of at least 80 percent should be achieved. Life-cycle-cost analysis evaluates all significant time-equivalent costs attributable to a given building design, system or component, and its impact on the productivity in the space, thus enabling a choice among alternative systems. The costs included are the investment (first cost), non-fuel operation and maintenance costs, energy costs, and a monetary value for enhanced productivity resulting from improved environments. Criteria for economic performance may be expressed as: • The selected system should incur minimum life-cycle cost, wherein the comparison of alternatives includes weighting for productivity improvements in the environment. CONCLUSIONS The process described above is applicable for use in virtual and existing buildings, and for different stages in a building's life cycle. For virtual buildings, performance criteria are essential at the design conception stage. When transformed to prescriptive terms, the criteria become useful for design and contractual documents. Prescriptive criteria also form the basis for testing, balancing and commissioning of systems. Once the systems are operational, i.e. in existing buildings, the performance criteria (system, exposure and human response) again become effective, for, human response and the corresponding exposures will ultimately determine the acceptability of the indoor environment. Performance criteria should be reestablished when adaptive reuse of buildings is contemplated. These should then be translated into prescriptive criteria to aid in the redesign of building systems. For the lower bound, while the human response, exposure, and system criteria serve as constraints, energy and economic criteria provide the desirable values which should preferably be achieved. By establishing the rational basis for the transformation of criteria, it is possible to assess the efficacy of building systems in meeting the primary goals of building performance. ACKNOWLEDGEMENT We are pleased to acknowledge the partial support of Philip Morris USA for this research. REFERENCES 1. ASHRAE. ANSI/ASHRAE 62-1989. Ventilation for acceptable indoor air quality. American Society of Heating, Refrigerating and Air-Conditioning Engineers, Inc., Atlanta, GA, 1989. Woods JE, Janssen JE, Krafthefer BC. Rationalization of equivalence between the ventilation rate and air quality procedures in ASHRAE Standard 62. In: IAQ '86. Managing Indoor Air for Health and Energy Conservation. 1986; 181-191. Berglund. B, T Lindvall, I Samuelsson, and J Sundell. Prescriptions for healthy buildings. In: Berglund B and Lindvall T, ed., Proc of CIB Conference Healthy

Buildings '88. Conclusions and recommendations for healthier buildings. Swedish Council for Building Research, Stockholm, 1991. 4. World Health Organization. Constitution of the World Health Organization. Official Record of the World Health Organization. 1946; 2, 100. 5. Sensharma NP, Edwards PK, Woods JE, Seelen J. A characterization of methodologies for assessing human response to indoor environments. Submitted for publication: Indoor Air '93. 6. Rohles FH, JE Woods and PR Morey. Indoor environment acceptability: The development of a rating scale. ASHRAE Transactions. American Society of Heating, Refrigeration and Air-Conditioning Engineers, Inc., Atlanta, GA, 1989; 95(1): 23-27. 7. ASHRAE. ASHRAE Revised Standard 55-1981R (revised draft).Thermal environmental conditions for human occupancy. American Society of Heating, Refrigerating and Air-Conditioning Engineers, Inc. Atlanta, GA, 1991. 8. CEN. CEN/TC156/WG6 N7 (Draft Document). Ventilation for buildings: Design criteria for the indoor environment, 1991. 9. ISO. ISO 7730 (modified version). Document CEN/ITC156/WG6 N8. Moderate thermal environments - determination of the PMV and PPD indices and specification of the conditions for thermal comfort. 10. Swedish Indoor Climate Institute. Classified indoor climate systems: Guidelines and specifications. SCANVAC, Sweden. 11. Molhave L. Volatile organic compounds, indoor air quality and health. Proc of Indoor Air '90. 1990; 5:15-33. 12. Fanger PO. Introduction of the olf and decipol units to quantify air pollution perceived by humans indoors and outdoors. Energy and Buildings. 1988; 12:1-6. 13. Leaderer B, Cain, WS. Air quality in buildings during smoking and nonsmoking occupancy. ASHRAE Transactions. American Society of Heating, Refrigeration and Air-Conditioning Engineers, Atlanta, GA. 1983; 89(2B):601-613. 14. Personal communication with Dr. Brian Leaderer, John B. Pierce Foundation and Associate Professor, Department of Epidemiology and Public Health, Yale University School of Medicine, New Haven, CT.