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| PMV | |
|---|---|
| Name | PMV |
| Field | Thermal comfort, Environmental engineering, Occupational health |
| Introduced | 1970s |
| Inventor | Fanger (Ole Fanger) |
| Related | Predicted Percentage Dissatisfied, ASHRAE Standard 55, ISO 7730 |
PMV
Predicted Mean Vote is a quantitative index used to assess thermal comfort in built environments. It synthesizes human thermal sensation with environmental metrics to predict the mean subjective vote of a large group of occupants, linking measurements with design targets in standards such as ASHRAE Standard 55 and ISO 7730. Developed to inform HVAC design and occupational guidelines, it is widely cited in studies involving Indoor air quality, building simulation, and ergonomic assessment.
Predicted Mean Vote describes the average thermal sensation of a large group of people on a seven-point thermal sensation scale developed from sensation surveys; the scale ranges from cold to hot and corresponds to votes used in field studies such as those by Fanger, whose work underpins modern terminology in thermal comfort. Related metrics include Predicted Percentage Dissatisfied (PPD) and operative temperature, which are referenced in ASHRAE Standard 55, ISO 7730, and guidance from organizations like CIBSE. Terminology also draws from standards developed by bodies such as the International Organization for Standardization and professional societies including the American Society of Heating, Refrigerating and Air-Conditioning Engineers.
The PMV concept originated from empirical and thermophysiological research in the 1970s led by researchers including Ole Fanger at institutions that collaborated with industrial partners and standards committees. Early validation used climate chamber experiments and field surveys spanning sites comparable to those in studies of thermoregulation and human-environment interaction. Subsequent decades saw integration into international standards (ISO 7730, ASHRAE Standard 55) and adoption by building performance researchers and manufacturers involved in projects like those by Danish Building Research Institute and academic centers at universities such as Technical University of Denmark and Massachusetts Institute of Technology. Debates about cultural, regional, and adaptive influences led to alternative models like adaptive comfort models promoted in guidance from organizations including the World Health Organization and metropolitan research institutes.
Calculation of PMV uses inputs including air temperature, mean radiant temperature, air velocity, humidity, clothing insulation expressed in clo units, and metabolic rate in met units, following formulations originally presented by Fanger. Instruments used in practice include thermometers, globe thermometers for mean radiant temperature measurements, anemometers, and hygrometers; data logging and modelling are performed with software tools and simulation platforms employed by firms such as TRNSYS users and practitioners in consulting firms collaborating with standards committees. The mathematical model combines heat balance equations for the human body with empirical coefficients derived from chamber studies and incorporates thermophysiological parameters studied by researchers at institutions such as Karolinska Institute and Imperial College London.
PMV is applied in HVAC design to size systems and set control strategies in commercial buildings, hospitals, and laboratories referenced in case studies by firms linked to ASHRAE guidance. It is used in energy-performance simulations in projects affiliated with research centers like Lawrence Berkeley National Laboratory and consultancy reports for corporations and public bodies including municipal authorities and healthcare trusts. Occupational-exposure assessments for industrial workplaces draw on PMV outputs alongside standards from agencies such as Occupational Safety and Health Administration and institutes like NIOSH. Urban building retrofit projects, university campus master plans, and certification schemes referenced by organizations like LEED and BREEAM incorporate PMV-based analyses.
PMV is sensitive to individual and environmental variables studied across research networks including laboratories at Stanford University and ETH Zurich. Key factors include metabolic rate differences documented in occupational physiology literature, clothing insulation explored in textile research at institutions such as North Carolina State University, and indoor environmental parameters like radiant temperature influenced by building envelope characteristics examined in studies involving Lawrence Berkeley National Laboratory. Cultural adaptation and acclimatization discussed in publications by scholars at University College London and public-health bodies can alter subjective responses, while transient phenomena studied in thermal comfort experiments at facilities like National Research Council (Canada) also affect PMV.
Critiques of PMV arise from research showing discrepancies between PMV predictions and field survey results in naturally ventilated or culturally diverse contexts, highlighted in comparative studies by researchers at universities such as University of Cambridge and University of Tokyo. Limitations include assumptions of steady-state conditions, reliance on averaged group responses, and sensitivity to uncertain inputs like metabolic rate and clothing insulation; these concerns are central in methodological discussions within committees of ISO and ASHRAE. Alternative approaches, including adaptive comfort models and probabilistic frameworks developed by scholars at institutions like Universidade de São Paulo and Monash University, address some criticisms by incorporating occupant behavior and adaptive opportunities documented in fieldwork.
PMV is embedded in international and national standards, notably ISO 7730 and ASHRAE Standard 55, which provide procedures for assessment and thresholds for acceptable conditions, and influence building codes and guidelines produced by agencies such as European Committee for Standardization and national standards bodies. Regulatory application appears in procurement specifications for public buildings, healthcare facility guidelines, and occupational safety regulations where thermal comfort metrics are referenced by authorities including Health and Safety Executive and municipal building departments. Standards committees continue to revise normative language drawing on research from universities and laboratories worldwide to reconcile PMV methodology with adaptive and evidence-based practices.
Category:Thermal comfort