LinkingLinking EnvironmentalEnvironmental ConditionsConditions toto ProductivityProductivity
Professor Alan Hedge, PhD, CPE Cornell University Dept. Design & Environmental Analysis NYS College of Human Ecology Ithaca, NY 14853-4401
(email: [email protected])
(Abbreviated slideshow based on a presentation at the Eastern Ergonomics Conference and Exposition, New York, June, 2004) IEQIEQ EffectsEffects onon ProductivityProductivity zz ScatteredScattered studiesstudies thatthat mostlymostly showshow evidenceevidence ofof anan associationassociation betweenbetween indoorindoor environmentenvironment conditionsconditions andand somesome measuremeasure ofof performance.performance. zz ResearchResearch issues:issues: – Laboratory vs. field studies – Single vs. multiple contaminants/conditions – Surveys vs. interventions – Short-term vs. longer-term – Single exposure vs. multiple exposure – Time-lagged effects – Acute vs. chronic health effects IEQIEQ EffectsEffects onon ProductivityProductivity
System Environmental Productivity Impact experience
Heating, z Thermal comfort z Performance decreases when too cold Ventilating and z Indoor Air Quality z Performance decreases when too hot Air Conditioning Air Conditioning z Background noise z Performance decreases in polluted air System z Mechanical z Performance decreases when too noisy vibration z Performance decreases when z Personal person/equipment vibrates control/stress z Performance decreases with no control (perceived or real) IEQIEQ EffectsEffects onon ProductivityProductivity
System Environmental Productivity Impact experience
Lighting System z Illumination level/ z Performance decreases when too dim or distribution too bright z Glare z Performance decreases when too glaring z Ambient/task z Task demands and user age change light systems requirements z Color z Affective changes in environmental z Room ambience desirability (shadows) z Disrupts visual inspection/ interpersonal z Personal interactions control/stress z Performance decreases with no control (perceived or real) IEQIEQ EffectsEffects onon ProductivityProductivity
System Environmental Productivity Impact experience
Sound z Background noise z Performance decreases with loud/annoying conditioning z Speech noise system/ privacy/intelligibility z Performance decreases with poor privacy Acoustic design z Noise stress z Performance decreases with noise stress z Personal z Performance decreases with no control control/stress (perceived or real) IEQIEQ factorsfactors andand HumanHuman PerformancePerformance Lighting - Bright Sound -Dim Temperature -Noise -Glare -Hot - Disturbance -Cold
Productivity
Indoor Air Quality Vibration - Acute - Segmental - Chronic Personal - Whole-body Control OptimalOptimal IEQIEQ ConditionsConditions
OPTIMAL IEQ
Too cold Thermal conditions Too hot
Too quiet Acoustic conditions Too loud
Lighting conditions Too dim Too bright
Indoor air quality Too polluted
Vibration Too vibrating
(Source: Stanton, Hedge et al. (2004) Handbook of Human Factors and Ergonomics, CRC Press) ProductivityProductivity –– IndividualIndividual WorkWork PerformancePerformance
z Productivity research traditionally has focused at the coarse, aggregate level of the building and the occupants. z Aggregate measures cannot define precise associations between IEQ conditions and individual productivity. z Laboratory studies have investigated performance and exposure to specific pollutants and mixtures, but exposures are short-term, non-cumulative and use simulated work tasks z Research need is to focus on the performance of the individual and the environment experienced by that the individual. z Individual measures: – Self-reports – Task Performance (time, accuracy, quantity, quality) IEQIEQ andand ProductivityProductivity ResearchResearch z New Research Approach – Combining spatio- temporal IEQ and Productivity Datasets – IEQ measure needs to include air temperature and relative humidity because thermal conditions are known to influence work performance, and consequently could confound any associations with air pollutants. – Most HVAC systems are designed to regulate thermal conditions, and HVAC systems respond to thermostat controls. – Thermal conditions impact levels of VOCs and other pollutants – Thermal conditions are an indicator of ventilation quality. High temperatures can indicate poor ventilation which in turn can indicate high pollutant loads. IEQIEQ DataData LoggingLogging zz IEQIEQ logginglogging unitsunits thatthat cancan be:be: – Widely dispersed throughout a building – Small size – Silent operation – Self-powered – “Inexpensive” – Frequent logging/data storage capabilities – Ideally, work computer synchronized – Ideally, collect data on a wide array of IEQ variables. AverageAverage DailyDaily TemperatureTemperature PatternPattern zz InsuranceInsurance companycompany (Florida)(Florida) – 9 workstations for 16 work days AverageAverage DailyDaily HumidityHumidity PatternPattern zz InsuranceInsurance companycompany (Florida)(Florida) – 9 workstations for 16 work days
52. 0
50. 0
48. 0
46. 0 an RH 44. 0 Me
42. 0
40. 0
38. 0 8: 8: 9: 9: 7: 15 16 1 17 17 18 18 19 19 1 10 11 1 12 12 13 13 14 14 1 5 6 0 1 15 45 15 4 00 :1 :1 :1 :4 :1 :4 :1 :1 :4 :4 :1 :4 :4 : : : : : : : 5 45: 15: 45: 15: 45: 15: 45: :0 :0 :0 : : 5 5 5: 5: 5: 5: 5: 5: 5: 5: 5: 5: 5: 00. 00. : : 0. 0. 0. 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00. 00 00 00 00 00 .0 .0 .0 .0 .0 .0 .0 .0 .0 .0 .0 .0 .0 .0 .0 . . . .0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 Time ElectronicElectronic ProductivityProductivity MeasuresMeasures z Keystrokes/errors/mouse activity z Utilize existing networked data collection software (EMS) z Data file – every work minute the software records a count of: – Correct keystrokes – Errors – Mouse activity – Longitudinal data (e.g. every 15 minutes for 16 days) ElectronicElectronic ProductivityProductivity MeasuresMeasures zz ExampleExample ofof datadata structurestructure (does not show errors column) AverageAverage DailyDaily KeyingKeying PatternPattern zz InsuranceInsurance companycompany (Florida)(Florida) – 9 workstations for 16 work days
50 0
40 0 minutes 5 30 0 per 1 es
trok 20 0 Keys
10 0 Mean
0 8:15:00.00 9:15:00.00 7:00:00.00 8:45:0 9:45:0 15 16:15:00. 16: 17:15:00. 17:4 18:15:00.0 18:45 19:15:00.00 19:45 10: 10:45:00. 11:1 11:45:00.0 12:15 12:45:00.00 13:15 13:45:00.00 14:15:0 14 15:15:00 :45:00.00 :45:00.00 45:00.00 15:00.00 5 5 :00.00 :00.00 :00.00 :00.00 :00.00 :00.00 0 0 .00 .00 0 .00 .00 00 00 00 0 0 Time AverageAverage DailyDaily MousingMousing PatternPattern zz InsuranceInsurance companycompany (Florida)(Florida) – 9 workstations for 16 work days AverageAverage DailyDaily ErrorError PatternPattern zz InsuranceInsurance companycompany (Florida)(Florida) – 9 workstations for 16 work days
100
80 tes minu 60 15 r pe s
ror 40 Er n Mea 20
0 8:15:00 8:45: 9:15:00.00 9:45:00.00 7:00 16:15:00.00 16:45:00.00 17:15:00 18:15:00.00 18:45:00.00 19:15:00.0 19:45:0 10:15:00.0 10:45:00 11:45:00.00 12:15:00.00 12:45:00. 13:45:00.00 14:15:00.00 14:45:00. 15:15:0 1 17 11 13 5 :45:00.00 :45:00.00 :15:00.00 :15:00.00 :00.00 00.00 .00 0 0 .00 .00 .00 .00 0 0 0 0 0 0 Time KeystrokesKeystrokes andand MousingMousing zz InsuranceInsurance companycompany (Florida)(Florida) – 9 workstations for 16 work days
2500
2000
1500 per 15 minutes
1000 Keystrokes
500
0
0 200 400 600 800 Mouse seconds per 15 minutes HumidityHumidity andand KeystrokesKeystrokes zz InsuranceInsurance companycompany (Florida)(Florida) – 9 workstations for 16 work days
2500
R Sq Linear = 0.001 2000
minutes 1500 per 15
1000 Keystrokes
500
0
30.0 35.0 40.0 45.0 50.0 55.0 60.0 RH LightLight andand KeystrokesKeystrokes zz InsuranceInsurance companycompany (Florida)(Florida) – 9 workstations for 16 work days TemperatureTemperature andand KeystrokesKeystrokes zz InsuranceInsurance companycompany (Florida)(Florida) – 9 workstations for 16 work days
2500
R Sq Linear = 0.006
2000
minutes 1500 per 15
1000 Keystrokes
500
0
19.00 20.00 21.00 22.00 23.00 24.00 25.00 26.00 TempC TemperatureTemperature andand ErrorsErrors zz InsuranceInsurance companycompany (Florida)(Florida) – 9 workstations for 16 work days
300 R Sq Linear = 0.01 nutes 200 mi Errors per 15 100
0
19.00 20.00 21.00 22.00 23.00 24.00 25.00 26.00 TempC MouseMouse SecondsSeconds
Dependent Variable: Mouse Seconds
95% Confidence Interval Std. Lower Upper Parameter B Error t Sig. Bound Bound Intercept 176.333 3.505 50.308 .000 169.461 183.206 Temperature2 (nTa°C) 5.325 2.301 2.314 .021 .814 9.836 RH2 (nRH) -.207 .101 -2.050 .040 -.405 -.009
Mouse seconds=176.33 + 5.33(nTa) 2 - .21(nRH)2
Note: Environment variables normalized KeystrokesKeystrokes
Dependent Variable: Keystrokes
95% Confidence Interval Std. Lower Upper Parameter B Error t Sig. Bound Bound Intercept 204.522 5.411 37.798 .000 193.913 215.131 Light (nL) 2.446 .348 7.029 .000 1.764 3.128 Temperature (nTa°C) 33.087 5.444 6.078 .000 22.413 43.761 Temperature2 19.306 4.373 4.415 .000 10.732 27.879
Keystrokes=204.52 + 2.45(nL)+ 33.09(nTa) + 19.31(nTa)2
Note: Environment variables normalized ErrorError KeysKeys
Dependent Variable: Error Keys
95% Confidence Interval Std. Lower Upper Parameter B Error t Sig. Bound Bound Intercept 48.584 1.128 43.058 .000 46.371 50.796 Temperature (nTa°C) -3.694 .937 -3.941 .000 -5.531 -1.856 RH (nRH) .525 .188 2.800 .005 .157 .893 Light (nL) .716 .059 12.165 .000 .600 .831 Temperature2 2.021 .743 2.722 .007 .565 3.477 RH2 -.082 .032 -2.515 .012 -.145 -.018
Errors=48.58 – 3.69(nTa)+.53 (nRH)+.72 (nL) + 2.02 (nTa) 2 - .08 (RH)2
Note: Environment variables normalized TemperatureTemperature andand PerformancePerformance
100 Keying 90 Errors
80
70
60 t en
c 50 r Pe 40
30
20
10
0 20.6 21.0 21.3 21.7 22.1 22.5 22.9 23.2 23.6 24.0 24.4 24.8 Air Temperature (deg.C) TemperatureTemperature andand CostCost z Assumptions: – Employee earns Estimated Keying Error Costs per Hour $16 per hour (assuming $16/hr wage) – Keying time = 4.00 900-mouse time 3.50 seconds 3.00
– Total keys = s r 2.50 correct + error lla
correct + error o
D 2.00 keys t s o – Cost/key = keying L 1.50
time/total keys 1.00
– Error costs = error 0.50 keys X costs per key 0.00 key 20.6 21.0 21.3 21.7 22.1 22.5 22.9 23.2 23.6 24.0 24.4 24.8 – Hourly costs = 4 x Air Temperature (deg. C) error costs ResearchResearch ConclusionsConclusions z Results show clear associations between office work performance and indoor environment conditions z Results suggest that performance improves as conditions approach a predicted thermal comfort zone z Raising temperature from 20°C to 25°C: – Reduces energy consumption (less cooling) – Reduces costs – Reduces errors by 44% – Increases keying output by 150% – Saves ~$2.00 per worker in lost productivity z With optimization of other environmental conditions the cost savings will be even greater! ResearchResearch ConclusionsConclusions z Study confirms the utility of this new metric for assessing the performance and financial impacts of IEQ changes. z Associations between changes in specific indoor environmental variables and consequent productivity changes can now be investigated. z The impact of IEQ changes (e.g. different lighting, different HVAC systems) on productivity can now be tested. z The impact of any ergonomic changes (e.g. new chairs, new workstations, keyboard trays) on productivity can now be tested. z Data for IEQ standards that can incorporate productivity impacts can now be gathered. QuestionsQuestions