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Until energy use in buildings became a major consideration, most research on the indoor environment focused on optimising subjective comfort and avoiding negative effects on health. It is now essential to be able to quantify the added value of an improved indoor environment in terms of its positive effects on productivity. Thermal and air quality control account for a large proportion of any building’s first and running costs, and in the last 30 years our ability to predict thermal and air quality effects on performance has advanced considerably. Pawel sets out what has been determined by research and suggests the most essential topics for future research.
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SATISFACTION AND SELF-ESTIMATED PERFORMANCE IN RELATION TO INDOOR ENVIRONMENTAL PARAMETERS AND BUILDING FEATURES
Pawel Wargocki1 (Monika Frontczak1,2, Stefano Schiavon2, John Goins2, Ed Arens2 and Hui Zhang2) 1International Centre for Indoor Environment and Energy, DTU Civil Engineering, Technical University of Denmark 2Center for Built Environment, University of California, Berkeley, USA
28-10-2012
Research regarding thermal and air quality effects on performance
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Outdoor air supply rate (L/s per person)
Per
form
ance
0 10 20 30 40 50 60
1.01
1.00
1.02
1.03
1.04
1.05
Ventilation and performance of office work (in relation to 6.5 L/s per person)
Source: Wargocki and Seppanen (2006)
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Temperature and performance of office work
15 20 25 30 35 0.75
0.80
0.85
Temperature (°C)
0.90
0.95
1.00
Per
form
ance
Source: Seppanen et al. (2005)
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BACKGROUND Occupants of buildings are exposed to all indoor
environmental parameters simultaneously It is likely that comfort is a result of a combined effect of
different IEQ parameters It is also likely the quality of building including furniture,
colors and other building amenities contribute to satisfaction with indoor environment
Standards for IEQ provide requirements for single parameters not their combination
Very few studies on the combined effects of IEQ parameters and building features on human comfort and satisfaction
Some studies have shown that satisfaction with IEQ is related with the self-estimated job performance
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HANEDA ET AL. 2008
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OBJECTIVES
To investigate which subjectively evaluated indoor environmental quality parameters and building features mostly affect satisfaction and self-estimated job performance in office buildings
To examine the link between occupants’ satisfaction with their personal workspace and self-estimated job performance
To quantify the size of the effects
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DATA Data collected by the survey conducted by Center for the Built
Environment (CBE) Data collected over a 10-year period in 600 buildings (offices,
hospitals, schools,…) Present study: 52,980 responses from occupants in 351 office
buildings, mainly located in the U.S. (397 surveys) Background questions (gender, age, type of work performed,
office type, distance from a window) Questions re. perceived satisfaction and self-estimated
performance Building information form filled out by building facility manager
providing information about the building and its systems: building’s age, location and size, number of floors, number of occupants, type of HVAC system, solar shading and controls, buildings’ LEED rating, energy use and cost of building construction, etc.
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PERCEIVED SATISFACTION
Amount of space Visual privacy Ease of interaction Furniture comfort Furniture adjustability Color & texture of surroundings Temperature
Air quality Amount of light Visual comfort Noise level Sound privacy Building cleanliness Workspace cleanliness Building maintenance
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OBSERVED SATISFACTION LEVELS
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SELF-ESTIMATED JOB PERFORMANCE
Office layout Office furnishings
Air quality Thermal comfort Lighting quality Acoustic quality Cleanliness and maintenance
of the building
……………………………
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OBSERVED SELF-ESTIMATED JOB PERFORMANCE
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IMPACT OF INDOOR ENVIRONMENTAL QUALITY AND BUILDING FEATURES ON SELF-ESTIMATED JOB PERFORMANCE
24%: no effect 33%: job
performance decreased by environmental conditions by at least 5%
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STATISTICAL ANALYSIS Workspace satisfaction = f(satisfaction with environmental
and building parameters) using proportional odds logistic regression (odds ratios: the strength of association between variables)
Self-estimated job performance = f(satisfaction with personal workspace) using simple linear regression (regression coefficient: percentage change of self-estimated job performance caused by a unit change of a predictor variable)
Self-estimated job performance = f(satisfaction with environmental and building parameters) using multivariate linear regression (regression coefficient: percentage change of self-estimated job performance caused by a unit change of a predictor variable)
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WORKSPACE SATISFACTION AS A FUNCTION OF INDOOR ENVIRONMENTAL PARAMETERS AND BUILDING FEATURES
All parameters statistically significant (p<0.05)
The most important parameters: satisfaction with amount of space, noise level and visual privacy
Satisfaction with amount of space the most important regardless occupants’ gender and age, type of office (single office, shared office, cubicles) and distance from a window
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AMOUNT OF SPACE VS. AREA PER PERSON
Satisfaction with amount of space almost independent of area per person Spearman rank correlation
ρ=0.03, p<0.001
Limitations A rough estimation of real
area per person No data on amount of
storage space in a vertical direction
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SATISFACTION VS. OFFICE TYPE
Occupants in private offices more satisfied with workspace than those in shared offices or cubicles (p<0.001)
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SATISFACTION VS. WINDOW DISTANCE
Occupants close to a window more satisfied with workspace than those further from a window (p<0.001)
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SELF-ESTIMATED JOB PERFORMANCE AS A FUNCTION OF SATISFACTION WITH INDOOR ENVIRONMENTAL PARAMETERS AND BUILDING FEATURES
The most important parameters: satisfaction with temperature, noise level and air quality
One-unit (~15%) increase in satisfaction with temperature would increase self-estimated job performance by about 1%
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SELF-ESTIMATED JOB PERFORMANCE AS A FUNCTION OF SATISFACTION WITH WORKSPACE
Workspace satisfaction affects self-estimated job performance Statistically significant (p<0.001) Regression coefficient with 95% CI: 3.72 (3.67-
3.78) One-unit (~15%) increase in satisfaction with
workspace would increase self-estimated job performance by about 3.72%
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90
92
94
96
98
100
0 10 20 30 40 50 60 70Dissatisfied with air quality
Perfo
rman
ce
%
%
(R2=0.784; P=0.008)
Simulated office work (lab)
Source: Wargocki et al. (1998; 2004)
Elevated temperatures and poor air quality can affect performance of adults by 5% (laboratory) to 10% (field), and schoolwork of children by over 20% (field)
90
95
100
105
110
0 10 20 30
Per
form
ance
Outdoor air supply rate
(L/s per person)
Office work (call centre)
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CONCLUSIONS
Lowest satisfaction levels observed for sound privacy and temperature
Building occupants generally satisfied with their personal workspace
In order to increase overall satisfaction with personal workspace, increase firstly satisfaction with amount of space, noise level and visual privacy
Self-estimated job performance affected by workspace satisfaction
The biggest increase in self-estimated job performance achieved by increasing satisfaction with temperature, noise level and air quality
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DISCUSSION OF DISCREPANCY BETWEEN RANKING OF PARAMETERS RE. THEIR IMPORTANCE FOR SATISFACTION AND PERFORMANCE
No clear explanation Amount of space is likely related to the status
and position at work, the higher status the higher satisfaction
Status may not be related to performance Changes to indoor environmental parameters
easier “correlated” (memorized) by individuals with work performance than building features
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IMPLICATIONS
Present results can guide building users, operators and employers in making decisions on how working indoor environment can be improved most effectively by selecting these parameters which promote comfort and working morale at the most
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THE EFFECTS ARE SUFFICIENTLY HIGH TO PROMOTE INVESTMENTS IN HIGH INDOOR ENVIRONMENTAL QUALITY
Source: Wargocki and Seppänen (2006); Building Value, Energy Design Guidelines for State BuildingsOffice of the State Architect, California (1976
Productivity gain of just 10% would offset the full running and installation costs
Although there is some level of uncertainty to which extent IEQ affects productivity even improvements <1% are COST-EFFECTIVE
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The primary purpose of
office building is to provide an optimal
conditions for work
and not to conserve energy
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BUILDING CERTIFICATION SCHEMES, LEED
LEED Section Possible Points Sustainable sites 26 Points
Water efficiency 10 Points
Energy and atmosphere 35 Points
Materials and resources 14 Points
Indoor environmental Quality 15 Points
Total 100 Points
Innovation in Design 6 Points
Regional priority 4 Points
Provide a framework to design and build green buildings as well as to assess sustainable building performance.
Is voluntary, though considered prestigious. Have been on the construction market for the last 15 years and are
not anymore a niche segment.
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BREEAM adopts a ‘balanced score-card’ approach to the assessment and rating of building performance; to achieve a particular level of performance the majority of BREEAM credits can be traded. BREEAM sets minimum standards of performance in key areas like energy, water, waste etc.
BUILDING CERTIFICATION SCHEMES, BREEAM
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