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.

1. 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

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Research regarding thermal and air quality effects on performance

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Outdoor air supply rate (L/s per person)
Performance
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
Performance
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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9092949698100010203040506070Dissatisfied with air quality Performance % % (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
Performance
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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THANK YOU, QUESTIONS?

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paw@byg.dtu.dk
Thank you