OCCUPANT SATISFACTION IN RESPECT TO INDOOR … · occupant satisfaction in respect to indoor...
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Fig. 1: summary of final score (GBI, 2010) (Shafii, 2009)
OCCUPANT SATISFACTION IN RESPECT TO INDOOR ENVIRONMENTAL
QUALITY IN ENERGY EFFICIENT CERTIFIED BUILDINGS IN MALAYSIA
Abstract
Malaysia’s Green Building Index (GBI) encourages non-residential building to save energy
and provide a high quality environment to the occupants. The highest point which is 35, will
be awarded for energy efficiency and the second one 21 point, for indoor environmental
quality (GBI, 2009). This challenging task to the building designers is in shaping the
realization of the occupants’ indoor environmental comfort while controlling energy use for
office working space.
This study has been conducted to investigate the occupants’ satisfaction in the working-space
of energy-efficient office building in a tropical country, Malaysia. Two office buildings,
which have been classified as energy efficient buildings in the Klang Valley, Malaysia were
selected for case study. One of them is a Low Energy Office (LEO) Building, designed for low
energy consumption and the other is a Green Energy Office (GEO) Building which was
designed with renewable energy. The results showed that the occupants were satisfied with
their work-space, with “slightly greater satisfaction” in the LEO building than in the GEO
building.
Keywords: Comfort; Satisfaction; Indoor environment; Building Energy Efficiency.
INTRODUCTION
In 2009 The Government of Malaysia launched the formal framework of Green Building
Index (GBI), to provide measurement rating system for the accreditation of green buildings in
Malaysian. Six criteria have been considered for the measurement (Fig.1).
United States Green Building Council (USGBC) classifies green buildings as buildings which
have been designed with consideration of reducing or eliminating negative impacts on the
occupants and environment (USGBC, 2009). Malaysia’s Green Building Index for non-
residential buildings includes indoor environmental quality as the second important aspect to
be measured.
A study conducted by Abbaszadeh (2006), found that the occupants of a building which has
been classified as one of the green buildings in the United States, were dissatisfied with its
lighting and acoustic quality. The occupants have suggested the need of improvements in
controlling the lighting system, and recommended innovative strategies, to accommodate
sound privacy needs in open plan or cubicle office layouts. Another study conducted by
Galasiu (2006) showed that the application of day lighting for office buildings required the
inclusion of energy-efficiency lights, which are suitable to occupants, into the lighting
system. Another study conducted by Hummelgaard (2007) showed results with high degree
of satisfaction among the occupants. The building indoor environment was with natural
ventilated workspace. Similarly, a study showed that a naturally ventilated and passively
cooled buildings can be highly appreciated by occupants if they are designed with proper
indoor climate (Wagner, 2006).
EE Buildings should be energy efficient compared to conventional buildings. In order to
ensure good performance, the architects should take occupants’ interactions with the building
control systems into account at the design stage. This study was conducted to measure and
evaluate the indoor environment quality of the two EE Buildings which looked into the
occupants’ response; such as how energy efficiency buildings are performing from the
occupants’ perspective. If they are performing well, this indicates that the goal is being
achieved. A questionnaire survey requires the occupants to rate their workspace environment
in terms of the most important indoor parameters in the tropics which influence the occupant
satisfaction on the workspace; dry bulb temperature, humidity and air movement (Ariffin,
2002), in addition to lighting. The survey assesses indoor environmental quality (IEQ) in
energy efficient office buildings requiring the occupants to directly respond on their
satisfaction with IEQ in the workspace.
The comfort of building occupants is dependent on many environmental parameters including
air speed, temperature, relative humidity and quality in addition to lighting and noise. The
main physical parameters affecting IEQ are air speed, temperature, relative humidity and
quality (Omer, 2008). The indoor comfort is dependent on several factors that include air
temperature, air humidity and air movement (Zain-ahmed, 2002).
OBJECTIVE
The study aims to investigate how the two energy efficient buildings, LEO and GEO, have
succeeded with their goal as EEB from the occupants’ perspective, bringing User-Centered
Design approach to the energy efficient issue, and the users satisfaction with their workspace;
in terms of thermal comfort, air movement and visual comfort.
The significance of the paper comes from the fact that the imitation of the showcase building
without evaluating, involves the repetition of mistakes. Similarly surveying the occupant
satisfaction in the two buildings would be as occupancy evaluation to upcoming buildings.
Thus the main purpose of this post occupancy evaluation study is to provide recommendation
to improve the indoor environment of upcoming energy efficient building in tropics,
Malaysia.
RESEARCH METHODOLOGY
A three phases of methodology are adopted in this study. The first phase was to define the
area of the study; local climate and building description. The second phase of the study is
based on physical measurement of the buildings environment. Finally, the third phase of the
study relied of questionnaire survey to collect responses from building occupants and this
constitute a source of data to declare the occupants’ perspective on their satisfaction at their
workplace.
The study was carried out in the months of September and October 2009. A direct survey was
conducted in the two chosen buildings. This is to evaluate the important parameters of indoor
environment quality, that might be influenced the satisfaction of occupants on the workspace.
Whilst the physical measurement is to compare the responses of the occupants to the same
environment judged against the Malaysian Standard (MS 1525).
100 responders were selected from the two EE buildings were collected. The sample size is
50 responders per building. In addition to more general questions, the questionnaire address
directly related to the workspace indoor environmental quality parameter such as;
temperature, humidity (dampness), air movement and lighting,. The questionnaire survey
collected have been evaluated together with measured data; outdoor/indoor temperatures, day
lighting, air-velocity and humidity from SKYE and BABUC/A data loggers. The survey took
one week to make reliable evaluation for indoor environment quality in the two buildings.
Local Climate
As Malaysia is an equatorial country (Kula Lumpur 3.13°, 348 km north), therefore its
climate characteristics are relatively uniform throughout the year (Fig. 2). There are no large
variations in temperature, relative humidity, and solar radiation during the daytime of the
year, the variation significantly accurse throughout the day. The mean monthly temperature
vary not more than 1.40C. From the mean average of 27
0 C was found in November to 28.4
0
C in May. The average mean temperature in a day ranges from 31.580 degree Celsius during
the daytime to 24.56 0 C during the night.
The monthly average of solar radiation in Kula Lumpur; Subang station is 3.71-4.89 kWh/m²,
with monthly sunshine duration ranging from 9 to 13 hours. The high solar radiation arises
during August to November, (the survey and field measurement of this study contacted
within this period), and January to February, while the low solar radiation occurs in April and
May with 13.72 and 13.04 respectively.
Fig.3: Monthly average of Relative Humidity and
its relation to average max. and mean
Temperature. (source: author besed on 10 years
Subang J. station)
Fig.2: Stereographic diagram to Kuala
Lumpur, Malaysia Latitude: 3.10
(12 Sep., 14:00hr)
Also the humidity is uniformly high all through the year due to the large body of water
surrounding the peninsular Malaysia. The mean monthly relative humidity over the period
was 82 % found in August and never falls below 75.79 % in November.(data based on 10
years 1999 to 2008, Subang Station) (Fig. 3).
Buildings and Experimental Settings
In Malaysia about 70% of energy consumption is used for cooling the environment (Abdul
Rahman, 2006), this is why passive strategies is so important to efficiency reducing energy
consumption in office buildings. The two office buildings LEO building and GEO building
were selected to represent an energy efficient office building in the region and are built to be
a showcase to the public. The LEO building (Fig 4) was awarded the ASEAN Energy Award
in 2006 (Hong, 2007). It was built with ambitious goal of energy saving more than 50%
compared to conventional new office building in Malaysia, with energy index of
114 kWh/m2 year compared to typical conventional of 275 kWh/m2 year (Lau, 2009).
Whereas, the GEO building, (Fig. 5), has been stated in Malaysian’s GBI as a showcase to
Green Energy Office and the details of the building is cited on GBI website (GBI, 2009). The
GEO building energy index of 65 kWh/m2 year compared to typical conventional of 250 to
300kWh/m2year (Lau, 2009).
Fig. 6: (a) Setting up the indoor data logger, (LEO building; (b) setting up the indoor data
logger, GEO
(a) (b)
Fig.4: Low Energy Office (Wagner)
Building, Putrajaya. (Source PTM)
Fig. 5: Green Energy Office Building (PTM),
Bandar Baru Bangi. (Source PTM)
Instrumentation
“Babuc /A” data logger for indoor and “Skye” data logger for outdoor logging with a number
of sensors (outdoor/indoor temperature, air movement, lighting, and RH sensors) were
connected to the data logger, (Fig. 6-a&b). The outdoor temperature sensor was placed in a
balcony in, LEO, at about 2m away from the building façade whereas placed on the roof in
GEO case. The indoor temperature, air movement and RH sensors were stationed on a tripod
located at about 1.0 m above the floor level. The readings of each sensor were recorded by
the logger at 5 minutes interval for twenty-four hours duration in two weeks.
The satisfactory level of occupants was tested and obtained with a questionnaire and rate their
satisfaction perceptions on their workplace environment covering most factors influencing
the IEQ (Ho et al., 2009), they are lighting:( glare, brightness), thermal comfort (
temperature, dampness, and air movement). The satisfaction level evaluated at two different
locations of working space which is near window within less than 3 meter distance and away
from window which is more than 3 meter distance. The questionnaires were given to 50 staff
of each building. The number of responses was 40 (80%) in the GEO office, and 30(60%) in
the LEO office. A likerts 5-point scale was used to range the level of satisfaction with
endpoints from -2“very dissatisfied” to 2“very satisfied” level 0 of satisfaction is considered
as positive or satisfied as the occupants who claim that were not complaining on any
advantage or disadvantage.
RESULTS
Measurements
The finding shows (Fig. A-1, Appendix), the workspace air temperature and the relative
humidity in LEO building and GEO building measured during the sunny 7 days, the same
days as the questionnaires were administered. LEO building showed the peak temperatures
average of the 5 working days at 15:00h with 21.97 °C. While in the GEO it was 23.75 °C at
16:00h. The difference of indoor air temperatures between the two buildings were
approximately 1.78 °C higher in GEO than in LEO. Differently on the off days the peak
temperatures at 16:00h were approximately 0.75 °C higher in LEO than in GEO. The Figure
A-1 shows also that the indoor temperature in the two buildings were lower than outdoor
temperature before the office core hours. At 08:00h. the difference in LEO between indoor
and outdoor was 23.40 °C and 25 °C respectively with 1.60 °C lower on indoor. In GEO
indoor was lower with 1°C, as 24/25 °C indoor/outdoor. The measured relative humidity
varies 60.03 % at 08:00h to 58.94 % at midday in LEO. Likewise in GEO relative humidity
varies with 59.83 at 08:00h to 55.33 at midday. The indoor air movement in both buildings is
approximately zero; with maximum average recorded were 0.01m/s.
The illuminance level of both buildings shows (Fig. A-2, Appendix) at distance less than 3m
from the window and height of 0.75 m from the floor reaches to 300 lux, in LEO open plan
workspace, before 09:00 a.m. and after 05:00 p.m. and never reaches to 400lux. For GEO the
illuminance was 300lux after 10:00 a.m. and before 05:00 p.m., and exceeds 400 lux at
01:00p.m.
Questionnaire
Comparing the results of surveys in the two EE buildings, showed the occupants in LEO
building are more satisfied in the following areas (Fig. 7): Air movement; humidity,
temperature and; overall satisfaction with workspace, whereas the occupants in GEO building
are quite more satisfied in lighting than in LEO building. In both building away to window
the study (Fig. 8) found that the occupants are more satisfied with two indoor parameters:
temperature and; lighting than those near the window. Similarly the figure 9 shows the
occupants in GEO express dissatisfaction with day lighting and they prefer to work with
artificial light. Whilst in LEO the occupants state their satisfaction to the mixed-mode with
slightly more preference to day ligting.
Fig.7: Illustrate the responses of occupants in the two buildings to all indoor environment
parameters.
Fig.8. Illustrates the occupants’ preference to workspace location with respect to the
distance from the window
Figure 10 shows the votes in both of EE buildings, within the category “_2 to 2”. the survey
found that the occupants in LEO are largely satisfied with their workspace, only less than 5%
rating it as unsatisfied and 95% of them felt satisfied in their workspace with the thermal
aspects, and 93% satisfied with visual aspects. Whereas in GEO about 58% of occupants
stated a satisfaction to the thermal comfort parameters, and there are about 41% of the
occupants are unsatisfied. On the contrary, the occupants in GEO show positive response to
the visual comfort with 93% are satisfied.
Fig. 9. Perceives the votes of occupants in both buildings to their preference with respect to
lighting and temperature control
Fig. 10. Relationship between overall satisfaction in LEO and GEO. As the “0” is
considered positive the chart shows that the occupants are satisfied with their workspace in
both buildings with “slightly more” satisfaction in LEO than in GEO
DISCUSSION
Based on field measurements, energy efficient buildings are perceived to be satisfied for their
occupants. For thermal comfort the ideal conditions for Malaysian has been found to be
between 22°C to 26°C (Zain-Ahmed, 1998) (Ministry of Science, 2007). Another studies
presented the variation of thermal comfort in Malaysia of about 24°C to 28°C (Abdul
Rahman, 2006) (Lee Chung Lau, 2009). The analysis of the two buildings (Fig. A1&7),
shows that introducing air-con to sustain the indoor environment will increase the occupant
satisfaction as occupants in LEO building show more satisfaction to temperature 22°C, than
those in GEO with 23.75 °C, after employs air conviction system to indoor environment.
However, physical measurement found that the indoor temperature lies on comfort range of
Malaysian standard, which is below 24 °C; the mean recommendation of MS1525. However,
the indoor temperature in the two buildings was found lower than outdoor temperature before
the office core hours, 08:00h. Nevertheless, the occupants show desire to implement
additional mechanical controlling to maintain their indoor environmental quality. Linked to
this and more highlighting on occupant judgment the study found that the occupants in both
buildings away to window are more satisfied than those near the window. This proposes that
the amount of heat gain and glare are still a problem near the window in these two energy
efficient buildings.
The results also showed that the workspace lighting of the two buildings lies in an acceptable
range for most of the time, complying the Malaysian Standard (2007) which recommends that
the interior lighting for offices should be between 300 and 400 lux. The difference in the two
buildings is that the occupants in LEO building show the occupants’ preference are in mixed-
mode, where it should be consistent with what was proposed at its design stage, to attain
reduction in energy consumption of 18% for lighting when this data compared to other
government buildings (Lee Chung Lau, 2009). In GEO the day lighting was implemented
with almost 100% (PTM, 2009), however the impact showed the occupants in GEO are less
satisfied with its lighting system due to the brightness and glare, the LEO occupants shows
their preference to use blinds with artificial light to get a satisfied luminance level and avoid
the glare.
The ideal comfortable thermal environment for Malaysia is to have a sufficient air movement
and a cool surrounding (Abdul Rahman, 2006). The recommended air movement to obtain
satisfaction in workspace is varied from 0.15 to 0.7 m/s (Ministry of Science, 2007). This
study showed occupant’s judgment was negative to the air movement in the workspace. This
confirms the result from measurement that found the air movement in two buildings is
(0.01m/s maximum), which is lower than the air movement recommended to air-conditioning
office in tropics (Ministry of Science, 2007).
According to ASHRAE when 80% of occupants are satisfied, this indicates to be an
acceptable environment for building (ASHRAE, 1992). With respect to this concept, the
survey found that the occupants in LEO are largely satisfied with their workspace, this due to
implementing additional affective mechanical cooling and controllable interior blinds. In
GEO building about 58% of occupants stated a satisfaction to the thermal comfort
parameters. This is probably due to the orientation and their workspace position against the
windows. A study suggested providing each occupant a flexible adjustment to their personal
working space indoor comfort with for example, ceiling fans and open-able window (Nicol,
2007). For tropical climate as in Malaysia the reduction of thermal condition by passive
design in where the average air temperature is about 33°C with relative humidity of about
80% is not enough to reach to the occupants comfort without the additional of active systems
(Abdul Rahman, 2006), particularly for introducing the ample air movement to control the
high humidity of tropical climate.
CONCLUSION
The study examines satisfaction at the two EE buildings, in Klang-Valley, Malaysia, in the
context of occupants. The study found, in general, that the occupants are in satisfaction with
indoor environment quality of their workspace in the two buildings with preference to LEO
building where implementing air-con. The study concluded that the strategies employed in
energy efficient buildings have been, on average, effective in improving occupant satisfaction
by eliminating air movement that was seen by not to their satisfaction. This position was
confirmed from measurement was registered on workspace.
Comparing the measurement and occupants’ responses of environmental quality in the
workspace of the energy efficient buildings in Klang-Valley, Malaysia, revealed that
responses were based on the occupant’s experience with the questionnaire surveys.
Therefore, it is important to take occupant’s interactions with the control systems into
account when designing EE buildings, especially within tropical climate.
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APPENDIX
Fig. A-1. Illustrate the main indoor thermal comfort parameters: Air Temperatur; Relative Humidity; and Air
Movement to workspace of Energy Efficient, LEO building & GEO building.
Fig. A-2. Illustrate the indoor Lighting of workspace during working Hours to Energy Efficient Buildings; LEO
& GEO.