Daylight performance and users' visual appraisal for green building offices in Malaysia PDF

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Energy and Buildings 141 (2017) 175–185 Contents lists available at ScienceDirect Energy and Buildings journal homepage: www.elsevier.com/locate/enbuild Daylight performance and users’ visual appraisal for green building offices in Malaysia Gene-Harn Lim a,∗ , Michael Barry Hirning b , Nila Keumala ...

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Energy and Buildings 141 (2017) 175–185

Contents lists available at ScienceDirect

Energy and Buildings journal homepage: www.elsevier.com/locate/enbuild

Daylight performance and users’ visual appraisal for green building offices in Malaysia Gene-Harn Lim a,∗ , Michael Barry Hirning b , Nila Keumala a , Norafida Ab. Ghafar a a b

Faculty of Built Environment, Universiti Malaya, Kuala Lumpur, Malaysia IEN Consultants, Kuala Lumpur, Malaysia

a r t i c l e

i n f o

Article history: Received 13 August 2016 Received in revised form 23 January 2017 Accepted 11 February 2017 Available online 20 February 2017 Keyword: Daylight factor Daylighting Discomfort glare Green building Visual appraisal

a b s t r a c t Lighting energy savings, as well as visual and non-visual user benefits have been widely attributed to daylighting. This paper explores daylight design strategy, visual appraisal, Daylight Factor (DF), lighting energy usage and discomfort glare using two green building offices in Malaysia, which have incorporated daylighting into both fac¸ade and interior design. Visual appraisal surveys were collected from 39 and 145 subjects in the open plan working space of the Energy Commission Building (ECB) and Public Works Department Block G (PWD), respectively. The survey focused on task brightness, colour appearance, uniformity and lighting preference. Discomfort glare assessed via occupant point-of-view luminance maps was juxtaposed here from a glare study involving the same buildings. Illuminance loggers were used to monitor artificial lighting usage as well as the DF on a selected floor of each building. There were no significant differences in occupant responses to the visual appraisal survey for both office spaces. Using MS1525:2014 and Green Building Index (GBI NRNC) tool as baselines, the DF performance of both offices differs significantly: PWD had a 45.5% daylit area, with ECB a 14.8% daylit area for DF >1%. However, lighting energy usage results show substantial savings of 53% and 41% occurred from daylighting. These findings of visual appraisal, DF, lighting energy savings and discomfort glare show a discrepancy in using only the DF to justify the daylight performance of an office space in a tropical climate such as Malaysia. The findings suggest that equivalent consideration should be given to interior design to facilitate daylighting, which is often beyond the control of designer, but in the hands of office end users. © 2017 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).

1. Introduction In the wake of energy efficiency practices to mitigate the effects of climate change, various sustainable building assessment tools have been established since the late 20th century [1]. The building sector has the highest potential to reduce its carbon output given the same mitigation costs across various other sectors such as transportation and agriculture [2]. In response, the Malaysian government intends to reduce its greenhouse gas emissions intensity by 45% (scaled by GDP) by the year 2030 from its 2005 intensity by introducing various environmental related policies and programs [3–5]. One such program was the establishment of Malaysia’s Green Building Index (GBI) in 2009, which signified the start of the green building movement in Malaysia [1]. To date, there are multiple green building certifications in use in Malaysia, such as LEED, Green Mark, GBI and MyCREST,

∗ Corresponding author. E-mail address: [email protected] (G.-H. Lim).

which similarly evaluate the sustainability of a building, taking into account various aspects of design and construction; such as energy efficiency, water efficiency, indoor environmental quality (IEQ), sustainable site management and materials & resources [1,3]. Daylighting is an important aspect of green building design. The benefits of good daylighting to both energy efficiency and visual comfort are well known, as are the consequences [6–9]. Presently, the justification for what constitutes “good” versus “bad” daylight design in green buildings is measured via the Daylight Factor (DF). This paper evaluates the success of the Daylight Factor in producing a well day-lit space in the tropics using two GBI platinum rated government office buildings in Malaysia. 1.1. Daylighting and visual appraisal The human preference for daylight over artificial light for office spaces is well established [7,10–12]. Daylight both stimulates and regulates our circadian system, which subsequently affects our alertness and mood [13,14]. It also provides variation of luminance and colour that influence the attractiveness and desirability

http://dx.doi.org/10.1016/j.enbuild.2017.02.028 0378-7788/© 2017 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4. 0/).

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of spaces [15]. Provision of windows satisfies the occupants desire for a connection to the outside, consequently improving their mood [12,16]. Carter & Marwaee [17] found that people were more satisfied with the lighting when they had windows, even if windows were not appreciably affecting the lighting at their task location. Galasiu & Veitch [12] also found that glare may be better tolerated from daylight than from artificial light if there was a good view available. A survey of readers’ satisfaction at Raja Tun Uda Public Library in Malaysia found 74% of the respondents agreed that their seating preference is affected by daylight [18]. There are also claims that daylight improves work productivity, however as pointed out by Sullivan, Donn, & Baird [19], the findings from laboratory research are not very reliable as people usually take days to adjust to a different luminous environment. This intangible connection between productivity and daylight has constrained the economic feasibility aspect of daylighting to only consider energy savings, which does not take occupants’ well-being into account [20].

1.2. Daylighting and energy efficiency Daylighting can reduce the reliance on artificial lighting, which has been shown to help reduce the cooling load and building energy demand [21]. This is possible as diffuse daylight has a higher luminous efficacy, 110–130 lm/watt, than most artificial lighting, 70–100 lm/watt [22]. Yu & Su [8] reviewed 20 papers and found daylight harvesting can lead to energy savings in lighting of 20–87%. However, these calculations were assessed from non-field measurement methods such as simulation and algorithm calculations. In the context of tropical skies, Kamaruzzaman et al. [23] evaluated the Klang District Office in Malaysia and found an average lighting consumption saving of 37% due to daylighting. However, it is important to note that occupancy and usage trends will impact energy savings. A study of 4 offices in Korea revealed that despite a 43% reduction in lighting energy use due to automatic dimming, the change in occupancy patterns lead to an increase in lighting energy use by up to 50% [24].

1.3. Current recommendations for daylighting office spaces in Malaysia The local Malaysia standards required for new green office buildings are the Green Building Index Non-Residential New Construction (GBI NRNC) tool and MS1525:2014 Code of Practice for Energy Efficiency and Use of Renewable Energy for Non-Residential Buildings. Under the daylighting credit EQ8 (for GBI NRNC) points are awarded based on the percentage of coverage of the Net Lettable Area (NLA) that achieves a Daylight Factor (DF) of 1.0–3.5% measured at the work plane [25]. A separate credit on the Post Occupancy Comfort Survey, EQ15, requires that if 20% of occupants are dissatisfied with the overall comfort, including lighting level and glare problems, then corrective action must be taken [25]. There is no specific credit awarded for reducing lighting energy from daylight harvesting; however, there is a collective credit that looks into the reduction of total building energy consumption (Credit EE5 Advanced EE Performance). This means that in design it is possible to score credits in daylighting through DF performance alone. This requires a simulation model without any interior fittings during the Design Assessment stage, which is not representative of the actual interior office condition [26]. MS1525:2014 briefly mentions a recommended DF of 1.0–3.5%, the same as GBI NRNC EQ8. It also recommends an average illuminance of 200 lx for infrequent reading and 300–400 lx for general office spaces [27]. However, these illumination ranges are for artifi-

cial lighting only and not optimized for skylight or daylight design in Malaysia [7,28,29]. 1.4. Daylighting in Malaysia A survey of 41 rooms in 5 office buildings across Malaysia showed that none of these office spaces achieved more than 0.5% DF due to the deployment of internal shading devices [28]. Despite the offices having deep overhangs to block direct sun, glare from the high luminance ratio of the window to internal surfaces caused occupants to engage their internal shading. Lim et al. [30] identified 18 government offices in Malaysia with identical fac¸ade design, and placement of individual occupant rooms at the perimeter. A simulation study showed that a light shelf could have reduced excessive daylight illuminance and improved uniformity in these offices. A recent (2016) survey of discomfort glare in six office buildings in Malaysia, including three GBI certified green office buildings, found the most common source of glare in green buildings came from windows [31]. With glare from windows in green buildings experienced by 35% of occupants compared to just 7% in non-green office buildings [31]. In tropical climates, a view of the bright sky is a major glare concern. These findings highlight that fac¸ade design principles adopted from temperate climates may not adequately utilize daylight in the tropics [32]. 2. Methodology 2.1. Buildings This daylight performance study took place in two government offices, the Energy Commission Building (ECB) and Public Works Department Block G (PWD) located in Putrajaya and Kuala Lumpur respectively (Figs. 1 and 2). The ECB, completed in 2010, is a multiaward winning green building which obtained GBI Platinum and Green Mark Platinum awards in the Non-Residential category. It was recognised as the ASEAN Energy Award Winner (2012) and ASHRAE Technology Award Runner-Up (2013) [33]. Completed in 2013, PWD was the first high rise building to be certified GBI Platinum [34]. Nikpour et al. [35] explicitly studied the daylight quality of ECB. Despite having an office depth of 18 m, the daylighting strategy of ECB focuses on using a light shelf and atrium to reflect only diffuse daylight into the space. In addition to the removal of ceiling panels and using white finishes for internal surfaces, the cubicle was designed to facilitate daylight across the office space by using translucent partitions (Fig. 1). Roller blinds were provided for occupant’s visual comfort at the vision glazing below the light shelf, while louvers between the light shelf and ceiling prevented low angle direct sun from entering the space from above the light shelf. Also of note is the usage of an automatic blind system at the atrium opening which allows only diffuse light from the sky. This was designed to block direct afternoon insolation, which would bring excessive heat gain into the building. PWD is a 37 storey office tower that allows daylight penetration by taking advantage of perforated horizontal louvers along the vision window (Fig. 2). The closing angle of the horizontal louver is limited to ensure there is a minimum opening for diffuse daylight to enter. Fundamentally, both buildings have daylighting strategies that allow occupants to manually adjust blinds in response to brightness at the window whilst not jeopardizing the abundance of diffuse daylight. Both buildings emphasize daylighting strategies, though different in approach, in an attempt to achieve benefits in energy efficiency and visual comfort [26]. Both office spaces use efficient luminaires (Philips Essential 2 × 28W T5 Fluorescent) controlled by on/off daylight sensors with a set point of 250 lx. The

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Fig. 1. Pictures of Energy Commission Building office in Putrajaya.

Fig. 2. Pictures of PWD Block G Level 31 office in Kuala Lumpur. Table 1 Comparison of daylight design strategy for both offices. Design Feature

ECB

PWD

Window to Wall Ratio Glazing Transmittance Blinds Transmittance Ceiling/Wall/Floor Reflectance Orientation of Openings

50% 53% 8% 90%/70%/30%

90% 54% 30% 90%/70%/30%

Notable Daylight Harvesting Strategy

Occupancy Density Depth of Office Space Workspace Typology

Cubicle Partition Transmittance

All Orientations with Core All Orientations with occupying South Segment Core occupying South Segment Light Shelf, Atrium Perforated horizontal Opening blinds, high transmittance interior partitions 27.15 m2 /pax 11.89 m2 /pax 18 m 13 m Mixture of private rooms Open Plan concept and cubicles with with partitions below partitions above sitting sitting eye level level 90%

horizontal illuminance was designed to comply with MS1525:2014 (300–400 lx) [27]. The design features of each building are listed in Table 1. 2.2. Visual appraisal survey The parameters of the office space that affect daylighting were evaluated by occupants via an online visual appraisal survey. The survey (in Malay language) was sent out by the administration of both office spaces during the measuring period in 2015 (August for ECB, October for PWD). It assessed occupant demographics, controllability of the lighting environment and visual appraisal under paper work and computer work. It is known that visual appraisal and cognitive performance differ under different luminous environment parameters, such as illuminance, colour temperature and uniformity [36–38]. A 6 points Likert scale was used which consisted of “Strongly Dissatisfied”, “Dissatisfied”, “Somewhat Dis-

satisfied”, “Somewhat Satisfied”, “Satisfied”, “Strongly Satisfied”, and also had an additional option of “No Opinion” at the end (see Appendix A). A six point Likert scale was chosen as the neutral option of a 5 or 7 point Likert scale may be misrepresented as no opinion, thus causing misleading results [39]. Responses from private rooms or any other non-open plan working area were excluded from the results, as were surveys with responses of “No Opinion”. Subsequently, a total of 39 and 145 surveys from ECB and PWD were analysed using the Mann-Whitney U Test via IBM SPSS Software. The Mann-Whitney U Test is used to compare the differences between two independent groups with an ordinal dependent variable. 2.3. Daylight factor The DF is defined as the ratio of the internal horizontal illuminance on the work plane to the external horizontal illuminance measured under CIE overcast skies. It has been well documented that the CIE overcast sky is an idealised sky condition available only in simulation and is impossible to observe in reality [43,44]. Three units of TENMARS TM-203 illuminance loggers were synchronized to record at 1-s intervals. Two units (Logger B & C) were placed on the roof of the building to ensure there were no surrounding obstructions. A mirror was used to shade one logger against the direct sun while the other was left unobstructed (Fig. 3). Using this setup, the readings from loggers were compared to determine if there was any direct sunlight. If both loggers registered a global horizontal illuminance value below 60,000 lx, and both readings were within 10% of each other, the sky condition was considered as overcast and suitable for DF calculation. This method eliminated relying solely on visual inspection to assess sky conditions. The sky condition in Malaysia is predominantly intermediate (85.6%), followed by overcast (14%) [41]. Weather data from the measurement period (August and October) was extracted from IWEC (International Weather for Energy Calculations) weather data, which is derived from up to 18 years of hourly weather data (Table 2) [42]. This data was used a guide to accept only horizontal illuminance readings below 60,000 lx for DF calculations. Concurrently, dur-

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Table 2 Comparison of Weather Data of September and November [42]. Month

Global Horizontal Radiation (Avg Daily Total)

Direct Normal Radiation (Avg Daily Total)

Diffuse Radiation (Avg Daily Total)

Cloud Cover (Occurrence)

Global Horizontal Illumination (Avg Hourly)

August October

4336 Wh/sq m 4219 Wh/sq m

1044 Wh/sq m 853 Wh/sq m

3521 Wh/sq m 3533 Wh/sq m

83%–92% 85%–92%.

40,730 lx 40,203 lx

Fig. 4. Method of identifying luminaire activation. Fig. 3. Illustration of the DF Measurement Settings.

ing acceptable overcast conditions, the third logger (Logger A) was used to measure the indoor illuminance at 800 mm from the floor throughout the entire space. The illuminance measurement points covered all work desks and walkways, with a spacing of 1.5–2 m between points. All measurements were completed in about thirty minutes for each building. The positions of the blinds were not disturbed, and the electric lights were switched off. This procedure measured a total of 201 and 304 points for ECB and PWD respectively. The DF was obtained by the illuminance ratio of Logger A to Logger B. The DF performance was evaluated using two different approaches. The first approach calculated the number of measured points achieving the recommended DF range (1–3.5%) by GBI NRNC and MS1525:2014. This was then divided by the total number of measuring points to express the percentage of points in the recommended DF range. The second approach inserts the DF value of each coordinate into the layout plan. Then the area of the recommended DF range is calculated from the layout plan (Figs. 10 and 11). Similarly, the area of recommended DF was divided by the total area to express the percentage of area in the recommended DF range. This made it easy to compare both approaches.

2.4. Lighting circuit usage A typical floor layout of each building was selected to conduct both the DF (see Section 2.3) and lighting usage study. Level 31 of PWD and Level 2 of ECB were selected for monitoring as they were occupied by administration departments, and expected to have consistent occupancy patterns throughout the measuring period. The usage trend of the recessed artificial light circuits was tracked with HOBO-U12 loggers (in 5 min intervals) over a one month period during working hours (8.30 a.m.–5.30 p.m.) for both ECB and PWD respectively. The loggers were hung 10 cm below each lighting circuit, and were considered activated upon exposure to high illuminances >2000 lx (Fig. 4). Another two units of HOBOU12 loggers were placed 1 m from the perimeter of the glazing to record the vertical illuminance of daylight from windows. This allowed a check of the responsiveness of electric lighting controls to the available daylight. A total of 11 and 6 lighting circuits were monitored for ECB and PWD respectively (Fig. 5). Energy savings in lighting were computed by considering the duration that lighting circuits remained

inactive compared to if all light circuits were activated throughout the working hours (8:30 a.m.–5:30 p.m.).

2.5. Discomfort glare The visual comfort in both ECB and PWD were assessed independently of the DF and lighting usage studies using data from a published study by Hirning et al., assessing discomfort glare in Malaysian buildings [31]. Both ECB and PWD were buildi...