OTTV (SNI 03-6389-2011) and ETTV (BCA 2008) Calculation for Various Building’s Shapes, Orientations, Envelope Building Materials: Comparison and Analysis

Abstract

The Indonesian National Standard SNI 03-6389-2000 adapted the 1983 Singapore’s Handbook on Energy Conservation and limited the Overall Thermal Transfer Value (OTTV) of the building envelope to 45 Watt/m2. In 2008, the Singapore’s Building and Construction Authority (BCA) shifted to Envelope Thermal Transfer Value (ETTV) value of 50 Watt/m2, while SNI 03-6389-2011 continues to use OTTV. This paper reviewed the new SNI 03-6389-2011 and compared it with BCA by calculating OTTV and ETTV of prismatic buildings with eight different shapes and building orientations, 11 Window to Wall Ratio, and 27 building envelope materials. This study also tested those variables to find the best building shape and orientation for an energy saver building. The result shows that ETTV (BCA) is stricter than OTTV (SNI 03-6389-2011) except the OTTV with black building envelope, while parallelogram shape building with North-South orientation is the best combination of energy saver building.

Full text

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Civil Engineering Dimension, Vol. 17, No. 2, September 2015, 108-116 CED 2015, 17(2), DOI: 10.9744/CED.17.2.108-116
ISSN 1410-9530 print / ISSN 1979-570X online
OTTV (SNI 03-6389-2011) and ETTV (BCA 2008) Calculation for
Various Building’s Shapes, Orientations, Envelope Building
Materials: Comparison and Analysis
Loekita, S.1 and Priatman, J.2*
Abstract: The Indonesian National Standard SNI 03-6389-2000 adapted the 1983 Singapore’s
Handbook on Energy Conservation and limited the Overall Thermal Transfer Value (OTTV) of
the building envelope to 45 Watt/m2. In 2008, the Singapore’s Building and Construction
Authority (BCA) shifted to Envelope Thermal Transfer Value (ETTV) value of 50 Watt/m2, while
SNI 03-6389-2011 continues to use OTTV. This paper reviewed the new SNI 03-6389-2011 and
compared it with BCA by calculating OTTV and ETTV of prismatic buildings with eight
different shapes and building orientations, 11 Window to Wall Ratio, and 27 building envelope
materials. This study also tested those variables to find the best building shape and orientation
for an energy saver building. The result shows that ETTV (BCA) is stricter than OTTV (SNI 03-
6389-2011) except the OTTV with black building envelope, while parallelogram shape building
with North-South orientation is the best combination of energy saver building.
Keywords: Building shape; building orientation; envelope building material; ETTV; OTTV.
Introduction
People started to pay attention on energy conser-
vation due to increasingly high demand of energy,
especially in residential and commercial building
sectors. Specifically in Singapore and Indonesia, air
conditioning uses most energy in commercial buil-
dings. Therefore, it is essential to understand the
condition of air system when designing a building
since the amount of energy usage must be esta-
blished early on [1].
Energy consumption in Indonesia is regulated by
limiting the Overall Thermal Transfer Value (OTTV)
[2,3], adopting the Handbook on Energy Conser-
vation in Buildings and Building Services published
by the Development & Building Control Division of
Public Works Department of Singapore in 1983 [4].
In the meantime the new regulation in Singapore
published by the Building and Construction Autho-
rity (BCA) [5] uses Envelope Thermal Transfer
Value (ETTV) instead of OTTV. According to BCA
[5] the later research works revealed that OTTV did
not reflect accurately the relative performance of the
different elements in an envelope system.
1 Department of Civil Engineering, Faculty of Civil Engineering and
Planning Petra Christian University, Surabaya, INDONESIA
2 Department of Architecture, Faculty of Civil Engineering and
Planning Petra Christian University, Surabaya, INDONESIA.
* Corresponding author; e-mail: jpriatman@petra.ac.id
Note: Discussion is expected before November 1st 2015, and will be
published in the “Civil Engineering Dimension” volume 18, number
1, March 2016.
Received 24 February 2015; revised 12 July 2015; accepted 17
August 2015.
The difference between OTTV [2,3] and ETTV [5] is
in the limiting value and the level of sun radiation
absorption. The OTTV in SNI 03-6389-2011 is
limited to 35 W/m2 and considers sun radiation
absorption (α) due to the color of building envelope in
the formulation. While the limiting ETTV value
according to BCA is 50 W/m2, and no sun radiation
absorption coefficient α. in the formulation.
Concept of OTTV
The foundation of an energy efficient building starts
with its design process. The main issue in creating
an energy efficient building comes from the
absorption of the building’s solar heat load through
its air conditioning system. Aligning the direction of
the building’s façade to East and West and choosing
light colors for wall finish are some examples of the
common design practice to reduce solar heat input.
Limiting OTTV is one of the energy efficiency
strategies. OTTV takes into account the elements of
heat gain through the external wall of a building,
such as: heat conduction through opaque walls and
glass windows as well as solar radiation through
glass windows. OTTV value is measured by taking
the average measurement of these three elements
over the whole envelope area of the building.
OTTV based on SNI 03-6389-2011[3]
To calculate the OTTV of an external wall, the
following basic equations shall be used:
OTTV = α [Uw (1-WWR) TDek] + (Uf WWR ΔT) + (SC
WWR SF) (1)

Loekita, S. et al. / OTTV (SNI 03-6389-2011) and ETTV (BCA 2008) / CED, Vol. 17, No. 2, September 2015, pp. 108–116
109
Where more than one type of material and/or
fenestration is used, the following equation shall be
used:
OTTV = [α1{Uw1 A1/ΣA (1- WWR) TDek + α2{Uw2
A2/ΣA (1- WWR ) TDek} + ………+ αn{Uwn
An/ΣA (1- WWR) TDek}] + (Uf WWR ΔT) +
(SC WWR SF) (2)
While to calculate the OTTV for the envelope of the
whole building, the following equation shall be used:
0i0201
0i0i02020101
A ..... A A
)OTTV (A ...... )OTTV (A )OTTV (A
OTTV



(3)
In Equations 1 to 3:
α = sun radiation absorption, depending on
the material and color of the exterior
wall
Uw = thermal transmittance of opaque wall
(Watt/m².K).
WWR = window-to-wall ratio (%)
TDek = equivalent temperature difference for wall
(10oK for brick wall)
SC = shading coefficients of fenestrations, spe-
cified by the manufacturer
SF = solar factor (W/m²), depends on building
orientation
= 130 for North (N), 113 for North East
(NE),112 for East (E), 97 for South East
(SE), 97 for South (S), 176 for South
West (SW), 243 for West (W), 211 for
North West (NW)
Uf = thermal transmittance of fenestration
(Watt/m².oK)
ΔT = temperature difference between exterior
and interior design condition (5oK)
A1 = wall area with material 1 (m²)
A2 = wall area with material 2 (m²)
An = wall area with material n. (m²)
ΣA = A1+A2+…………+An
A0i = gross area of exterior wall 0i (opaque
wall area + fenestration area). (m²)
OTTV0i = overall thermal transfer value from wall
0i (W/m2)
For the purpose of energy conservation, the maxi-
mum permissible OTTV is set to 35 Watt/m2.
ETTV based on BCA of Singapore [5]
Since 1979, the Building Control Regulations had
prescribed an envelope thermal performance stan-
dard known as OTTV. The OTTV standard applied
only to air-conditioned non-residential buildings. A
major review of the OTTV formula was carried out in
the early 2000 to provide a more accurate measure of
the thermal performance of building envelope. The
new formula is named Envelope Thermal Transfer
Value (ETTV) to differentiate from the original
OTTV formula. The ETTV requirement does not
apply to non air-conditioned buildings.
The ETTV formulas are given as follows:
ETTV = 12 (1-WWR) Uw + 3.4 (WWR) Uf + 211
(WWR) (CF) (SC) (4)
To calculate the ETTVfor the envelope of the whole
building, the following equation shall be used:
0i0201
0i0i02020101
A ..... A A
)ETTV (A ...... )ETTV (A )ETTV (A
ETTV



(5)
where:
ETTV = Envelope Thermal Transfer Value
(Watt/m²)
WWR = Window-to-Wall Ratio (Fenestration
area/gross area of exterior wall) (%)
Uw = Thermal transmittance of opaque
wall (Watt/m².K)
Uf = Thermal transmittance of fenestra-
tion (Watt/m².K)
CF = Correction Factor for solar heat gain
through fenestration (Watt/m²), de-
pends on pitch angle and orientation.
Pitch angle is the numerical mea-
surement of the slope of a wall. The
pitch angle used for this study is 90o.
SC = Shading Coefficients of fenestration,
specified by the manufacturer
A01, A02, A0n = gross areas of the exterior wall for
each orientation (m2)
For the purpose of energy conservation, the maxi-
mum permissible ETTV is set to 50 Watt/m2.
Buildings Considered
This study uses data and building specification from
Singapore Reference Office Building Description [6].
The buildings that will be analyzed are hypothetical
buildings with eight different building shapes and
eight different building orientations.
In this study, the Authors calculated OTTV [3] and
ETTV [5] of prismatic buildings with eight different
shapes, eight building orientations, 11 Window to
Wall Ratio (WWR), and 27 alternative for building
envelope material for OTTV as shown in Table 1,
and nine alternative for building envelope material
for ETTV as shown in Table 2.
The Authors then compared the results to find the
OTTV/ETTV value that fits the energy-saver
building standard. The eight hypothetical building

Loekita, S. et al. / OTTV (SNI 03-6389-2011) and ETTV (BCA 2008) / CED, Vol. 17, No. 2, September 2015, pp. 108–116
110
shapes; circular, equilateral octagon, equilateral
triangle, parallelogram, square, rectangle, ellipse,
and trapezoid with eight orientations (N, NE, E, SE,
S, SW, W, NW) are shown in Figure 1. Each
hypothetical building is ten story with four meters
floor to floor height. The overall floor area is 625 m2
with 100 m2 core, leaving the total floor that requires
cooling as 525m2. Total area of the whole building is
5250 m2.
There are three materials considered for the building
envelope.
1. Wall I: Aluminum Composite Panel 4 mm, Alu-
minum Frame, Steel Bracket, and Gypsum Board
9 mm (UwI= 3.007 W/m2.K)
2. Wall II: Glass Fiber Reinforced Concrete 12.7
mm, Steel Bracket, and Gypsum Board 9 mm
(UwII = 2.961 W/m2.K)
3. Wall III: Brick wall, plaster and ceramic tile 9
mm (UwIII = 2.741 W/m2.K)
For outdoor painting, the Authors chose three
different colors to represent: the largest α, overall
black painting (α1 = 0.95), the medium α, medium
green or blue painting (α2 = 0.57), and the smallest α,
white varnish (α3 = 0.21)
For single glazed window, the Authors used high
shading coefficient of SCH = 0.88, UfH = 3.069
W/m2.K, medium shading coefficient SCM = 0.62, UfM
= 3.069 W/m2.K, and low shading coefficient SCL =
0.37, UfL = 3.08 W/m2.K. Only one building material
is used for each alternative envelope building. WWR
started from 0% to 100% with 10% interval.
Table 1 shows 27 different alternative combinations
of materials for building envelope in OTTV
calculation (marked with “” in Table 1). On the
other hand, there are only nine different alternative
combinations of materials for building envelope in
ETTV calculation because ETTV calculation does not
include the variable α (Table 2).
Table 1. 27 Alternatives of Building Envelope Materials on OTTV

Building Envelope
Glass



UwI
UwII
UwIII
UfH
UfM
UfL
SCH
SCM
SCL
0.95
0.57
0.21
3.007
2.961
2.741
3.063
3.069
3.08
0.88
0.62
0.37
Alternative 1




Alternative 2




Alternative 3




Alternative 4




Alternative 5




Alternative 6




Alternative 7




Alternative 8




Alternative 9




Alternative 10




Alternative 11




Alternative 12




Alternative 13




Alternative 14




Alternative 15




Alternative 16




Alternative 17




Alternative 18




Alternative 19




Alternative 20




Alternative 21




Alternative 22




Alternative 23




Alternative 24




Alternative 25




Alternative 26




Alternative 27





Loekita, S. et al. / OTTV (SNI 03-6389-2011) and ETTV (BCA 2008) / CED, Vol. 17, No. 2, September 2015, pp. 108–116
111
Table 2. Nine Alternatives of Building Envelope Materials on ETTV
Building Envelope
Glass
UwI
UwII
UwIII
UfH
UfM
UfL
SCH
SCM
SCL
3.007
2.961
2.741
3.063
3.069
3.08
0.88
0.62
0.37
Alternative 1



Alternative 2



Alternative 3



Alternative 4



Alternative 5



Alternative 6



Alternative 7



Alternative 8



Alternative 9



Figure 1.a. Four Building Shapes (Circular, Equilateral Octagon Equilateral Triangle, and Parallelo-
gram) and Eight Building Orientations [7]

Loekita, S. et al. / OTTV (SNI 03-6389-2011) and ETTV (BCA 2008) / CED, Vol. 17, No. 2, September 2015, pp. 108–116
112
OTTV Calculation
Table 3 shows a typical result of OTTV calculation
on prismatic building, with circular shaped [7]
using27 different materials and WWR from 0% to
100% with 10% interval. The shaded cells denote
buildings with OTTV satisfying SNI 03-6389-2011
ETTV Calculation
Table 4 shows a typical result of ETTV calculation on
prismatic building, with circular shape. This
building was built with nine different materials with
WWR from 0% to 100% with 10% interval. The
shaded cells denote buildings with ETTV satisfying
BCA 2008
Figure 1.b. Four Building Shapes (Square, Rectangle, Ellipse, Trapezoid) and Eight Building Orientations [8]

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Table 3. OTTV for Prismatic Building with Circular Shape (Alt 1-27)
WWR (%)
Alt 1
Alt 2
Alt 3
Alt 4
Alt 5
Alt 6
Alt 7
Alt 8
Alt 9
0
28.57
28.57
28.57
28.13
28.13
28.13
26.04
26.04
26.04
10
40.21
36.38
32.70
39.82
35.99
32.31
37.94
34.11
30.43
20
51.85
44.20
36.84
51.50
43.85
36.49
49.83
42.18
34.82
30
63.50
52.01
40.98
63.19
51.71
40.67
61.73
50.24
39.21
40
75.14
59.83
45.11
74.88
59.56
44.85
73.63
58.31
43.60
50
86.79
67.64
49.25
86.57
67.42
49.03
85.52
66.38
47.98
60
98.43
75.46
53.38
98.25
75.28
53.21
97.42
74.45
52.37
70
110.07
83.27
57.52
109.94
83.14
57.39
109.32
82.51
56.76
80
121.72
91.09
61.66
121.63
91.00
61.57
121.21
90.58
61.15
90
133.36
98.90
65.79
133.32
98.86
65.75
133.11
98.65
65.54
100
145.01
106.72
69.93
145.01
106.72
69.93
145.01
106.72
69.93
WWR (%)
Alt 10
Alt 11
Alt 12
Alt 13
Alt 14
Alt 15
Alt 16
Alt 17
Alt 18
0
17.14
17.14
17.14
16.88
28.13
16.88
15.62
15.62
15.62
10
29.93
26.10
22.42
29.69
35.99
22.18
28.56
24.73
21.05
20
42.71
35.06
27.70
42.50
43.85
27.49
41.50
33.84
26.48
30
55.50
44.01
32.98
55.32
51.71
32.79
54.44
42.95
31.92
40
68.29
52.97
38.26
68.13
59.56
38.10
67.38
52.06
37.35
50
81.07
61.93
43.53
80.94
67.42
43.40
80.31
61.17
42.78
60
93.86
70.89
48.81
93.75
75.28
48.71
93.25
70.28
48.21
70
106.65
79.84
54.09
106.57
83.14
54.01
106.19
79.39
53.64
80
119.43
88.80
59.37
119.38
91.00
59.32
119.13
88.50
59.07
90
132.22
97.76
64.65
132.19
98.86
64.62
132.07
97.61
64.50
100
145.01
106.72
69.93
145.01
106.72
69.93
145.01
106.72
69.93
WWR (%)
Alt 19
Alt 20
Alt 21
Alt 22
Alt 23
Alt 24
Alt 25
Alt 26
Alt 27
0
6.31
6.31
6.31
6.22
6.22
6.22
5.76
5.76
5.76
10
20.18
16.35
12.68
20.10
16.27
12.59
19.68
15.85
12.17
20
34.05
26.40
19.04
33.98
26.32
18.96
33.61
25.95
18.59
30
47.92
36.44
25.40
47.85
36.37
25.33
47.53
36.04
25.01
40
61.79
46.48
31.76
61.73
48.42
31.70
61.46
46.14
31.43
50
75.66
56.52
38.12
75.61
56.47
38.07
75.38
56.24
37.84
60
89.53
66.56
44.48
89.49
66.52
44.44
89.31
66.33
44.26
70
103.40
76.60
50.84
103.37
76.57
50.82
103.23
76.43
50.68
80
117.27
86.64
57.21
117.25
86.62
57.19
117.16
86.53
57.09
90
131.14
96.68
63.57
131.13
86.67
63.56
131.08
96.62
63.51
100
145.01
106.72
69.93
145.01
106.72
69.93
145.01
106.72
69.93
OTTV satisfying the requirement of SNI 03-6389-2011
Table 4. ETTV for Prismatic Building with Circular Shape (Alt 1- 9)
WWR (%)
Alt 1
Alt 2
Alt 3
Alt 4
Alt 5
Alt 6
Alt 7
Alt 8
Alt 9
0
36.08
36.08
36.08
35.53
35.53
35.53
32.89
32.89
32.89
10
52.15
46.65
41.36
51.66
46.15
40.86
49.28
43.78
38.49
20
68.32
57.22
46.63
67.78
56.77
46.19
65.67
54.66
44.08
30
84.30
67.78
51.91
83.91
67.40
51.52
82.06
65.55
49.67
40
100.37
78.35
57.18
100.04
78.02
56.85
98.45
76.43
55.27
50
116.44
88.91
62.46
116.16
88.64
62.18
114.84
87.32
60.86
60
132.51
99.48
67.73
132.29
99.26
67.51
131.23
98.20
66.46
70
148.58
110.05
73.01
148.41
109.88
72.84
147.62
109.09
72.05
80
164.65
120.61
78.28
164.54
120.50
78.17
164.01
119.97
77.65
90
180.72
131.18
83.56
180.66
131.12
83.50
180.40
130.86
83.24
100
196.79
141.75
88.83
196.79
141.75
88.83
196.79
141.75
88.83
ETTV satisfying the requirement of BCA, 2008

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114
Table 3 shows that for circular building the mini-
mum WWR (WWRmin) that can satisfy the OTTV
requirement is 10% with building envelope material
of Alt 3, 6, 8-27, while the maximum WWR
(WWRmax) is 40% with building envelope material
of Alt 21, 24, 27. Through interpolation, the Authors
determined that the WWRmin satisfying the OTTV
requirement (35 Watt/m²) as 5.52% with building
envelope material of Alt 1, while the result of
WWRmax is 45.57% with building envelope material
of Alt 27.
Table 4 shows that for circular building the mini-
mum WWR that can satisfy the ETTV requirement
is 10% with building envelope material of Alt 2, 5, 7,
8 while the maximum WWR is 30% with building
envelope material of Alt 9. WWRmin satisfying the
ETTV requirement (50 Watt/m²) is 8.66%, with
building envelope material of Alt 1, while the result
of WWRmax is 30.59%, with building envelope
material of Alt 9.
Interpolating other OTTV and ETTV for the rest of
the buildings gives WWRmin and WWRmax as
presented in Table 5.
Based on Table 5, the smallest WWR value for
building material Alt 1(1 = 0.95, UwI = 3.007,UfH =
3.063, SCH = 0.88) that satisfies OTTV requirements
is Trapezoid TR7s(WWR = 4.66%). With the same
building material (UwI = 3.007, UfH = 3.063, SCH =
0.88), this WWRvalue is smaller than the WWR
value that satisfied ETTV requirements (WWR =
7.69%). This phenomena was influenced by the
inclusion of the largest  value black-painted on
OTTV formula.
On the other hand, the largest WWR value that
satisfies OTTV requirements could be seen in
parallelogram JG5 (WWR = 51.86%) that used
building material Alt 27(3 = 0.21, UwIII = 2.741, UfL =
3.08, SCL = 0.37). For the same building material
(UwIII = 2.741, UfL = 3.08, SCL = 0.37), WWR value
(WWR=35.89%) that satisfies ETTV requirement is
smaller than 51.86%.
The Authors also calculated the WWR value for
building material Alt 10 (2 = 0.57, UwI = 3.007, UfH =
3.063, SCH = 0.88). The WWR value that satisfied
OTTV requirement for parallelogram JG5 is 16.33%,
while the WWR value that satisfied ETTV require-
ment is 9.87%.
The comparison of WWR maximum that satisfied
OTTV and ETTV requirement is presented in Table
6.
Table 5. WWRmin and WWRmax (%) Satisfying OTTV
and ETTV Requirements
OTTV = 35 Watt/m²
ETTV = 50 Watt/m²
Material
(alt 1)
Material
(alt 27)
Material
(alt 1)
Material
(alt 9)
WWR min
(%)
WWR max
(%)
WWR min
(%)
WWR max
(%)
Circular
5.52
45.57
8.66
30.59
Octagon
5.52
45.57
8.66
30.59
Triangle
ST1
5.83
47.50
9.31
33.40
ST2
5.88
47.79
8.73
30.88
ST3
5.38
44.64
8.13
28.36
ST4
5.85
47.59
8.73
30.88
ST5
6.13
49.28
9.27
33.22
ST6
5.38
44.64
8.60
30.32
ST7
5.39
44.72
8.01
27.88
ST8
5.16
43.25
8.66
30.59
Parallelogram
JG1
6.34
50.55
9.92
36.13
JG2
6.27
50.10
9.44
33.98
JG3
4.91
41.62
7.70
26.58
JG4
4.92
41.64
7.98
27.73
JG5
6.57
51.86
9.87
35.89
JG6
5.98
48.41
9.51
34.29
JG7
4.79
40.78
7.73
26.71
JG8
5.11
42.90
7.93
27.52
Square
BS1
5.60
46.06
8.72
30.85
BS2
5.44
45.12
8.60
30.32
Rectangle
PP1
6.10
49.13
9.39
33.75
PP2
5.51
45.49
8.58
30.25
PP3
5.18
43.37
8.15
28.42
PP4
5.39
44.68
8.61
30.39
Ellipse
E1
5.31
44.18
8.36
29.30
E2
5.49
45.35
8.67
30.61
E3
5.77
47.07
8.99
31.98
E4
5.56
45.77
8.65
30.54
Trapezoid
TR1
6.30
50.31
9.88
35.95
TR2
5.24
43.76
8.51
29.93
TR3
5.07
42.70
7.78
26.89
TR4
5.02
42.29
8.56
30.14
TR5
6.56
51.81
9.84
35.77
TR6
5.74
46.88
8.68
30.65
TR7
4.66
39.95
7.69
26.54
TR8
5.89
47.87
8.65
30.55
Table 6. The Value of WWRmax that Satisfies OTTV/ETTV
Requirement for Energy Efficient
Building Shape
WWRmax
OTTV (Alt 27)
ETTV (Alt 9)
Circular
45.57%
30.59%
Equilateral Octagon
45.57%
30.59%
Equilateral Triangle
49.28%
33.40%
Parallelogram
51.86%
36.13%
Square
46.06%
30.85%
Rectangle
49.13%
33.75%
Ellipse
47.07%
31.98%
Trapezoid
51.81%
35.95%

Loekita, S. et al. / OTTV (SNI 03-6389-2011) and ETTV (BCA 2008) / CED, Vol. 17, No. 2, September 2015, pp. 108–116
115
Conclusions
The requirements of ETTV for outdoor paintings
with medium  2) and the smallest  3) are
stricter than OTTV requirement. But for outdoor
painting with the largest  1), OTTV has stricter
regulation than ETTV.
From this study, the Authors concluded that the
Parallelogram shape building with building orienta-
tion JG5/JG1 is the best combination of energy saver
building. This combination created the biggest WWR
value that satisfies the requirement of OTTV/ETTV
regulation.
This study also highlighted the need for further
analysis to determine the  value needed for creating
a stricter ETTV value.
References
1. Koo, T.K., A Study on The Feasibility of Using
The Overall Thermal Transfer Value (OTTV) on
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