ASHRAE Journal - February 2015 - S12

Building Orientation Optimization
External surfaces of the building experience varying solar
heat gain as direct radiation is greatly dependent on azimuth,
e.g. the building roof gets heated by solar radiation continuously from sunrise to sunset; the external building walls can
be mutually shaded or subjected to radiation depending on
sun orientation and angle.
The intensity of direct solar radiation on any surface is
expressed as follows:

Where An is the azimuth angle of the wall and IAn is the intensity of direct solar radiation on the wall. Thus, the intensity of
direct solar radiation on the wall is at a maximum when An= AS0,
that is, the wall with the solar azimuth AS0 relative to Imax has the
strongest direct solar radiation gain. The solar azimuth AS0 varies with the season. It moves from the south in the winter to the
east and west in the summer, which accounts for the strongest
solar radiation on the external walls being on the south wall in
winter and on the east and the west walls in summer.
Thus, south is the optimum orientation of building both for
winter - for solar heat gain - and summer. Hence, the larger
surfaces of wall should face south with the least exposure on
west and east.
Thus, in the selected building, north-south orientation contributed up to 2% saving on the annual energy consumption,
reducing it from 9,120 mWh to 9,020 mWh per year (Figure 5).
It is important to note that the flexibility of modifying building
orientation may not be possible in all cases and hence there are
other means of protecting the building from direct solar gains.

Figure 5: Graph highlighting impact of building orientation on energy
consumption.

Window-to-Wall Ratio Optimization
The next step is to establish the optimum openings area on
the façade in order to cut down unwanted heat gain without
compromising on the daylight quality within occupied spaces.
The building façade or envelope is often the first line of
defense against undesirable external elements. In a country like India, where cooling of the building is the primary
requirement in summers, minimizing direct solar radiation
helps reduce heat gains. Thus, it is important to determine
the area and type of glass and create a balance with aesthetics
in order to minimize solar heat gain, giving due consideration
to both capital and operation costs. Although glazing technology has advanced significantly in recent years, a typical high
performance glazing unit (U value of 1.7 W/m²K) still has five
times the heat transmission of an insulated spandrel panel (U
value of 0.35 W/m²K). Glass should, therefore, be placed and
orientated to optimize views and day-lighting whilst avoiding
heat gains.
In the case study, adjusting the window-to-wall ratio (WWR)
of the building envelope affected the amount of heat entering
the space, as opaque enclosures generally resist heat transfer
better than glass (Figure 6).
12

FEBRUARY 2015

Figure 6: Impact of WWR on building loads.

Figure 7: Graph highlighting impact of WWR on energy consumption.

Hence, an optimized WWR of 20% contributed up to 15%
saving on the annual energy consumption of the building,
reducing it from 9,020 mWh to 7,590 mWh per year and



ASHRAE Journal - February 2015

Table of Contents for the Digital Edition of ASHRAE Journal - February 2015

Contents
ASHRAE Journal - February 2015 - Cover1
ASHRAE Journal - February 2015 - Cover2
ASHRAE Journal - February 2015 - 1
ASHRAE Journal - February 2015 - 2
ASHRAE Journal - February 2015 - Contents
ASHRAE Journal - February 2015 - 4
ASHRAE Journal - February 2015 - 5
ASHRAE Journal - February 2015 - 6
ASHRAE Journal - February 2015 - 7
ASHRAE Journal - February 2015 - 8
ASHRAE Journal - February 2015 - 9
ASHRAE Journal - February 2015 - 10
ASHRAE Journal - February 2015 - 11
ASHRAE Journal - February 2015 - 12
ASHRAE Journal - February 2015 - 13
ASHRAE Journal - February 2015 - 14
ASHRAE Journal - February 2015 - 15
ASHRAE Journal - February 2015 - 16
ASHRAE Journal - February 2015 - 17
ASHRAE Journal - February 2015 - 18
ASHRAE Journal - February 2015 - 19
ASHRAE Journal - February 2015 - 20
ASHRAE Journal - February 2015 - 21
ASHRAE Journal - February 2015 - 22
ASHRAE Journal - February 2015 - 23
ASHRAE Journal - February 2015 - 24
ASHRAE Journal - February 2015 - 25
ASHRAE Journal - February 2015 - 26
ASHRAE Journal - February 2015 - 27
ASHRAE Journal - February 2015 - 28
ASHRAE Journal - February 2015 - 29
ASHRAE Journal - February 2015 - 30
ASHRAE Journal - February 2015 - 31
ASHRAE Journal - February 2015 - 32
ASHRAE Journal - February 2015 - 33
ASHRAE Journal - February 2015 - 34
ASHRAE Journal - February 2015 - 35
ASHRAE Journal - February 2015 - 36
ASHRAE Journal - February 2015 - 37
ASHRAE Journal - February 2015 - 38
ASHRAE Journal - February 2015 - 39
ASHRAE Journal - February 2015 - 40
ASHRAE Journal - February 2015 - 41
ASHRAE Journal - February 2015 - 42
ASHRAE Journal - February 2015 - 43
ASHRAE Journal - February 2015 - 44
ASHRAE Journal - February 2015 - 45
ASHRAE Journal - February 2015 - 46
ASHRAE Journal - February 2015 - 47
ASHRAE Journal - February 2015 - 48
ASHRAE Journal - February 2015 - S1
ASHRAE Journal - February 2015 - S2
ASHRAE Journal - February 2015 - S3
ASHRAE Journal - February 2015 - S4
ASHRAE Journal - February 2015 - S5
ASHRAE Journal - February 2015 - S6
ASHRAE Journal - February 2015 - S7
ASHRAE Journal - February 2015 - S8
ASHRAE Journal - February 2015 - S9
ASHRAE Journal - February 2015 - S10
ASHRAE Journal - February 2015 - S11
ASHRAE Journal - February 2015 - S12
ASHRAE Journal - February 2015 - S13
ASHRAE Journal - February 2015 - S14
ASHRAE Journal - February 2015 - S15
ASHRAE Journal - February 2015 - S16
ASHRAE Journal - February 2015 - 49
ASHRAE Journal - February 2015 - 50
ASHRAE Journal - February 2015 - 51
ASHRAE Journal - February 2015 - 52
ASHRAE Journal - February 2015 - 53
ASHRAE Journal - February 2015 - 54
ASHRAE Journal - February 2015 - 55
ASHRAE Journal - February 2015 - 56
ASHRAE Journal - February 2015 - 57
ASHRAE Journal - February 2015 - 58
ASHRAE Journal - February 2015 - 59
ASHRAE Journal - February 2015 - 60
ASHRAE Journal - February 2015 - 61
ASHRAE Journal - February 2015 - 62
ASHRAE Journal - February 2015 - 63
ASHRAE Journal - February 2015 - 64
ASHRAE Journal - February 2015 - 65
ASHRAE Journal - February 2015 - 66
ASHRAE Journal - February 2015 - 67
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ASHRAE Journal - February 2015 - 69
ASHRAE Journal - February 2015 - 70
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ASHRAE Journal - February 2015 - Cover3
ASHRAE Journal - February 2015 - Cover4
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