CHAPTER 3 Window design for day lighting, ventilation and to

CHAPTER

3 Window design for day lighting, ventilation and to

reduce solar heat gains

3.2 Mandatory clause

3.2.1 For air-conditioned buildings

!"!#$$% & # '()! !"!#$$% & * '()! # !"!#$$%

Table 3.2.1: Vertical fenestration U-factor and SHGC requirements as recommended in ECBC 2007

Climate Maximum U-factor _(W/m2

-K) Maximum SHGC for WWR 40% Maximum SHGC for 40% < WWR 60%

Moderate 6.9 0.4 0.3

3.2.2 For naturally ventilated non-air-conditioned buildings

-3.3 Technical guidelines

3.3.1 Windows in air-conditioned buildings

. . / + (0.! # + + (0.! 1 , , (0.! / / . ,

Figure 3.3.1: Types of heat energy flow

occurring through window

/ + 2 1 2 , , 3 & 3 & ) , / -. , ,

Figure 3.3.2: Types of double pane

glass with low-E coating and gas fills

+ ,

. , ,

-Figure 3.3.3: Heat flow through a double-pane glass , , , 2 , , , , , , 4 , , ' 2 2 2 '()! , , & , , . , '()! , , '()! ' , , 2 5 ' 1 '()!

- , , , , , , , '()! 1 -, 2 6 2 , 1

Figure 3.3.4: Projection factor for a window

1 1 - 1 '()! -'()! 785 1

Table 3.3.1: SHGC “M” factor adjustments for overhangs and fins

Overhang 'M' factor for the projection factor Vertical fin 'M' factor for the projection factor factor for projection factors Overhang + vertical fin 'M' Location Orientation 0.25 −0.49 0.5−0.74 0.75−0.99 1.0 +

0.25 −0.49 0.5−_0.74 0.75−_{0.99 1.0 +} 0.25−0.49 0.5−_0.74 0.75 −0.9 9 1.0 + N 0.88 0.8 0.76 0.73 0.74 0.67 0.58 0.52 0.64 0.51 0.39 0.31 E/W 0.79 0.65 0.56 0.5 0.8 0.72 0.65 0.6 0.6 0.39 0.24 0.16 North latitude 15° _or greater S 0.79 0.64 0.52 0.43 0.79 0.69 0.6 0.56 0.6 0.33 0.1 0.02 N 0.83 0.74 0.69 0.66 0.73 0.65 0.57 0.5 0.59 0.44 0.32 0.23 E/W 0.8 0.67 0.59 0.53 0.8 0.72 0.63 0.58 0.61 0.41 0.26 0.16 Less than 15° north latitude S 0.78 0.62 0.55 0.5 0.74 0.65 0.57 0.5 0.53 0.3 0.12 0.04 9 , , , 2 " , , ) / 4 44: ;

Figure 3.3.5: Wall and window dimensions used for the calculation of the WWR

- / 745 7(5 75 75 44: ; < - =( -4 0 + 06 ,

Figure 3.3.6: Photograph showing wall and window position in a building

9 2

.

, 5

,

, - &

**% /

Figure 3.3.7: Day-lit zone explained in the figure as per the description above

/ 9 <#-> 4 <?@ @ , ## , 06

Figure 3.3.8: Diagrammatic representation of the light shelf integrated in the window for daylight

enhancement ## , 06 , ,

Figure 3.3.9: Height to the separation ratio (H/S) between buildings

Figure 3.3.10: Graph displaying required WWR and VLT for various H/S ratio

4 ,

A (=' ,

44: 06

For Various H:S, VLT and WWR

0 10 20 30 40 50 60 70 80 90 20% 30% 40% 50% 60% WWR VLT H:S - 1:5 H:S - 1:4 H:S - 1:3 H:S - 1:2 H:S - 1:1

3.3.2 Windows in non-air-conditioned buildings

Figure 3.3.11: HSA and VSA measurement

' ** -+ ' 2 **

-Figure 3.3.12: Commonly found shading devices ('. 0'.

,

Table 3.3.2 Solar angles for various cardinal directions

Solar angles to be cut on various cardinal directions

Cardinal directions HSA (°°°°) VSA (°°°°)

North 37.8 79.4 East - 33.2 West - 58 South -68.9 85.1 North-east (NE) 44 42.3 North-west (NW) -50.9 68.3 South-east (SE) -46 43.3 South-west (SW) 39.1 64

. . 2 ('. -A C * , ('. DC° 0'. E$° 9 0'.

Figure 3.3.13: Horizontal shading devices used for cutting VSA E$° FD 1 D$F %C$

** *

DC° #H$% EC% EC% ** D , 2 2 , /

Figure 3.3.14: Vertical shading

devices used for cutting HSA

9 <' -G

H$− ('.I

A ('.,

+ 2

Figure 3.3.15: Comparison between amounts of daylight penetration for deep overhang and louvers

+ , & , (=' & 44: /

Figure 3.3.16: Height-to-separation ratio (H/S) between buildings Table 3.3.3 Height-to-separation ratio and the required minimum WWR for adequate daylight in commercial buildings (non-air-conditioned)

H/S ratio

(H/S between buildings) Minimum WWR (%) required for adequate daylighting

1:5 20 1:4 20 1:3 20 1:2 20 1:1 20 & , (=' & 44: /

Table 3.3.4 Height-to-separation ratio and the required minimum WWR for adequate daylight in residential buildings (non-air-conditioned)

H/S ratios

(H/S between buildings) Minimum WWR (%) required for adequate daylighting

1:5 10 1:4 10 1:3 10 1:2 20 1:1 20 2:1 50 3:1 60 - (=' 44: ! 44:, , F -; H (=' <( =' < F=H <#= ' , (=' #/ , 44: , & , C$J 4 & . . + , , , , /

! K

L " !

#$$C 'KD/ ( 2 A : &

"

-Table 3.3.5: Desirable wind speed (m/s) for thermal comfort conditions: Clause 5.2.3.1, National Building Code 2005

Dry bulb temperature (°°°°C) Relative humidity (%) 30 40 50 60 70 80 90 28 * * * * * * * 29 * * * * * 0.06 0.19 30 * * * 0.06 0.24 0.53 0.85 31 * 0.06 0.24 0.53 1.04 1.47 2.10 32 0.20 0.46 0.94 1.59 2.26 3.04 ** 33 0.77 1.36 2.12 3.00 ** ** ** 34 1.85 2.72 ** ** ** ** ** 35 3.20 ** ** ** ** ** **

Table 3.3.6: Air change schedule SP41: Handbook on Functional Requirement of Buildings

K

Space to be ventilated in residences Required air change per hour

Bedrooms 3−6

Living rooms 3−6

9 / -9 + , 4 2 , ! , -, 2 L .

Fig.3.3.18: Image to illustrate wind speed with increasing height of the building ) L " 2 -' 2 ,

Fig.3.3.19: Diagrammatic representation of stack effect in a room L B , DC A #$−*$J , *$J , -- D$J + 2 FCJ

Table 3.3.5: Critical height requirement for physiological cooling

/ 2

2

, Activity-based occupancy Recommended height of the bottom side of

the opening For sitting on chair 0.75 m

For sitting on bed 0.60 m

Payback Period 0 100 200 300 400 500 600 700 800 1 2 3 4 5 6 7 8 9 10 Years A m ou nt in la kh ru pe es Incremental Investment Cumulative savings ,

3.4 Benefits