vertical sky component

Slider_VSC

  • LUA can calculate very quickly the vertical sky component of any aspect of a building or object within a 3D .skp model.
  • VSC is the amount of skylight falling on a vertical wall or window.
  • VSC is expressed as a % ratio of the skylight illuminance on a surface compared with the illuminance on unobstructed horizontal ground. VSC calculations are normally carried at the centre of the outside pane of a window.
  • For VSC calculations the maximum value is nearly 40% for a completely unobstructed vertical plane.
  • In most conventional window design situations a VSC of 27% or greater will usually provide a reasonable daylighting level.
  • When measuring the impacts of new buildings on existing buildings measurements can be taken to assess the VSC impacts, by comparing both before development VSC with after. If the VSC is less than 0.8 times its before value occupants will notice a reduction in daylight.
  • LUA takes into account window reveals, occlusions and obstructions, either from solid objects or trees.
  • VSC calculations do not include reflected light.

 

LUAs VSC calculations have been verified against Table F1 of BR209: Site Layout for Daylight and Sunlight: A Guide to Good Practice by Paul Littlefair, BRE.

 

 

Obstruction angle on building

Equivalent spacing to height ratio

Equivalent VSC %

LUA VSC %

16

3.5

32

32.35

18

3.1

31

31.29

20

2.7

30

30.18

22

2.5

29

29.06

24

2.2

28

27.95

25

2.1

27

26

2.1

27

26.73

28

1.9

26

25.54

30

1.7

24

24.41

32

1.6

23

23.22

34

1.5

22

21.99

36

1.4

21

20.71

38

1.3

20

19.53

40

1.2

18

18.2

42

1.1

17

17.13

44

1

16

16.02

46

1

15

14.84

48

0.9

14

13.66

50

0.84

13

12.48