Figure 8: Notation system of the Skylight-Dimensioning Method

This existing method can be applied to determine the minimal necessary area of transparent surfaces of those skylights that are effected by the hole hemisphere (that "can see” the whole hemisphere).

Ff represents the necessary transparent area of the skylight, it can be calculated with the following equation:

{2}

eaverage a • b m2

100 Tg — Ts -Td ■ ka ■ ^

Nomination of the initial coefficients and parameters:

e average a, b,h r Pc, Pw, Pf

p, q,m Pa

a

: the average illumination coefficient [%],

: the main dimensions — width, depth, height — of the interior space [m],

: the distance between the reference plane and the floor level [m],

: the average reflection coefficients of the surfaces — ceiling, walls, floor — of the interior space [%],

: the main dimensions — width, depth, height — of the light-well [m],

: the average reflection coefficient of the internal surface of the light-well [%],

: skylight transmittance modification coefficients: rg — transmittance, rs — obstruction and rd — dirt coefficients [-].

: the efficiency of the light-well [-],

: the efficiency of the internal space [-].

Calculation and determination of values of the initial coefficients and parameters:

eaverage : the required illumination coefficient, which can be determined using

standards and tables or preliminary recommendations, or it also can be calculated using the En interior (function) specific nominal illumination:

eaverage = EE^ 100%]. {3}

Ekm

Tg, rs, rd : the Tg — transmittance, rs — obstruction and rd — dirt modification values of the

transparent surfaces of the skylight can be determined using existing standards and tables according to the type of the applied — glazing, — structure or depending on the actual environment, for instance:

Tg	As	*d
simple, clear glazing	0.9	structural glazing	1	countryside, regular cleaning	0.8
double, clear glazing	0.8	metal structure	0.9	countryside, accidental cln.	0.55
simple wire-gazing	0.77	timber structure	0.8	residential, regular cleaning	0.7
double wire-gazing	0.63	RC structure	0.8	residential, accidental clean.	0.4
plastics	0.8			industrial, regular cleaning	0.55
				industrial, accidental cleaning	0.25
				clean state at handover	1

Table 2: Approximate Transmittance, Obstruction and Dirt modification values

a

: the efficiency of light-well, that can be determined using the following equation, where i is the light-well index and pa is the average reflection value of the internal surface of the light-well:

i = m-(p + q)

2 • p ■ q

The value of ka can be determined using the light-well efficiency table bellow:

kr

kr

{5}

a ■ b (a + b)-(h — r)

: the interior coefficient can be calculated using the following equation:

П

: the efficiency of the interior can be determined with the help of the following table (the kr interior coefficient values and the actual pc — ceiling, pw — wall and pf — floor average reflection coefficients shall be also substituted to the table):

pf	0,3	0,1
Pc	0,8	0,5	0,8	0,5	0,3
Pw	0,8	0,5	0,3	0,5	0,3	0,3	0,5	0,3	0,3
kr
0,6	0,63	0,39	0,33	0,39	0,33	0,34	0,37	0,33	0,32
0,8	0,76	0,53	0,45	0,51	0,45	0,45	0,50	0,45	0,44
1	0,88	0,62	0,54	0,60	0,54	0,53	0,58	0,53	0,50
1,25	0,95	0,71	0,63	0,68	0,62	0,62	0,66	0,60	0,60
1,5	1,02	0,78	0,70	0,76	0,69	0,68	0,72	0,68	0,66
2	1,1	0,89	0,81	0,85	0,78	0,77	0,80	0,77	0,74
2,5	1,14	0,96	0,88	0,91	0,85	0,83	0,85	0,82	0,80
3	1,17	1,01	0,94	0,95	0,89	0,87	0,88	0,86	0,84
4	1,21	1,07	1,01	1,00	0,95	0,92	0,93	0,90	0,89
5	1,23	1,12	1,06	1,03	0,98	0,95	0,96	0,93	0,92