Model Building By-Laws

Alcoves in daylighted rooms	5	Increase in area of required daylight openings.	Table V
Areas of required daylight openings		Interpretation of term	1
increase in	Table V	Lighting on stairs and in passages	11
minimum permissible areas of required daylight openings	Table I	Natural Lighting alcoves in daylighted rooms	5
Artificial Lighting augmentation of natural lighting	10	areas of required daylight openings	4
Instead of natural lighting	9	artificial lighting instead of	9
Daylight openings	4	Lighting requirements for non-habitable rooms	8
Areas of required depth of room permitted for various areas of	Table II	Maximum depth of daylighted rooms	6
minimum permissible areas	Table I	Open space outside required daylight openings	7
		position of required daylight openings	3
minimum permissible areas depth of open air measurement opposite required.	Table III	required daylight openings.	2
Open space outside required	7	Non-habitable rooms lighting requirements.	8
position of required	3	Passages lighting in	11
required	5	Stairways lighting on	11
Daylight rooms		Standard service illuminance table	schedule
alcoves in	5
maximum depth of	6
Daylight space in relation to height of building
minimum plan dimensions	Table IV
Depth of daylight rooms maximum	6
Floor lighting	12
Illuminance table of standard service	schedule

1. Interpretation of Terms.

In this Chapter—

“Habitable room” means any room design for human occupation, but excluding bathrooms, water-closets, stairways, passageways, lift-cars, photographic dark rooms, sculleries, domestic laundries, cold rooms or garages used for parking alone.

2.Required Daylight Openings.

(1) Subject to the provisions of Part II, in all buildings, every habitable room (except shops conducting, every habitable room (except) shops conducting retail business, restaurants, tea-rooms, storerooms, cinemas, theatres, bars and kitchenettes having a floor area of less than 5 square meters), shall be provided with openings for the direct admittance of daylight.

(2) Such openings as make up the area required by section 4 are hereinafter referred to as “required daylight openings”.

3.Position of Required Daylight Openings.

Only openings or portions of openings which are situated above the level of 300 millimeters above the floor of a room shall be included in the area of required daylight openings.

4. Areas of Required Daylight Openings.

(1) General requirements. —Subject to the provisions of this section, required daylight openings in any room shall have a total area admitting daylight, that is excluding the frame-members in accordance with the requirements of Table I

Table I
Minimum permissible areas of required daylight openings.

1	2
Type of habitable room	Minimum permissible area of required daylight openings in a room expressed as a percentage of the floor area of that room.
Kitchen	12
workshop or workroom	15
All other habitable rooms	10

(2) Required daylight openings under projections. – If a required daylight opening is overhung by an open veranda, balcony, eaves or other projection so that the projection cuts a line drawn from any refence-point, positioned as described in subsection (4), away from the building in a plane at right-angles to the plane of the wall containing the opening, and at 4 degrees to the horizontal, then the required area of the daylight opening shall be increased by 1 per centum of the floor area of such room for every 300 millimeters of projection of such veranda, balcony, eaves or other projection beyond such line.

(3) Where a projection, as described in subsection (2), projects over an opening so as to cut a line drawn from any reference point (positioned as set out in subsection (4) ) away from the building in a plane at right-angles to the plane of the wall containing the opening, and at 30 degrees to the horizontal, that opening shall not be considered a required daylight opening:

Provided that, where there shall be additional natural or artificial sources of light to the satisfaction of the local authority, the provisions of this subsection may be relaxed by the local authority..

(4) Any reference-point referred to in subsection (2) or (3) shall be in the plane of the daylight opening concerned, and within the width of such opening, and at a height of the sill of such opening, or 300 millimeters above the floor-level of the room served by such opening, whichever is the higher level.

5. Alcoves in Daylight Rooms.

(1) In a room having required daylight openings, the sum of the floor areas of alcoves and the like, which are not directly visible from at least one required daylight opening, shall not exceed 10 per centum of the total floor area of the room.

(2) Portions of screens and partitions which are glazed with clear white glass from a height of 1 metre above the floor-level to the top of the screen or partition shall not be regarded as restricting visibility.

6. Maximum Depth of Daylight Rooms.

No part of a room having daylight openings shall be farther from the plane of such an opening than the distance measured perpendicular to that plane, set out in Table II for the area of daylight openings provided in the room.

Table II
Depth Of Room Permitted for Various Areas of Daylight Openings

1	2
Area of provided daylight openings in the room expressed as a percentage of the floor area of that room.	Maximum permissible distance from a daylight opening expressed in multiples of H
10	2,0
15	2,5
20	3,0
25	3,5

• For intermediate values of daylight opening areas, the corresponding maximum permissible distance shall be found by linear interpolation.
  ** H is the height above floor-level of the head of the daylight opening concerned.

7. Open Space Outside required daylight openings1.

(1)space outside required day-light openings shall comply with the provisions of this section.

(2) Where a daylight opening faces directly towards a permanently unobstructed open space within the stand on which the building is located, or a street, or a public place, or any combination of these which totals more than 4,5 meters in width, the height of the building above the sill of the daylight opening concerned shall not exceed that show in Table III, for the “depth-of-open-air-measurement” opposite the daylight opening.

TABLE III
MINIMUM PERMISSIBLE DEPTH-OF-OPEN-AIR-MEASUREMENT OPPOSITE REQUIRED DAYLIGHT OPENINGS

1	2
Maximum permissible height of building above sill concerned in meters	Depth of air measurement opposite required daylight opening in meters.
6	4,5
9	5,4
12	7,2
15	9,0
18	10,8
21	12,6
24	14,4
27	16,2
30	18,0
36	21,6
42	25,2
48	28,8
60	36,0

*For intermediate values of permissible height of building, the minimum depth-of-open-air-measurement shall be found by linear interpolation

(3) The “depth-of-open-air-measurement” required in subsection (2) shall be the distance measured in a horizontal plane, at the level of the sill of required daylight opening concerned, and at right-angles to the plane of the wall-face containing such opening, from the farther boundary of open space, street or public place described in that subsection, to the face of the wall containing the opening:

Provided that, where a cornice, balcony or similar projection from the building containing such opening extends over such line of measurement by a distance greater than 500 millimeters, the measurement shall be made to a vertical line drawn through the edge of the widest overhanging projection.

1The requirements of section 7 do not necessarily ensure adequate open space about buildings. This may be controlled by the town planning scheme in force in the area of jurisdiction of the local authority, and such requirements must, if necessary, be amended, to avoid conflict with the town planning scheme.

(4) Where a required daylight opening does not face such open space, street or public place as described in subsection (2), it shall face an unobstructed open space, termed a “required daylight space” which complies with the following requirements—

a) it shall cover an unobstructed plan area in the space of a rectangle or parallelogram with dimensions D and W, as described in paragraphs (c) and (d), not less than the dimensions set out in Table IV;

b) the plan area of the required daylight space shall be measured beyond the boundary of an adjoining stand, or beyond the centre-line of an adjoining street or public place;

c) the dimension W (the width) of the plan area shall be measured always parallel to the face of the wall containing the daylight opening, and shall, wherever measured, always be bisected by the line of measurement of dimension D, as illustrated in the Figure;

d) the dimension D (the depth) of the plan area shall be measured from the mid-point of the sill of the daylight opening and at an angle β to the plane of the wall containing such opening, the angle β being not less than 30 degrees, as illustrated in the Figure;

e) the required daylight space shall be measured clear of any obstructions projecting from the surrounding walls at levels above that of the sill of the daylight opening, unless such projecting obstructions are less than 500 millimeters in width, in which case such obstructions may be disregarded.

(5) If the required daylight space is a parallelogram in plan, the minimum area admitting light of the daylight opening shall be increased above that set out in Table I by the percentages set out in Table V corresponding to the value of the angle β

TABLE IV
MINIMUM PLAN DIMENSIONS OF REQUIRED DAYLIGHT SPACE IN RELATION TO HEIGHT OF BUILDING

1	2	3
Height of building	Minimum permissible measurement D in meters	Minimum permissible measurement W in meters
6	1,8	1,85
9	2,7	2,00
12	3,6	2,15
15	4,5	2,30
18	5,4	2,45
21	6,3	2,60
24	7,2	2,75
27	8,1	2,90
30	9,0	3,05
36	10,8	3,35
42	12,6	3,65
48	14,4	3,95
60	18,0	4,55

*For intermediate heights, the values of D and W shall be found by linear interpolation

(6) Where the height of the building from the sill of the daylight opening is referred to in subsection (2) and in Tables III and IV, such height shall be measured as the vertical distance from the level of the sill at the daylight opening concerned to the eaves or the top of the parapet, or, where this does not apply, and in the case of stepped buildings, to such other positions as the local authority may consider to be the top of the building containing the daylight opening.

REQUIRED DAYLIGHT SPACES

TABLE V
INCREASE IN AREA OF REQUIRED DAYLIGHT OPENINGS IN TERMS OF SECTION 7 (5)

1	2
Angle	Percentage by which area required by section 4 must be increased.
30	100
32	90
34	80
36	71
38	63
40	56
45	42
50	31
55	23
60	16
65	11
70	7
75	5
80	2
Above 80	Nil

*where β, as measure, is intermediate to the values given in this Table, the appropriate percentage increase in area of required daylight opening shall be obtained by linear interpolation.

8. Lighting Requirements for Non-Habitable Rooms.

Those rooms specifically excluded from the requirements of section 2, and also all non-habitable rooms, shall be provided with means of artificial lighting to the satisfaction of the local authority, or, failing such provision, shall comply with the requirements of section 2 relating to the daylighting of habitable rooms.

9. Artificial Lighting Instead of Natural Lighting.

The local authority may permit artificial lighting to be used instead of natural lighting in rooms or buildings, taking into account the function of such rooms or buildings.

10. Augmentation of Natural Lighting by Artificial Lighting.

The local authority may require artificial lighting to be provided to augment natural lighting in any case where, in spite of compliance with the provisions of this Chapter, the natural lighting in a room is, in the opinion of the local authority, inadequate.2

2For the guidance of local authorities, a table of standard service illuminance recommended by the illuminating Engineering Society of London, Great Britain, is set out in the Schedule, and is not to be constructed as part of the provisions of this Chapter. The Schedule is not fully comprehensive of all requirements.

11. Lighting on Stairways and in Passages.

(1) Every owner of a building which contains a stairway or passage designed to be used by more than one tenant shall install and maintain a lighting system capable of producing illumination at any one point of not less than 50 lux on all such stairways or passages

(2) Lights on landings and on other parts of such a stairway and in a passage shall be kept on through-out the hours of darkness, or a any time when the illumination would otherwise fall below 50 lux, or switches shall be provided and so arranged that the light may be switched on above or below each flight of stairs or at either end of the passage.

(3) Where passageways and stairways are only artificially lit they shall be provided with emergency lighting of not less than 20lux at floor level.

12. Floor-Lights.

Floor-Lights of glass or other translucent and brittle material shall not be allowed in floors between the storeys of a building, unless they and their supporting frames are able to sustain the design floor-load and to comply with any other requirements of these by-laws, relating amongst others to fire protection.

13. Application of Chapter 11.

Lighting arrangements must also comply with the provisions of Chapter 11

For the guidance of local authorities, a table of standard. service illuminance recommended by the Illuminating Engineer- ing Society of London, Great Britain, is set out in the Schedule, and is not to be construed as part of the provisions of this Chapter. The Schedule is not fully comprehensive of all requirements.

SCHEDULE
(for guidance only)
TABLE OF STANDARD SERVICE ILLUMINANCE
(Taken from the Illuminating Engineering Society of London, Great Britain, for various locations and occupations: I.E.S. Code 1973)

	Standard service illuminance lux	Position of Measurement	Limiting Glare Index	Color Appearance of Light Source
A. LOCATIONS
Hospitals- Laboratories	500	Bench	19	Intermediate or warm
Operating theatres- General	400	Trolley Height	–	Intermediate
Tables.	special lighting	–	–	–
Wards- Bedheads
General	30-50	Pillow	–	Intermediate or warm
Reading	150	Book Plane	–	Intermediate or warm
Circulation space	150	Bed Height	–	Intermediate or warm
Office buildings- General office	500	Desk	19	Intermediate or warm
Executive office	500	Desk	16	Intermediate or warm
Conference-rooms	750	Tables	16	Intermediate or warm
Drawing offices Drawing boards	750	Board	16	Cool Intermediate or warm
Reference tables.	500	Table	16	Cool Intermediate or warm
Libraries- Shelves, book stacks	150	Vertical at floor	19	Intermediate or warm
Reading tables.	300	Table	19	Intermediate or warm
Closed bookstores	100	Vertical at floor	19	Intermediate or warm
Book-binding	500	Desk	19	Intermediate or warm
Cataloguing, sorting	500	Desk	19	Intermediate or warm
Public halls
Auditoria-
Multi-purpose	500	Horizontal at seat level	–	Intermediate or warm
Foyers	75 SCALARS	1,2 meters above floor	19	Intermediate or warm
Schools Gymnasia	300	Floor	–	Intermediate or warm
Art rooms	500	Easel	19	Cool or Intermediate
Kitchens- General	500	Working surface	22	Intermediate or warm
Food stores	150	Floor	–	Intermediate or warm
Dining-rooms	300	Tables	22	Intermediate or warm

The average illuminance over the whole surface of a very small sphere located at a given point.

	Standard Service illuminance lux	Remarks
B. OCCUPATIONS Rough work. Routine work Demanding work Fine work Very fine work Minute work.	300 to 500. 500 to 750 750 to 1,000 1 000 to 1500 1 500 to 3000 3 000	Rough machining and assembling Offices, control rooms, medium machining and assembling Drawing or business machine offices, inspection of medium machining Color discrimination, textile processing, fine machining and assembly Hand engraving, inspection of fine machining or assembly. Inspection of very fine assembly.

Note. For detailed tables, see the 1.E,S. Code 1973, of the Illuminating Engineering Society of London, Great Britain.