Sunday, February 21, 2010

ILLUMINATION CALCULATION AND DESIGN FOR MULTI-FAMILY DWELLING UNIT








Interior lighting.

(1) Within all buildings of three or fewer storeys in building height, having a building area not exceeding 600 square metres and used for residential occupancies, business and personal services occupancies, mercantile occupancies or medium and low industrial occupancies.

(1) Every exit (except those serving not more than one dwelling unit), public corridor or corridor providing access to exit for the public shall be equipped to provide illumination to an average level of not less than 50 lux at floor or tread level and at all points such as angles and
intersections at changes of level where there are stairs or ramps.

(2) Emergency lighting shall be provided in:

(a) Exits;

(b) Principal routes providing access to exit in an open floor area;

(c) Corridors used by the public;

(d) Underground walkways; and

(e) Public corridors.

(3) Emergency lighting required in Subsection B(1)(b) shall be provided from a source of energy separate from the electrical supply for the building.

(4) Lighting required in Subsection B(2)(b) shall be designed to be automatically actuated for a period of not less than 30 minutes when the electric lighting in the affected area is interrupted.

(5) Illumination from lighting required in Subsection B(2)(b) shall be provided to average levels of not less than 10 lx at floor or tread level.

(6) Where incandescent lighting is provided, lighting equal to one watt per square metre of floor area shall be considered to meet the requirement in Subsection B(5)(e).

(7) Where self-contained emergency lighting units are used, they shall conform to CSA C22.2 No. 141-M, “Unit Equipment for Emergency Lighting”.

(8) Every public or service area in buildings, including a recreational camp and a camp for housing of workers, shall have lighting outlets with fixtures controlled by a wall switch or panel.

(9) When provided by incandescent lighting, illumination required in Sentence (1) shall conform to Table § 629-36B(1).

(j) When other types of lighting are used, illumination equivalent to that
shown in Table 36.B.(1) shall be provided.





(2) Within all buildings exceeding three storeys in building height or having a building area exceeding 600 square metres or used for other occupancies not described in Subsection B(1).

(a) An exit, a public corridor, a corridor providing access to exit for the public, a corridor serving patients or residents in a Care and Treatment occupancy or Care occupancy, a corridor serving
classrooms, an electrical equipment room, a transformer vault and a hoistway pit shall be equipped to provide illumination to an average level not less than 50 lux at floor or tread level and at angles and intersections at changes of level where there are stairs or ramps.

(b) Rooms and spaces used by the public shall be illuminated as described in Subsection B(1)(h),(i) and (j).

(c) Elevator machine rooms shall be equipped to provide illumination to an average level of not less than 100 lux at floor level.

(d) Every place of assembly intended for the viewing of motion pictures or the performing arts, shall be equipped to provide an average level of illumination at floor level in the aisles of not less than two lux during the viewing.

(e) Every area where food is intended to be processed, prepared or manufactured and where equipment or utensils are intended to be

(2) Within all buildings exceeding three storeys in building height or having a building area exceeding 600 square metres or used for other occupancies not described in Subsection B(1).

(a) An exit, a public corridor, a corridor providing access to exit for the public, a corridor serving patients or residents in a Care and Treatment occupancy or Care occupancy, a corridor serving
classrooms, an electrical equipment room, a transformer vault and a hoistway pit shall be equipped to provide illumination to an average level not less than 50 lux at floor or tread level and at angles and intersections at changes of level where there are stairs or ramps.

(b) Rooms and spaces used by the public shall be illuminated asdescribed in Subsection B(1)(h),(i) and (j).

(c) Elevator machine rooms shall be equipped to provide illumination to an average level of not less than 100 lux at floor level.

(d) Every place of assembly intended for the viewing of motion pictures or the performing arts, shall be equipped to provide an average levelof illumination at floor level in the aisles of not less than two lux during the viewing.

(e) Every area where food is intended to be processed, prepared or manufactured and where equipment or utensils are intended to be

In a service space in which facilites are included to permit a person to enter and to undertake maintenance and other operations; and On a shelf and rack storage system, which includes walkways, platforms, unenclosed egress stairs and exits providing means of egress.

(j) The minimum value of the illumination required by Subsections B(2) (h) and (i) shall be not less than one lux.

(k) In addition to the requirements of Subsections B(2)(h) to (j), the installation of battery-operated emergency lighting in health care facilities shall conform to the appropriate requirements of CSA Z32, “Electrical Safety and Essential Electrical Systems in Health Care
Facilities”. C. For parking lots, walkways, stairs, porches, verandas, loading docks, ramps or other similar areas, a minimum level of illumination of ten lux (0.90 foot-candle) at ground or tread level and at angles and intersections at changes of level where there are stairs or ramps.



Introduction to the Lumen Method

The lumen method is applicable to design of a uniform (general) lighting scheme in a space where flexibility of working locations or other activities is required.




The lumen method is applied only to square or rectangular rooms with a regular array luminaires as shown in Figure 2.





2. Lumen Method Calculations

The lumen method is based on fundamental lighting calculations. The lumen method formula is easiest to appreciate in the following form.

(1)


where E = average illuminance over the horizontal working plane

n = number of lamps in each luminaire

N = number of luminaire

F = lighting design lumens per lamp, i.e. initial bare lamp luminous

flux

UF = utilisation factor for the horizontal working plane

LLF = light loss factor

A = area of the horizontal working plane

2.1 Light Loss Factor

Light loss factor (LLF) is the ratio of the illuminance produced by the lighting installation at the some specified time to the illuminance produced by the same installation when new. It allows for effects such as decrease in light output caused by

(a) the fall in lamp luminous flux with hours of use,

(b) the deposition of dirt on luminaire, and

(c) reflectances of room surfaces over time.

In fact, light loss factor is the product of three other factors:

(2)


where LLMF = lamp lumen maintenance factor

LMF = luminaire maintenance factor

RSMF = room surface maintenance factor

2.1.1 Lamp Lumen Maintenance Factor

Lamp lumen maintenance factor (LLMF) is the proportion of the initial light output of a lamp produced after a set time to those produced when new. It allows for the decline in lumen output from a lamp with age. Its value can be determined in two ways:

(a) by consulting a lamp manufacturer's catalog for a lumen depreciation chart, and

(b) by dividing the maintained lumens by the initial lamps.

2.1.2 Luminaire Maintenance Factor

Luminaire maintenance factor (LMF) is the proportion of the initial light output from a luminaire after a set time to the initial light output from a lamp after a set time. It constitutes the greatest loss in light output and is mainly due to the accumulation of atmospheric dirt on luminaire. Three factors must be considered in its determination:

(a) the type of luminaire,

(b) atmospheric conditions, and

(c) maintenance interval.

2.1.3 Room Surface Maintenance Factor

Room surface maintenance factor (RSMF) is the proportion of the illuminance provided by a lighting installation in a room after a set time compared with that occurred when the room was clean. It takes into account that dirt accumulates on room surfaces and reduces surface reflectance. Figure 4 shows the typical changes in the illuminance from an installation that occur with time due to dirt deposition on the room surfaces.

2.2 Utilisation Factor

Utilisation factor (UF) is the proportion of the luminous flux emitted by the lamps which reaches the working plane. It is a measure of the effectiveness of the lighting scheme. Factors that affect the value of UF are as follows:

(a) light output ratio of luminaire

(b) flux distribution of luminaire

(c) room proportions

(d) room reflectances

(e) spacing/mounting height ratio


2.2.1 Light Output Ratio of Luminaire

Light output ratio of luminaire (LOR) takes into account for the loss of light energy both inside and by transmission through light fittings. It is given by the following expression.

(3)

Example 1

The total, upward and downward lamp output from a lamp are 1000 lm, 300 lm and 500 lm respectively. Calculate upward light output ratio (ULOR), downward light output ratio (DLOR), light output ratio (LOR) of luminaire and percentage of light energy absorbed in luminaire.

Amount of light energy absorbed in luminaire = 100 - 80 = 20 %

A greater DLOR usually means a higher UF.

A simple classification of luminaires according to their distribution is based on flux fractions, as shown in Figure 5. Upward flux fraction (UFF) and downward flux fraction (DFF) are used as a basis of comparison.

Example 2

For data given in Example 1 determine upward flux fraction (UFF), downward flux fraction (DFF) and flux fraction ratio (FRR).

Figure 5 Flux Fraction of Various Luminaires


2. Lumen Method Calculations

The lumen method is based on fundamental lighting calculations. The lumen method formula is easiest to appreciate in the following form.

(1)

where E = average illuminance over the horizontal working plane

n = number of lamps in each luminaire

N = number of luminaire

F = lighting design lumens per lamp, i.e. initial bare lamp luminous

flux

UF = utilisation factor for the horizontal working plane

LLF = light loss factor

A = area of the horizontal working plane

2.1 Light Loss Factor

Light loss factor (LLF) is the ratio of the illuminance produced by the lighting installation at the some specified time to the illuminance produced by the same installation when new. It allows for effects such as decrease in light output caused by

(a) the fall in lamp luminous flux with hours of use,

(b) the deposition of dirt on luminaire, and

(c) reflectances of room surfaces over time.

In fact, light loss factor is the product of three other factors:

(2)

where LLMF = lamp lumen maintenance factor

LMF = luminaire maintenance factor

RSMF = room surface maintenance factor

2.1.1 Lamp Lumen Maintenance Factor

Lamp lumen maintenance factor (LLMF) is the proportion of the initial light output of a lamp produced after a set time to those produced when new. It allows for the decline in lumen output from a lamp with age. Its value can be determined in two ways:

(a) by consulting a lamp manufacturer's catalog for a lumen depreciation chart, and

(b) by dividing the maintained lumens by the initial lamps.

2.1.2 Luminaire Maintenance Factor

Luminaire maintenance factor (LMF) is the proportion of the initial light output from a luminaire after a set time to the initial light output from a lamp after a set time. It constitutes the greatest loss in light output and is mainly due to the accumulation of atmospheric dirt on luminaire. Three factors must be considered in its determination:

(a) the type of luminaire,

(b) atmospheric conditions, and

(c) maintenance interval.

2.1.3 Room Surface Maintenance Factor

Room surface maintenance factor (RSMF) is the proportion of the illuminance provided by a lighting installation in a room after a set time compared with that occurred when the room was clean. It takes into account that dirt accumulates on room surfaces and reduces surface reflectance. Figure 4 shows the typical changes in the illuminance from an installation that occur with time due to dirt deposition on the room surfaces.

2.2 Utilisation Factor

Utilisation factor (UF) is the proportion of the luminous flux emitted by the lamps which reaches the working plane. It is a measure of the effectiveness of the lighting scheme. Factors that affect the value of UF are as follows:

(a) light output ratio of luminaire

(b) flux distribution of luminaire

(c) room proportions

(d) room reflectances

(e) spacing/mounting height ratio

2.2.1 Light Output Ratio of Luminaire

Light output ratio of luminaire (LOR) takes into account for the loss of light energy both inside and by transmission through light fittings. It is given by the following expression.

(3)

Example 1

The total, upward and downward lamp output from a lamp are 1000 lm, 300 lm and 500 lm respectively. Calculate upward light output ratio (ULOR), downward light output ratio (DLOR), light output ratio (LOR) of luminaire and percentage of light energy absorbed in luminaire.

Amount of light energy absorbed in luminaire = 100 - 80 = 20 %

A greater DLOR usually means a higher UF.

A simple classification of luminaires according to their distribution is based on flux fractions, as shown in Figure 5. Upward flux fraction (UFF) and downward flux fraction (DFF) are used as a basis of comparison.

Example 2

For data given in Example 1 determine upward flux fraction (UFF), downward flux fraction (DFF) and flux fraction ratio (FRR).

Figure 5 Flux Fraction of Various Luminaires

2.2.2 Flux Distribution of Luminaire

Direct ratio is the proportion of the total downward luminous flux from a conventional installation of luminaires which his directly incident on the working plane. It is used to assess the flux distribution of luminaire. Since the intensity distribution pattern of the light radiated from a luminaire in the lower hemisphere will affect:

(a) the quantity of the downward flux falls directly on the working plane and

(b) the quantity of flux available for reflection from the walls in a given room,

Direct ratio depends on both the room proportions and the luminaires. Direct ratio has a low value with a narrow room (small room index) and a luminaire which emits most of its light sideways (BZ 10), and on the contrary, a high value with a wide room (large room index) and a luminaire which emits most of its light downwards (BZ 1).

2.2.3 Room Proportion

Room index (RI) is the ratio of room plan area to half the wall area between the working and luminaire planes.

(4)

where L = length of room

W = width of room

Hm = mounting height, i.e. the vertical distance between the working plane and the luminaire.

2.2.4 Room Reflectances

The room is considered to consist of three main surfaces:

(a) the ceiling cavity,

(b) the walls, and

(c) the floor cavity (or the horizontal working plane).

The effective reflectances of the above three surfaces affect the quantity of reflected light received by the working plane.


2.2.5 Spacing to Height Ratio

Spacing to Height ratio (SHR or S/Hm) is defined as the ratio of the distance between adjacent luminaires (centre to centre), to their height above the working plane. For a rectangular arrangement of luminaires and by approximation,

(5)

where A = total floor area

N = number of luminaires

Hm = mounting height

Under a regular array of luminaires the illuminance on the working plane is not uniform. The closer spaced the luminaires for a given mounting height, the higher the uniformity; or the greater the mounting height for a given spacing, the greater the uniformity. If uniformity of illuminance is to be acceptable for general lighting,

(a) SHR should not exceed maximum spacing to height ratio (SHR MAX) of the given luminaire as quoted by the manufacturer, and

(b) geometric mean spacing to height ratio of the luminaire layout should be within the range of nominal spacing to height ratio (SHR NOM) of the given luminaire as quoted by the manufacturer, i.e.

(6)


3. Summary of Procedures for Lumen Design Method

(a) Calculate the room index.

(b) Determine the effective reflectances of the ceiling cavity, walls and floor cavity.

(c) Determine the utilisation factor from the manufacturer's data sheet, using the room index and effective surface reflectances as found in (a) and (b) above.

(d) Determine the light loss factor.

(e) Inert the appropriate variables into the lumen method formula to obtain the number of luminaires required.

(f) Determine a suitable layout.

(g) Check that the geometric mean spacing to height ratio of the layout is within the SHR NOM range:

(h) Check that the proposed layout does not exceed the maximum spacing to height ratios (SHR MAX).

(i) Calculate the illuminance that will be achieved by the final layout and check against the standard.

Example 3

Design a lighting installation for a college seminar room so that the average illuminance is 500 lux on the horizontal working plane, using the data listed below. Suggest the layout and check appropriate spacing to mounting height.

Room dimensions: 12 m long x 8 m wide x 3.2 m high

Working plane at 0.7 m above floor

Reflection factors: Ceiling 70 %

Walls 50 %

Working plane 20 %

Light Loss factor: 0.779

Luminaires: 1800 mm twin tube with opal diffuser

Ceiling mounted

Downward light output ratio 36 %

SHR MAX 1.60 : 1

SHR NOM 1.50 : 1

Dimensions : 1800 mm long x 200 mm wide

Lamps: 1800 mm 75 W plus white

5800 average initial lumens per lamp

2 lamps per luminaire


Solution

(a) Initial calculation

From manufacturer's photometric data sheet (Table 3), utilisation factor (UF) is 0.5336 by interpolation.

Therefore, the number of luminairs is 10.

Initial check on S/Hm ratio gives:

From the manufacture's photometric data, maximum S/Hm is 1.6 : 1. Therefore, it should be possible to use 10 luminaires.

(b) Proposed layout

A 5 x 2 array is proposed fro the lighting installation. (A 10 x 1 array is an alternative.)

(c) Checking the proposed layout

Since 2 x 1.8 m = 3.6 m < 8 m (width of room), the proposed layout will fit.

(Usually checking only the linear dimension of the fitting for space is enough as the other dimension (i.e. 200 mm in this case) is much smaller.)

For long axis,

For short axis,

Note that if the checks had worked out to be unsatisfactory, the number of luminaires should be reconsidered and the calculations on the illuminance should be repeated. For example, a 3x3 array for lower lux level or a 4x4 array for higher lux level.


Distribution

One of the primary functions of a luminaire is to direct the light to where it is needed. The light distribution produced by luminaires is characterized by the Illuminating Engineering Society as follows:
  • Direct ( 90 to 100 percent of the light is directed downward for maximum use.
  • Indirect ( 90 to 100 percent of the light is directed to the ceilings and upper walls and is reflected to all parts of a room.
  • Semi-Direct ( 60 to 90 percent of the light is directed downward with the remainder directed upward.
  • General Diffuse or Direct-Indirect ( equal portions of the light are directed upward and downward.
  • Highlighting ( the beam projection distance and focusing ability characterize this luminaire.
The lighting distribution that is characteristic of a given luminaire is described using the candela distribution provided by the luminaire manufacturer (see diagram on next page). The candela distribution is represented by a curve on a polar graph showing the relative luminous intensity 360 around the fixture ( looking at a cross-section of the fixture. This information is useful because it shows how much light is emitted in each direction and the relative proportions of downlighting and uplighting. The cut-off angle is the angle, measured from straight down, where the fixture begins to shield the light source and no direct light from the source is visible. The shielding angle is the angle, measured from horizontal, through which the fixture provides shielding to prevent direct viewing of the light source. The shielding and cut-off angles add up to 90 degrees.

The lighting upgrade products mentioned in this document are described in more detail in Lighting Upgrade Technologies.

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