**Lighting Buildings**

by Dr.Mina Kaboudarahangi

by Dr.Mina Kaboudarahangi

Light & Form

Ambient lighting

Accent lighting

Task Lighting

Signage lighting

Light source beam spread

Light measurement

Lumen method calculations

Daylight Factor calculation

Ambient Lighting

is known as

general

lighting,

it radiates a

comfortable

level of

brightness

without glare

and allows you to see and walk

about safely

Task Lighting

task lighting is

focused on a specific area

to make the completion of visual tasks easier

it can make the work environment

more pleasant

Accent Lighting

it

emphasizes

on an area or an object in a room

This lighting

adds to the

drama or style of a room

by highlighting certain aspects of a room’s decoration

Decorative lighting

another way of enhancing the

b e a u t y

a n d character of the

building both interior a n d e x t e r i o r

Light Measurement

Light source beam spread

Common terms in selecting a light bulb are“

Flood

” light or “

Spot

” light

These are designations of beam angle

The beam angle is the

degree of width

that light comes from a light source

Typically a

narrow beam angle

is a

“spot”

of light and a

broader beam angle “floods”

an area with light, called a

flood light

There are a number of much more specific designations of beam angle

They are not used consistently between all the light bulb manufacturers, but several use this general terminology:

Narrow Spot :

5 – 15 degrees

Spot :

16 – 22 degrees

Narrow flood :

23 -32 degrees

Flood :

33 – 45 degrees

Wide flood :

45+ degrees

Natural Light

Daylight Factor the ratio of outside illuminance over inside illuminance, expressed in per cent

DF = (Ein / Eext)*100

Artificial Lighting Calculation

Lumen Method – determines

average light levels

in large open areas

Point Calculations – determines light levels at a

specific point

on an object or surface

we are interested to calculate illuminance level (lx or lm/m2)

what is Foot Candle?

One foot-candle is equal to one lumen per square foot (lm/ft2) or approximately 10.764 lux

for ease in calculation, 1 FC could be considered 10 Lux

1 foot candle (FC) = 1 Lumen (Lms) divided by 1 square foot (area / A)

1 FC = 1 LM ÷ A

Illuminance (E) (amount of light falling onto an object measured in foot candles) = Lumens divided by Area (in sq. ft.)

E = Lms ÷ A (sq. ft.)

Example:

calculate Illuminance(E) Level if;

Room 10’ x 15’

5 down lights

1000 Lumens each down light

E = Lms ÷ A

Illuminance = Lumens divided by Area

A = 10’ x 15’ = 150 sq. ft.

1000 Lumens x 5 down lights = 5000 lumens

E = 5000 Lms ÷ 150 sq. ft.

E = 37.5 Lms per sq. ft.

E = 37.% foot candles (FC)

Lumen Method

The quantity of light reaching a certain surface is usually the main consideration in designing a lighting system

This quantity of light is specified by illuminance measured in lux, and as this level varies across the working plane, an average figure is used

The Lumen Method is used to determine the number of lamps that should be installed for a given area or room

Example 1

• A production area in a factory measure 60

metres x 24 metres.

• Find the number of lamps required if each lamp

has a Lighting Design Lumen (LDL) output of

18,000 lumens

• The illumination required for the factory area is

200 lux

• Utilisation factor = 0.4

• Lamp Maintenance Factor = 0.75

N = ( 200 lux x 60m x 24m )

18,000 lumens x 0.4 x 0.75

• N = 53.33

• N = 54 lamps

http://studentnotes.co.uk/2360/lumen_method.php

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

Spacing to Height ratio

A drawing class 16 m × 11 m and 3 m high has a white ceiling and light-coloured walls.

The working plane is 0.85m above the floor. 5100 lm double-lamp luminaires are to be used and their normal spacing-to-height ratio

SHR is 1.75. (required illuminance for drawing class 600)

a) Calculate the number of luminaires needed

b) Sketch the layout arrangement of luminaires

c) Find the electrical power consumption of the lighting

system, if the electrical power consumption of each luminaire is 140 W.

Example:

H =(3 − 0.85) m=2.15 m

Room Index =3.3

From Table 3, for a room index of 3, utilization factor=79%=0.79

number of fittings=600× 16× 11 / 0.79 × 0.9×500= 29.12

The ratio of the spacing between rows to the height H above the working plane is:

SHR = S/H= 1.75

Therefore, S =1.75 H

=1.75 × 2.15 m

=3.76 m

Three rows of 10 luminaires are required, as shown in Fig. 1 giving 30 luminaires and a slightly increased illuminance

The electrical power consumption of each luminaire is 140 W. For the room the power consumption will be 30×140 W, that is, 4200 W, which is:

4200 W/16 m × 11 m

= 23.86 W/m2 floor area

This is not an end

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