1) This classroom has _______. A) Too much lighting B) Not enough lighting C) About the right amount of lighting
Transcript
Slide 1
1) This classroom has _______. A)Too much lighting B)Not enough
lighting C)About the right amount of lighting
Slide 2
2) For which of the following conditions would you increase the
weighting factor by +1 in a lighting design? A)A room used
exclusively by high school students B)A circular room with mirrors
for walls C)A room used exclusively by government employees (i.e.
speed/accuracy of task not important) D)A room used for cutting
dark stone
Slide 3
Objective Use room geometry to calculate coefficient of
utilization (CU)
Slide 4
Now what? We now know how much light we need. How do we get it?
Zonal cavity method Calculate CU How much light makes it from the
fixture to the work surface of interest Graphical methods (similar
to stress strain) Ray tracing Computationally intensive
Slide 5
Illumination Calculation I ws = N LPL LOF CU / A N = number of
fixtures LPL = rated lumens per fixture LOF = lamp operating factor
Ballast, voltage, temperature, position (HID) CU = coefficient of
utilization Fraction of light that meets the work surface A = room
area
Slide 6
Lamps are Not the only thing Fixtures (luminaires) Lamp type
and number Power requirements Ballast Application requirements
Mounting Fixture control Special features Distribution
Slide 7
Ref: Tao and Janis (2001)
Slide 8
S/MH Fixture height to have even illumination
Slide 9
3) In lighting design, the coefficient of utilization
__________. A)Determines the fraction of light fixtures in a room
that are actually used. B)Measures the fraction of emitted light
that reaches a working surface. C)Is lower in a room with
light-colored walls than in one with dark walls. D)Depends on the
type of task performed, accuracy required by the task, and on the
ages of occupants in a room.
Slide 10
Zonal Cavity Method Purpose is to get CU fixture efficiency
What parameters do you need?
Slide 11
Figure 16-1 Ref: Tao and Janis (2001)
Slide 12
Calculate Cavity Ratios CR = 2.5 PAR h PAR = perimeter to area
ratio = P/A PAR = 2 (L+ W)/(L W) h = height of cavity What about CR
for non-rectangular rooms? CR = 5 (L+ W)/(L W) h
Slide 13
Reflectance Experience White ceiling, R c = 70 80 % = c White
walls, R w = 60 - 70 % = w Medium to light colored walls, R w = 50
% = w Dark wood paneling, R w = 25 % = w Floor, R f = 10-30 % = f
Convert to effective reflectances ( cc, w, fc ) Tables in Tao and
Janis (pg 92-93, 102-107) or from manufacturer
Slide 14
Calculation Procedure Goal is to get CU (how much light from
the fixture gets to the work surface) 1.Data collection Room
geometry Surface reflectances Fixture tables 2.Preliminary
calculations CR for room, floor, and ceiling
Slide 15
Calculations (continued) 3.Table 16.8 cc and fc (assume fc =
20% if no other information given) 4.Table 16.9 CU Multiplier if fc
20% 5.Fixture table CU based on cc, R w, RCR 6.Use CU by multiplier
from step 4.
Slide 16
Example Classroom (30 30 9) White ceiling, blackboards on 2
sides, light floor Students working on desks Fluorescent fixtures
at ceiling level Use standard tables
Slide 17
Data So Far PAR = 2 (L+ W)/(L W) = 120ft/900ft 2 CCR = 2.5 PAR
h c = 0 RCR = 2.5 PAR h r = 2.17 FCR = 2.5 PAR h f = 0.83 cc = R c
= 70% (b/c CCR = 0) rc = R w = 30% fc = 20% (assumption)
Slide 18
Variations Fixture 2 (pg 92), 1 ft from ceiling Actual fixture,
original height Original fixture, 30% reflective floor
Slide 19
Fixture 2 PAR = 2 (L+ W)/(L W) = 120ft/900ft 2 CCR = 2.5 PAR h
c = 0.33 RCR = 2.5 PAR h r = 1.83 FCR = 2.5 PAR h f = 0.83 cc = 64%
(Table 16-8) rc = R w = 30% fc = 20% (assumption, could use Table
16-8)
Slide 20
Ref: Tao and Janis (2001)
Slide 21
Actual Fixture PAR = 2 (L+ W)/(L W) = 120ft/900ft 2 CCR = 2.5
PAR h c = 0 RCR = 2.5 PAR h r = 2.17 FCR = 2.5 PAR h f = 0.83 cc =
R c = 70% (b/c CCR = 0) rc = R w = 30% fc = 20% (assumption)
Slide 22
More Reflective Floor PAR = 2 (L+ W)/(L W) = 120ft/900ft 2 CCR
= 2.5 PAR h c = 0 RCR = 2.5 PAR h r = 2.17 FCR = 2.5 PAR h f = 0.83
cc = R c = 70% (b/c CCR = 0) rc = R w = 30% fc = 30% (given, could
use Table 16-8 Tao and Janis)
Slide 23
4) If a building owner hires Persephone to determine the amount
of lighting in an existing building, Persephone would need to know
which parameters? A)Type of activity performed, age of occupants,
speed needed to perform activities in the building B) Shape of the
rooms, distance from light fixtures to work surfaces, reflectance
of surfaces, types of light fixtures in the building C)Color
rendering index, evenness of lighting, thermal properties of
lighting in the building
Slide 24
5) If a developer hires Francisco to determine the required
lighting levels for a new building, Francisco would need to know
which parameters? A)Type of activity performed, age of occupants,
speed needed to perform activities in the building B) Shape of the
rooms, distance from light fixtures to work surfaces, reflectance
of surfaces, types of light fixtures in the building C)Color
rendering index, evenness of lighting, thermal properties of
lighting in the building
Slide 25
Illumination Calculation I ws = N LPL LOF CU / A N = number of
fixtures LPL = rated lamp lumens per fixture LOF = lamp operating
factor Ballast, voltage, temperature, position (HID) CU =
coefficient of utilization Fraction of light that meets the work
surface N = I ws A / (LPL LOF CU)
Slide 26
Distribution Direct 90 100 % downward Semi-direct 60-90% down,
rest upward Direct-indirect/general diffuse Semi-indirect
Indirect
Slide 27
Ref: Tao and Janis (2001)
Slide 28
Slide 29
Summary Calculate number of fixtures need for a specific space
Calculate CU Tuesday Accent lighting Daylighting Lighting quality
Thursday Review