Daylighting

Illumination and Acoustics
Daylighting Design Strategies
BY-
Dr. Abdultawab Qahtan
Illumination & Acoustics-Daylighting

Illumination & Acoustics-daylighting
Contents:
Daylighting design, part2:
I. GOALS OF DAYLIGHTING
II. SKY CONDITIONS
III. DAYLIGHT FACTOR DF
IV. DAYLIGHTING SOURCES
V. COMPONENTS OF DAYLIGHT
VI. GUIDELINES FOR INITIAL DAYLIGHTING DESIGN.
VII. DESIGN ANALYSIS METHODS
VIII. DAYLIGHTING SIMULATION PROGRAMS
I. Building Design Recommendation for Daylighting

Contents:
I. The Daylighting Opportunity
II. Energy Savings With Daylighting.
III. Human Factors In Daylighting Design.
IV. Daylighting Strategies

1. THE DAYLIGHTING OPPORTUNITY
 Designing with daylight can improve energy efficiency by minimizing the
use of electricity for lighting as well as reducing associated heating and
cooling loads.
 Daylighting is a critical design factor to those concerned about global
warming, carbon emissions, and sustainable design—in addition to visual
comfort. Research has found daylight to be an important factor influencing
human behavior, health, and productivity.
 Windows admitting daylight provide occupants with a view and a temporal
connection with the outdoors.

2. Energy Savings with Daylighting
To obtain lighting energy savings in a building, six “essential” components
for daylighting design are recommended by the Illuminating Engineering
Society of North America (IESNA):
1. Plan interior space for access to daylight.
2. Minimize sunlight in the vicinity ‫جوار‬ of critical visual tasks.
HOW?
3. Design spaces to minimize glare. HOW?
4. Zone electric lighting for daylight‐responsive control.
HOW?
5. Provide for daylight‐responsive control of electric lighting.
6. Provide for commissioning and maintenance of any
automatic controls.

3-HUMAN FACTORS IN
DAYLIGHTING
DESIGN
(a) Windows and View
(b) Productivity and Satisfaction
(c) Controlling Daylight in Interior Spaces
(d) Minimize Glare

4. DAYLIGHTING
STRATEGIES
A variety of strategies are available to control and enhance
daylighting.
Illumination & Acoustics
1. Design consideration in different region
2. Site design.
3. Orient the majority of the glazing north-south, with
secondary glazing to the west if necessary.
4. Building plan form.
5. Illuminate the ceiling as much as possible.
6. Protect against direct sunlight.
7. Balance light from the window wall with reflected daylight on
the opposite wall. (Aperture Strategies: Side-lighting & Top-
lighting )

Acoustics & Lighting
4.1. DESIGN CONSIDERATIONS
IN DIFFERENT REGION
Daylighting in the tropical region:
- Use shading – to prevent the transmission of the direct sun beam.
- preventing brightness from exterior surfaces that reflects sunlight.
Daylighting in the arid region – hot & dry:
- Small windows
- High level of windows. (IRC reflected from
ceiling )
- Aperture opens to the Courtyard

4.2. -SITE DESIGN-
(sky exposure angle.)
Site obstructions such as neighboring buildings,
trees, and landforms will determine the
maximum available daylight on a site and the
maximum project envelope that will preserve
daylight access to adjacent properties

4.3. BUILDING ORIENTATION.
• Orient the majority of the glazing north-
south, with a maximum exposure to more
easily controllable daylight.
• South, is desirable because direct solar
radiation received by the south facade is
easier to control to prevent excess solar
gain. Daylight is relatively uniform.
• North light is the best for daylighting
because it is not direct and constant diffuse
skylight. It is facade is advantageous for
uniform and soft daylighting.
• Toward the east and west the sun is very
low—almost horizontal—so it is hard to
control.

4.4. BUILDING FORM
Maximize perimeter to daylight.
 Long and narrow footprints are better than square one for access to
daylight. Buildings can be arranged as a series of wings to minimize land
requirements while still allowing access to daylight. The space between
the wings should not be too narrow that they shade one another.
Although square buildings have lower heating loads, daylighting the
interior is difficult and the imbalance between perimeter heating loads and
interior cooling loads requires a complex HVAC system.
Multiple-story buildings benefit the most from narrow plans that keep
work areas within 10 meters of the exterior.

Refer to: Fig. 8.5 in the textbook.
The illustration shows how building
layout affects cooling, daylighting,
and heating opportunities.
The effect of building form
on environmental control
strategies.

4.5. -ILLUMINATE THE CEILING AS MUCH AS POSSIBLE.
Clerestory windows should locate as high as possible on the wall to
illuminate the ceiling and grab the maximum amount of daylight.
The light shelf is an extremely useful to reflect light falling above the vision
window up onto the ceiling .
4.6. PROTECT AGAINST DIRECT SUNLIGHT
Daylight and sunlight are two terms that should
not be confused. Daylight is described as
“the diffuse light of the overcast sky, similar in all
orientations, bright above and dark at the horizon…
soft and cool of both temperature and color.
” Sunlight is warmer and stronger.

Higher windows and the use of light
shelves with clerestories will give a larger
depth of penetration for daylight.
To get daylight on the interior wall as well
as the window wall, use a skylight or roof
monitor near the interior wall, or simply
place the opposite wall no more than 2.5
times the window head height from the
window wall
4.7.1. SideWindowdesign
The higher the window, the deeper the
daylighting zone
4.7. ROOM GEOMETRY
The configuration of fenestrations has a significant impact on the distribution of
daylight within a room. The different fenestration types are discussed below:

a) Minimizing contrast between the window and the wall by
splaying or rounding the inside edges of the window.
Window will create less glare if the adjacent walls are not dark
relative to the window. Splaying or rounding the edges will create a
light transition that is more comfortable to the eye.

The average daylight factor equation can be used to estimate the
require window-to-wall ratio (WWR) for adequate daylighting.
(Expressed as a fraction)
Where,
A glazing is the net glazing area (window area minus mullions and framing, or
approximately 80% of the opening)
A cross Wall is the gross exterior wall area (width of the bay by floor-to-floor
height)
b) Window sizing.

http://windows.lbl.gov/daylighting/designguide/section4.pdf
c) Glazing technology
The solar spectrum can be broken into
three main groups:
-Ultraviolet (UV) energy is mostly
invisible and embodies only about
7 % of the energy in sunlight.
-Infrared (IR) energy is also
invisible and contains about 46 % of
the energy in the solar spectrum.
-Visible (light) spectrum contains
about 47 % of the energy in the
solar spectrum.( Brian M. Deal, Rober,…..
1998.(p19))

Cont…Glazing technology
Careful choice of glazing is one of the most direct ways in which designer can
control the indoor climate.
Glass and tints :Tints are absorptive materials that absorb a portion of the
incident solar radiation, (gray, bronze, blue and green.)
Solar control films: Most retrofit films will improve the performance of the
glazing but are typically not as effective as glass that is coated during
manufacture.
Gaze fills: Double- and triple-pane window voids were air-filled. The most
common alternative gas fills are inert gases.
Switchable glazing: Switchable optical windows, or smart windows, have the
ability to change their physical properties based on predetermined
conditions.
Reflective coatings; low-e: were developed in the early 1970s, Most low-e
coatings reflect 40 to 70 percent of infrared, Low-e usually a thin layer of
silver or tin oxide on the glass surface.

4.7.2.Top-light.
There are several top-lighting methods:
 Skylights and
 clerestories.

What is the recommended skylight slope in
a building located in Najran city?
Najran Latitude: +17.5 (17°30'00"N)
Skylights are an effective means of getting
daylight deeper into the building plan, but are
only useful on the top floor of the building...
Skylight

Kimbell Gallery: Louis Kahn
skylight detail

Clerestories

Sustainable lighting design, part2:
Contents:
I. GOALS OF DAYLIGHTING
II. SKY CONDITIONS
III. DAYLIGHT FACTOR DF
IV. DAYLIGHTING SOURCES
VI. GUIDELINES FOR INITIAL DAYLIGHTING DESIGN.
VII. DESIGN ANALYSIS METHODS
VIII. DAYLIGHTING SIMULATION PROGRAMS

I. Goals of Daylighting
Why daylight?
1. Improved aesthetics
2. Good daylighting design is beneﬁcial to health.
3. Daylighting to humans is important in that it is necessary for visual comfort and
providing psychological needs
4. Using natural light from the sun costs nothing to the environment but pays big
dividends to building occupants.
5. Reduce lighting costs. The overall objective of daylighting is to minimize the
amount of artificial light and reduce electricity costs.
6. it can also lower HVAC costs as well. Electrical lighting produces a lot of heat,
whereas, if properly controlled, natural lighting generates hardly any heat at all.

II. SKY CONDITIONS
(a) Standard Overcast Sky
(b) Clear Sky With and Without Sun
(c) Partly Cloudy Sky
Bright sunlight 100,000 lux
Dull, overcast day 5,000 lux
General office 500 lux
Domestic lounge 50 lux
Moonlight 0.1 lux
Table: Typical of the range of illumination we
commonly experience during our lives are:

The amount of light striking the earth’s surface varies by
latitude due to the angle of incidence and amount of light
absorbed by the atmosphere.

III. Daylight Factor DF
When a building is designed to rely
on daylighting, a major design
concern is the daylight factor (DF),
which is expressed as the ratio of
interior illuminance (Ei) to available
outdoor illuminance (EH) under
overcast skies.

Recommended
Daylight Factor DF

Example 1
Calculate the illuminance at a point in a room given the daylight factor of
5% if the external illuminance is 9500 lux.
Therefore:
Internal illuminance = ( Daylight factor x External illuminance ) / 100%
Internal illuminance = ( 5 x 9500 ) / 100%
Internal illuminance = 475 lux
Area
Average
Daylight
factor
Minimum
daylight
factor
Commercial Buildings:
General office 5% 2%
Classroom 5% 2%
Dwellings:
Kitchen 2%
Living room 1%
Bedroom 0.5%
Example

Example
Example 2
Calculate the illuminance at a point in a domestic kitchen if the average
external illuminance is 5000 lux.
From the above table the recommended daylight factor for a kitchen is 2%.
Internal illuminance = ( Daylight factor x External illuminance ) / 100%
Internal illuminance = ( 2 x 5000 ) / 100%
Internal illuminance = 100 lux
Area
Average
Daylight
factor
Minimum
daylight
factor
Commercial Buildings:
General office 5% 2%
Classroom 5% 2%
Dwellings:
Kitchen 2%
Living room 1%
Bedroom 0.5%

IV. Daylighting
Sources
Daylight sources may be categorized as
Direct (direct sunlight and diffuse skylight).
Indirect (light from reflective or translucent diffusers
that were originally illuminated by primary or other
secondary sources).
Daylighting and sunlight?
Sunlight is the direct
component of light while
daylight is the total light
from the sky dome.

Understanding the components of daylight is important to the
design of apertures and the selection of materials. Daylight
illuminance in a building consists of three components:
1. Sky component (SC)
2. Externally reflected component (ERC)
3. Internally reflected components (IRC1 + IRC2
DF is the sum of these three
components, each calculated
individually for each location.
DF = SC + ERC + IRC.

1. Sky component (SC): is the portion of total daylight illuminance at
a point received directly from the area of the sky visible through an
aperture.

2. Externally reflected component (ERC): represents light reflected
from exterior obstructions onto the point under consideration. This does
not include ground‐reflected light. ERC is of significance only in built‐up
areas (where there are structures opposite an aperture)
…and can be estimated as the portion of the SC for that area of
obstructed sky, reduced by the percentage of the sky obstructed (RD)
and the reflectance factor (RF) of the obstruction; that is,
ERC = SC × RD × RF
Example:
if 25% of the sky is obstructed by a building
with a 20% RF, we have
ERC = SC × 0.25 × 0.20
For this particular example, then
ERC = 5% of SC
COMPONENTS OF DAYLIGHT

3. Internally reflected components (IRC1 + IRC2): represents the light
received at the point under consideration that has been reflected from
interior surfaces. IRC is subdivided into reflected skylight (IRC1) and
reflected ground light (IRC2)
COMPONENTS OF DAYLIGHT

VI. Guidelines for Initial Daylighting Design
• Guidelines useful for the designer during the conceptual and
schematic stages of design. These guidelines assume
overcast sky conditions:

Continued--Guidelines for Preliminary Daylighting Design
(a) The 2.5H Guideline
Fig. 8.30 Section shows the 2.5H guideline, which assumes
that sufficient daylight for the desk plane will be delivered at a
depth 2.5 times the height of the window above the desk plane.

Continued- Guidelines for Preliminary Daylighting Design
(b) The 15/30 Guideline
Fig. 8.31 Plan shows the 15/30
guideline, which assumes that
sufficient daylight will be delivered to
the desk plane at a 15‐ft (4.6‐m)
distance from the window wall. The 15‐
to 30‐ft (4.6‐ to 9.1‐m) daylight zone
will need supplementary electric
lighting, and the zone beyond 30 ft (9.1
m) will receive virtually no daylight.

Continued- - Guidelines for Preliminary Daylighting Design
• (c) The Sidelighting and
Toplighting Daylight Factor
Guideline
FIG. Daylight Factor
Design Estimates for
Overcast Sky Conditions
(Table 8.5, in the textbook)
The size of windows, clerestories,
or skylights may be estimated by
using the simple formulas in Table
8.5,
Parts A and B, which provide target
daylight factor values. These design
guidelines consider two factors: the
height of the window in the wall and
the window or skylight area
compared to the floor area for each
daylit space.

VIII. DESIGN ANALYSIS METHODS
In the following sections, several interior daylighting analysis methods
are described:
(a) CIE Method.
A simple, rapid, straightforward, and
reasonably accurate daylighting
calculation method.

This system is based upon the
daylight factor described previously as
applied to the standard overcast CIE
sky.
Dresler developed a set of more
than100 curves covering rooms of
varying proportions and fenestration.
A typical curve is shown in Fig.
Continued--DESIGN ANALYSIS METHODS

(a) CIE Method.

(c) IESNA Lumen
Method
Fig. 8.41 Standard conditions in a room for daylighting calculations:
sidelighting. (IESNA, Recommended Practice for the Lumen Method of
Daylight Calculations, RP‐23‐89.)
(b) Graphic Daylighting Design Method
(GDDM)

DAYLIGHTING SIMULATION PROGRAMS
Desktop Radiance (http://radsite.lbl.gov/deskrad/):
Known as Radiance, this program
integrates a realistic rendering package
(Fig. 8.42) with a computer‐aided design (CAD) input environment. Libraries of
materials, glazings, luminaires, and furnishings facilitate dataentry. Lawrence
Berkeley National Laboratory, Pacific Gas and Electric, and the California Institute
for Energy and Environment developed this
program.
Autodesk Ecotect Analysis (http://usa.autodesk
.com/ecotect‐analysis/)>
DIALUX
So on….

Scale-down model--
https://ssb2014clements.wordpress.com/2014/12/07/assignment-4_integrated-studio-project-part-2-
analog-daylighting-simulation/

Case Study—Daylighting Design

Quick Revision
I. Questions:
1.List the possible methods of interior daylighting analysis?
2.Define ‘daylight factor’.
3.Why should the orientation of a window affect the daylight
factor?
4. What daylight considerations should be used for:
(a) a tropical region,
(b) a hot-dry region?
7. Calculate the illuminance at a point in a domestic kitchen if
the average external illuminance is 5000 lux. (the recommended
daylight factor for a kitchen is 2%.)

II. Use DIALUX to calculate:
Classroom, here are the conditions of the problem:
Location: NU, Najran
Latitude: 17.5656° N
Room: 7.6 m long, 5.5 m deep, with a 3‐m ceiling
Window: height 1.5 m above a 760‐ mm working plane; total length, 5.5 m
Transmittance: 85%; net glass area 92%
Ground reflectance: Not previously specified. Assume an extensive area of
mixed grass, asphalt, and concrete walkways, with an average overall
reflectance of 20% For a more accurate calculation of reflectance, see the
method described in the IES Recommended Practice for the Calculation of
Daylight Availability (IESNA, 1994).

Calculation.
Illuminance Ei will be found at the five points shown in Fig. 8.41 for a spring
day and a winter day at 10:00 a.m. and 2:00 p.m. Assume that the sky is
overcast so that a direct comparison with other methods can be made.
Reflectances are assumed to be 70% for the ceiling, 50% for the wall, and
30% for the floor to correspond to the IESNA method standard conditions.
Fig. 8.41 Standard
conditions in a room
for daylighting
calculations:
sidelighting. (IESNA,
Recommended
Practice for the
Lumen
Method of Daylight
Calculations,
RP‐23‐89.)

Thank you.

Daylighting

Recommended

Recommended

More Related Content

What's hot

What's hot (20)

Similar to Daylighting

Similar to Daylighting (20)

Recently uploaded

Recently uploaded (20)

Daylighting