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					                     A

                 WRITE-UP

                   ON

 DESIGN AND EXAMPLES OF VERTICAL

            SHADING DEVICES
              COMPILED BY

 AIYESA O.O        ARC /05 /5580

ABODUNRIN B .B    ARC/05/5568

TAIWO B.E          ARC/05/5644

 DEPARTMENT OF ARCHITECTURE

FEDERAL UNIVERSITY OF TECHNOLOGY,

                 AKURE

                            MARCH,2008.
T ABLE OF CONTENTS
1.0 ABSTRACT

2.0 INTRODUCTION

3.0 AIM AND OBJECTIVES

4.0 SHADING DEVICES

4.1 EXTERNAL SHADING DEVICES

5.0SHADING DESIGN

5.1 SHADOW ANGLES

 5.1.1 HORIZONTAL SHADOW ANGLES

 5.1.2 VERTICAL SHADING ANGLES


6.0 EXAMPLES OF VERTICAL SHADING DEVICES

6.1 TREES

6.2 TRELLESES

6.3 SHADE SCREENS

6.4 AWNINGS

6.5 OVERHANGS

6.6 WINDOW COATINGS

6.7 WINDOW SHADES
7.0 CONCLUSION

8.0 REFERENCES.
1.0 ABSTRACT

    There is a popular saying that there is no iota of perfection in
anything .However,shading devices are materials that cannot be
overruled so as to get close to perfection.
\

2.0 INTRODUCTION
       It is of great importance to note that shading devices are paramount and
important aspect of building design. They are meant to provide the building with
natural protection against the disturbing effects of solar radiation which when not
controlled will cause a state of discomfort within the building interior. However, when
these are put in place a considerable state of comfort which aids proper functionality
of the building would be reached. This is a very good notion that must be considered
in architectural design.
3.0 AIMS AND OBJECTIVES
    The aim of this write-up is to vehemently and vividly analyses the basic materials
and devices in vertical form used in building or architectural design




4.0 SHADING DEVICES
       Shading devices are materials used in regulating the amount of heat or solar
Radiation admitted into the building so as to attain an appreciable level of thermal
comfort.
       In any building surface such as windows, walls and room that is exposed to the
sun can admit solar radiation ,to avoid the inflow of heat either directly or indirectly,
the surface on which the sun falls must be protected. Many types of fenestration
control are available for windows, but as each environment requires a different
solution, the selection of a more suitable one necessitate careful consideration.
       In designing shading devices, there are some prominent points that must be
considered and they are highlighted as follows;
-minimizing glare
-control of solar heat
-protection against rain and wind
-provision of adequate ventilation
-control of insects and dust
-provision of privacy
       In architectural design, vertical shading devices can take different forms which
can be either natural devices (building orientation ,trees, shrubs, landforms and water
bodies)or artificial devices (curtain, metal venetian blind ,film coating or chemical
€sprays, roof overhangs, louvers i.e. vertical and horizontal absorbing glasses).

4.1 External Shading Devices

      In the tropical regions, an architect should take into cognizance solar radiation of
         Opaque solid elements of the building's envelope where possible. Special care
        should be taken to shade the windows to reduce the incoming heat and the risk
                                              of Overheating.
5.0 SHADING DESIGN
  The design of shading devices can be quite complex. Computer programs exist to
accurately shape shades for very specific purposes. However, in their absence, and
with a little understanding of the mechanics of sun position and sun-path diagrams,
manual methods can be used.
  External shading devices are preferable and more effective than internal ones. This
includes devices fixed to the outside of the window or attached to building envelope.

  Among the operable units are louvers made of wood or metal, exterior venetian
blinds, shutters, awnings and fixed or movable overhangs. However,there are some
important features to know when shade designing and are hereby discussed below;

5.1 Shadow Angles

When attempting to shade a window, the absolute azimuth and altitude of the Sun are
not as important as the horizontal and vertical shadow angles relative to the window
plane. These can be calculated for any time if the azimuth and altitude of the Sun are
known.

5.1.1 Horizontal Shadow Angle (HSA)

  This is the horizontal angle between the normal of the window pane or the wall
surface and the current Sun azimuth. The normal to a surface is basically the direction
that surface is facing its orientation. If the orientation is known,
HSA is given by:HSA = azimuth orientation

5.1.2 Vertical Shadow Angle (VSA)

 The vertical shadow angle is more difficult to describe. It is best explained as the
angle a plane containing the bottom two points of the wall/window and the centre of the
Sun, makes with the ground when measured normal to the surface. It is therefore

VSA = atan(tan(altitude) / cos(HSA))

It is the VSA that determines the depth of the required shade. The diagram more
adequately describes the derivation of the VSA
6.0 EXAMPLES OF VERTICAL SHADING DEVICES

  Shading is like putting a hat on your building. While there's no dispute about the
general benefits of shading, nailing down actual savings can be difficult. Energy
savings range anywhere from 10 to50 percent. Place the highest priority on the
surfaces that receive the most summer heat. That's usually the east and west. The best
shading occurs before the sun's heat reaches the building.

Shading options in order of effectiveness are: trees and shrubs, trellises, overhangs,
awnings, shade screens, window coatings and interior shades. With natural cooling,
you can't just turn the whole problem over to a subcontractor. Instead, you'll need to
combine a number of methods, including site design, shading, ventilation and
insulation. Shading should be your first line of defense against excessive heat gain.

6.1Trees and Shrubs

  Trees offer excellent natural cooling.They throw shade over the walls and roof. They
also will shade driveways, sidewalks and patios that can bounce heat to the building.
Since big trees give more shade than little ones, devise a site plan that preserves as
many existing trees as possible.

Then plant new trees immediately after
construction. Trees provide a cooling bonus. To
keep themselves coo l, trees pump water from
the ground into their leaves. As this water
evaporates from the surface of the leaves, it cools
the tree. This "evaporative cooling" cools the
surrounding area, too.

  Deciduous trees are best for south yards, because their canopies are broad and
dense. When the leaves fall in the winter, many deciduous trees allow solar heat to
reach the building. Evergreens can work well for north and northwest yards. The closer
a tree is to the building, the more hours of shade it will give. To be effective, tree
should be planted between 5 and 20 feet from the building. Shrubs offer less shading,
but they have several other advantages. They usually cost less, reach mature size more
quickly and require less space. Shrubs can shade walls and windows without blocking
roof-mounted solar panels.




                                  6.2 Trellises

                                   Trellises are permanent structures that partially
                                  shade the outside of a building. Clinging vines
                                  growing over the trellis add more shade and
                                  evaporative cooling. A special trellis to shade air
                                  conditioners, heat pumps and evaporative coolers
improves the equipment's performance. Be sure not to restrict air flow to the
equipment.

  Fast growing vines create shade quickly, while trees can take years to provide useful
shade. Deciduous vines, such as grape and Wisteria lose their leaves in winter allowing
the sun's heat to strike the building. Trellises and climbing plants are a design solution
that's attractive and flexible.




6.3 Shade Screens

  Outside shade screens prevent sun from entering a
window. Put these only on windows exposed to direct
sunlight.

These devices are often called "sun screens," "shade
cloths" or "solar shields." The screens & emdash;
made from aluminum or plastic & emdash; are
lightweight, durable and easy to install. Unlike insect
screens, shade screens are specially made to block a
certain amount of the sun's energy &emdash; usually between 50 and 90 percent of
the energy striking the outside of the window. The term "shading coefficient" describes
the amount of heat that penetrates the screen & emdash;lower numbers mean less
energy gets through. While you can see through a shade screen, the view is obscured.




                         6.4 Awnings

                           Awnings work like the visors on baseball caps by blocking
                         high-angle sunlight. On buildings, awnings can cover
                         individual windows or sections of outside walls. They are most
                         effective on the south side of the building.

                           Awnings come in a variety of shapes, sizes and colors to
                         match many building designs. Some awnings stay in a fixed
                         position. Others can be rolled up in the winter to allow low-
angle sun to reach the building. No matter how they work,awnings are an easy way to
add shading to an existing building. Awnings have the disadvantage of blocking the
view from the top half of the window.




6.5 Overhangs

  Most homes have a built-in shading device.
Overhangs block the high-angle, summer sun, but
allow the lower winter sun to strike the building.
As shading devices, overhangs have several
limitations. For example, a roof overhang on a two
story house will not shade a first story window.
Nor will overhangs provide relief for east and west
windows. Fixed overhangs will always be a compromise, since the sun's angle is the
same in spring and autumn. You might want solar gain in March, but not in September.
(For more information on overhangs, see The Passive Solar Energy Book by Ed Mazria.)
                             6.6 Window Coatings

                               Most window manufacturers offer optional heat-
                             reflecting coatings that block heat gain, but allow
                             penetration of natural light. Windows that receive large
                             amounts of direct or reflected sunlight are good candidates
                             for window coatings. This is a great choice for west-facing
                             view windows. For most residential applications low-
emissivity (low-e) coatings are sufficient. They can cut heat gain up to 25 percent
without changing the window's appearance. You may think of low-e as a wintertime
heat saver that cuts heat loss from a building. Low-e coatings also reduce summer
heat gain. Manufacturers often configure low-e coatings for either heating or cooling
climates. This is sometimes called northern and southern low-e. If you build in the
north, but want to reduce heat gain for west-facing glass, you may need to special
order the proper low-e arrangement. When selecting glazing, you should start by
looking at two important specification :

U-value is the rate of heat transmission (lower is better) and the solar heat gain
coefficient (lower means less heat gain). Also consider visible light transmittance
(higher is better).

6.7 Window Shades

  Interior window shades, such as roller shades,
blinds and drapes, can reduce heat gain. However,
interior shades don't block sunlight as well as
exterior shades. Interior shades work in three ways.
They reflect sunlight back out the window before it
can turn into heat. They block the movement of hot
air from the area around the window into the room.
They insulate the room from the hot surfaces of the
window glass and frame. To give you the most benefit, interior shades should: have a
light colored surface on the side that faces the window; fit tightly to prevent air
movement into the room;Your shades do not need all these features, but the more they
have the better they'll work. Roller shades work best, followed by venetian
blinds.Curtains help only a little.




7.0 CONCLUSION
       It can be said that vertical shading devices are of utmost importance in
architectural design and also very essential in regulating the amount of heat
penetrating into the interior of a building.A good knowledge of it when known and
put into use in design will produce effective result which ensures adequate
comfortability of people staying within a building.




8.0 REFERENCES
http\\;www.oikos.com –An article which appear in Energy Source Builder no 34,August
.copyright 1994,Iris Communications Inc. Retrieved march 20, 2008

http\\learn-londonmet.ac.uk\-Adapted from an article on shading devices, retrieved on
march 20, 2008.

				
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