ANALYSIS OF SHADING SYSTEM FOR THE REDUCTION OF SOLAR INTENSITY IN INDOOR SPACES IN NIGERIA.

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ANALYSIS OF SHADING SYSTEM FOR THE REDUCTION OF SOLAR INTENSITY IN INDOOR SPACES IN NIGERIA.

Abstract

 

Industrial Design involves systematic planning of processes, machinery, and techniques geared

towards mass production. The use of external shading devices proves to be the most efficient passive design strategy for direct solar control in buildings especially in Nigeria. Today, the use of exposed glazed façade as found in curtain walls and large window panes in buildings seems to be the norm. This research looked into the use of external shading devices on buildings indoor Nigeria, by first taking account of the various shading devices and design strategies available and then undertaking a study of select indoor in Nigeria       that employed external shading as a passive design strategy and adapting a style to meet our comfort need. This research discusses the impact of shading devices on the indoor space in Nigeria, particularly the air temperature and air flow. The investigation was performed on two rooms; one with a shading device and the other one without a shading device. Both rooms are similar in area, window to wall ratio (WWR), as well as their orientation (188°). The measurement of air temperature and air flow was conducted in these to rooms, using environmental data equipment. The analyzed data showed that the shading device reduced the amount of heat gain through window and increased the air flow into indoor space, which indicating that the room with a shading de vice seemed to be more comfortable than the room without a shading devices. (humanities 2008).

 

 

 

 

 

 

 

 

 

 

 

 

 

 

CHAPTER ONE

1.0 INTRODUCTION

1.1 BACKGROUND OF STUDY

 

According to Mohammed Bakhlah, 2008, A device placed between the sun’s rays and the window prevents solar radiation from being transmitted into a room. The primary functions of exterior shadings are to reduce the thermal heat gain in a building as well as to control the levels of directlight. Exterior devices are generally more effective in de creasing heat buildup because they block, absorb or reflect solar heat before it gets into windows. It is either a device attached to the building skin or an extension of the skin itself, to keep out unwanted solar heat. Exterior shading devices include awnings, louvers, shutters, rolling shutters and shades and solarscreens. Adjustable shading is particularly useful for east andwest facing windows. The low angle of the sun makes it difficult to get adequate protection from fixed shading. Adjustable shading offers greater control over daylight sun and views. Appropriate adjustable systems include sliding screens, louver screens, shutters, retractable awnings and adjustable exterior blinds. Awnings are very effective because they block direct sunlight. They are attached above the window and extend down and out. A properly installed awning can reduce heat gain up to 65% on southern windows and 77% on eastern windows, and light -colored awning does double duty by also reflecting sunlight (US Department of Energy, 1994). Draperies improve the thermal resistance of windows by 40% and reduce heat losses by 30% (Grasso et al, 1990). The screen must be installed on the exterior of a window.

Louvers are attractive because their adjustable slats control the level of sunlight entering home and, depending on the design, can be adjusted from inside or outside house. The slats can be vertical or horizontal. Louvers remain fixed and are attached to the exteriors of window frames. Fixed horizontal louvers set to the midwinter sun angle and spaced correctly allow full winter  heating and total summer shading (Humanities 2008)

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

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Standard horizontal overhang

 

 

 

 

Use louvers in place of solid overhang
Substitute louvers for the solid dropped edge to let
Vertical louvers or fins for east and especially west facades

 

Figure 1.0:Different design of exterior shading devices. Source: Lee, Rubinstein &Selkowitz (1997)
Slope it down for lessfor less projection.

 

Break up an overhang forless projection
Drop the edge forless projection.
Break up anoverhang for less

 

1.2 SUN SHADING DEVICES

 

The performance of solar passive cooling technique such as solar shading, insulation ofbuilding components was analyzed by (Kumar, Garg and Kaushin). The research revealed a reduction of inside temperature by about 2.5oc to 4,5oc was observed when solar shading devices were integrated. The result was further modified by the use of insulation material and a controlled air exchange rate showed a more significant decrease of 4.4oc to 6.8oc of the indoor temperature. The analysis suggested that solar shading is quite useful to development of passive cooling system to maintain indoor room air temperature lower than the conventional building without shade. The windows are the main element through which the greatest amount of heat enters the building; hence protecting them through the use of shading elements provides the greatest protection. The solar load is made up of three components (direct, diffuse and reflected). To prevent the window from passive solar heating, when it is not desired, it must always be protected from direct solar components and sometimes diffuse and reflected components.

 

Decision on integration of shading elements (where and when) can have an effect on the thermal comfort level of a closed space. Achieving shading from solar radiation can be done in the following ways:

 

  • Recessing the external envelope of the building

 

  • Integration of fixed or automated external blinds or louvers.

 

  • Permanent shading provided by vegetation or existing building.

 

  • Integrating reflective canvas, earthen pot, vegetation on the roof. (International journal of scientific and engineering Research volume 8, issue 12, December 2017).

 

1.3.   Shading by use of overhangs, louvers and Awning Etc.

 

Shading device and sun control devices that are perfectly designed to integrate either as part of the building or separately placed from a building façade; can decrease heat gain in the building, its cooling demand as well as enhance the quality of natural lighting in the interiors of the building.

 

Solar orientation of a particular building façade affects the design and type of shading device to be integrated for effective usage.

The following are the classification of shading device:

 

  1. Louvers: They can be fixed or adjustable; it affects air movement to a certain extent and provides shade to the building from radiation of the sun.
  2. Movable Opaque: Curtains, roller blinds, awnings etc. reduce solar gain but affects air movement and obstruct the view.

 

  1. Fixed: Overhang of roofs provides protect ion to the wall and opening against sun and rain. (International journal of scientific and engineering Research volume 8, issue 12, December 2017).

 

 

The effects of the intense heat on the comfort of building occupants has continually risen and has reached a critical point for designers to be concerned, especially in the advent of today’s Green Architecture and much talk about Energy Efficient Buildings that climax at Net Zero Energy Buildings (NZEB). Therefore, a major challenge of designing in the tropics is how to reduce heat gain and glare in building interiors. (Nkomo, J.C.,Nyong A.O. and Kulindwa K., (2006).

 

 

 

 

 

 

 

 

 

 

 

 

Figure 1.3:Glareresultingfromuncontrolled direct sunlight used for day lighting (visual discomfort)

 

Figure 1.2: Internal heat gain resulting from direct solar radiation (thermal discomfort)

 

 

 

Imagesources:(Autodesk SustainabilityWorkshop,2014

 

 

 

 

 

 

 

Aside factors like proper building orientation, adequate fenestrations, the use of landscape features and sustainable materials, providing appropriate external shading devices stand pivotal to the promotion of thermal comfort, visual comfort and energy efficiency in buildings (Figures 2a and 2b).

 

In Nigeria however, focus seems to be shifting from protecting the building envelope from the intense solar radiation to aesthetic facades. The need for designers to embrace the use of passive design strategies that addresses the prevailing climatic conditions in Nigeria cannot be overemphasized. With regard to the present international style, Ogunsote (2002) referred to them as not respecting local conditions of weather and that the resulting buildings often depend mainly on artificial means (active strategies) to achieve comfort (Nkomo, J.C.,Nyong A.O. and Kulindwa K., (2006).

 

Figure1.4: Different types of shading device Source: https://image.slidesharecdn.com/shading-170206211526/95/shading-6-638.jpg?cb=1486415889

 

 

An analysis was conducted by Givoni to find out the effective -ness of various types of fixed shading device in several orientations, and reached the conclusion that the horizontal shading device is more effective than a vertical shading device in any orientation.

 

Some advantages of horizontal shading device over vertical shading device include:

 

  1. Vertical shading device is not used to shade the whole length of the building.

 

  1. Vertical shading device reduce the amount of daylight that goes into the building.

 

  1. Vertical shading device reduce the extent of external view (sustainable building, 2010).

 

With buildings having different forms and located in different climates, it becomes hard to generalize the design of shading device; nevertheless, these design recommendations can be applied generally

 

  1. Knowledge of the sun angle is important for designing the shading device.

 

  1. The movable blinds help to decrease the convective heat gain in hot and dry climates, in warm and humid climates where the airflow is desirable, they tend to obstruct ventilation. In composite climates, the colored blinds block the solar radiation effectively.

 

  1. Limit the amount of glazing on the east/west façade. Glass on these exposures is harder to shade from the morning sun coming from east and the evening sun from west.
  2. Fixed shading devices using the right size of over-hangs or porches or design the building to be self-shading. Fixed shading device must be carefully de -signed to allow the penetration of the sun only during predetermined times of the year.

 

  1. Internal shading such as curtains or blinds is often used to prevent the unwanted solar gains entering the building. Curtains or blinds with darker colors can reduce the penetration of the sun into the space, yet it is not as effective as exterior shading device because it still converts

 

most of the sunlight into heat within the building envelope since heat has already penetrated the building M.A Wilkinson, (2010, October 20).

 

 

 

 

1.4 External Shading Devices and Strategies

 

Sunlight provides the only option for daylight and passive heating in buildings. Much asdesigners need to use adequate fenestration in their designs for admittance of daylight required for visual tasks, care must be taken to prevent heat and glare. Hence, the need for the use of external shading devices in buildings, which according to Givoni (1976), is considered more effective than internal ones (Figures 3a and 3b).

 

 

 

 

 

 

 

 

 

 

 

 

Figure 1.6: Internal shades block direct solar radiation
Figure 1.5a: External shades block direct solar

 

 

 

Image sources: (Autodesk Sustainable Workshop, 2014)

 

 

Shading against direct solar heat gain is the most efficient method of passive cooling in buildings (Energy Publication, 2010).

 

External shading devices are design shading options incorporated onto a building envelope with the intent of preventing the admittance of direct solar radiation and its accompanying heating effect on the interiors. Predominantly, they are used in institutional buildings, commercial buildings and high-rise residential apartments.

 

External shading devices can broadly be grouped into;

 

  1. Fixed

 

  1. Movable

 

Examples of fixed shading devices are; horizontal and vertical overhang, fins and egg crate sun screen, while the movable shading device includes; the vertical and horizontal louvers, awnings, retractable canopy, external venetian blind etc.

 

 

 

 

1.4.1: Horizontal and Vertical Overhang

 

Figure 1.8: Overhang across window
Figure: 1.7: Overhang placed above opening

These are elements positioned over and across an opening as a form of sun shield horizontally or vertically. In Nigeria, they are mostly referred to as “window hoods”. The more the depth of the hoods the greater the shade it provides. For effectiveness, the depth of the overhang is determined based on calculations done with the solar altitude of

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Image source: Author’s 3D illustrations

 

 

 

1.4.2 Sunscreen

 

These are aluminum projections that come in the form of louvers installed vertically or horizontally over openings to limit solar penetration. Perhaps, it is highly favorable due to its lightweight and aesthetic qualities.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Figure 1.9a: Sunscreen used in combination with

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Figure 1.10:Sunscreen used horizontally in place of overhang for more diffused light while still shading.

 

Image source:Author’s 3D illustrations

 

1.4.3 Fins

 

Fins come in vertical form, protruding from the building envelope at varying depth by the sides and across openings, and are arrayed at intervals based on calculations done with the solar azimuth of the building locale.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Figure 1.12: Slanted Vertical Fins used as sun
Figure 1.11: Vertical Fins used as sun shade.

 

 

Image source: Author’s 3D illustrations

 

 

1.4.4    Egg crate

 

This possesses a combination of fixed horizontally and vertical projections, mostly made out

of concrete or aluminum.

 

 

 

 

 

 

 

 

 

 

 

Figure b: Egg crate with vertical and movable horizontal combined

 

 

 

 

 

Figure 1.13a: Egg crate with horizontal and vertical

 

 

 

Image source: Author’s 3D illustrations

 

 

 

 

 

 

 

 

 

Figure 1.14: Egg crate with horizontal and slanted vertical combined.

 

Image source:Author’s 3D illustrations

 

 

1.4.5 Vertical louver

 

They come in the form of slats which are installed in an adjustable manner. Sometimes they could also be automated as popularly used in the developed world. They are however, capital intensive and require regular maintenance.

 

 

 

 

 

 

 

 

 

 

Figure 1.16: Hood Awning made of fabric protruding opening.
Figure 1.15: Vertical Louvers installed over a window

 

Image source: Author’s 3D illustrations

 

 

1.4.6 Awnings

 

Made of fabric or metal, awnings are used as protruding, sloping cover over and beyond openings. It is quite effective in reducing heat gain into an indoor space. They could equally beretractable. Hood awning as also known provides a good shade from solar radiation and when mounted at 45 degrees looks good to the sight.

 

1.4.7 External venetian blind

 

Figure 1.17: External venetian blind installed over a window opening.

Made of metal (aluminum) and in the form of slat as covering on windows, they offer protection against the excessive penetration of direct sunlight and the concomitant heat and glare. Its operation and control are simply by pulling a cord which drives the s ingle control rod.

 

 

 

 

 

 

 

 

 

Image source:Author’s 3D illustrations

 

1.4.8 Others

 

Apart from the afore-mentioned, some balconies and verandahs are so designed to serve the function of a shading device to prevent direct solar radiation from getting to the openings below them. Likewise, “Recessed Window” also known as “Deep Reveal”isused as design strategies on building envelope. Exaggerated eaves are another solar shading technique worth mentioning.

Figure 1.18: Balcony and verandahs and exaggerated aves designed for shading device.

 

 

 

 

 

 

 

 

 

 

 

Image source:Author’s 3D illustrations

 

 

In the same vein, trees are also used as “Sun Breakers” (Figure13). They are strategically planted around the building as an integral part of the landscape, but also doubles as sun breakers to passively shade the required parts of the building taking into account the building orientation vis-à-vis the sun path of the locale (Nkomo, J.C.,Nyong A.O. and Kulindwa K., (2006).

 

 

 

 

 

 

 

 

 

 

 

 

 

Figure 1.19: “Deep Reveal”.Trees used as Sun Breakers.

 

 

Image source: Author’s 3D illustrations

 

1.5. PROBLEM OF STATEMENT

 

  • What is the value of shading device for penetration opening in buildings?

 

  • How can proper orientation and shading device help in reduction of solar impact in buildings spaces?

 

  • What are the effects of sun shading device on improving thermal comfort in buildings.

 

1.6. AIM

 

The aim of these study is to ascertain the extent to which solar shading devices help to reduce solar impact in building interior spaces.

 

1.7. OBJECTIVES

 

The objectives of this research are follows

 

  • the study understands the existing literature of various concepts for in shading device

 

  • To study the strategies of shading device.

 

  • To examine application of shading devices in building. Adopt adapt.

 

 

4: Statement on how, it is applied in my research finding the application shading device,

Adopt and adapt in design of the factory building.

1.8. SCOPE OF STUDY

 

The study area for this research is Abuja. Abuja is the Federal capital city of Nigeria which is found around the center of the country. Abuja is located on the latitude of

 

9.0765˚N and longitude 7.3986˚E with a total area of 1769km 2. It is a tropical region consisting of dry and wet season. The warmest month is April, and the driest month is December. 25.7˚C is the average temperature and the average annual rainfall is about 1389mm, the month with the highest record of rainfall is September with about 284mm. This study considers the warm sunny climate of Abuja in Nigeria for emphasis application shading devices

ANALYSIS OF SHADING SYSTEM FOR THE REDUCTION OF SOLAR INTENSITY IN INDOOR SPACES IN NIGERIA.

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