DESIGN OF ENERGY-EFFICIENT BUILDINGS AND BENEFITS OF ENHANCING RELIANCE ON NATURAL LIGHTING THROUGH MAXIMIZING THE EXTERNAL REFLECTED COMPONENT Journal of Al Azhar University Engineering Sector Vol. 11, No. 41, October, 2016, 1321-1325 DESIGN OF ENERGY-EFFICIENT BUILDINGS AND BENEFITS OF ENHANCING RELIANCE ON NATURAL LIGHTING THROUGH MAXIMIZING THE EXTERNAL REFLECTED COMPONENT A. M. Saleh Professional Engineer (Private Sector) ملخص البحث يركز البحث على الفوائد العملية و الصحية للمستخدم نتيجة اإلعتماد على اإلضاءة الطبيعية داخل تصميم المساحات و يقدم البحث عدد من البيانات التخطيطية التى تمكن المصمم من تقدير . (ERC)الداخلية بالمبانى بإستخدام معامل . اإلضاءة الطبيعية إعتمادا بشكل رئيسى على معامل اإلنعكاس الخارجى و ذلك لجميع الواجهات و عند كل األدوار ABSTRACT Daylight can be provided via windows and glazed doors, as well as via skylights and other forms of top lighting. These glazed openings are collectively referred to as "fenestration." The placement, design, and selection of materials for fenestration are extremely important and can tip the balance between a high performance and low performance building. Fenestration impacts building energy efficiency by affecting cooling loads, heating loads, and lighting loads. Visual comfort is strongly affected by the window location, shading, and glazing materials. Well-designed windows can be a visual delight. But poorly designed windows can create a major source of glare. Thermal comfort can also be compromised by poor fenestration design. Poorly insulated windows add to a winter chill or summer sweat, while windows with low U-values keep glass surface temperatures closer to the interior air temperature, improving thermal comfort. In addition, east-west windows and unshaded south windows can cause excessive cooling loads. And although windows and skylights provide opportunities for natural ventilation, they must be designed to ensure a safe, secure, and easily maintained facility. The table below specifies the recommended minimum illumination levels. Any shortage in meeting these levels should therefore be supplemented via artificial means. According to Hofman in his textbook Handbook of Lighting Design, the table below (Table 1) provides a summary of the minimum illumination levels measured in lux. The Lx value indicated for each building use is the required illumination level needed to perform the specific task. The table also provides codes that should later be used by the designer in another table(s) to aid in the final selection of an efficient lighting source. The above steps should be carried out after completion of the daylighting analysis and design. In order to establish a complete, energy efficient, and sustainable lighting design, the designer must implement an integrated approach for the entire facility. This dictates consideration of both Natural and Artificial design elements withing the Egyptian building code of lighting. 2. BUILDING PERFORMANCE A high performance, cost-effective, comfortably daylighted building requires the design team to practice integration as per the following points:  Adopt a holistic design approach, where the building is viewed as a whole and not just a collection of parts. Common practice often fails to address the critical interactions DESIGN OF ENERGY-EFFICIENT BUILDINGS AND BENEFITS OF ENHANCING RELIANCE ON NATURAL LIGHTING THROUGH MAXIMIZING THE EXTERNAL REFLECTED COMPONENT between the building façade (which admits heat and light) and the electric lighting system, resulting in an uncomfortable and inefficient building that is expensive and difficult to maintain.  Share appropriate decisions across disciplines.  Regularly evaluate decisions for any building wide ramifications. Table 1 - Guide values for illuminance E for various areas of activity in accordance international standards 3. OCCUPANT PERFORMANCE Studies indicate that well-designed daylighting is associated with enhanced student performance, evidenced by 13% to 26% higher scores on standardized tests, while poor Natural + Artificial DESIGN OF ENERGY-EFFICIENT BUILDINGS AND BENEFITS OF ENHANCING RELIANCE ON NATURAL LIGHTING THROUGH MAXIMIZING THE EXTERNAL REFLECTED COMPONENT daylighting design has been shown to correlate with reduced student performance. The study confirms that it makes sense that students and teachers perform better in stimulating, well-lit environments. It provides evidence that Daylighting can provide high quality light, stimulating views, and an important communication link between the classroom and adjacent spaces. Fig. 1 - Gentle, diffuse daylight permeates a classroom with both sidelight and toplight. Note that all surfaces are painted white to distribute light more efficiently and reduce contrast glare 4. ENERGY SAVINGS Daylighting can save energy and reduce peak electricity demand if electric lights are turned off or dimmed when daylight is abundant. According to a study conducted in the United States, K-12 schools spend more than $6 billion a year on energy (1) . Daylighting, however, saves no energy unless the electric lighting system is appropriately controlled. To be effective, daylighting must be thoughtfully designed, avoiding glare and overheating, and must include dimming or switching of the electric lighting system, preferably with automatic photocell control. Daylighting is the use of light from the sun and sky to complement or replace electric light. Appropriate fenestration and lighting controls are used to modulate daylight admittance and to reduce electric lighting, while meeting the occupants' lighting quality and quantity requirements. Daylighting is a beneficial design strategy for several reasons, Until recent years most workspaces were lit by tungsten or fluorescent lamps, with high- pressure discharge lamps sometimes being used for sports-related and industrial buildings that require additional lighting. But newer compact metal halide and high-pressure sodium lamps with good colour rendering characteristics are now being used in offices and shops, particularly for decorative or display lighting. The development of „energy-efficient‟ lamps, in addition to the availability of a wider range of luminaire designs, has made possible very significant energy savings in general purpose lighting and has brought extreme lighting effects within reach of relatively modest budgets. The table below provides examples of some of today‟s lighting sources available in the market: 1. Egan, M. David and Olgay, Victor W.; "Architectural Lighting", McGraw-Hill, 2nd edition, 2003 DESIGN OF ENERGY-EFFICIENT BUILDINGS AND BENEFITS OF ENHANCING RELIANCE ON NATURAL LIGHTING THROUGH MAXIMIZING THE EXTERNAL REFLECTED COMPONENT The table above provides basic general data of different lamp illumination levels and corresponding life spans. This was an effort which was later analyzed further by Dr. Philips in the following page in order to assess each type of lamp efficiency measured in (Lm/W), in addition to general data such as Rated Average Life, and Colour Temperature (K). Table 3 - List of Artificial Light Sources Lamp 100W Tungsten Lumens/W 14 Hours 1000 20W 38mm Fluorescent 36 9000 18W 26mm Fluorescent 50 9000 20W Compact Fluorescent 60 8000 18W Low Pressure Sodium 66 7000 250W High Pressure Sodium 96 12000 40W LED Bulb 800 10000 Table 2 – Lighting Sources and Corresponding lifespans and energy dissipation DESIGN OF ENERGY-EFFICIENT BUILDINGS AND BENEFITS OF ENHANCING RELIANCE ON NATURAL LIGHTING THROUGH MAXIMIZING THE EXTERNAL REFLECTED COMPONENT In order to realize considerable cost/energy savings, the designer must carefully select a combination of artificial lighting sources from the list above, to cover the deficit from natural lighting. One of the problems has been in the „cheap energy policy‟ of Governments; there may be other good reasons for this, but it has led in the past to excessive use of cheap energy, and it is only recently, with a looming energy crisis, that governments have woken up to the vital need for savings to be made. The first line of defence must be in avoidance of waste; particularly a situation when a building with every light burning in the middle of the day when daylight is quite adequate, or after dark when the building is largely unoccupied. Dr. Philips argues that the total amount of energy wasted on a daily basis may not have been calculated, but it is considerable and equals the amount of savings which can be made in other ways (2) . He provided the example of a transport building where artificial light is used all day irrespective of the level of daylight. There is no doubt a need for the level of daylight never to drop below the statutory design level, but this can be solved by adopting a system of control which links artificial light to the available daylight to ensure that the design level is maintained, whilst allowing significant reductions in the use of artificial light, which can be off for most of the day. REFERENCES 1. Mardaljevic, John and Kevin Lomas, ``Creating the Right Image,'' Building Services / The CIBSE Journal, Vol 15, No. 7, July 1993, pp. 28-30. 2. Philips, Derek, with Gardner, Carl. “Daylighting, Natural Light in Architecture”, Architectural Press, Oxford, 2004. 3. Hofmann, Harald, “Handbook of Lighting Design”, ERCO Leuchten, Berlin, 1992. 4. Egan, M. David and Olgay, Victor W.; "Architectural Lighting", McGraw-Hill, 2nd edition, 2003.