Design of energy-efficient buildings and benefits of enhancing reliance on natural lighting through maximizing the external reflected component

Abstract EN

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.