Energy Effeciency in Building

The innovative daylighting systems (IDS) seek to meet the illumination requirements in buildings, where inadequate amount of daylight is provided by the conventional daylighting systems. Many IDS have been commercially launched, but challenges, such as high initial cost, utilization difficulties, and application limitations, prevent their widespread use. Most of these challenges can be overcome, but no IDS is likely to overcome all of them at once. Alternatively, a number of systems that efficiently suit different circumstances is a more practical approach. This study reviews the IDS whether commercially released or not, and discusses the challenges associated with their utilization within buildings. Solutions and recommendations have been suggested. The study makes the capabilities and limitations of the different IDS clearer for both architects and users, and discusses the challenges and promises facing developers and lighting designers.

Daylight was the main source of lighting in vernacular architecture, and building design accordingly responded to its strategic limitations. Needs for new types of buildings in conjunction with the great development of electric lamp led to the ascendancy of electric lighting. However, a return to the interest in natural lighting emerged with the energy crises in the 1970s. In order to meet the new requirements, new optical materials and technologies have been combined to produce innovative daylighting systems able to deliver daylight long distances into buildings. There is a need to maximize the utilization of daylight, to optimize the integration between daylighting and electric lighting systems so as to increase the potential application of daylighting system. The development of the hybrid lighting systems (HLS) aims to satisfy these desires. 
HLS seek to maximize the utilization of daylight by tracking sunrays, and in most cases they are concentrated to minimize the light guidance size, which eases the installation and in turn increases the potential application of HLS. Prior to delivery of daylight, electric lighting source is added to instantly top up any possible shortage of daylight. A control system works to regulate this process to minimize the energy consumption. The one output device for both sources used in the HLS made it possible to no longer need for two distinct lighting systems to be installed in one space.
Investigations in this work have measured HLS performance in terms of light delivery, light quality, energy saving and economic performance. Potential applications of HLS in different buildings types and across a wide geographical region have been investigated. An overall evaluation of HLS has been carried out. Furthermore, methods to estimate illuminance data, where measured data is unavailable, have been developed to help investigating systems performance over different geographical locations. Illuminance data produced using the developed methods showed superiority over that produced using other available methods, with the additional advantages of simplicity and universal application.
HLS performance and potential application are influenced by many variables including system characteristics, building types, and location features. The research showed that the most important variable is the concentration ratio of the light collector. This determines HLS ability to collect daylight, and thus its applicability in different geographical locations. It also stipulates light collector and guidance size, and thus HLS applicability in different building type, influences the delivered light quality, and thus occupants’ perception of daylight, and influences HLS initial and running costs. Delivered light by HLS may not be perceived as daylight due to the absence of the outside view, the likely change in daylight colour because of the mixing with electric light, the fade awareness of the seasonal and diurnal changes in daylight colour and intensity because of the instant and continuous top up. The challenges of cost, light quality and integration in building design are the most serious barriers confronting HLS ability to penetrate the market and to be used widely. This work makes suggestions to overcome these problems.

The utilisation preference of glazed facades in the hot regions is accompanied by serious environmental and economic impacts. Attempts are continuing to fulfil an optimum balance between minimising heat gains and maximising daylighting benefits; in an economical approach. This study was conducted in Egypt, where a real case study was investigated to evaluate the thermo-visual performance of a building with glazed facades. Improvements of the thermo-visual performance are pursued via the application of five different glazing alternatives in the first phase of the study. In the other two phases, further enhancement is sought via the addition of parametric lightshelves and perforated double skin facades; creating a total of 138 possible configurations. The best configuration that combined clear glass and a lightshelf has significantly improved the thermal comfort and daylighting uniformity, but it also slightly improved the availability of daylight. This ultimately leads to an energy saving, however, further economic assessment is required.