The basic model described here is a graphical representation of the lighting process showing the factors influencing energy flows.The purpose of this model is to show on a conceptual level the relevant processes and their interrelations in lighting design and usage. Design will of course strongly determine energy performance. Proper maintenance and control which are to be anticipatred while designing can save a lot of energy on top of that. How all these factors are related is shown in the model and explained in more detail in the rest of this document.
Part A is an overview of the project definition process in which all the relevant tasks and site properties are analyzed (1), the appropriate codes and standards are observed (2), and wishes of the user translated into system efficiency requirements (3). This is also where the human aspects play a role. As a result of the important though often underestimated task of defining a project a technical brief (4) is compiled.
Part B focuses on the influence of environmental factors on a lighting design. In terms of the basic model this means that it describes the incoming radiance, in terms of the local climate and under the influence of obstructions and other characteristics of the location (1). It also has to deal with the thermal and the optical properties of the building itself (2), as building mass and shape for instance may strongly influence energy flows and inevitably affect lighting design. Another important factor is the strong energy impact which the lighting system has on the climate conditioning installation (HVAC system (3)) in the building , due to its heat production and the influence of windowed surface and orientation.
Part C describes the complex task of designing . If the lighting of a room has to be really energy efficient, daylight (1) and electric light (2) have to be complementary. This means that already in an early stage of design a number of decisions have to be made in which both daylight and electric light play an important role. In complex buildings with rooflights, often space has to be reserved, e.g. in the roof construction, for the luminaries, so the daylight may be optimally supplemented with electric light. Many examples exist, where luminaries are installed afterwards, in such a way that they obstruct daylighting.
Part D is concerned with lighting control (1) and maintenance (2). The design of the installation of course normally includes setting up a maintenance scheme and for complex installations also the development of electronic control strategies. However, in many cases things change in the course of time. People move to other rooms, new use is made of rooms, or maybe a new building is erected facing the existing building. In many situations modifications are necessary and sometimes even new strategies have to be developed.
All aspects of the components applied in lighting are described in part E. It is here that system and other requirements stemming from the brief and the design have to be translated into practical (and affordable) energy efficient solutions matching window and daylighting components (1), component efficiency requirements (2), and electric lighting components (3).
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L.Zonneveldt@bouw.tno.nl