Energy performance in non-domestic buildings varies over a wide range, even when comparing buildings of similar type. We can identify three factors which lead to this variation:
The first factor is of particular relevance early in the development of the design by the architect. Furthermore, it is clear that basic building design is not amenable to later modification, whereas services can be improved and good management can optimise the effects of occupants.
How does the energy consumption of a building relate to the early design parameters? Lighting energy and fan power represent the major energy input to most larger buildings and have to be provided permanently to those interior areas away from the perimeter. Thus, these areas should be kept to a minimum. The LT Method is concerned with the design and maximising of the perimeter zones, or passive zones, of the building, and provides a means of estimating the relative energy performance of different options.
The interactions between heating, cooling and lighting energy of a building are complex and a mathematical model of such a system requires many input parameters. Most of these are unavailable early in the design process, or are often of peripheral interest to the architect. However, the LT Method uses energy performance data produced by a mathematical model, where most of these parameters have been given assumed values. Only a few key design variables, mainly relating to building form and facade are left for the user to manipulate.
It follows that LT should not be regarded as a precision model producing an accurate estimate of the performance of an actual building. Rather LT should be used to evaluate the energy performance of a number of options and to make comparisons.
Furthermore, the energy breakdowns of heating, cooling and lighting, which are evident from carrying out the LT Method, will give a picture of the relative importance of various energy components. The method can be applied to a range of non-domestic building types, in particular schools, offices, institutional buildings and health buildings (hospitals). It has limited application to certain manufacturing buildings. It is a manual procedure requiring pencil and calculator. Proposed building data and energy values from the graphs are combined into a single worksheet.
Finally, although cooling energy is one of the outputs of the LT Method, it should not be interpreted that the method advocates the use of air-conditioning. Rather, it should be used to show that the cooling loads can be reduced to a low level, where passive cooling techniques offer a viable alternative.