ENERGY-CONSCIOUS PLANNING AND ZONING
3.2.3 Aids for the Study of Sunlight Conditions

Horizontoscope

A simple but very useful aid for the preparation of images showing buildings at an existing location is the "Horizontoscope" (Figure 3/14) developed by TONNE and produced by the Institute for Daylight Technology in Stuttgart (www.ift-stuttgart.de), this is no longer available, but because of its clarity helpful. The Horizontoscope consists of a Plexiglas half-sphere with a level, equally transparent bottom, which can be placed on a diagrammatic disk as shown in Figure 3/12. At the location to be examined, the device is held horizontally by means of an integrated compass. When viewed from above, the reflective half-sphere then shows the building picture in polar projection. In this way the building picture is reflected on the underlying diagram, allowing an immediate evaluation of the sunlight conditions.

Computer Simulation Programs

These shading diagrams can of course also be produced with appropriate programs when digital plans are available. The computing model SHADOW has been developed specially for the assessment of shortwave radiation (sunlight) in a model area. It can be used both for studies in urban areas and for issues of land climatology or agrarian meteorology, as the program takes into consideration the topography of the land in addition to the arrangement of shading objects. For example, with RayMan ( Matzarakis et al. , 2010) in addition to answering various urban climate issues also Horizontogramme or shadows are calculated and displayed (see Figure 3/15 and 3/16).

More intricate aids are necessary for the assessment of sunlight conditions in complex built-up areas. For this purpose, GORETZKI (1990, 2012) developed a computer model (GOSOL) as a basis for energy simulations, which makes possible the assessment of the solar-energy characteristics of a planning concept as well as its spatial depiction.

The basis is a three-dimensional computer model including buildings, vegetation with seasonal foliage and topographic conditions.

One of GOSOL"s characteristic features, which shall be expressed by the description "solar+energetic", is the creation of complete energy balances for every single building or in the form of sum and average values for the whole development plan area. Thermal heat balances contain the building"s specific heat losses (depending on the heat insulation standard, the heating system and the building geometry) as well as interacting passive and thermal solar gains at a particular orientation or shadowing of the building. Faulty optimisations can be avoided by balancing the opposing thermal gains and losses in the variable "heating or primary energy requirement depending on the living space". It is also possible to determine the photovoltaic potential of solar energy and thus a total energy balance of the planning area.

Furthermore, the reasons for reduced solar gains or increased heating requirements are determined for every building within the area under investigation, and this itemised in the categories: