An OTTV is a measure of the energy consumption of a building envelope. Its formulation allows authorised persons such as registered structural engineers and others responsible for the design and construction of buildings to innovate and have the freedom to vary important envelope components such as type of glazing, windows size, external shading to windows, wall colour and wall type to meet the maximum OTTV criteria.
In Hong Kong, the external walls and roofs of a building to which the building regulation applies should be designed and constructed to have the following OTTV:
The IES Hong Kong OTTV navigator is a tailor made logical workflow to guide users through the OTTV calculation process without the need of tables. With the help of a 3D model and sunpath solar shading technique, the OTTV calculation can be performed with a few simple steps and it can even be used for complex building design. IES VE software can also import 3D geometry from other platforms like Revit® and SketchUp™, which allow wider connectivity in preparing a model.