Energy Simulation Modelling Dubai, UAE

A manual load calculation is used primarily to select equipment size based on maximumload conditions. It uses the space loads, as discussed above, and it is done only for the single instance of peak load conditions. For example, when selecting an air conditioning system for a building, a consultant makes a load calculation to estimate the peak cooling requirement. This is done by calculating the individual load components, and then adding them. For cooling, the load components are solar gain, conduction gain through the walls and roof, heat gained by air leakage, and dehumidification. Heat generated from lighting system, people and equipment in the building, together referred as “internal heat load”, also contributes significantly to buildings loads. Basic peak-load calculations are simple. They can be done manually and they are adequate for many applications. However, manual calculations are not always accurate. One cause of error is that the components of load do not all peak at the same time. Another limitation is inability to deal with thermal storage effects. The degree of detail is limited, e.g. it is not practical to include the precise orientation of the surfaces in a manual calculation.

As a result, a number of computerized load calculation programs are now available. They provide greater accuracy, eliminate the drudgery of arithmetic and provide a checklist to make sure that all load components are included. There is a range of complexity among computerized programs. Some are relatively simple.

For this reason, many designers and contractors do not use load calculations and instead they select equipment capacity using simple rules of thumb, based on the size and mass of the building. To promote energy efficient designs, “rules of thumb” should be discouraged.