Load calculations are an essential element of all good mechanical design. Mechanical engineers use them when they select equipment to ensure that even when using the most economical items, comfort conditions will be maintained.
However, it is impossible to regulate the quality of assumptions made by designers or their judgment undertaking load calculations. The problem is that there are numerous variations on assumptions used when doing load calculations including the climate and future additions, as well as the designer’s experience.
Building inspectors don’t normally review load calculations for accuracy, which makes this a primary responsibility of the designer.
A similar scenario applies to equipment and system sizing, which, like load calculations is a vital element of good mechanical design. In addition to the availability and cost of equipment, there are a number of parameters that designers must consider, including sensible and latent loads, duct design, airflow, operating warm-up and cool-down sequences, and the location where equipment will be installed. While Standard 90.1 does take various parameters into account, in reality, there are so many possibilities, their requirements don’t have any practical effect on energy consumption.
Sizing requirements, like load calculations, aren’t explicitly enforced by building departments and local authorities. However, engineers have a legal responsibility to size and specify system equipment properly. Ultimately, the requirement is for systems and equipment to be specified correctly on the plans, and then, if necessary, a field inspector can do on-site inspections to ensure the system has been built in accordance with the approved plans.