Energy modeling with a computer program can be used to simulate a building for all 8760 hours of the year for a given location’s ‘typical’ climate. With today’s higher performing buildings and inclusion of passive solar design and fancy mechanical systems, advanced energy modeling can be a useful tool in the design process.

Simple energy modeling procedures such as ACCA’s Manual J don’t take certain things into account. Solar gains and thermal mass effects aren’t considered in these simpler models, but can make a significant difference in reality. Advanced modeling can give an incredible amount of information with a moderate increase in modeling time.

Above, the home’s passive-solar gains are analyzed. The difference between the two models is south-facing window areas. The graph below shows the ‘free-running’ temperature inside the home for a short 6-day period from January 15th through January 20th. This is the temperature that is experienced inside the home without inclusion of a mechanical heating system. This is a powerful design tool when looking at the effect of shading, window sizing, and thermal mass effects.