Actual weather data are used to “calibrate” the simulation to match observed gas and electricity consumption.

The annual simulation totals can readily be made to match the actual consumption by adjusting heating and cooling system efficiencies, thermostat setpoints, operating schedules, and the building infiltration rate.  In an accurate energy model, the usage curves will also match on a monthly basis.

In this example, the usage patterns of the previous occupants were unknown. Given the available information, in order to achieve a close match of annual energy use, the “calibrated” simulation underestimates energy use in the spring and overestimates summer usage.

Energy Modeling Results show how the building is operating and where the energy is being consumed. The top right graph shows how heat losses in the top left graph are balanced with internal heat gains, solar heat gains and auxiliary heating requirements and when auxiliary cooling is required to maintain summer comfort.

This chart summarizes energy simulations for various remodeling options. The options are presented in the approximate order of the building owner’s priorities. The “Existing House” energy consumption is the as-purchased house calibrated to the previous owner’s energy use.  The “Base” case represents the “existing house” updated to reflect the new owner’s occupancy patterns, anticipated basic enclosure changes and with some baseboard electric heating incorporated into the central gas-fired forced air heating system.  Energy conservation measures 1 through 13 could potentially reduce the initial annual energy consumption by 60%.  Budgetary constraints are expected to limit the owner’s actual work to about a 40% decrease from the Base case.  Note that meeting Architecture 2030 guidelines for new homes in 2010 is beyond the entire group of energy conservation measures that were considered and underscores the difficulty of achieving Architecture 2030 targets for remodeled buildings.

The Existing house had some electric resistance heating which is replaced in the Base case with an extension of the natural gas heating system.  Since electricity is 3 to 4 times more expensive per BTU than natural gas, this change creates an immediate savings in operating costs even though the overall energy use in the Base case is greater.

Whereas the previous page shows that if energy conservation improvements are made through Case 5, energy use is reduced 30%, this graph shows that the corresponding reduction in operating cost is greater than 40% or about $1500 in the first year.