Energy modeling helps determine which energy saving features are most cost effective

 Energy modeling software is an important design tool that helps builders identify the least expensive measures required to create a zero energy home. Modeling should be conducted in multiple iterations of the design, analyzing the energy impact of different design choices, such as a ground source heat pump versus an air source heat pump, or comparing the impact of R-30 wall insulation with that of R-60 wall insulation.

Energy modeling can be done as soon as the designer creates preliminary plans with dimensions, elevations, basic floor plan, windows, and doors. The plans can then be adjusted based on the modeling results so that the project will reach the zero energy goal at the lowest cost possible. Decisions made during energy modeling must be reflected in the final plan and construction documents. The payback on the costs of energy modeling itself – a matter of a couple of months – is surprisingly short.

Any energy-saving upgrade that costs less per kWh saved than the cost per kWh of installed PV would be considered cost effective and should be integrated into the plan. By using energy modeling to help ensure the cost effectiveness of energy saving measures, the added costs of constructing a zero energy home can be as low as 5% of the sales price, after rebates and tax incentives, depending on the state.