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.
It is important to factor in the cost of each improvement when comparing their relative energy savings. Further upgrades will give smaller returns, so that upgrading an energy saving feature beyond a certain point may not be cost-effective any longer. Similarly, upgrading one component will affect the impact of upgrading other components. Energy modeling will help determine the point at which returns in efficiency are no longer cost effective as well as what combination of energy saving measures amounts to the highest savings.
It’s challenging to pinpoint the exact net cost of different energy saving measures because they vary over time and across home building markets. But while energy modeling only provides an estimate, it gives useful guidance as to the relative cost/benefit of each energy-saving measure considered.
Energy Modeling Software
The following links provide information about some of the different energy modeling software that is available:
Energy Gauge, Florida Solar Energy Center
Energy 10, Sustainable Buildings Industry Council (SBIC)
REM Design While not the most accurate or comprehensive energy modeling program available, it is relatively easy to use and quickly provides some of the most helpful energy modeling comparisons. A functionally identical program called REM/Rate is used by certified home energy raters.
EnergyPlus Published by the U.S. Department of Energy, this is a highly sophisticated modeling engine.
BeOpt, National Renewable Energy Laboratory. BeOpt is unique because it allows many options to be compared directly. By entering the cost of each option, the program suggests an optimum package for cost-effectively designing a zero energy home. This provides a graphical user interface for EnergyPlus. Learn more about BeOpt from the Green Building Advisor.
HEED shows how much energy and money and carbon you can save by making various design or remodeling changes to a home with this free new easy-to-use program. You can draw in the floor plan of a house, then click and drag windows to their correct location.
Passive House Planning (Design) Package, (PHPP), Passive House Institute. PHPP may well be the ultimate in energy modeling, however it requires very detailed information and can be time-consuming and expensive. To use this program effectively, you must attend Passive House Consultant training.
Building Energy Software Tools Directory, U.S. Department of Energy. This is a comprehensive and alphabetical directory of energy modeling programs, gathered by the U.S. Department of Energy.
Carbon Foot Print and Life Cycle Assessment Software
Reaching net zero energy for building operation is only the first step. Ultimately, buildings must reach carbon neutrality, which includes accounting for total carbon emissions of materials and construction processes in addition to operational energy. Life Cycle Assessment (LCA) software helps builders and architects assess the carbon impact of their plans and alter them as needed to lower that impact. One example of LCA software is One Click LCA, which allows designers to import building data from X-cel, Revit, and BIM packages to run standards-based life cycle assessments, carbon footprinting, and job costing. Four steps to carbon neutral construction includes descriptions of a variety of Life Cycle Assessment software tools that are currently available .