Energy Savings Comparison Chart
Bruce Sullivan of BaseZero, LLC created the following chart based on a house in Bend, Oregon. It provides a rough sample of the relative energy savings from boosting the efficiency of specific components. Because results will vary depending on building details, climate and other factors, it is recommended that designers and builders conduct a similar exercise for each net zero energy project.
||Energy Savings in BTUs
|Wall from R30 to R40
|Floor from R38 to R44
|Windows from U-0.28 to U-0.22
|Heat Pump HSPF from 9.5 to 10.5
|ACH from 2.5 to 1.5
|Adding 1 kWh of PV panels
|Adding one 180 Watt PV panel
|Ceilings from R50 – R60
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 nearly impossible to pinpoint the exact net cost of different energy 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 Directory
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.
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.