The last few weeks we have talked about Energy Code Compliance, the prescriptive path and the performance path.
This week we are going to discuss the final compliance method, a new compliance method in the 2015 IRC, the Energy Rating Index.
Energy Rating Index, or ERI, is a calculated number on a linear index scale constructed with the ERI reference design having a value of 100 and a residential building that uses no net purchased energy has an index value of 0. A one percent change in the total energy use of the rated design relative to the total energy use of the ERI reference design shall be represented by a change of 1 on the index scale. So, an ERI of 55 means that the proposed design outperforms the ERI reference design by 45%.
So, for the purpose of the Energy Rating Index, the code identifies that the ERI reference design shall meet the minimum requirements of the 2006 International Energy Conservation Code prescriptive requirements.
The next step for ERI is to identify the maximum energy rating index allowable by climate zone, here is the appropriate table:
Finally, a report that shows the proposed design meets the requirements of the Energy Rating Index is required using energy calculations from an energy modeling software tool, like:
- REScheck™
- COMcheck™
- EnergyPro
- Elite RHVAC
- Wrightsoft Right-J8
- Florida Solar Energy Center’s EnergyGauge
The ERI compliance method is new to the 2015 code and offers another way to provide compliance when building high performance systems.
Stay tuned next week as we continue to discuss the interesting world of spray foam insulation.
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