In July of 2015, EnergyLogic began informing you about upcoming software changes. As a reminder, the Residential Energy Services Network (RESNET) began to align the energy rating reference home to the 2006 IECC almost two years ago. The reference home, which currently reflects the 2004 IECC supplemental code, is what your home is compared to in order to create the HERS Index score. RESNET has gone through a process of taking the rule set for how to develop the HERS Index score through the ANSI process in order to create the ANSI/RESNET/ICC 301-2014 Standard for the Calculation and Labeling of the Energy Performance of Low-Rise Residential Buildings using an Energy Rating Index. The main impetus for this ANSI Standard arose from the desire to use the Index Score for code compliance and the adoption of the Energy Rating Index (ERI), a HERS path, as a compliance matrix for the 2015 IECC.
The alignment with the 2006 IECC has three primary effects on the HERS reference home.
- First, the updated 2006 IECC reference home infiltration rate became tighter to better reflect the improved tightness levels of newly constructed homes.
- Second, the updated 2006 IECC reference home window solar heat gain coefficient (SHGC) went from 0.55 in climate zones 4 through 8 to a SHGC of 0.40 in those climate zones. This updated value reflects the market penetration of improvements in basic window technology and is in alignment with the 2006 IECC.
- Lastly, revised mechanical ventilation requirements are used in the HERS reference home which are now aligned with the ASHRAE 62.2-2013 ventilation standard.
Scores to Increase by 2 to 6 Points
Philip Fairey, Deputy Director of the Florida Solar Energy Center and a consultant for RESNET, performed research on the impact of these changes on the HERS Index values of rated homes in all eight climate zones. His research has demonstrated that the HERS Index values will increase across all climate zones by a range of 2 to 6 points due to the reference home alignment with the 2006 IECC that occurred through the creation of the ANSI/RESNET 301-2014 Standard. EnergyLogic has been working with the newly released software, and we are seeing results that are consistently on the high end of the range (3-8 HERS Index points) when comparing homes that were rated with software developed prior to the ANSI standard adoption. RESNET is mandating that HERS providers begin using the new software on January 1, 2017. EnergyLogic has worked with RESNET to find ways to reduce the impact of the implementation of the ANSI standard software. A few things are, or have been, changed but the impact of the score increase will remain significant, affecting every home across the country.
Incorporating Water Heating
The development of the ANSI standard has also given RESNET the opportunity to include additional features related to water heating. This is specific to energy use related to hot water distribution and does not take into account water conservation. RESNET is working on a Water Index score that will address water conservation. The ANSI standard addendum allows the HERS Index score to quantify the efficiency or loss of energy through; pipe runs from the water heater to the farthest fixture, hot water pipes that are insulated, on-demand recirculation systems, high-efficiency low flow fixtures, and drain water heat recovery systems. If all of these systems are deployed in a home, the technologies can provide builders approximately 1-3 point reduction in the HERS Index.
It is important to also understand that if a builder is currently utilizing a water delivery system that is not delivering the hot water efficiently then the HERS Index would be penalized. For example, if you are currently using a timer or continuous recirculation loop to deliver hot water, your home’s HERS Index will be penalized. This will result in a higher score than the normal transition to the ANSI approved software. So, in this example, if the transitioning to the ANSI approved software took a HERS Index from 60 to 65, the inefficient hot water circulation system could add another 5-10 points, taking the score to 70 or 75. It is important to evaluate your current specifications and choose the most efficient water distribution systems, such as an on-demand hot water recirculation system, or stop installing them all together.
Summary: All Homes will Be Affected
These changes will affect every home that is rated but should have minimal impact on the use of the Index score for demonstrating compliance with programs such as EnergyStar, as the program’s energy Index target will fluctuate in unison with the home that is being rated. In the same way, these changes should have minimal effects on code compliance when utilizing the Simulated Performance path as the code reference home is separate from the HERS reference home. For those few builders utilizing the 2015 IECC Energy Rating Index path (ERI), these changes will be significant. Lastly, builders utilizing the Index score in their marketing efforts will need to update HERS related marketing collaterals.
Principal / Director of Builder Relations
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