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RESNET/ACCA Standard 310: A New Hope

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Several years ago, Residential Energy Services Network (RESNET) and ACCA began discussions about how the Home Energy Rating System (HERS) Index should reflect the installation of the largest energy-using appliance in homes across America, the HVAC system. Three years ago, RESNET formed a working group to draft the standard, which is now out for public review until 4 May 2020. To review and comment on the draft standard, visit RESNET’s Standards here.

What Is RESNET / ACCA Standard 310?

The standard outlines five separate tasks to be performed by a HERS Rater to evaluate and grade aspects of the HVAC system’s installation and performance. These tasks are non-intrusive or have minimal impact (make a hole for a static pressure probe). Additionally, each task has an alternate compliance path that allows an independent verification report to provide the necessary information.

The standard’s five tasks consist of two prerequisite tasks that must be passed before the process can continue, and three functions that contribute to the HERS / ERI score improvement.

  1. Prerequisite: HVAC System Design – Ensure the dwelling’s attributes are correctly modeled, and ensure the dwelling was built per the design. This looks at key contributors to the homes heat loss/gain, and confirms those elements are present as specified.
  2. Prerequisite: Total Duct Leakage – confirm that the duct system is tight. Leaky ducts could mask problems that exhibit low static pressure and low fan watt draw. However, the conditioned air could be leaking into unconditioned space where it does not promote comfort.
  3. Task: Airflow – Several different methods can be used to confirm that system airflow is within a tolerance of the design airflow.
  4. Task: Fan Watt / Cfm – This metric is not cited in the ACCA 5 QI Standard at this time; however, this metric reflects the duct system’s efficiency. A fan that uses less energy to move the design airflow is more desirable than a fan that must draw heavily to turn the fan to achieve the same airflow.
  5. Task: Refrigerant Charge – The Rater takes a series of temperature measurements indoors, outdoors, and at the refrigerant lines. Or proof the weigh-in method was used is also accepted.

The critical question is, what will be the impact of the above standard on the HERS or ERI scores? The calculations to determine the effect of these measurements are under development by another committee. This standard focuses on forced-air cooling and heat pump heating; therefore, climates, which are cooling dominant or regions that use heat pumps, will see the potential to lower (improve) their HERS Index / ERI scores.

What’s In It For Me

RESNET has heard from Homebuilders that if they demonstrate compliance with the standard, it will help them meet the qualifications to earn the 45L tax credits. (To learn more about the 45L Tax Credit read this.) This is the first potential financial incentive for home builders to hire HVAC professionals who will deliver quality installations. These incentives can earn the Homebuilder a $2,000 tax credit. This is not a tax deduction that reduces their tax bill slightly, but a tax credit that reduces what they owe or is owed. Builders who earn the credit would have a $2,000 incentive to hire an HVAC professional who delivers a quality installation. An HVAC system that is properly designed, with commissioned equipment and a tight duct system.

This will appeal to home builders who have their homes rated as proof they have met the low HERS / ERI score required to earn the tax credit. These builders will have at least two options. They can have their Rater perform the tests required by RESNET/ACCA 310, or they can use an independent verification report, possibly provided by ACCA.

So, we need your feedback. Please respond to this survey and answer five questions about whether ACCA should modify the QI mobile app to earn the HERS or ERI points for a home builder. The QI app is currently only for retrofit or replacement systems in existing homes. However, you can download the app and experiment with how to use it.
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