New Findings Emerge from HERS Program

With more than 2 million homes HERS rated, data sheds light on energy efficiency and energy codes.

Over the summer, the U.S. eclipsed 2 million HERS rated homes, with rated homes in all 50 states and the District of Columbia. According to research done by the National Renewable Energy Lab, HERS rated homes made up 22 percent of all new homes in 2016. The Home Energy Rating System (HERS) created by RESNET, began as, and still continues to be a largely market driven option for labeling the energy efficiency of homes. However, the introduction of the Energy Rating Index (ERI) Compliance Alternative into the 2015 International Energy Conservation Code (IECC) now makes the HERS Index an attractive energy code compliance option for many builders.

Giving consideration to the ERI and IECC requirements, this blog will present some data points from homes that received a HERS rating between August 1, 2015 and July 31, 2017. Using data from homes built in the last two years can help shed light on recent construction practices and how they relate to energy code compliance.

During the two-year period of this data, there were just over 320,000 single-family homes rated. Here are some of the findings:

Index Scores. Nearly 55% of homes received a HERS Index Score of 62 or less. This means all of those homes would have complied with the maximum ERI score allowed in the recently published 2018 IECC. The average index score of all homes during this period was a 61. For HERS and ERI scores, lower is better and a score of zero represents a net-zero energy home; while a score of 100 is a home built in compliance with the 2006 IECC.

Equipment Efficiency. Although furnace and air conditioner minimum efficiency requirements are set by Federal Statutes and are not eligible to count toward compliance in the prescriptive or performance paths in the IECC, the ERI compliance path does account for equipment efficiency. For this reason, many builders choose ERI to capture the impact of their efficient furnace and air conditioning equipment. Nearly 45% of homes in the data set had a furnace with an efficiency rating of 92 AFUE or better and nearly half of all homes had an air conditioner efficiency of 14 SEER or better.

Envelope Air Leakage. Since the 2009 edition, envelope air leakage testing has been included in the IECC. The 2009 IECC requires an air leakage rate of seven air changes per hour (ACH), while the 2012, 2015 and 2018 editions require five ACH in climate zones 1 and 2 (southern U.S.), and three ACH in climate zones 3 through 8 (middle and northern U.S.). RESNET’s data shows that nearly 90% of homes have an ACH of 5 or less and 99% have an air leakage rate of 7 or less. This data clearly shows that the air leakage requirements in the IECC are obtainable.

Continuous Wall Insulation. Over the last decade, continuous wall insulation has gone from an optional way of complying with the IECC for wood frame wall insulation in two climate zones to being mandatory in three climate zones; and optional in three more. This means that builders in six of the eight IECC climate zones could be using continuous insulation to comply with the prescriptive wall insulation requirements. HERS Rated homes data for the last two years shows that 39% of homes are being built with continuous insulation. One benefit of using the ERI path to comply with the IECC is that it allows a builder the flexibility to determine how they insulate their homes and what type of equipment they use as long as they meet the target index score.

Windows. Window U-values and solar heat gain coefficients (SHGC) have been made consistently more efficient over the past decade. RESNET’s data shows that 58% of homes have a window U-value of 0.32 or lower and 61% of homes have a SHGC of 0.25 or lower. Both of those window values would comply with the 2015 IECC and all previous editions.

Use of Solar Power. One of the most contentious debates during the 2018 IECC development process revolved around the use of renewable energy in the ERI path. While the 2015 IECC doesn’t make any reference to renewable energy, the 2018 edition requires builders that opt to use renewable energy to meet the 2015 IECC envelope requirements. For builders not using renewable energy in the ERI path, they must have an envelope that is as good or better than the 2009 IECC levels. The number of HERS Rated homes using on-site power production in the past 24 months is less than 7%.

Striving toward net-zero. The acceptance of renewable energy into the 2018 IECC is important to the discussion of achieving net-zero energy homes—meaning a home produces at least as much energy as it consumes, annually. RESNET’s data sheds some light on the number of homes achieving net-zero or nearly net-zero status. Over the last two years 415 homes have achieved a HERS Index score of zero or less, compared to the two years prior where only 277 homes achieved that status. More than 1,000 homes in the last two years received a score between 0 and 25. A more impressive figure is a doubling of the number of homes scoring between a 1 and 50 in the past two years, compared to the two years prior. That represents more than 10% of rated homes in the last two years.

More than half of all HERS rated homes in the last two years would comply with the ERI target scores in the 2018 IECC. Based on the data, roughly half of these HERS rated homes are installing efficient mechanical equipment and windows; about a third are using continuous insulation and nearly all have tight building envelopes. Although the use of on-site power production is low, that number is likely to increase as more consumers realize the benefits of a net-zero energy home. Backed by consumer demand and code compliance, the work of the nation’s more than 1,900 RESNET certified HERS Raters will continue for the next two million homes and beyond.

Want to learn more? Check out this free webinar Dec 15: What Code Officials Need to Know About HERS and the Energy Rating Index

With more than 2 million homes HERS Rated, code officials can expect to see more permit requests using the Energy Rating Index (ERI) Compliance Path for energy code compliance. The ERI Compliance Path was introduced in the International Energy Conservation Code (IECC) in the 2015 version and is also included in the 2018 IECC. Fifteen states and over 300 local jurisdictions allow the ERI path for energy code compliance. The most common way to demonstrate compliance with the ERI is through the RESNET Home Energy Rating System (HERS) Index.

This webinar will provide code officials with a complete understanding of the process for using the HERS Index to comply with the ERI compliance path by covering the following topics:

  • What it takes to become a Certified HERS Rater
    • What are Rating Field Inspectors?
    • What is the difference between a Confirmed, Projected and Sampled Rating?
    • RESNET Approved Software for calculating the ERI
    • ANSI/RESNET/ICC Standard 301 (ERI Standard)
    • ANSI/RESNET/ICC Standard 380 (Duct and Envelope Leakage Testing)
    • RESNET’s Quality Assurance procedures
    • What to ask for in order to verify compliance?

To learn more, register for this free webinar on December 15, 2017 at 1 PM EST by CLICKING HERE and you will receive a confirmation email with further details.