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Big Changes Underway for Home Energy Rating System

Dramatic changes in the Home Energy Rating System (HERS), which is used to measure a home’s energy efficiency, are now underway and will be completely phased in by the start of next year, according to the NAHB Research Center.

Although sure to add some confusion initially and to create some challenges for builders marketing the index to potential customers, the new system is intended to bring the ratings into line with the most recent energy code and to include lighting, appliances and on-site energy production into the HERS rating, the Research Center says.

The new HERS systems turns the old ratings — where 100, on a scale of one to 100 indicated the best possible score — virtually upside down.

The new HERS index is based on the 2004 International Energy Conservation Code, with a home built to code receiving a score of 100. For every 1% reduction in annual energy consumption, the HERS index is lowered by one point. Under this system, a zero-energy home would score a “0” and a house using twice as much energy as the “code” home would have a HERS index of 200.

Under the old system, a score of 86 or higher was needed to obtain the Energy Star® label. Under the new HERS index, to meet Energy Star® requirements, a home in a cold climate needs a HERS index no higher than 80 (20% more efficient than the reference home). In moderate or hot climates, an index no higher than 85 is required.


HERS Index   

HERS Score

Reference code/standard

2004 International Energy Conservation Code

1993 Model Energy Code

Total Energy Consumption
in the rating system

• Heating
• Cooling
• Water heater
• Lighting
• Appliances
• O
nsite energy production
• Plug loads

• Heating
• Cooling
• Water heater

Comparison to the "code" home

For every 1% reduction in total energy consumption, -1 point.

For every 5% reduction in total energy consumption, +1 point.

"Code" home score



Zero energy home score



EnergyStar® home

Climate zone 6-8: < =80
Climate zone 1-5: < =85

> =86

Completely phased in

Jan. 1, 2007


The previous HERS score included only heating, cooling and water heating, and was based on comparison with the 1993 Model Energy Code. Under the old system, a home that met the energy code requirements but included high-efficiency lighting and appliances had the same rating as a code-compliant home with standard-efficiency lighting and appliances.

The Research Center points out that many of its EnergyValue Housing Award (EVHA)-winning builders rate every home they build.

Arkansas home builder Stitt Energy Systems tests the tightness of the house twice, once before drywall is installed and again upon completion of the home. The pre-drywall testing allows the builder to identify any problems before they are enclosed behind drywall.

Don Ferrier, president of Ferrier Builders, says that getting a HERS test is one of the best things his company does to ensure quality control.

Some EVHA-winning builders have in-house raters, according to the Research Center, while others subcontract the work. Having an in-house rater requires some upfront investment in equipment, software and training, but may be cost-effective in the long run.

The cost of a HERS rating varies widely based on economy of scale, local market conditions, travel distance for the rater and other factors. The national average is about $450, and some production builders pay less than $200 per home.

Star ratings may be somewhat helpful for builders promoting the energy-efficiency of their homes, the Research Center says. The best homes — those scoring 50 or less — receive a five-star-plus rating. However, there may still be some confusion because under the star ratings, even a home with an index of 400 or 500 — one that uses four to five times the energy of the reference home — receives one star.

The new HERS index for meeting Energy Star® requirements will apply to homes permitted after July 1 and be completely phased in by next January.

Local HERS raters are probably the best source of information about the new ratings.

For detailed information from the 2006 Mortgage Industry National Home Energy Rating Systems Standards, click here.

To find a home energy rater, go to the Energy Star® Web site, or the RESNET site.

For more information about the EnergyValue Housing Award or to obtain a 2007 EVHA application, click here.

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