Over a thousand home performance contractors, weatherization experts, HERS raters, and energy nerds are gathered in Kansas City, Missouri, this week to attend the ACI Home Performance conference (formerly known as the Affordable Comfort conference).

At one well-attended workshop, energy consultant Michael Blasnik and Shaun Hassel of Advanced Energy Corporation shared a roundup of data on the performance of Energy Star homes — data which are unlikely to be happily received at the U.S. Environmental Protection Agency (EPA). Among the findings presented by Blasnik and Hassel:

• A 2002 study by Wisconsin Energy Star homes showed that Energy Star homes used only 10% less natural gas than new homes without an Energy Star label.
• A NYSERDA study of 1,974 homes built between 2004 and 2006 showed that Energy Star homes used slightly more energy than the average home in New York state. High-scoring Energy Star homes did not use any less energy than low-scoring Energy Star homes.
• A study of 2,998 Energy Star homes in Phoenix showed that Energy Star homes used about the same amount of energy as baseline homes without an Energy Star label.
• A massive study of 23,000 Energy Star homes in Houston showed that Energy Star homes use a little less energy for cooling than baseline homes, but use a little more electricity overall. As codes and appliance standards have increased in stringency over time, the slight performance advantages of Energy Star homes compared to baseline homes have eroded.

“The Energy Star program started with a low bar,” noted Blasnik. “No one has found that Energy Star homes use 25% less energy than other homes.”

Explaining the findings, Hassel noted, “Baseline homes are not as bad as many models assume, and Energy Star homes are not as good as many models assume.”

More Mandatory Requirements
As codes have become more stringent, the Energy Star program has been struggling to play catch-up. In many states — most notably in California and Florida — Energy Star lost the battle for a while, slipping below minimum code.

At an evening workshop in Kansas City, Sam Rashkin, the national director of the EPA’s Energy Star Homes program, explained the details of the EPA's latest proposal to raise the bar on requirements for Energy Star homes. Set to be released for public comment within a few days, the proposal is known as the 2011 Specification.

The highlights of the new requirements:

• All insulation will need to be installed according to Grade One installation standards.
• Builders will need to adopt one of five strategies to reduce thermal bridging through walls (advanced framing practices, exterior foam sheathing, SIPs, ICFs, or double stud wall framing).
• Mechanical ventilation meeting ASHRAE 62.2 will become mandatory.
• Hot water distribution systems will need to be designed to reduce heat loss due to long piping runs. To meet this requirement, builders will need to include either a “wet wall” (plumbing core) design, a manifold system, or a demand hot-water circulation system.
• Attic ducts will be required to have R-8 or better duct insulation.
• In homes with forced-air HVAC systems, jumper ducts, transfer grilles, or ducted returns will be mandatory in bedrooms.
• A “size adjustment factor” will be used to ensure that large Energy Star homes include more stringent measures than smaller homes.

Of course, Energy Star’s proposed 2011 Specification is subject to change after the public comment period. Stay tuned.