Have we been brainwashed to consider only R-values?
POSTED ON DEC 20 BY SCOTT GIBSON – GREEN BUILDING ADVISOR

Beefing up R-values and reducing air leaks are the twin
rallying cries of builders focusing on energy efficiency.
Regardless of the particulars of the house design, more
insulation and fewer air leaks make houses more
comfortable, more durable, and less expensive to heat and
cool.
No one seems to argue that point. But Al Cobb wonders
which is more significant.
“My real goal is to find the tipping point when a leaky
building loses more energy via air changes then via the
insulated envelope,” he writes in GBA’s Q&A forum. “I’ve
had many answers where the losses from air leakage have
been as low as 10% or as high as 50%.”
Cobb believes home buyers have been “brainwashed” into
thinking only about R-values, as energy codes give short
shrift to the importance of airtightness. Energy modeling is
especially frustrating, he says, because it asks for highly
specific information on R-values but only broad
generalizations when it comes to airtightness.
“Therefore, I’m looking for a study or analysis of homes (real or not)
that have been modeled to the extent that heat loss from conductive
and air infiltration losses are clearly defined,” Cobb adds. “It only
makes sense that as leakage rates increase, the decision to ignore airsealing
can be shown as a critical mistake.”
Ain’t no such animal
Good luck and God speed, suggests Robert Riversong: “Your question
is similar to, ‘What’s the difference between an apple?’,” he writes.
“The answer could range from near zero to near 100%, and is entirely
dependent on whole-house R-value and whole-house air exchange
rate during normal operation (not under blower door testing). If
you’re asking about ‘average’ existing housing, there is some data on
that. If you’re asking about a particular new construction project, you
have to do the heat loss analysis for that specific building including
design or actual air exchange losses.”

Why you should get a HERS rating.

by Max Strickland

In case you didn’t know it, there is a rating for your home similar to the miles per gallon rating for your car. It’s called a HERS Rating (Home Energy Rating Services) and was developed by the Residential Energy Services Network (RESNET).

The first effort to establish a national home energy rating system was started in 1981 by the mortgage industry with the goal to establish a measurement system which factored the energy efficiency features of the home into the mortgage loan. The effort evolved over time and in 1998 the mortgage industry, RESNET and the National Association of State Energy Officials adopted the current HERS Rating system.

A HERS rating can be used for either existing homes or new homes.

For existing homes:

A HERS Rating on an existing home can benefit  current homeowners by providing them with professional, unbiased  information (by someone not trying to sell them a product or service) when they are considering home improvements or additions. An example that I have encountered several times is a homeowner who is experiencing ice dam issues. The home has sloped ceiling areas in a second story and the most cost-effective fix would be to access the sloped ceiling/roof cavity to fix the problem from the roof side (not the ceiling side) but they just replace the roof last year. Obviously no one wants to disturb a brand-new roof to fix an air sealing/insulation problem under it, but that would have to have been the most cost-effective solution if done before the new roof was installed. Consequently they live with the issue and it’s collateral damage or try to address it from the inside; neither of which is a good choice.

If you’re considering buying an existing home, it would make sense to ask the seller to provide a HERS Rating so you can compare the energy efficiency of the home before making an offer. Common sense would dictate that if a home is energy efficient it has more value than one that isn’t.

For new homes:

If you’re buying a newly built home,  a HERS Rating gives you good information to make comparisons. A home built to the 2006 Michigan Uniform Energy Code (MUEC) would have a HERS Score of 100 and a home built to the 2009 MUEC would have a HERS score of 87 (lower is better, every point on the HERS Score represents 1% less in energy cost.

A HERS Rating, if done before final construction decisions are committed to, allows you to do “what if’s” . An example of this is,  if 1 inch of rigid foam insulation is added to the outside of the above grade walls,  how many BTUs of energy will be saved.  Or, if you upgrade your water heater to a heat pump water heater how much energy and dollars will you save.

One local builder has posted his HERS Ratings on his job signs because he believes his prospective customers deserve good information to make home purchase decisions on.

A HERS Rating is the accepted national standard for assessing the energy efficiency of existing and new homes and is being adopted as a credible measure of energy efficiency by appraisal and mortgage industries,  state and federal governments for tax incentives and credits and most Green Building programs like Energy Star, National Green Building Standard and Leed for Homes. In addition, many real estate multiple listing services around the country are using the HERS rating in their listings. The Traverse Area Board of Realtors has been a leader and innovator in this effort.

 The take away here is we have a credible tool to help us make good decisions when making the biggest financial investment most of us will ever make and I encourage you to make use of this tool.