The 2015 Energy Code Will Have a HERS Rating Compliance Path

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Great news, everyone! (If you read that in the voice of Professor Hubert Farnsworth, please don't let your imagination run away with you. This really is great news.) The HERS Index will part of the 2015 International Energy Conservation Code. Why does that matter?

Because it will help home builders build better homes.

Because it explicitly states what HERS Index is needed for each climate zone.

Because more home buyers will know what kind of performance to expect.

A coalition of groups has been pushing a proposal to use the HERS Index, and just this week, the International Code Council adopted it, with some modifications. The groups include RESNET, Natural Resources Defense Council, Air Conditioning Contractors of America, Leading Builders of America, and Institute for Market Transformation.

The HERS Index thresholds

Here's the HERS Index that each climate zone (CZ) must meet:

  • CZ 1 & 2                  52 
  • CZ 3                         51
  • CZ 4                         54
  • CZ 5                         55
  • CZ 6                         54
  • CZ 7 & 8                  53

Yeah, those are pretty low numbers, but the 2015 IECC takes another big step toward energy efficiency in every path. They're lower than NRDC and the other groups had proposed, too.

For more background on this change, here are a few resources that go into the details of the proposal. There's not a lot of news out yet about the actual code change.

David Goldstein's article in the NRDC blog

Factsheet on adding the HERS Index compliance path

Energy Efficiency Wins Big in New Residential Building Codes - press release from the Institute for Market Transformation (10/10/13)

How is this different from the current performance path?

The performance path has been in the energy code for a while now. It's used in the 45L tax credit for new homes, for which home builders have to show that the homes they're trying to qualify use at least 50% less energy than the 2006 IECC requires and then get $2000 if they make it.

The performance path in versions of the IECC up to 2012, however, specifies neither a HERS rating nor a HERS Index. It's based on annual energy costs. The proposed design has to have lower energy costs than the standard reference design, which is specified in the code. (See section 405 in the IECC.) It's also limited to the energy used for heating, cooling, and water heating only. Lights and appliances are not included.

The new compliance path requires that a home meet a certain HERS Index. That means that lights and appliances count, too. And with Indices of 51 to 55, the energy savings will be considerable. Homes being built to the 2009 IECC probably have a HERS Index in the 80s. The HERS Index scale is based on the 2004-06 IECC, with 100 being the HERS Index of a home that just meets that version of the code.

HERS Index scale

For a full explanation of the HERS Index, see my article, Everything You Ever Wanted to Know about the HERS Index.

What will this mean?

It remains to be seen how much this will really affect the energy efficiency of homes. Dr. Goldstein makes the case that it will save billions of dollars, writing, "Our proposed 2015 update will accumulate to a national cost savings of over $100 billion by 2030 compared to the 2006 code." I think that's a bit of hyperbole because the savings generated by this new compliance path will come from builders using it rather than one of the other paths in the 2015 IECC. Anyone on that code will be building much more energy efficient homes compared to the 2006 IECC.

Still, it's a great option. In the state of Florida, most builders use the compliance path and hire HERS raters. Before we know what will happen with this new path, I think we need to see what's going to happen to answer these questions:

How many states will adopt the 2015 IECC?

How many builders in the states that adopt the 2015 IECC will go the HERS Index route?

However things develop, I think it's great news that we'll at least have this as an option, explicitly spelled out in the 2015 IECC.


Related Articles

Everything You Ever Wanted to Know about the HERS Index

Do You Know Your Building Science Climate Zone?

Forget the People — A Home Energy Rating Is an Asset Label

A Home Energy Rating Is Not an Award



Now if we could limit the size of the HVAC per sqft in each zone. Contractors are STILL using the 500sqft per ton rule, regardless how tight the house is... Furnaces also are way oversized...

David Eakin

@Stephen - this will only be for new construction; all previous new construction requirements never applied to existing buildings (unless being heavily remodeled). 
However, this brings up a very good point - maybe we need a minimum requirement for occupancy that increases with advances in building science. This would be a total game changer for the real estate industry that currently espouses that "there is no bad house; you just need to find the right buyer". This would create a re-vitalized energy auditing and home performance/remodeling industry. It would also improve occupant comfort/health, reduce home energy costs, and decrease our reliance on foreign energy suppliers. The only exception I could logically see would be for historical purposes - and that has its own "can of worms" to deal with.

David Butler

@Steven, legislation has been proposed to require HERS ratings for existing homes upon sale or refi. But in that case there's no maximum, just disclosure. Even still, the real estate industry would have none of that.  
David E wrote: "...maybe we need a minimum requirement for occupancy (for existing) that increases with advances in building science." 
At least from an EE standpoint, a dramatic increase in energy prices or a carbon tax would have the same effect. Otherwise, I'm not sure there's a political path. To Craig's point, the more the energy code ratchets down, the more states are choosing to opt out.

Peter Brown

While the HERS Index (and the work of RESNET) is a useful tool industry professionals it is not the ideal information to provide to consumers. A prospective buyer cannot use the HERS score the compare one home to another to evaluate energy efficiency. A 6,000 square foot home and a 1,600 sq ft home can both have the same HERS score. In Oregon we use an energy rating that is analogous to a vehicle MPG, miles per gallon. Called the Energy Performance Score (EPS), the score is simply the estimated MMBtu's/yr for heating, cooling, plug loads and appliances based on RESNET inspection protocols and modeling. An EPS of 54 means the asset (home) is designed to consume 54 MMBTu's/yr if occupied by a normal family size.  
To move our market we need to do a better job of getting relevant, easy to understand information into the hands of consumers and other market actors. The EPS tells the consumer what the score would be if that home were built to the Oregon code in effect at the time. So that home with an EPS of 54 might have had an EPS of 85 if built to code, and both of these numbers, along with the estimated annual energy costs and salient technical energy specifications of the home, are displayed on the scorecard. 
An important point here is the EPS baseline, or built to code score, is the code in effect in the state at that time. This is much more relevant than a code from many years ago that your state likely never adopted, or heavily amended. I work with builders every day, and not one of them can tell me what the insulation levels in the 2006 IECC were for their climate zone. Naturally, some states have more stringent energy codes. When I moved to Oregon in 2010 a code built home had a HERS score of about 85. Finally, when, or if, RESNET moves their baseline bar up to a more recent IECC code, all of those old HERS scores become meaningless. This is an inherent problem for relative scores. Because the Energy Performance Score remains constant it is a better tool for the marketplace, and therefore a better energy rating.


Requiring a HERS test at the time of closing for a purchase or a refi just adds to the already out of control closing costs. Sorry, no deal. We have enough government interference/regulation in our lives already. HERS rating should be OPTIONAL selling feature, or at least limited to new construction. 
IMHO it's much easier to simply limit the energy consumption/size of the HVAC system based on sqft and climate zone. Let the build decide if he wants to install higher AFUE/SEER equipment or make the house/ductwork tighter.

Allison Bailes

Bob: Right-sizing is already in the code. It's a matter of enforcement. 
Steven D.: I don't think that's what anyone wants of this. 
David E.: I agree with David Butler that energy prices, especially transportation costs, would do that more effectively than codes or laws. 
Craig S.: Yeah, one of my two big questions at the end of the article was about how many states will actually adopt this code. 
David B.: Yep. 
Peter B.: Thanks for bringing up the EPS again. I really do need to write an article about it. Regarding your suggestion that RESNET change the baseline energy code the HERS Index uses, I don't think there's any plan to do that, nor would it be a good idea. It doesn't matter how many states were ever on the 2004/06 IECC; it simply serves as our reference point. As you point out, if RESNET does change it, all previous Indices are no longer comparable. 
Bob: You must be talking about this: An AC Sizing Benchmark for High-Performance Homes 


The problem with current "right sizing" codes is it's based on ManJ and whatever inputs the contractor wants to plug in. Basing it on sqft and climate zone gets rid of the ability for the contractor to add fudge factors when doing the calculations to get the result he wants. 
Limiting by sqft/climate zone forces proper installation of the HVAC equipment and a reasonably tight building in order to avoid comfort complaints.

kim shanahan

Allison, I think a lot more states would have been inclined to adopt 2015, even over 2012 version, if the final numerical equivalencies had not been so drastically reduced in Atlantic City. CZ 5 went from 63 down to 55. BIG difference, as each lower index point becomes increasingly more expensive. Feels a little bait and switchy and not the numerical equivalency we supported. One wonders how an equivalency metric could have dropped 8 index points on the floor of the ICC final action hearings. Please investigate and help us understand how politicking can overcome what should be a consensus metric.


What is a typical HERS index for a 1950's house that hasn't had any weatherization done? The older homes that have never had anything done since 1962 when grandma moved in are using 2x-3x the energy of a typical new home?

Craig Senglin

I've looked at the EPS tool you mentioned (marketed by "Cake Systems"?). It looks like a great, & more accurate alternative to REM, but the steep monthly license + per use fee ensures it will never gain traction toward widespread acceptance, unfortunately.

Peter Brown

The EPS you found is for existing homes, not new construction. Yes, it is produced by CakeSystems, although CakeSystems can be customized to produce a score card that is unique to a local market. If you're a home performance contractor the cost is a wise investment, as CakeSystems is fast, easy and accurate. Plus, it increases the professional appearance of your company and produces meaningful homeowner reports that have been shown to increase conversion rates. 
The EPS I was referring to is for new homes, and is only used in Oregon. Here's what the scorecard looks like: 
The value is it's an easy to understand energy rating and steers the consumer towards thinking about consumption. It's produced using REM/Rate. In addition to providing the total annual energy consumption for the home as built, it also tells the consumer what the energy consumption would be if that house was built to code and what the energy consumption is of a similar sized existing Oregon home (using a blend of existing housing stock age and characteristics). This is useful information a consumer can understand and benefit from when buying a home. 
Being a relative score, the HERS Index is almost impossible for a consumer to understand. I work with builders in Southwest Washington who use the HERS Index and can't adequately explain what it means. I've eavesdropped in many model homes and never once have I heard a salesperson explain it well. That leads to a confused customer and a missed opportunity, both for the builder and our industry. 
The comparison of how much more energy efficient a home is compared to the 2006 IECC is not something buyers can grasp. In seven short years will we still be comparing a home to the 2006 code? Imagine it's 2020 and a salesperson who can explain the HERS Index tells a customer that this score tells you how much better your house was built compared to the 2006 IECC? That will sound dated and decidedly prejudicial. It's like having a metric that compares the MPG of a car to a car built in 1970 and is an inherent problem anytime you date yourself.

Craig Davis

Well, I figured it would happen sooner than later. Another bunch trying to create an industry and jobs for themselves at the builders expense. Energy conservation is one the most important things in the building industry, but do we need a self imposed bunch of HERS Raters making a living off the builders ?? As a consumer and home buyer, I want the freedom of choice to upgrade and make energy choices on my own without placing it on a 30 year loan with interest. This sounds like a typical government program so they can make the money by controling our decisions. 
I say, if HERS Raters are so in tuned with putting regulations on new homes, why don't they become a home builder so they can explain to first time buyers and low income buyers why they can't qualify for a new home due to the cost increases on new homes. What ever happened to freedom of choice ?? Oh yeh, the Government !! 
That comment should bring out the HERS supporters. 

David Butler

@Craig, perhaps you missed the part about HERS being an OPTIONAL compliance path? Jeez.