Aspen, Colorado Dumps Energy Rating Index

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Aspen, Colorado energy code

The city of Aspen, Colorado has bucked the trend. Well, actually two trends, but first things first. The 2015 International Energy Conservation Code (IECC) introduced another pathway for code compliance using what's called the Energy Rating Index (ERI). Since the only thing that qualifies as an ERI right now is a HERS Index, RESNET and HERS raters have been pushing hard to get this into state and local codes. Several jurisdictions have already adopted it and some builders are using it. Aspen, however, just adopted the 2015 IECC but they threw out the ERI compliance pathway. That's bucked trend number one. Bucked trend number two is the motivation for what they substituted in place of the ERI. Keep reading to find out what that motivation was.

IECC compliance pathways

Before jumping into the details of the new Aspen energy code, let's do a quick review of the different ways you can get a new home to comply with the IECC. Also, in case I don't make it clear in every instance, I'm writing only about the residential energy code, not commercial.

If you're building a new house in a place that's on one of the recent versions of the IECC, you have a choice of how you show your building department that you comply with the code. The 2015 IECC has three compliance pathways, as a matter of fact. They're listed right at the beginning of the residential section of the code. To pass, you have to choose one of the three options below and meet all the requirements therein:

  1. Sections R401 through R404.
  2. Section R405 and the provisions of Sections R401 through R404 labeled “Mandatory.”
  3. An energy rating index (ERI) approach in Section R406.

The first one has a sub-choice for you to make, too. When deciding on the building enclosure specifications for insulation and fenestration (windows and doors), you can go with the prescriptive values in the tables or you can do some tradeoffs using the UA alternative. In addition, there are requirements for mechanical systems, lights, and other energy-using parts of the building.

The second one is often referred to as the performance path. You have to model the home as it is built and compare the energy costs to the same home modeled with a set of design specifications given by the IECC in Tables R405.5.2(1) and R405.5.2(2).

The third one is the ERI. The only way to get an ERI right now is to do a home energy rating.

OK, now we're ready to talk about what Aspen is doing.

Meet the simplified alternative

That heading is your clue to the second trend that Aspen is bucking. If you talk to enough builders, code officials, and other stakeholders, you'll find that a lot of people think codes are too complicated. Now, I agree with Albert Einstein on this subject: "Everything should be made as simple as possible, but not simpler." The electrical code, naturally, has to have enough complexity to keep houses from burning down and people from getting electrocuted. Energy codes, however, certainly have room for simplification.

And that's what Aspen has done. The way they chose to do that is something I've written about before. Their list of compliance pathways looks like this:

  1. Sections R401 through R404.
  2. Section R405 and the provisions of Sections R401 through R404 labeled “Mandatory.”
  3. Simplified Equivalent Compliance Alternative in Section R406 [emphasis added]

The only thing different is the last one. To the chagrin of HERS raters, Aspen dumped the ERI path. Don't bring your HERS results to the Aspen building department because they won't take them. Instead, they've created a truly simplified path. You don't need a HERS rater. You don't need to make sure you've got the proper R-values in the home. You just need to do three things. Make sure the building:

  1. has minimal heating and cooling loads
  2. reduces hot water consumption
  3. cuts energy used for lighting

This compliance pathway in the code is so simple, in fact, I can put the whole thing right here. It's only 189 words. Ready? Don't blink.

Section R406.1 Equivalent building option. Dwellings that meet both of the following criteria shall be deemed in compliance with this chapter.

1. The ratio of the air conditioning capacity to conditioned space is less than or equal to 1 ton per 1000 square feet.

2. The ratio of the space heating system capacity to floor area of conditioned space is less than or equal to 32,000 Btu/h per 1000 square feet.

Section R406.2 Equivalent hot water.

The distance from the hot water supply outlet to hot water pipe to the hot water entry to a room where hot water is used shall be no more than 10ft. This shall apply to the kitchens, bathrooms with showers or tub, and rooms with a clothes washer.

Section R406.3 Equivalent lighting.

Dwellings in compliance with at least one of the following requirements shall be deemed in compliance with Section 404:

1. Lamps over 15 watts shall be CFL, LED, or have an efficacy not less than 90 lumens per watt.

2. At least 90% of the lamps or fixtures shall have an efficacy not less than 75 lumens per watt.

That's it. All you have to do is meet the requirements in those three little sections and you're in.

The part of most interest to me is the first one. (Hey, I'm more of an enclosure and mechanicals guy than a hot water or lighting guy.) That's what I wrote about before when I posted the video of Chris Benedict and Henry Gifford and their one-act play on what they called the Perfect Energy Code.

Now, the trick to doing this kind of code is choosing the correct numbers. Aspen has an insignificant cooling load (says this guy who was born in Houston) so the part about installing a cooling system with a capacity no more than one ton (12,000 BTU/hr) per 1,000 square feet isn't real important...for Aspen.

But the heating part is important. Their number is 32,000 BTU/hr for each 1,000 square feet of conditioned floor area. I asked Stephen Kanipe, head building official for the city of Aspen, how they arrived at that number. "We talked to mechanical engineers with a lot of experience in the area," he said, "and this was the number they told us would be better than code but still achievable."

Here's a little background for you, too. This simplified alternative was proposed for the IECC itself during the recent deliberations for the 2018 version. I spoke to Craig Conner, who was involved in that proposal, and he told me that although it didn't pass, it was well received. The main reason it didn't pass was that they didn't have the numbers fleshed out for the different climate zones. I think they'll probably pick it up again for the 2021 code cycle.

Where will this go?

This is a big deal in the world of energy codes. It could change the direction things have been going and HERS raters don't like it. Mark McLain, an architect and HERS rater in the Aspen area, protested the change as a relaxation of energy conservation codes. He wrote about it in his blog, where he also published the letter he sent to the Aspen city council.

I think Aspen's onto something with their new code. I don't agree that this is a relaxation of the code. If they did get the right number for heating capacity, it should be better than the prescriptive path. I'm sure it's not perfect, but this is a good way to keep things simple and enforceable.

It'll be interesting to see how many builders choose the Simplified Equivalent Compliance Alternative and what they do to meet it. They've got to get the enclosure right, though, to be able to heat their homes within that capacity limit of 32,000 BTU/hr per 1,000 square feet. And as a side benefit, they can save on the cost of strip heating to keep ice dams off the roof. If they truly get the enclosure right, they won't need them.

building enclosure roof ice dam heat strips aspen

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Jan 24 2017 - 9:55am

What I don't understand is the notion of 'dumping' one for another. People put in a lot of work to develop codes in the first place and if Aspen decides they have a better method then that is absolutely fine. What bothers me greatly is that they don't accept the ERI method at all. Why not allow the ERI to stand if builders want to use it and accept the simplified method in lieu of? Other professions don't seem to have this problem that I know of. How about if we do away with appraisers and use simplified valuation appraisals based on size, type, usage and age of the building? Why bother with requiring an engineer's stamp on plans and blueprints instead of just requiring that the plans be on a certain size of paper with acceptable colors of ink? Appraisers and engineers are required because they provide valuable, needed services. I suggest that raters also provide valuable services that cannot be replaced by a checklist.

Jan 24 2017 - 11:00am

The issue for all of Aspen's code options as well as the IECC is confirmation and accountability of results. As an Architect, HERS blower door tests important since they verify the design and systems are working appropriately. If the envelope is not functioning properly neither do the systems.

Jan 24 2017 - 11:51am

Ken is right, they should have kept the ERI/HERS as an option. The problem with stair-step codes is scale. How many BTUs required for a 1500 square foot home? 64,000 or 48,000? HERS ratings can account for the nuances.

Jan 24 2017 - 1:37pm

If my own HERS rated house is anything to go by this seems like an improvement. My house meets none of these requirements listed above. And when the HERS rater just rubber-stamps whatever the builder throw up, it give little credibility to the rating. Like did nobody notice that the Manual J has the front door pointing north but it is actually pointing east....did he measure the airflow in the ducts? Because supply/return is less than 800CFM on a 3 ton system....and I could go on and on. I truly regret spending money on a Energy Star home. And not to mention there is a whole neighborhood with houses like mine.

Jan 24 2017 - 2:03pm

The issue I see here is that the ERI path is significantly burdensome for a builder. In essence the builder has to do much more to comply with the ERI path than they would have to do to comply with the prescriptive path or the performance path. So, I do not believe that the ERI path will be widely used regardless unless jurisdictions weakening the pathway during the adoption process which I don't think they should do. As a byproduct of the Simulated performance path builders should be getting a HERS Index so they should have an understanding of what the ERI of their houses are while using a pathway that allows them to figure out the most cost effective way to meet the intent of the code.
The issue that I see here is that Aspen did not adopt the flexibility already built into the code. The code has the ability to help builders build homes that perform really well if jurisdictions would adopt it as written. There is no way for the Department of Energy and others to understand the impact of a code on the efficiency of house in relation to other code when significant amendments are made to the code. So, adoption and enforcement become the big issue. Offering additional flexibility, as Aspen did, might be fine but where is the data that demonstrates that the performance of their new section R406.1 is equal to the performance of the 2015 IECC as written. It might but it might not?
I think a big driver here is still first cost vs cost of ownership and a builder driven perceptions of cumbersome code processes that they perceive do not add value. People who do code compliance work using the performance or ERI pathways need to ensure they fully understand the code and all that it takes to inspect and enforce. For example, the ERI path requires much more than just an ERI score to meet the intent of the code. If everyone, from code officials, to builder, to raters, do not understand that, then the additional value of the process is very difficult to justify from an economic or code and building performance perspective. Value is not in the ERI itself, the value is in the process of evaluating a house that the ERI or simulated performance path imposes on the house to ensure that the house works, and that mainly comes from ensuring that the mandatory aspects of the code are carried out well.

Jan 24 2017 - 5:40pm

The advantage of ERI versus "performance path" is that the ERI can factor other things besides the envelope. It is especially confusing because people choosing the ERI path believe, correctly, that they are following a "performance path". Better to call the performance path the "whole-house UA trade-off" path, since neither it nor the ERI guarantee performance at all, they only predict performance. Being able to account for mechanical equipment, appliances, light bulbs, orientation and source energy, none of which are captured in the "performance path", is a real benefit to the builder seeking code compliance with complex client and architect-driven projects. Furthermore, if we actually believe we will have codes someday in the future that mandate net-zero energy homes, we will only be able to accomplish that with an ERI requirement that allows for all manner of inputs. A non used BTU is a non-used BTU whether it comes from a solar panel or a tight envelope. Yes, the envelope is the first place to find the cost effective saved BTU, but we will never create a prescriptive path that will get us to zero unless the prescriptive path is one that simply says "Get a ERI of zero"

Jan 25 2017 - 8:18am

Interesting and well explained. Thank you! Will be sharing with my EDGE green buildings team at IFC working on code work in developing countries.

Jan 25 2017 - 9:13am

Regards to my friends in Aspen, but the devil is always in the details.

I certainly agree that you can hide the details as has been done by adopting section R406.

I don't agree that R406 makes life simpler, except on paper. It is still just as hard to build a reliable high performance home in Aspen's climate and requires just as many validated load calculations to confirm that you have reached that performance level today as it did before R406 was adopted.

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