If you are in the building industry, you are probably no stranger to the 2021 IECC. This is the most recent iteration of the International Energy Conservation Code (at the time of this writing), and it has really tightened up certain construction requirements for newly built homes.

One of its most significant changes has been insulation requirements. In the past versions of the IECC, insulation levels have been more monetarily manageable, but the 2021 version has increased insulation requirements significantly. Most notably a call for R30 in the walls and R60 in the ceilings in Colorado’s climate zone.

If you choose to go “by the book” or take the prescriptive path when building, and adhere completely to IECC 2021 guidelines, your insulation costs are going to go up relative to prior years. However, there is an alternative route…

For the first time, the ERI performance route of the IECC codes is starting to be the more cost-effective option, and performing a HERS Rating could potentially save some serious cash on insulation!

What is HERS Rating?

First, let’s have a quick refresher. HERS, which stands for Home Energy Rating System, is a method used by architects, builders, and energy raters, to determine the overall energy use of a home. The Residential Energy Services Network (RESNET) established the HERS index, the standard that measures a home’s energy efficiency. Note that HERS is the RESnet branded term for Energy Rating Index (ERI), which is the terminology specifically used in the 2021 IECC.

In order to calculate the HERS Score of a building, a certified HERS rater must evaluate all energy-based facets of the home, including insulation, windows, heating/cooling units, etc. The rater then uses specialized software to calculate the score of the home – the lower the score, the better.

Where the HERS Rating system really stands out is that it gives you a level of flexibility through “trade-offs.” In other words, a certain aspect of the home with super high energy efficiency can compensate for another area that isn’t as energy efficient. For example, if the home is utilizing high-efficiency heating, cooling, and water heating methods, the wall and attic insulation could possibly have reduced R-values and still have a similar HERS score. With this trade-off, the overall score of the home can still be IECC-compliant, despite the lower energy efficiency of the insulation. Do you see where this is going?

To learn more about HERS Ratings, check out our 4-part article, The Ultimate HERS Rating Guide: Part 1, Part 2, Part 3 & Part 4.

Prescriptive Compliance Vs. Performance Compliance

Section R401.2 of the IECC 2021 states that, in order to reach compliance, there are several options you can take. The first option is the prescriptive path. This is the “by-the-book” method, where the builder must follow the guidelines established in 2021 IECC in sections R401 through R404. This route has generally been more common. However, now that requirements are stricter, it is becoming more difficult and costly to stay within the prescriptive path.

As mentioned above, insulation standards have tightened significantly from 2018 IECC to 2021 IECC. While attic insulation previously had to be at a minimum of R49, it has been raised to R60. Similarly, wall insulation has been raised from R23 to R30 cavity (or R20 cavity + R5 exterior rigid continuous insulation). These new levels are much harder to attain (especially in a standard 2×6 wall) and it drives up insulation costs drastically.

That is where the performance path can really come to the rescue. The performance option is a less rigid route that allows builders to design the home in a fashion they see fit, as long as it meets the 2021 IECC requirements for total energy performance. For this route, design teams have the liberty to employ various combinations of design strategies, and technologies to provide the greatest energy savings for the lowest overall cost.

For Colorado, there are two viable performance options in the 2021 IECC  handbook: The Total Building Performance Option, which is explained in section R405; or The Energy Rating Index (ERI) Option, described in section R406.

The two options are similar. They both require the use of a HERS rater to do pre-reports for a permit, then do all the verification steps during construction, and produce final reports at the end of construction. The main difference is that The Total Building Performance Option produces an IECC Compliance report (further explained in R405), while the ERI Option requires a full ERI report (further explained in R406).

Saving Money with Performance Compliance

There are multiple ways to save money when taking the performance route. We’ve already mentioned it, but let’s just drive it home – doing a HERS rating can save you big bucks on insulation! If you are taking the Total Building Performance route, insulation levels must at least meet 2009 IECC levels. But anything at or above that is acceptable, as long as the home meets the 2021 IECC requirements in total performance.

On the contrary, the ERI method does not technically require an insulation minimum. As long as the home yields an overall score of 55 or less, you can take liberties with the insulation thickness. This provides you with the freedom to plan the most budget-friendly approach to your building project.

Say you do end up going with insulation that meets the 2021 IECC prescriptive standards. Using a HERS rating may give you the flexibility to save money on other components of the home.

Also keep in mind that, whether you are taking the prescriptive or performance path, you will be required to get duct leakage and blower door tests. It just so happens that our HERS service packages include both duct leakage and blower door tests. So when taking the total performance or ERI route, you will be bundling all the necessary energy tests (i.e. duct leakage and blower door) and adding that extra flexibility with trade-off options.

While every job is different and each county’s requirements vary, an analysis with a HERS Rating has the potential to unlock more freedom within your build.

HERS Rating with Scott Energy Services

At Scott Energy Services, a division of Scott Home Services, we are your one-stop shop for all your energy needs. Our energy specialists are well-versed in Colorado energy code, and can advise you on your requirements based on your municipality. We offer all the required onsite testing for a standard HERS rating, from the planning to the finished product.

We know that when it comes to energy codes, there is a lot to take in. So if you have any questions, feel free to call us. One of our energy specialists will be happy to help.

If you are in need of HERS ratings services on your next project, visit us online to learn more, or contact us to book your services now.

One question that we are asked frequently is when and where is a HERS rating required in Colorado? A HERS rating can be an alternative solution to following the building codes when building a Colorado home. We covered many of the benefits of performing a HERS rating in our earlier blog about performance vs prescriptive pathways.

However, that does not necessarily mean that a HERS rating is required or preferred. It is typically just an alternative solution to meeting the requirements. As energy codes are updated and tightened up, they can phase out specific design options on homes that can only be achieved by using trade-offs, which are easier to achieve with a HERS rating.

A HERS rating can be a great option to meet the energy requirements, but in some cases can be overkill. In an effort to substantiate the HERS rating system, however, and give consumers more insight into how good a home’s energy performance will be, some counties and cities in Colorado have required or “incentivized” the HERS rating system.

In this part of HERS rating guide, we will cover where and when a HERS rating is more than just an alternative.

Where is a HERS Rating Required In Colorado? One place. Boulder.

Boulder has always been a community bullish on energy efficiency. They are continually pushing the boundaries and have emerged as a leader in this area. They have become a role model for the state of Colorado and the nation between their SmartRegs program to their goals of reducing carbon emissions by 80% by 2050.

Both the City of Boulder and Boulder County building departments require a HERS rating in most instances, but they differ on their specific requirements. In general, the city has more stringent requirements as listed below.

City Of Boulder HERS Rating Requirements:

The city of Boulder requires a HERS rating on most larger projects. A HERS rating will need to be performed on new construction projects over 500 sqft, additions where the floor area of the addition is over 1000 sqft, or interior remodels where the square footage of the project is greater than 50% of the area of the current home. When a HERS rating is required, it must meet the required HERS Score represented in the below table. These requirements are outlined in the cities code documents.

The city has created its own internal building code called the City of Boulder Energy Conservation Code (COBECC). This code is based on the IECC energy code, but with many additions to make homes even more efficient. This code will be updated in 2020 and will include even smaller building projects and remodel projects that do not add additional square footage. More information can be found about this update here.

The HERS score of a home needs to meet a certain level based on the proposed square footage. The larger the home, the more energy efficient it must be, meaning the HERS score needs to be lower as well. The table below represents the HERS scores needed per square footage. As you can see, all homes built over 5000 sqft need to have a HERS score of 0. This means the home is net zero.

Boulder County HERS Rating Requirements:

The county follows a similar path as the city does. However, they are slightly less stringent as to when a HERS rating actually needs to be done vs following the prescriptive tables. Most dramatically, they raise the square footage caps.

Currently, a HERS rating will need to be performed on new construction projects over 3500 sqft or additions where the floor area of the addition is over 1000 sqft. You can see these requirement changes in the county’s easy to use BuildSmart Checklist.

You have many options in the county to defer to an Energy Smart Assessment over a HERS rating when the project is smaller. This consists of an energy audit being performed prior to construction. But the table also shows that you can use a HERS rating instead, which in some cases, can end up being easier in the long run. Read the full set of building energy requirements here.

These codes are always changing, but this gives a brief overview of what Boulder is looking for. If you have questions on HERS ratings or a Boulder code requirement feel free to contact us.

Denver’s Energy Rating Index system

The City of Denver has overhauled its energy requirement system in the last few years. From switching to IECC 2015 building codes, to requiring blower door testing, to creating many code amendments, the city clearly sees the value in energy efficient building.

While a HERS rating is not required in the City of Denver, it is one of the few places that outlines what they want to see when choosing a HERS rating over the traditional prescriptive pathway. A copy of the code requirements can be found here.

Their residential provision documents state that if you do decide to go with a HERS rating for a new construction home, you will need to meet a HERS score of 55 or less.

If you are building an addition, and it is difficult to isolate what section of the home will need to meet the energy codes and what will not, it may be beneficial to use a HERS rating. In this case, the City of Denver has made it very simple. You will need to have a certified HERS rater model the home before construction to get an initial HERS score. Then the post construction HERS score just needs to beat the initial score showing that there was an efficiency improvement. This should be a very easy way to gain compliance on complex additions.

On top of these 2 simple requirements, the city has also added one incentive to use a HERS rating. When submitting your HERS rating for a permit, they offer a $150 discount to offset the cost of the rating. This will help level the cost playing field between prescriptive and performance and give builders more flexibility on the route they choose to take.

Energy Star Certified Homes

One wild card to throw into the mix is when builders are looking to build an Energy Star Certified home. Energy Star has its own set of requirements that a home must meet in order to obtain the familiar blue seal on your project.

These requirements are slightly more difficult than the standard energy codes, which ensures buyers that they are purchasing an efficient and comfortable home.

One of the requirements of Energy Star is to work with a HERS rater that is trained in the Energy Star program to determine a target HERS score. This number will then need to be met during the planning and construction process.

So even if the county does not require an energy rating, if you are planning on building an Energy Star Certified home, you will be needing one anyway. Our HERS raters are certified with the Energy Star program as well and can help with your HERS rating and planning. Learn more about our HERS rating services here.

On The Horizon

Above are the current HERS Rating Requirements in Colorado. However, things are changing rapidly in this state. As the construction boom roars on, we are continuously hearing more information from building officials about upcoming changes.

HERS ratings have been a nationwide success in many states, aiding builders with complex building codes, and bringing energy efficiency into the marketplace. We predict that the demand for these services will continue to rise, and city building departments will begin to adopt the rating system.

Until then, we hope this article helps. If you are interested in talking to us about your next project please visit our HERS rating service page.

As we talked about in the earlier parts of this HERS rating guide, a HERS rating is a calculated score that quantifies the energy efficiency of a home. When a HERS rating is performed before a home is built, it can be used as a method to comply with energy efficiency code requirements instead of following the standard IECC pathway.

This is commonly referred to as prescriptive vs performance energy compliance. When building a home, using the prescriptive pathway requires following the code requirements line by line for each section of the home. Currently, this is more common but as the codes tighten it is becoming increasingly more difficult to meet every line item in the energy code.

The other option is the performance pathway. This includes using secondary reports such as HERS ratings or RESchecks to validate that a home is energy efficient enough to meet the current code standards.

It is called the performance path because you are measuring the physical energy performance of the building as opposed to following a set of guidelines.

This option gives builders the flexibility to alter sections of the home to be lower than the minimum required energy standards and make up for that deficiency elsewhere. This nets an equally energy efficient home as one built on the prescriptive codes but allows builders and architects to be more creative with their techniques and designs.

The above process is called a Trade-Off, and it is what we will be going through in this article.

Common Trade-Off Scenarios

There are endless scenarios where using a trade-off can help the building process but there are ones that come up frequently. A common trade-off trigger is window efficiency.

Trade-Offs: Window Efficiency

Say you are building a home with very large windows covering an entire wall. This is great to maximize your view, but energy efficient windows of this size that meet the prescriptive path U-value can be very expensive and difficult to find.

Because of this, many builders will opt for slightly less efficient windows and make up for it with a more efficient heating/cooling systems, for example.

You may lose more heat through the less expensive windows but it is now more efficient and less expensive to heat your home. This results in an energy neutral trade-off, and through the HERS model, the performance of the home should remain the same.

Trade-Offs: 2×4 Framed Exterior Walls

Occasionally, a builder or architect will want to use 2x4s to frame the exterior walls instead of the standard 2x6s. This typically cannot be done while following the prescriptive tables because the required exterior wall insulation is more than what can fit in 4 inches of space, or would require the use of more expensive closed-cell spray foam insulation.

However, this can be accomplished with a trade-off. The decrease in exterior wall insulation will cause your HERS score to increase. This can be offset by adding higher efficiency HVAC equipment, adding more insulation in other areas, or adding solar or other power generation techniques.

Rewards For Going Above and Beyond

Aside from trade-offs alone, going further than minimum expectations will decrease your HERS score as well. This means you get rewarded for being a great builder. If you have a duct leakage test performed, and the results are better than what was projected on the original HERS report, the HERS score will decrease.

This gives you extra room to make changes in the future if needed. A buffer zone in case you need to make an unforeseen trade-off. When building on the prescriptive path, you cannot capitalize on areas where you are more energy efficient than what is required.

The Trend Towards Performance

Because of the benefit of trade-offs, consumer understanding, and the demand for EnergySTAR homes, HERS ratings are becoming more and more popular and relevant in the building community.

To gain the maximum benefit from a HERS rating and the trade-off component, it is important to work with an experienced HERS rating company. A professional HERS rater will be able to identify where using trade-offs can save money and building time to ensure your project moves forward smoothly.

If you are interested in our HERS rating services, learn more here. We would be happy to talk to you about your project and answer any questions you may have.

You may have heard the term “HERS rating” used regarding home construction and energy efficiency.  You may have even seen and read through a HERS report, or you may have a HERS certificate for your own home. Or you may have read our first blog in this series, What Is A HERS Rating.  Many have heard the term, but might not fully understand how to decipher the final product: The HERS Score.

To review, HERS is an acronym that stands for Home Energy Rating System. The HERS index, also known as the HERS score, is the industry standard that is used to measure a home’s energy efficiency.

A HERS rating can be used to compare a home’s energy efficiency to another home of similar shape and size.  Because the HERS index compares efficiency on a relatively “apples to apples” basis, the HERS score can be used effectively to compare one home’s efficiency against other similar homes.

So what does the HERS Index look like?

The HERS rating process is well defined for the building community as a solution to meet specific building codes. But as a consumer, the HERS score is the official product of the rating that you can use to compare properties. So, how do you interpret the HERS Score Index?

With a HERS score, the lower the score, the more efficient the home is.  The HERS index uses a scale in which a HERS score of 100 indicates a standard new home score, and a HERS score of 0 indicates a home that uses zero energy.

The HERS Score can be useful when purchasing a home or when building a new home, as it can give you an easy-to-understand expectation of what your energy consumption, energy bills, and overall comfort will look like.

Many counties in Colorado are accepting or requiring a HERS Rating on new construction homes. Are you in need of a HERS rating? Learn more here. 

Here are a few examples of HERS scores, and what they mean:

• A home that scores a HERS  130 is 30% less efficient than a standard new home. You could expect that many existing homes older than 20 years old with minimal upgrades would score in this range.
• A home that scores a HERS 70 is 30% more efficient than a standard new home.  This is a big improvement, but is not as difficult to attain as many might think.  Many newer homes or retrofitted homes with good insulation levels, higher efficiency heating and cooling systems, and higher efficiency lighting will score in this range.
• A home that scores a HERS 50 is 50% more efficient than a standard new home.  This is where we’re really starting to see some extra effort put in toward green building.  This home will typically be designed with energy efficiency in mind, and will have above average insulation levels, high efficiency HVAC systems and water heating, and higher quality windows.
• A home that scores a HERS 0 is 100% more efficient than a standard new home, and is a net-zero energy home.  This is typically only attained when the home has an energy efficient design from top to bottom, along with renewable energy such as Photo-Voltaic solar installed on the home, to produce as much energy as the home uses.

These are rough examples, but many factors go into a HERS rating to determine the end score. An improved HERS score can be attained with numerous combinations of energy efficient measures.

RESNET has created an interactive tool to help consumers and builders understand a HERS score at every level. This breaks down the efficiency/health levels of the home, energy cost savings, and carbon emissions.

What construction changes affect a HERS Score?

A certified HERS rater models a home from top to bottom in HERS software. Each energy design change will slightly change the HERS Score as well. The following are some of the key factors that will affect the final HERS score of a home:

• The area and insulation levels of the thermal envelope, meaning all of the floors, walls, and ceilings of the conditioned space
• The windows, including window area,  orientation, shading, and the insulation quality of the windows
• The heating, cooling, and water heating equipment
• The lighting and standard appliances that will use energy in the home, such as all kitchen appliances and the clothes washer and dryer
• The overall air leakage rate of the home.  High air leakage results in more energy needed to keep the home heated or cooled.  Air leakage is measured on the finished home using a blower door test.

Changing one of the above items can have a range of effects on the outputted HERS Score. This is where an experienced HERS rater can help balance the inputs and help find ways to reach the desired HERS score on any type of property. This can also be used to a builder’s advantage as well by making trade-offs.

A trade-off is where a builder adds more of one energy efficient item to offset the lack of another. This is not used to bypass the energy codes, but it does help the builder when there are design issues that make energy compliance in certain areas more difficult to achieve. We will talk more about trade-offs in a later part of this guide.

You can see that having an efficiency score to assign to a home can be a very helpful tool.  We will explain in detail in upcoming posts how many municipalities are using the HERS index as the standard for meeting energy efficiency compliance in their building codes.  We will also show how a HERS rating on your home can be useful for resale or for determining the best ways to improve efficiency.

The HERS Rating Index, developed by RESNET:

More new homes are being built with a HERS Rating, particularly in Colorado.  The Home Energy Rating System (HERS) is a method used by architects, builders, and energy raters, to determine the overall energy use of a home.

RESNET, the Residential Energy Services Network, developed the HERS Index standard, which is a nationally recognized standard for measuring the energy efficiency of a home.  Many Colorado home builders use the HERS score to rate their homes, and several area municipalities use the HERS score to validate whether a home meets their energy codes, including the City and County of Boulder.

What does a HERS Rating say about a home?

The HERS rating measures a home’s energy efficiency and can tell you how efficiently it is operating and where you can make modifications for greater energy savings.  When you are selling a home, a low HERS Index Score can command a higher resale price.  And when buying a home you can anticipate the costs of energy bills and efficiency upgrades.

The video included in this post was published by RESNET to give an overview of the HERS Rating process. In the video, they mention a very important point about the HERS score. If a home has a lower HERS score, meaning it is more energy efficient, the price of the home should increase in value.

People want to buy more energy efficient homes. It reduces their monthly expenses, reduces their carbon footprint, and helps when they need to sell later. This shift has been reflected in many facets of the home buying industry. Just recently, the HERS score was added to many of the MLS providers so buyers can see a home’s efficiency when looking at the listing.

So what does a HERS Rating say about a home? A lot really. And because of that, it is becoming more and more popular among builders, building departments, and the general public.

Are you a Colorado Builder in need of a HERS Rating for your next building project? Learn more about our certified HERS Rating Services here. 

How does the HERS Index work?

To calculate the HERS Score, the rater performs a full energy rating on the home by analyzing information on the home’s energy aspects using a sophisticated software modeling tool. The results of the data analysis are compared against a “reference home” which is the same size and shape as the actual home, and from which a resulting HERS score is created.  The lower the score, the better. A lower score means the home is more comfortable and energy-efficient.

For example, a home with a HERS Index score of 70 is 30% more efficient than a standard new home, while a home with a score of 130 is 30% less efficient than a standard new home.  A HERS Index score of Zero would mean the home consumes net-zero energy and likely has renewable energy installed on the home, such as Photovoltaic (PV) Solar panels.

Field testing and verification is performed on all HERS ratings, including verification of insulation levels, window specifications, heating, cooling, water heating specifications, appliance and lighting specifications, in addition to performing blower door air leakage testing.

We will go into even deeper detail of the HERS score index in part 2.

What does it take to complete a HERS rating?

Obtaining a HERS rating is a multi-step process. There are steps to take before, during and after the construction process, but the 3 main stages are as follows.

Projected HERS Rating: Typically, before ground is broken on a new construction project, a projected HERS must be completed. This is where a certified HERS rater takes the plans for the project and uses them to project what the HERS rating will be if the plans are followed exactly.

Mid-Construction Verifications: During construction, the HERS rater will need to verify that the builder is following the plans and that the rating is on track to meet the projected rating. Some of these items cannot be seen or altered when construction is complete. Because of this the rater will go to the site and check these items. This includes insulation levels and duct leakage ratings.

Final HERS: The final HERS inspection occurs just as construction is coming to an end. At this point, the rater will go out to the site, verify that everything that was projected was installed, complete the final tests like blower door testing, and collect the final data for the rating. This completes the HERS Rating process.

Certified HERS Raters on staff:

If your new construction or remodel/addition project in Colorado requires a HERS Rating, or you simply want to understand the energy performance of your home, contact Scott Home Inspection.

We have Certified HERS Raters on-staff who can help with your project.  We have completed hundreds of HERS Ratings on homes throughout Colorado, and have extensive experience in the City and County of Boulder, meeting the city of Boulder’s Energy Conservation Code and Boulder County’s BuildSmart program requirements.

For more information visit the Energy-Service page of our website.

Also for more information about RESNET and the HERS Rating Index, visit the RESNET website.

Also, keep an eye out for our follow up blogs, that will dive even further into the HERS process.