Massachusetts energy code updates: A preview of the future?

Massachusetts is leading the way when it comes to building energy code, but it’s not alone. California, Connecticut, and a number of other states have or will be enacting increasingly progressive codes. This means that even if you don’t live in one of these places, you might be interested in knowing where energy code is going next. Here’s a crash course on the ins and outs of Massachusetts energy code.  

To evaluate the efficiency of an entire house, you need a standardized grading method. In Massachusetts, compliance with stretch code is evaluated based on a HERS/ERI score. HERS stands for home energy rating system, and it was developed for this purpose by Resnet, a nonprofit organization. It provides a score on a linear scale drawn between zero and 100. A score of zero is a net-zero house — or a house that generates, through a renewable energy source, as much energy as it uses — and a score of 100 represents efficiency compliant to the 2006 IECC, the newest model code at the time of the HERS creation.

The HERS system is continually reviewed and updated, but the scoring system remains on a scale based on the 2006 IECC. For many years, this energy rating method was useful for tax credits and consumer confidence but was not a method of government energy code compliance. That changed in the 2015 edition of the IECC when the Energy Rating Index (ERI) was added as a method of compliance.

A HERS score and an ERI score are nearly the same, but much like “model code” and “government code,” A HERS scoring protocol is regularly updated and immediately applicable to the federal programs targeting consumers, such as ENERGY STAR, whereas an ERI score is specific to the government adoption of a particular code edition and edition of the rating standard it references. 

Because HERS is a trademarked term belonging to Resnet, the IECC instead references an ERI grade and an American National Standards Institute (ANSI) standard (301-19) detailing the process to determine the rating. 

The 2015 IECC designated a new minimum required score for code compliance, lower than the score of 100 in the 2006 IECC. A single design and verification method that can now meet both the code and provide federal consumer incentives was a win-win for builders.

The most recent edition of the IECC, 2024 not only mandates a maximum score of 51 to 54 as code compliant, depending on climate zone and not taking into account on-site power production, but also requires an additional reduction of this score. To simplify this in Massachusetts code adoption, which is all under one climate zone (5A), the code was amended to reflect a maximum score of 42 with fossil fuels and 45 when electric or solar energy is used. This reveals the almost 50 percent increase in minimum required efficiency since the 2006 edition’s passing score of 100.

The encouragement of increased efficiency, through codes and consumer programs, can be taken down to the level of individual components, such as windows. All methods of code compliance, including those in stretch codes, are heavily based on the efficiency of the thermal envelope. The better the envelope, the easier compliance will be with any method. 

To understand the performance of the envelope, a measure called U-Factor x Area (UA) is used to measure a building’s total heat loss. However, in the 2024 IECC, a new similar measure was introduced called Component Performance Alternative where the thermal conductance (TC) of the proposed building is measured slightly differently.  

Let’s start with UA. The total UA of the building is calculated by summing the individual U-Factors (thermal performance) of each component of a building assembly weighed by the area of that assembly compared to the area of the entire thermal envelope. 

TC is calculated by the same U-Factor x Area (UA) calculation for the building assembly, but it adds in the slab F-Factor x slab perimeter (ft). 

These bold efforts to enhance the energy efficiency of new housing are not unique to Massachusetts. In Colorado, there is no state-wide mandated building code, but there is a new legislative action that puts parameters around what local jurisdictions can adopt when they update their local energy code requirements. Any local CO government that adopts or updates their building code, must adopt the 2021 IECC, the Colorado Model Electric Ready Code, and the Solar Ready Code. In 2026, compliance with an enhanced version of the 2024 IECC will be required. 

Some states, like New York and Connecticut, are also preparing for adoption of the 2024 IECC. Other states and local governments may take longer to adopt the newest energy code. Regardless, if you aren’t building to the modern energy codes yet, you will likely be strongly compelled by the government to do so in the coming future. 

No matter where you live, choosing high-performing windows makes it easier to meet code compliance while also increasing occupant comfort. It’s also a choice that will keep your new home and new windows from quickly becoming “outdated” from future increases in performance requirements in both codes and consumer programs that are to be expected.