A project designed today could face new IECC enforcements by 2026 or 2027

Builders that have begun new structural designs without considering the updated requirements of the International Energy Conservation Code may be unpleasantly surprised as they encounter compliance issues. Here’s a look at some new energy efficiency requirements for industrial construction.

First, some answers to frequently asked questions:

What is the IECC?

The International Energy Conservation Code (IECC) is issued by the International Code Council, which provides standards for builders worldwide. The IECC, which is updated every three years, addresses issues of energy usage in new and existing homes and commercial buildings.

Are IECC standards mandatory for U.S. builders?

Nearly all states require adherence to the IECC for new construction. (California, the outlier, has its own energy efficiency standards under Title 24, which are generally even more rigorous.)

When do the IECC 2024 standards take effect?

The 2024 IECC updates were issued in July of that year. States have 24 months to determine how to apply them to their own codes, which creates a deadline of July 2026. Many states have already incorporated the IECC 2024 standards. Beginning dates for enforcement vary by state. For example, Rhode Island, the first state to adopt the new updates completely, began requiring compliance in February 2025.

IECC 2024 Changes on the Way

A New Priority: Continuous Insulation

Effective insulation is an important component of energy efficient design. Thermal bridging—the unwanted transfer of heat through heat-conducting elements of a structure—is a persistent challenge for building designers. Cavity insulation, commonly used in both commercial and residential construction, can expose structures to significant levels of thermal bridging, reducing their efficiency. In this approach, insulation is applied in the spaces between structural elements such as wood or steel studs. But heat can still be transferred through the studs.

Studies have shown that even well-insulated walls can lose 28 to 34 percent of heating efficiency through thermal bridging.

Thermal bridging can be reduced dramatically with continuous insulation. This is an uninterrupted layer of foam board, spray foam, or mineral wool applied to the entire envelope of a structure—roof, walls and floor. It is the most effective way to insulate a building.

While the IECC has long mandated continuous insulation for certain structures, the 2024 standards are more stringent than before. Specific requirements depend on a number of variables, including the type and age of the building and the region.

Continuous insulation is widely mandatory for buildings in Climate Zones 4-8, which includes all of the continental United States except the southernmost areas and parts of both coasts.

Other Requirements in IECC 2024

R-Value

R-value measures the ability of a particular insulation to resist heat flow. A higher R-value indicates better resistance. The 2024 updates to IECCH require R-values of 25-30 for above deck applications.

U-Factor

U-factor is a measurement of the rate of heat transfer through specific building components such as windows and doors. Lower U-factors, indicating less heat transfer, are preferable. IECC 2024 mandates U-factor levels as low as 0.35 for windows in commercial structures.

To meet these enhanced requirements, many builders now prefer insulated metal panels (IMP) over traditional fiberglass insulation. These units consist of a foam core sandwiched between two metal skins, typically made of steel.

Doors and Windows

Door and window frames can also be a source of thermal bridging. To counter this vulnerability, builders use thermal breaks, also known as thermal barriers, consisting of low-conductivity materials placed between the high-conductive layers.

Air barrier tightness refers to a building’s ability to resist uncontrolled air leakage. IECC 204 requires many structures to be subjected to commercial blower door testing to determine their performance in this area. In this process, openings are sealed and powerful fans are set up in doorways to measure a building’s airtightness. To meet IECC 2024 standards, leakage must not exceed specific thresholds.

The enhanced requirements of IECC 2024 can mean somewhat higher upfront costs, but these can be offset through lower HVAC bills and higher market value for the structure.

Fleming Construction – Proactive Pre-Construction

These changing standards don’t need to catch you by surprise. At Fleming Construction Group, we make it our priority to stay up-to-date with the changing requirements of building codes—both those that apply now and the ones that are coming. We can help in the pre-construction phase to make sure your design doesn’t get rejected in the permitting process. Being proactive enables us to future-proof your project, whatever stage it’s in.