What R-Value Is Needed for a Commercial Roof?

What R Value Is Needed for a Commercial Roof 1

Efficient and long-lasting insulation is a vital component of a building’s envelope, including the roof, especially when it comes to keeping a commercial structure energy efficient. And an important factor in determining the right insulation for any project is the R-value.

R-value is a rating system used to grade insulation products and materials. It is a measurement of thermal resistance and how well the insulation prevents the flow of heat. The higher the R-value, the higher the resistance.

But choosing the appropriate insulation with the correct R-value varies between projects, largely due to location and climate. Some buildings are in severe climate areas while others are in milder climate areas. Not every building needs excessive insulation, but underestimating R-value requirements could be a costly mistake.

So, it is important to know local and international codes to determine what type of insulation is best.

Step 1: Know Your International Codes

What R Value Is Needed for a Commercial Roof 2

The International Energy Conservation Code (IECC) is the model energy code that lays out minimum efficiency requirements for new construction. It includes standards for the structure’s walls, ceilings, floors, windows, doors, lighting, and duct and air leakage.

The IECC sets standards every year for insulation efficiency and R-Value, and it is important to know the codes for your project’s climate zone in order to choose the proper insulation products for your building.

Step 2: Know Your Climate Zone

The IECC sets efficiency standards for new structures based on nationwide climate zones, shown in the map below. The requirements differ the further north or south a project is in relation to a region’s seasonal temperatures and climates.

What R Value Is Needed for a Commercial Roof 3

The insulation R-value standards for each region are then dictated by their specific climate zone. The current requirements are:

  • Zone 1: R20

  • Zone 2-3: R25

  • Zone 4-6: R30

  • Zone 7-8: R35

The IECC publishes the climate zone map every year, and every three years officials meet to vote on proposed changes that incorporate new practices and building technologies. It is important to stay updated on any changes and new advancements to guarantee you are using the correct and most efficient materials.

What R Value Is Needed for a Commercial Roof 4

Step 3: Know Your Local Codes

What R Value Is Needed for a Commercial Roof 5

Not only do different regions have specific codes, but different cities may have their own set of special requirements as well. Here are just three examples.


While most states have their own uniform statewide building energy code, Arizona does not. In the state well-known for its deserts, building and energy codes are determined and enforced at the local levels.

And due to the wide range of daily temperatures, many local areas enforce a higher R-value rating than what is specified by the IECC, especially when modifying older homes.


Colorado also does not have a statewide building energy code. Instead, recent legislation required all local jurisdictions to adopt and enforce one of the three most recent versions of the IECC and update any other preexisting building codes. With the recent publication of the 2021 IECC, local areas are allowed to also use the 2018 and 2015 versions instead.

So, it is important to be aware of which version of the IECC your local jurisdiction enforces.


Wyoming is subdivided into 123 local jurisdictions that all determine and enforce their own advanced building and energy codes. As of 2018, many of the local jurisdictions adopted more stringent codes than those recommended by the IECC, and regular meetings are held to reevaluate their local requirements.

It is more common to see major cities adopt higher efficiency codes compared to smaller cities and towns in the country. But it is important to do the research and be aware of any special requirements that may affect your project.

Step 4: Pick the Right Insulation

What R Value Is Needed for a Commercial Roof 6

To get the right R-value and make sure your commercial building is energy efficient, you need the right insulation. And ThermalStar® Roof Insulation offers a list of benefits that make the insulation boards stand out against competitors.

ThermalStar® Roof Insulation offers high-performance rigid insulation for all your new and re-roofing needs. It comes in multiple thicknesses and strengths with custom design options available, and it has minimal long-term moisture retention with the ability to dry quickly should it get wet.

What R Value Is Needed for a Commercial Roof 7

Installing ThermalStar® Laminated Roof Insulation could not be easier, quicker or cleaner, which saves time, labor and your budget.

It is also an environmentally friendly option that does not include HCFCs, HFCs or formaldehyde, with a low global warming potential and zero ozone depletion potential. So not only will it help make the building perform more efficiently, it is environmentally healthier and safer than other insulation options on the market.

And ThermalStar® Roof Insulation has a stable, long-term R-value that does not depreciate over time and will consistently protect your structure for years to come. It also comes with a limited lifetime warranty for physical and thermal performance

Do Your Code Research & Choose the Right Insulation

Knowing the appropriate R-value needed for a roofing project is important to ensure the structure is up to code and operating as efficiently as possible. It is necessary to research not just the international building codes (IBC), but local codes as well, to make sure you pick the right insulation to protect the roof from its specific climate zone.

Contact an Atlas Molded Products expert to talk about your specific climate zone requirements and to learn more about ThermalStar® Roof Insulation and how it can help you get the right R-value for your project.