The Tar Heel State faces a wide range of temperature variations throughout the year with the change of seasons, often ranging from below zero to above 90℉. Depending on which part of the state you’re in, the climate can be dramatically different from the coast to the Western inland.
To keep buildings safe and running efficiently with its highly variable climate, representatives of the North Carolina Building Code Council (BCC) adopt and amend construction guidelines to oversee progress. In turn, this supports the construction of structures that are compatible with the climate and landscape.
If you’re building or remodeling in NC, it’s important to become familiar with these codes. While there are codes for everything from accessibility to plumbing and electrical—in this article, we’ll be focusing on the North Carolina building code insulation requirements.
Current NC State Building Code
Building codes are changing all the time. That’s why there is a council to review the codes and implement changes when necessary for the sake of safety or systems improvement. Find the current list of adopted codes on the NC Office of State Fire Marshal website.
A significant portion of the current version of NC building codes is based on the ICC 2015 International Codes and went into effect in 2019. This version is referred to as the 2018 NC Codes and it includes ten books.
Of those ten sets of guidelines, the two that we will focus on for NC building code insulation requirements are the following:
2018 North Carolina State Building Code: Energy Conservation Code
2018 North Carolina State Building Code: Residential Code
What Are the North Carolina Building Code Insulation Requirements?
Taking a look at the two code books listed above, we can decipher what the requirements are for NC building code insulation. Let’s take a look at both residential and commercial construction insulation code requirements.
First, we’ll break down the state by climate zone. North Carolina consists of three distinctive climate zones, including:
Climate Zone 3A: South and East NC (Warm Humid)
Climate Zone 4A: North and West NC (Mixed Humid)
Climate Zone 5A: Northwest corner of NC (Cool Humid)
Residential NC Building Code Insulation Requirements
North Carolina’s 2018 residential code for single and multi-family residential structures under three stories is based on the International Residential Code (IRC). The required values are shown in the table below for various wall types and other components of the building envelope.
Residential R-Value Code Requirements in NC:
*R-value requirements may be less for air-permeable/impermeable attics.
When evaluating North Carolina building code wall insulation requirements for homes, you’ll notice that in climate zones 4 and 5, you have the option to combine cavity wall insulation with continuous insulation. For example, if you’re constructing a building with wood studs, you can use R13 cavity insulation between the studs, plus R5 continuous insulation. The additional insulation, if polyiso is used, requires less than an inch of continuous insulation installed on the exterior side of the studs. ½” thick Rmax Durasheath® carries a thermal insulating resistance value of R3, which exceeds the code requirement for this construction application.
Commercial NC Building Code Insulation Requirements
The North Carolina Energy Conservation Code applies to non-residential, commercial structures including businesses, hospitals, and government buildings for both new construction and remodeling projects. This code follows the requirements of the ANSI/ASHRAE/IESNA 90.1 standard. You’ll find the R-value requirements for North Carolina commercial construction projects in the table below.
Commercial R-Value Code Requirements in NC*:
*These values may differ from the requirements of commercial buildings that contain residential dwellings, or from metal buildings.
As you can see in the chart above, the North Carolina building code wall insulation requirements show increased R-values for several applications in commercial buildings when compared to residential construction projects. One notable difference is the increased requirement of continuous insulation throughout the envelope, from the floor, up the walls to the rooftop.
Polyiso board insulation is one of the best products on the market to achieve continuous insulation assemblies and meet code requirements. For example, Rmax Thermasheath® carries an R-value of R6 per inch, so you can achieve R7.5 with a single layer of 1-¼” boards.
Meet North Carolina Building Code Insulation Requirements with Rmax
As a trusted manufacturer in the insulation industry for over 45 years, Rmax has been here throughout the years of evolving building codes and increased energy efficiency requirements. We have developed insulation solutions to meet and often exceed code standards and our North Carolina representatives can help make sure your next project is insulated with the right materials.
Reach out to your local Rmax representative today!