On January 1, 2019, the 2018 North Carolina Building Code (based on the 2015 IECC with amendments) went into effect. This new code should stay for at least 3 years, since NC typically runs a 3-year code cycle, and the 2012 NC building code was in effect for 6 years.
The building code requires certain R-values* for the state based on different locations and climates. Wake County is 4A zone, so walls, floors, ceilings, and slab insulation values are unchanged from the 2012 code. The prescriptive R-values for a new house in the new 2018 NC Building code are as follows:
- R-19 on floor system/garage ceiling
- R-15 on exterior walls
- R-38 for the ceiling/attic
So what does this mean for MPI Foam?
Please keep in mind that we are running a performance calculation of the insulation envelope for our inspectors during insulation inspection, since the spray foam that is installed typically doesn’t meet the prescriptive R-values in the walls and roof decks.
However, spray foam performs so much better than its prescriptive R-value because of the air sealing properties as well as the ability to create a complete fill on the walls and roof cavities. Thus, a performance or energy calculation is done by a third party energy rater, to prove that what we are installing with spray foam insulation in the walls, floor, and roofs meets and often times succeeds the current 2018 NC Building Code insulation R-Values.
*R-Value: The capacity of an insulating material to resist heat flow. The higher the R-value, the greater the insulating power.