This training video from TEACH Construction Community Education focuses on complying with the 2021 International Energy Conservation Code's insulation and air sealing requirements.
Transcript:
This house has just been insulated, and it's been insulated with a blown fiberglass product. The blown fiberglass product in a 2x6 wall provides about an R23, depending on the density.
There's a new section in the 2021 International Energy Conservation Code (IECC), specifically in Chapter 3, that requires the insulator to certify their installation. Because there is no R-value mark on this material, the insulator has to leave a certificate immediately after the installation that certifies the R-value of the material. I can’t look at it and tell you it’s an R23; I can make that assumption, but again, it is very dependent on the density of the insulation.
Advantages of Blown Fiberglass
Blown fiberglass is a great material to insulate with because it completely encloses any obstructions in the building cavity, such as wiring, electrical boxes, plumbing, or gas pipes. You can install the insulation, and it will fully surround these obstructions, resulting in a better-insulated cavity, a truer R-value, and strong performance overall.
We'll show you a picture of some other insulation—a bat insulation—that has been installed but hasn't been split around the wiring and other obstructions. You'll see the difference between the two methods in just a second.
Issues with Bat Insulation Installation
Previously, we saw how insulation can fully fill a cavity and completely enclose any obstructions. In this wall, however, we have a different type of insulation. This insulation needs to be manually split by hand around obstructions in the cavity. Here, the wiring in the cavity is compressing the bat insulation, which prevents it from reaching its rated R-value and from meeting the intent of the code.
To address this, the bat needs to be evenly split around the obstructions in the cavity, such as electrical boxes. This box should also be air-sealed in the back, where the wires enter the box, and after drywalling, the box should be sealed to the drywall it penetrates to meet code requirements.
Proper Insulation Installation Practices
When we look at insulation installation, we want it installed properly to fill the cavity from front to back, side to side, and top to bottom, with minimal gaps, voids, or compression. The box needs to be hand-sealed, or alternatively, a manufactured airtight box can be used.
Manufactured airtight boxes have a flange around the edge that seals the drywall to the box with a gasket. You might also be able to seal your vapor retarder to it as well. This type of box ensures that the wire penetration into the box is a sealed opening, which is manufactured directly into the box.
In some cases, installers will need to air-seal manually. Here, I'm going to show you an example on a wall that hasn't been insulated because it’s not a true exterior wall, but this illustrates the concept.
Air-Sealing Around Electrical Boxes and Wires
Here we see that the box itself has been air-sealed with foam where the wire passes through. Additionally, where the wire enters the building envelope component of the wall, it’s also been air-sealed. All of these air-sealing steps are essential.
Best practices would suggest using one wire per hole because, as you can see, there’s a small gap here that hasn’t been fully air-sealed. As we start building our homes to be tighter and tighter for more control and predictability over airflow, moisture flow, and thermal flow, these small gaps can make a difference.
Final Steps for Code Compliance
Lastly, remember that this box needs to be sealed to the drywall it penetrates. This task should fall within the builder's scope of work, likely for the painter, who can apply caulking at the drywall level before painting to ensure a full seal.
This group of mini-lessons was created to provide information about how the 2021 IECC is being put into practice. This video covers some common insulation topics covered in the 2021 Energy Code. This series was created through a collaboration between Shaunna Mozingo from Mozingo Code Group, and Robby Schwarz from BUILDTank Inc., and produced by TEACHconstruction.org