Continuous Insulation (CI) was introduced in 2012 as the preferred choice of the National Energy Code to raise the effective insulation of exterior walls. Adding an R5 CI to a 2×6 framed and insulated wall and an R10 CI to a 2×4 framed and insulated wall raised the effective insulation (not stated) by about 45%. This was a considerable gain in the exterior wall’s insulation value over 2×6 framed walls with R20 insulation in the chamber.

While the CI walls achieved higher insulation standards, they also brought significant financial implications. The primary challenge was the substantial cost and complexity added to the build process, a phenomenon we refer to as the ‘Extra Step Conundrum.’ Each additional ‘detail’ or ‘step’ introduced in the construction of CI exterior walls translates to increased labor and material costs. The installation of 1″ to 4″ of rigid insulation panels on the exterior wall assembly can be particularly costly. Since the publication of the 2012 National Energy Code, the states affected by the CI exterior wall change are still in the process of adopting the CI wall systems into their residential energy code requirements.

The point of CI walls is to address the lower R-value of the wood framing, which can be up to 30% of the exterior wall; by adding the R5 insulation panels to the 2×6 R6.6 framing, the total R-value of the framing and insulation panel is now R11.6. This increase in insulation value lowers thermal bridging energy loss through the framing. The chamber insulation is increased to R-25 for the overall effective insulation of about R19.40. A 45% increase in effective insulation value by adding one R5 thermal break to the outside of the exterior wall. Look at the values of the different CI walls highlighted in orange in this table vs. the R20 stated (R13.27 effective) reference exterior wall.

You see that we have chamber and framing insulation values. Framing is broken up into studs and plates, a single bottom and a double top plate. Look at the Wall Effective R-value rating for the CI walls; it varies from R19.40 to R20.91. That is about a 45-57% improvement in effective exterior wall insulation vs. the R13.27 from the reference stated R20 exterior wall with 2×6 framing. Notice that just adding insulation to the chamber, the 2×6 all 2 lb closed cell spray foam (SPF 5.5″)  R40.7 wall has a lower effective insulation value than the CI walls. Using 2 lb closed cell spray foam to fill the wall chamber full has been a popular insulation upgrade choice, simple but expensive, and not really that good of choice.

Next, take a look at the 2×6 and 2×8 EcoSmart™ Stud wall systems highlighted in green in the next table. These systems have different flash and fill insulation mixes.

Observe the varying Wall Effective R-value rating of the EcoSmart™ Stud wall systems, ranging from R17.60 to R37.59, depending on the insulation mix and the use of a 2×6 or 2×8 EcoSmart™ Stud. That is a 32.60-183% improvement in effective insulation over the reference 2×6 wall!

For climate zones 4-8, a U-0.045 (R22.2) effective wall insulation rating is required to meet the new 2021/2024 National Energy Code, Energy Star, and Energy Star ZERH requirements. The EcoSmart™ Stud wall systems, with their high-performance design, are capable of meeting these stringent requirements.

Upon closer inspection, you’ll notice that all of the National Energy Code CI walls fail to meet the code’s U-0.045 (R22.2) requirement, while some of the EcoSmart™ Stud wall systems successfully meet the requirement. This is because the CI walls and the new R30 stated exterior wall (2024 Energy Code) fall within the stated R-value section of the National Energy Code.  In contrast, the EcoSmart™ Stud wall systems, along with other high-performance exterior wall designs, are subject to the U-factor section of the Energy Code, which mandates a total wall calculation to meet the higher U-0.045 (R22.2) requirement.

The simple explanation is that with all insulating elements of the exterior wall added, such as siding, sheathing, drywall, etc., another R2 to R3 is added to the total R-value of the exterior wall assembly. This extra R-value is taken for granted in the stated R-value section of the Energy Code. In the U-factor section, we need each item’s U-factor (R-value) unless the insulation and studs exceed the requirement. Using the 2×8 EcoSmart™ Stud, this is the case; no extra calculations are needed. For the 2×6 EcoSmart™ Stud, once 2+” of SPF is used or the 2×6 EcoSmart™ Studs are framed 24″ on center, no additional calculations are required. These EcoSmart™ Stud wall systems far exceed the U-0.045 (R22.2) requirement with all insulation elements added in.

Add in the extra R2 to R3 just discussed and now all the National Energy Code CI exterior walls and all but 1 of the 2×6 EcoSmart™ Stud wall systems meet the U-factor requirements for climate zones 4-8. The one 2×6 EcoSmart™ Stud wall system that is just under the requirement for climate zones 4-8 is designed for climate zones 0-3, which has a lower effective R-value exterior wall requirement.

With the addition of the R30 stated insulation value in the 2024 National Energy Code, the EcoSmart™ Stud wall systems with an R30 in the chamber will be able to use the stated R-value section of the Energy code, no extra U-factor calculations needed.

While the EcoSmart™ Stud wall system does not use a continuous insulation layer, with 2 insulated thermal breaks in the 2×6 EcoSmart™ Stud and 3 insulated thermal breaks in the 2×8 EcoSmart™ Stud, it accomplishes and exceeds effective wall insulation values required in the 2021/2024 National Energy Code, Energy Star, and Energy Star ZERH programs. The EcoSmart™ Stud just solves the thermal bridging issue within the stud, rather than adding an extra layer.

Less cost and complexity, better insulation, but that is not all the EcoSmart™ Stud accomplishes, up next part 3, Resilience.