Skip to main content

2021 IECC Climate Zone 4C: Vented Attic, 2x4 wall with Exterior Insulation, Basement with Interior and Exterior Insulation

Image
2021 IECC Climate Zone 4C: Vented Attic, 2x4 wall with Exterior Insulation, Basement with Interior and Exterior Insulation
Courtesy Of
BSC

Notes

IECC Climate Zone 4C: Vented Attic, 2x4 Wall with Exterior Insulation, Basement with Interior and Exterior Insulation

  • Full depth of R-49 insulation to be maintained over top plate of exterior wall in order to allow for the reduction from the R-60 requirement.
  • Blocking and baffles to be installed to prevent wind-washing and disturbance of attic insulation at eaves.
  • Ceiling materials at the attic floor should be air sealed at joints and penetrations to form a robust air barrier.
  • The water-resistive barrier (WRB) is shown installed between the continuous insulation and the wall sheathing. Alternatively, the WRB can be on the exterior of the continuous insulation. In either case, all flashing details must ensure water is directed to the outside of the WRB.
  • The R-10 rigid insulation on the exterior of the wall framing allows the wall to be constructed without an interior vapor barrier according to the provisions in Section R702.7 of the 2021 International Residential Code. To maximize drying potential in the wall assembly, the interior side of this wall assembly should not have a Class I vapor retarder.
  • Rim joist insulation should align with R-value requirements for above-grade exterior walls.
  • Exterior cladding fastening requirements should follow guidelines from cladding manufacturer or Section R703.15 of the 2021 IRC.
  • A capillary break should be installed on top of footing prior to setting of wall forms and should consist of a liquid or membrane to prevent wicking of soil moisture into the foundation wall.
  • Do not install a vapor retarder on the interior or exterior side of the framed wall in the basement. This is to allow for drying in the insulated wall assembly.
  • Backfill placement should prevent damage to exterior continuous insulation.
  • The air gap between the interior framed wall and the foundation wall ensures a capillary break between the foundation wall and the interior wall assembly.
  • Exterior insulation should be protected above grade.

Disclaimer

This content is a work created with funding provided by the United States Department of Energy under Contract no DE-AC05-076RL01830 for the operation of Pacific Northwest National Laboratory. The information and guidance provided by Pacific Northwest National Laboratory (PNNL) in the content are intended solely for educational purposes only and do not constitute formal training or certification. It is provided with the explicit understanding that neither the United States Government nor the United States Department of Energy, nor the Contractor, nor any or their employees, nor any jurisdiction or organization that has cooperated in the development of these materials, makes any warranty, express or implied, or assumes any legal liability or responsibility for the accuracy, completeness, or usefulness or any information, apparatus, product, software, or process disclosed, or represents that its use would not infringe privately owned rights. Reference herein to any specific commercial product, process, or service by trade name, trademark, manufacturer, or otherwise does not constitute or imply its endorsement, recommendation, or favoring by the United States Government or any agency thereof, or Battelle Memorial Institute. The views and opinions of authors expressed herein do not necessarily state or reflect those of the United States Government or any agency thereof. Viewers assumes full responsibility for all actions that they may take from information provided in this content including ensuring the safety, code compliance, and proper functionality of any products they choose to install. Installation and use of such products should be performed in accordance with local regulations and manufacturer instructions.