Replies

1. 
   krackadile | Oct 24, 2024 11:48am | #1

   What R-value is required by the AHJ (authority having jurisdiction)? According to chapter 3 of the 2021 IECC (International Energy Conservation Code), which is available for free online, most of New York state falls into either a zone 5A or 6A climate. According to chapter 4 of the IECC it looks like you are required to have R-15ci or 19 or 13& 5ci. It looks like a minimum of 3" of XPS would provide R-15ci or you could go with 4" and get R-20. As far as drainage goes, I'd personally just use washed gravel on the exterior of the insulation but there is drainage board available from several different manufacturers. I think with the drainage board you'd still need the washed gravel on the exterior. You'd of course also need a foundation drain regardless. Good luck.

1. 
   sghar | Oct 24, 2024 11:29pm | #2

   Thanks for the response. Just to clarify. If I do not use a drainage board( I cannot seem to find one - located in Long Island- Nassau county) I can use bituthene then rigid insulation board and then use gravel from foundation to the top?
   Or the other option can I use bituthene- dimple mat-rigid board and backfill with a gavel and soil using a filter fabric in between.

   Thank you!

1. Expert Member
   MALCOLM TAYLOR | Oct 24, 2024 11:35pm | #3

   sghar,

   You may find this useful: https://www.greenbuildingadvisor.com/article/how-to-insulate-a-basement-wall

2. 
   FrankD | Oct 25, 2024 12:53am | #4

   Mineral wool board drains well without the need for a separate drainage mat.

1. 
   sghar | Oct 25, 2024 09:15am | #5

   Thank you. I’ll look into those.