Insulating Crawlspace 2 Layers - Bottom of Floor Joist

Crawlspace Insulation - 2 Layers In/Bottom of Floor Joist

Installation Instructions

This application meets the thermal performance requirements for new construction in the 2009, 2012 International Energy Conservation Codes for Climate Zones 1, 2, 3 and 4.

Note: This product is reflective on both sides and the direction of product installation is not pertinent to thermal performance.

  • Inspect the crawl space and make any needed repairs before installing InfraStop® double bubble insulation.

  • For floor joists that are 16” on-center, the installation is easiest with the InfraStop® Staple Tab (ST) product.

  • Determine if there are water pipes and heating ducts which hang below the floor joists. They will need to be insulated. InfraStop® Pipe Wrap and Duct Insulations are designed specifically for this use. There is no need to wrap water pipes or duct work that fall between floor joists. InfraStop® will provide adequate insulating without extra wrapping.

  • Begin at one end of the house and staple the first course of product to the top of the band board or the subfloor (also terminating this course in this fashion). Insert the InfraStop® half way up into the joist cavity and staple (at approximately 3” to 4” intervals) the edge of the product to the side of the joist. The resulting product installation will split the cavity into two approximately equal air spaces. It is easiest to utilize the InfraStop® double bubble insulation Staple Tab product for this step.

  • For cross bracing, refer to the type of bracing directly below for installation techniques: Solid Wood: Terminate the product at the brace. End staple to the middle of the brace. Continue with the installation on the opposite side, stapling the product to the brace at the approximate mid-point in the cavity. Metal or Wooden Slats - Cross Braced: Extend the product 5 inches beyond the brace. Cut the product perpendicular to the joist direction at this point. Cut a slit down the middle of the product 3 inches beyond the middle of the cross. Run each flap of product through the cross (one flap on each side), stapling the product to the side of the joist. Continue the product run on the opposite side of the cross brace as before. Tape all seams (horizontal and parallel) with InfraStop® Foil Tape.

  • Continue with the second course of product at one end of a joist cavity (after the first course has been installed) and secure the product “end” with staples to the band board. Proceed down the joists by stapling each edge (or middle of the double bubble insulation 48” wide product) to the face (bottom surface) of each joist. Staple the product at intervals of approximately 3” to 4”. At the end of the product run, staple the InfraStop® to the band board.

  • Seal the seams with InfraStop® Foil Tape. This product is a vapor barrier with the seams sealed, no additional vapor barrier products are necessary.

  • Any penetrations, openings, rips or tears shall be sealed with InfraStop® Foil Tape or an equivalent.

Crawlspace Insulation - Staple Tab Roll Sizes

Crawlspace Insulation - Square Edge Roll Sizes

Thermal Insulation

R-21 Crawlspace Insulation - Bottom and In Between Floor Joist

Product Information

InfraStop® Insulation products are a group of technologically advanced materials. They are ideal for new construction or retrofit applications in commercial, industrial, metal and post/frame buildings, along with many other DIY applications. When you think of insulation, you should think of InfraStop®. Our products are recognized for their thermal performance, easy installation, versatility, price and environmental friendliness.


  • Easy to handle and install
  • Convenient roll sizes
  • Class A / Class 1 Fire Rating
  • Inhibits dew point condensation
  • Vapor retarder (0.02 perms)
  • Does not compress, collapse or disintegrate
  • Non-toxic / non-carcinogenic

Testing and Certification

InfraStop® products are thoroughly tested at either nationally approved independent laboratories or leading universities. Tests are performed to current American Society of Testing and Materials (ASTM) standards when a standard exists. For a copy of an actual test report, please e-mail us at

  • Other Wall, Ceiling, or Crawlspace Projects

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