Crawl Space R-21


Note: Installation instructions and illustrated drawings are recommendations only, while proper local construction methods are the responsibility of the installer.

When considering options for a crawl space, Reflectix® Double Reflective Insulation is the easiest (to handle) choice available. It comes in convenient roll sizes that install clean and quickly. The product is dust and fiber-free, and does not require any protective garments or respirators to work with.

Product Description

The Reflectix® Double Reflective Insulation consists of two layers of highly reflective film (96% reflectivity) that are bonded to two tough layers of polyethylene. Two inner layers of insulating bubbles and a center layer of polyethylene provide this easy to handle product with high strength and reliability.


  • A labor reducer because of its easy to handle and install characteristics
  • No need to insulate ducts or pipes between the product and the sub-floor
  • Works great for retrofit installations
  • R-21 and fiber-free
  • Costs less to install than alternative insulations
  • Does not require protective clothing or respirators to install
  • Resists growth of fungi, mold & mildew
  • Does not promote nesting of insects or rodents
  • Vapor / Radon retarder
  • When properly installed, prevents ground moisture from causing dry rot
  • ISO 9001:2015 certified manufacturing location

Part Numbers and Sizes

  • HVST16050 (16”x 50’)
  • HVST24050 (24”x 50’)
  • HVST48050 (48”x 50’)
  • HVST16100 (16”x 100’)
  • HVST24100 (24”x 100’)
  • HVST48100 (48”x 100’)
  • HVST16125 (16”x 125’)
  • HVST24125 (24”x 125’)
  • HVST48125 (48”x 125’)

Technical Data

  • Temperature Range: -30 to 180 F
  • Nominal Thickness: 5/16 inch (.312)
  • Weight: 0.771 oz./sq. ft.
  • Flame Spread Index (ASTM E 84): Less than 25
  • Smoke Developed Index (ASTM E 84): Less than 50
  • Mounting Method (ASTM E 2599)
  • Fire Rating: Class A/Class 1
  • Linear Shrinkage: None
  • Reflectance (IR): 96%
  • Water Vapor Transmission (ASTM E 96): 0.02
  • Puncture Resistance: 60 lb./in.
  • Mold and Mildew: No Growth
  • Emittance: 0.04
  • Tensile Strength: 3.7 N/mm
  • Pliability: No Cracking
  • Hot Surface Performance: Passed (250 F)

Testing and Certification

  • Thermal Performance of Wall Systems ASTM C1363
  • Thermal Performance of HVAC Duct System ASTM C335
  • Thermal Performance of Crawl Space ASTM C1363
  • Hot Surface Performance ASTM C411
  • Heat Transfer (Heat Flow Up, Down, Horizontal) ASTM C1363
  • Thermal Performance of Reflectix® and Fiberglass in Walls ASTM C1363
  • Heat Transfer of Air-Handling Ducts with Reflectix®
  • Flame Spread and Smoke Density ASTM E84
  • Mounting Method ASTM E2599
  • Fungus Resistance Mil-Std 810B Method 508
  • Pliability Test ASTM C1224
  • Sound Absorption Test ASTM C423 and ASTM E795
  • Sound Transmission Loss ASTM E90 and ASTM E413
  • Water Vapor Transmission ASTM E96
  • Tensile Strength ASTM D751
  • Emittance Testing ASTM C1371
  • Thermal Performance of Water Heater Jackets
  • Intertek: Surface Burning Characteristics of Building Materials ASTM E84 (Taped Joint Detail) Test Report # 3166908SAT-012
  • Intertek: Surface Burning Characteristics of Building Materials ASTM E84 (Unslit) Test Report # 3166908SAT-011
  • R&D Services: Resistance to the Growth of Fungi ASTM C1338 Test Report # RD072713FR
  • State of California
  • State of California Licensed Insulation Manufacturer
  • State of Minnesota: Filed with Minnesota Insulation Standards Program
  • State of Wisconsin: Wisconsin Material Approval, Safety and Buildings Division Approval # 920088-1
  • R&D Services Emittance Testing
  • R&D Services: Physical Properties Sheet Width, Length, Pliability, Water Vapor Permanence and Aged Water Vapor Permanence
  • R&D Services: Water Vapor Transmission Test ASTM E96 (Dessicant Method)

Installation Instructions

This application meets the thermal performance requirements for new construction in the 2012, 2015 and 2018 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.

Note: For this application it is recommended to use at least 3/8 inch staples that are Heavy Duty or Galvanized.

  • Inspect the crawl space and make any needed repairs before installing Reflectix® Reflective/Bubble product.
  • For floor joists that are 16” on-center, the installation is easiest with the Reflectix® 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. There is no need to wrap water pipes or duct work that fall between floor joists. Reflectix® 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 Reflectix® 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 Reflectix® Reflective/Bubble/Bubble/Reflective, 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 Reflectix® 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 Reflective/Bubble/Bubble/Reflective 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 Reflectix® to the band board.
  • Seal the seams with Reflectix® 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 Reflectix® Foil Tape or an equivalent.


Review These Important Safety Guidelines Prior to Installation:

  • ALWAYS check local building codes before installing Reflectix®.
  • ALWAYS check the area you are insulating and make any needed repairs. Any worn wiring should be replaced before you begin installing Reflectix®.
  • ALWAYS make sure work areas are well ventilated and well lighted.
  • ALWAYS use eye protection when operating a staple gun.
  • ALWAYS use caution and common sense when using a staple gun. Be aware of electrical wiring locations. Stapling into a wire can cause severe shock or death. NEVER staple into electrical wiring.
  • ALWAYS be careful when working with large pieces of Reflectix® on windy days.
  • When installing Reflectix® on bright sunny days, it is best to wear sun glasses.
  • Do not work in areas such as attics when temperatures are too hot.
  • Please Note: The intention of these Installation Instructions and 3-D renderings are for the sole purpose of illustrating the correct location and relative position of the Reflectix® products in specific building assemblies. The correct construction methods and techniques are the responsibility of the installer or contractor. The methods outlined are recommendations on location of the Reflectix® products as a guideline. There are no claims on the part of Reflectix, Inc. that these building assemblies are finite standards or meet building code requirements (as they can vary by region).

Reflectix Fact Sheet per FTC


Pictured: 1. Double Reflective Insulation, 2. Double Reflective Insulation with Staple Tab, 3. Tools for Installation, 4. Product Installation