Post Frame Building - Product: Reflective Both Sides
Post Frame Building - Roof - Retrofit - Bottom of Purlin

Bottom of the Purlins
Metal Interior
R-11 Heat Flow Down (and a Radiant Barrier) | R-5.1 Heat Flow Up
Open Interior
R-9.0* Heat Flow Down (and a Radiant Barrier) | R-4.4* Heat Flow Up
Please Note: In addition to the stated R-value, this application also provides a Radiant Barrier. As a result, a 94% + reduction of the radiant energy that ordinarily would be transmitted to the interior of the building is blocked.

Reflectix® 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 Reflectix®. Our products are recognized for their thermal performance, easy installation, versatility and price.

Recommended Products:
Double Reflective Insulation
Reflective/Bubble/Bubble/Reflective - Roll
• BP48100 (48” x 100’)

• 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:
Reflectix® 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. To obtain a copy of our Product Testing Specifications, please refer to our website “Literature Tab” above. The documents are also available by e-mail at or call 800-879-3645.

Air Space Requirements:
Installation Instructions:

Download Post Frame - Roof - Retro - Bottom of Purlins Installation Instructions 0910.pdf
• Inspect the roof area for clutter in buildings where there is no ceiling.
• Measure the distance between the trusses. Many times, the distance will be 4’ or less. In some geographical areas, due to snow load, the distance will be as close as 2’.
• Cut pieces of the Reflectix® Reflective/Bubble/Bubble/Reflective product, 6” longer than the distance between the ridge pole and the bird’s mouth.
• Staple the product to the bottom of the purlins with 5/16” staples, 3” to 4” apart. Turn the edges down and staple to the side of the top cord of the trusses.
• Staple the top of the insulation to the ridge pole and the bottom to the top plate at the wall.
• Tape any butt seams with Reflectix® Foil Tape. Make sure the tape is applied so that a proper bond occurs.

* Includes thermal resistance of 1.32 UP and 4.55 DOWN for interior air film.

Calculation Disclaimer:
All values are calculated based on the “ASHRAE Handbook of Fundamentals” heat flow up and down.

Additional Resources:
F2 - Solutions for the Pro (Revised 0416)
Zip Code Zone Locator
This function provides regional installation recommendations for the following applications: Attic & Cathedral Ceiling
DIY Product Calculator Type:
Roof/Attic Application: Radiant Barrier Locate a Retailer
0 sq. ft. of roof/attic area 0 rolls
*Note: This calculator is for the convenience of our customers. These recommendations are for approximate product quantity.

Video Library:

For additional videos, click here.
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