Fire & Thermal Performance of Reflective Insulations in Metal Building Applications
eflective insulations, designed and marketed for use in residential building cavities, are also being used in some pole barns and metal buildings. Stated thermal and fire performance of these products are not consistent with their actual field applications in metal building construction. Although manufacturers of reflective insulations have claimed R-values as high as 15, independent testing of some manufacturers’ products has shown that the actual R-value is between 1 and 2.1 While manufacturers of reflective insulation claim their products meet the code requirement for fire safety, those reflective insulation products produced with plastic cores raise safety concerns because of the way they react to fire test conditions.
Why the Difference in Stated and Actual Performance?
Some marketers of reflective insulations make generalized efficiency and performance claims based on specific test configurations performed in “lab” conditions. But, upon further inspection, one will find that these performance details are not always well defined or are not typical of the installation configuration in a real world metal building application.2
Fire Safety
An important consideration when deciding whether reflective insulation is appropriate for metal buildings is fire safety. Building codes require exposed insulation to have a flame spread index of 25 or less when tested in accordance with ASTM E84. The ASTM E84 Tunnel Test is one of the primary test standards for determining the fire safety of building products. Because many reflective insulations have a plastic core, the nature of these reflective insulations requires a careful analysis of fire safety claims. ASTM E84 states: “Materials that drip, melt, delaminate, draw away from the fire or require artificial support present unique problems and require careful interpretation of the test results. Some of these materials that are assigned a low flame spread index based on this method may exhibit an increasing propensity for generating flame-over conditions Fire & Thermal Performance of Reflective Insulations in
Metal Building Applications Information from In this issue we analyze and discuss the fire and thermal performance claims of reflective insulations used in metal building systems. during a room fire test with increasing area of exposure of the material and increasing intensity of the fire exposure. The result, therefore, may not be indicative of their performance if evaluated under large-scale test procedures. Alternative means of testing may be necessary to fully evaluate some of these materials.”3 Reflective insulations are stiff enough to be self-supporting for an ASTM E84 test. When tested in this manner by a nationally recognized laboratory, flame spread indices in excess of 300 were measured. (SeeTable 1.) When these types of insulation materials were evaluated in the UL 1715 room corner test, they provide sufficient fuel, when exposed to a low energy fire, to cause a flash over situation. Samples of reflective insulation were tested in the UL 1715 test by a nationally recognized laboratory. The results were flash over fire conditions within 2.5 minutes for both samples tested.4 (See insert.) These results should cast serious doubts about the fitness for use of reflective insulations for any exposed application.
Thermal Performance Testing
Another important consideration in making an insulation choice is thermal performance. The R-values claimed by manufacturers of reflective insulations are usually for the total construction including inside and outside film coefficients, sheathing materials, interior finishing materials, and the air cavities that are present in the construction. The test conditions or R-value of their actual products are normally not specified. Over the last ten years, a sufficient body of testing data has been developed to quantify the thermal performance of these reflective insulations. The data was developed using accepted ASTM test methods such as ASTM C518 or ASTM C177 for materials and ASTM C236 or ASTM C976 for insulation systems. These test methods determine the thermal performance of both component materials and construction assemblies. Chapter 25 of the 2001 ASHRAE Fundamentals Handbook6 contains accepted and authoritative information on the application of reflective insulations.
