R-Values vs. Performance Values

Since the beginning of the insulation industry many decades ago a lab test was created to measure the thermal resistance values of a product. The results of the test were called R-Values. Since that time our construction world has used these test values to determine how much insulation was required in a building.

This test data was trusted and used by thousands of construction professionals such as builders, architects, contractors, home designers, Fire Marshalls, engineers & building inspectors worldwide. R-Values were considered a complete an accurate measurement of Thermal resistance. The old out dated R-Value tests were grossly incomplete. The tests only measured Conductive Heat that passed through a sealed glass tube.

The old outdated ASTM testing method does not take into consideration Radiant Heat or Convection Heat. The sealed glass tube test does not allow for air movement around and through the insulation being tested. Without air movement inside the tube the R-Value results give a much higher than actual number. So, the wall assemblies that you place an R-13 fiberglass batt in, may only be giving you a thermal resistance of R-8. Our hot attics struggle with Radiant heat & have even worse performances.

Let me further explain the necessity of accurate information. If you don’t know what a product’s real Performance Value is (how it actually performs in a real world environment) then you will cause all of the Mechanical Systems, the Air Conditioning and Heating systems to be oversized. If the A/C Systems are too large they will short cycle and the home or commercial building will have moisture accumulation issues, which may eventually result in mold problems. So, understanding all of this technical information, engineers within the spray foam insulation industry built mock wall and attic assemblies, placed them in real world environments and gathered their own Performance test data. This time the tests measured for all three types of heat transfer: Conductive heat, Convection heat, and the biggest challenge our buildings face, Radiant heat. Not only were all Heat types tested, the engineers also considered wind load conditions. They placed a 4 mile per hr movement of air around each tested insulation product, which is the average wind load on buildings in the U.S.

The results were amazing. 3 ½ inches of open cell foam (R14) outperformed 11 inches (R-32) of fiberglass, cellulose, and rockwool! Why? Conventional old insulation products such as fiberglass, cellulose and rock wool, allow air to flow through them. This air infiltration brings in hot or cold humid air with hundreds of gallons of moisture into our buildings each day. Causing our mechanical (A/C) systems to run for longer than necessary periods, resulting in Utility bills that are 40 to 60% higher than what they should be.

The bottom line is simple. When considering insulations and sizing of air conditioning systems you must know the Performance value of the insulation you are considering because performance value is the only true accurate test of thermal value.