Busting The Insulation Myths
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Long Term Thermal Resistance

Does LTTR go far enough to evaluate the long term performance of insulation?

Myth: LTTR is the true R-value of my insulation
Yes and No
Extruded Polystyrene and Polyisocyanurate Insulation
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Off Gassing
During the manufacturing process of Extruded Polystyrene (XPS) and Polysisocyanurate (ISO) insulation a gas blowing agent is formed into the cells. This insulation gas provides a initial higher resistance or higher R-value. (This concept is similar to Argon gas used in windows.) Starting immediately after the insulation is produced, a chemical transformation (Off Gassing) happens allowing this trapped gas to starts migrating from the insulation cells. This migration of gasses lowers the R-Value of the insulation over time.

You have seen this concept of Off Gassing before in Helium Balloons. When the party is over, those floating balloons are now down on the ground the next morning. Why? The helium gas has migrated out of the balloon.
The Shrinking R-Value
The off gassing of XPS and ISO is not just a one time event. This loss is a gradual escape of gasses into the surrounding environment. With the gasses goes the R-value loss of the insulation as well. We know that ISO starts out around 7 r/inch and after five years is at the 5.6 r/inch mark. The real question is how much does it go down, how fast and over what period. Long Term Thermal Performance (LTTR), does not take into account the shrinking R-value after the first 5 years. (Learn More)

Buildings are designed and built to last 50-100 years in most cases. If LTTR only gives use a clear picture of the first 5 years of insulation performance, how does that information effect the economies of the building? Does it cost more to operate than expected? Did we over pay for a insulation that has a shrinking R-value? Are their long-term health impacts from the off gassing?
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The Great Alternative - Expanded Polystyrene
Unlike ISO and XPS insulation, Expanded Polystyrene (EPS) does not suffer from off gassing or thermal drift like the others. EPS rigid insulation does not derive its R-value from trapped gasses. It traps regular atmospheric air. Air can be replace by air due to any migration but has no effect on R-value. EPS’s R-value staying consistent provides a huge financial benefit for years. Building Energy Models are consistent and more accurate. With EPS, what you pay for in R-value is what you get. The remaining fact is EPS is the best value in regards to r-value/inch. Learn More

We believe that higher priced rigid insulation, that losses much of its thermal residence over time, is not a good value or investment.
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“EPS - The Safe Insulation”

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“EPS - The Great Investment”

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