News From Go Plymouth Foam

Stopping Condensation in Metal Roof - What's the Secret?

Metal roofs over the past 10 years have exploded onto the construction sites. The ongoing problems and frustration for building contractors and design professionals of condensation in metal roofs has only increased exponentially. Solving this issue can be very difficult. Let's explore the benefits to rigid insulation and a secret, not known by many, in the building industry.

The biggest concern of condensation and its effects can be quit worrying for building owners and construction professionals. Water that forms in a system can cause damage such as:
Corrosion of metal panels and components which can structural weaken the system
Degraded and wet insulation reducing thermal performance
Mold and/or mildew growth that can increase health risks
Insect infestation which can contaminate systems

Condensation tends to occur in noticeable quantities and cause problems at surfaces where there is a sudden change of permeance, which causes an increase in local relative humidity sufficient to create dew point conditions. Condensation in metal roofs can be caused by air leaks around units, holes in vapor barriers/retarders, gaps in insulation just to name a few and no system is bullet proof. “Moisture moves by several mechanisms, including bulk drainage, diffusion (absorption), surface diffusion (absorption), capillarity, osmosis and convection.”

Condensation and metal roofs

Condensation can occurs on a hygroscopic surface, such as wooden sheathing or insulation, then moisture is absorbed, lowering the vapor pressure and increasing the vapor pressure gradient, driving more moisture toward that surface.

Picking an insulation that is resistant to moisture and help stop condensation is important, but no insulation is 100% waterproof. When Polyisocyanurate (Polyiso/ISO) or Extruded Polystyrene (XPS) gets wet, they dramatically loss their thermal effectiveness. Engineered Expanded Polystyrene (EPS) has the ability to resist moisture but when it get wet has the ability to expel moisture. Most metal roofing systems are not waterproof but rather watersheds. Therefore, air can travel and flow through the upper metal roof system allowing drying to occur. Learn More Here is the Secret: EPS is the BEST Insulation Solution for Metal Roofs because it can expel moisture caused by condensation. EPS's R-value will stay stable and be an overall better value.

View our Metal Roofing Products

LTTR - What does long-term R-value mean

What is your definition of long-term - 5, 10, 25 years? How should we judge the R-value of insulation long-term? LTTR (Long-Term Thermal Resistance) is a measure to quantify a comparative method of R-value in an attempt at trying to help architects, specifiers, builders, inspectors and owners. This measurement is achieved by the test methods ASTM C1303 or CAN/ULC-S770. I applaud the effort of developing these testing to quantify thermal performance, however a major adjustment may need to take place or at least the building industry need to understand these measurements - what they are and what they are not.

Early this year, the National Roofers Contractors Association, made a recommendation to it's members that Polyisocyanurate Insulation revise "its design in-service R-value recommendation to 5.0 per inch thickness." This declaration was the second time Polyisocyanurate's R-value was downgraded in the last 2 years. For some of us "Energy Aficionados," who understand the principles of insulation off-gassing, determined it was time to re-examine LTTR testing (
View Technical LTTR Bulletin).

LTTR really looks at Long-Term Thermal Performance of insulation as 5 years. Do we expect a building to last only five years? How is 5 years a true quantitative analysis of R-value performance?

We do not replace insulation in a building every 5 years, why would we think that is long-term? Most building in the U.S. are built to last 50 years, some 100 years. Long-term R-value should be figured at 50 years… right? We know off-gassing continues to happen after 5 years. Let's re-evaluate what we are doing as an industry and modify Long-Term Thermal Resistance to at least 50 years.

"Or Equal" - How about Better than Equal

Many construction architectural specs are written with a phrase that reads , “or equal.” This typically means that product must be at least equal to what is being called out. Many architect specify XPS (Extruded Polystyrene) for below grade insulation requiring an R-Value of 5 R/inch with a PSI of 15 or 25. Most times that foam board is specified as 2” thick to accomplish R 10. The real question may be, are their foam insulation boards that are “equal” to XPS below grade?

Plymouth Foam announced in January 2016, that they have
developed a new line of insulation products called Graphite Polystyrene (GPS). Working with BASF’s Neopor Plus ® this new foam insulation board delivers a stable higher R-value by infusing high-purity graphite particles into the Expanded Polystyrene cell structure. This new product has been tested and results conclude an R-value of 5.3 R/per inch* at 40 deg.

Neopor Specs
*The technical and physical metrics provided in this table are reference values for insulation products made of Neopor GPS.
The values and properties may vary depending on how they are processed and produced. The R-value properties are based on 1-1/32 in thickness.


The new innovative GPS foundation insulation certainly inhibits all the characteristics that make it an equal or better than equal to XPS insulation. In fact, GPS is far superior to XPS in a more stable r-value (see below grade insulation study), has the ability to expel moisture and even holds most of its r-value when wet. On the of other hand, XPS’s r-value decreases when the blowing agent escapes and when it gets wet.

The conclusion is simple, it is time start specifying Plymouth Foam’s GPS insulation for those foundations insulation needs.