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 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.
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