Dow High Performance Underlayment

Performance. Installation. Durability. Dow Building Materials is a leader in rigid insulation. In fact, we invented STYROFOAM* extruded polystyrene insulation. Today, we have a science-based insulating solution for every area of your home that includes extruded polystyrene insulation and polyisocyanurate insulation. Whether it's the foam's closed cell structure, unique slots and grooves that ease installation, or specialized facings for extra durability, added R-value, and moisture resistance, you'll appreciate the superior performance of STYROFOAM insulation products:

Closed Cell Foam Structure – STYROFOAM insulation products feature closed cell structure and maintain their R-value over time. The extruded polystyrene insulation products offer the highest moisture resistance of any foam plastic insulation. The result, high compressive strength and unparalleled resistance to water penetration. The polyisocyanurate insulation products do not readily absorb moisture.

R-Value – A measurement of resistance to heat flow. The greater the R-value, the greater the thermal efficiency—and a small increase makes a big difference. Cavity insulation only insulates between wood studs, leaving those studs un-insulated. Rigid insulation covers the entire wall, providing a continuous layer of thermal protection and increasing the overall R-value and energy efficiency.

A house with OSB and R-13 batts — a good start, but look at all the thermal shorts.	A house with OSB and R-13 batts, covered with 1/2" rigid foam insulated sheathing. NOW, you can see the difference adding insulated sheathing makes.
Heat loss is indicated on a scale of red, the most heat loss, to purple/blue — no heat loss.

Moisture Resistance – Some insulation products absorb and hold water which reduces insulation performance and is one of the necessary conditions for mold growth. STYROFOAM extruded polystyrene insulation resists water absorption and does not provide a nutrient source for molds. It offers the highest moisture resistance of any foam plastic insulation, provides long-term insulating performance while reducing the potential for mold growth within the insulation. The polyisocyanurate insulation products do not readily absorb moisture and do not provide a nutrient source for molds.

Strength and Durability – STYROFOAM insulation is rigid, so it's durable and maintains its integrity during installation and for years after. Yet, it's easy to cut and work with.

*Trademark of The Dow Chemical Company