There are a variety of insulation choices for residential and commercial construction, and two popular options are polyiso and graphite polystyrene (GEPS).

GEPS: The Basics

Graphite started being added to polystyrene insulation to create GEPS, or graphite-enhanced polystyrene. The addition of graphite enhanced the product’s thermal performance. In fact, GEPS can provide up to 20% greater energy savings compared to its traditional white expanded polystyrene counterpart sans graphite.

However, the downside of GEPS is that it can heat up rapidly in direct sunlight, so precautions should be taken to avoid material bending or distortion during the installation process. Be sure to shield the material or opt for a reflective facer when using in hot climates.

Upgrading... Polyiso

A close competitor to GEPS is polyiso insulation, and it delivers a plethora of benefits for installers, owners, and occupants. It is waterproof, flame retardant, lightweight, and eco-friendly. Polyiso insulation provides long-term energy savings by achieving higher R-values than standard wall insulation alone, such as spray foam, blown-in, or batts. This allows polyiso materials to reduce energy consumption in single-family residential, multifamily, or commercial buildings. Unlike GEPS, polyiso is not susceptible to temperature distortion, making it suitable for installation in hot regions.

Head-to-Head: Installation

GEPS products are less thermally efficient at equivalent thicknesses as polyiso. Therefore, GEPS products must be manufactured at a thicker consistency to achieve the same R-value as polyiso, which actually impacts installation. To use an example, a product such as OX-IS structural insulated sheathing with an R-value of R-3 comes in at ½-inch thick. By comparison, popular GEPS products of the same R-value measure at ¾-inch thick. While this minor difference may not seem like much, it has a significant impact on the design of a structure. This is because anything thicker than half an inch requires builders to change out the window jams to accommodate for the additional depth. If a thermal value of R-3 is appropriate for your project, choosing a thinner polyiso product will allow you to keep traditional window jams. It will also lead to a thinner yet still high-performing wall.

Otherwise, both GEPS and polyiso insulation are lightweight and efficient to install. They also both allow crews to install just one product (instead of three) by combining the structural, insulating, and weather-resistive components into singular solutions.

The Final Word

While both materials have their benefits, polyiso insulation stands out for its heat resistance and ability to achieve high R-values in a thinner design. This makes it a compelling choice for builders looking for energy-efficient, effective insulation designed to last for the life of a structure.

Learn more about how OX-IS structural continuous insulation saves money, time and helps meet code.