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XPS vs. GPS: Which One to Choose?

May. 25, 2022

What is XPS?

Expanded Polystyrene, referred to as XPS, is a closed-cell insulation product commonly used in remodeling and new construction applications. Due to the manufacturing process, XPS insulation is typically available only in standard dimension square or rectangular boards. Brands of XPS are generally recognizable by the color of the insulation: blue made by Dow, pink made by Owens Corning, green made by Kingspan, etc.


How is XPS Made?

XPS insulation begins as polystyrene crystals, which are combined with special additives and a gas blowing agent. The materials are fed into an extruding machine, where they are blended and melted into a thick liquid. The liquid is processed through a die, expanded into foam, shaped, cooled, and finally, trimmed.

What are the key features of XPS?

Just like with EPS, energy efficiency is the primary feature of XPS insulation. Due to its physical properties, XPS has a higher R-value than EPS at 4.7 per inch.


In the past, XPS manufacturers were able to claim R-values closer to 5.0 per inch. However, the blowing agents used in the manufacturing process were known to deplete over time, reducing the insulation value. Manufacturers are now reporting the Long Term Thermal Resistance (LTTR) of their XPS products to account for the reduction in R-value over time.


XPS provides increased stiffness and rigidity, making it suitable for use on roofs, below grade, below the slab, and other applications.

Foil-clad XPS

 Foil-clad XPS


What is GPS?

Graphite polystyrene insulation, or GPS, is made from Neopor beads, patented, and manufactured by BASF. Neopor gives GPS insulation a dark gray appearance and a higher R-value than traditional EPS insulation products. Click here to learn more about Neopor.


Similar to expanded polystyrene, GPS can be formed into many different shapes during the manufacturing process. Although GPS is relatively new in the United States, it has become the leading form of insulation in Europe over the last few decades.


How is GPS Made?

GPS is manufactured just like EPS insulation. The primary difference is the production of the raw material Neopor. BASF, the world’s largest chemical company, infuses the cell structure with graphite particles, which provide a reflective property and a distinctive dark gray color


Neopor beads are sent into a mold and hit with steam and pentane until they expand to many times their original size and fill the space. Because Neopor is naturally a dark grayish-black color, color additives are typically not used.

Double-slotted XPS

 Double-slotted XPS

Once the molding process is complete, the blocks of insulation are then aged and cut into the final shape using hot wires. Plastic film facers can also be adhered to the foam to provide more rigidity, reflective properties, installation guides, and more.


Since the manufacturing process is very similar to EPS, some manufacturers produce both EPS and GPS. This generally requires some additional equipment to avoid cross contamination between the two types of insulation.


What are the key features of GPS?

The key feature of GPS (Neopor) insulation is the r-value of 4.7 per inch, which is achieved thanks to the high purity graphite that is infused in the cell structure of the insulation.


Traditional EPS provides energy savings due to the trapped air pockets in the insulation, which slows down warm air as it moves towards cold air. This is what gives it an energy-efficient property.


As radiant heat moves through GPS insulation, it is reflected hundreds of times along the way thanks to the graphite particles, significantly slowing down the transfer of heat and making the insulation more energy efficient. When certain types of plastic facers are applied, the GPS can feature an r-value of up to 4.9 at one inch.


In addition to providing energy efficiency, GPS insulation without film facers has a perm rating of up to 5.0, depending on the density it is manufactured at. A perm rating is the measure of a product’s ability to let water vapor pass through it.


GPS insulation is more expensive than EPS due to the increased energy savings but is typically less expensive than XPS insulation.


Depending on your particular application, XPS, or GPS insulation could be right for your project. Cost, availability, and certain performance features can all impact your decision. Luckily, regardless of which product you choose, adding insulation to a home is always a great investment.

We recommend selecting the product that will provide the most value for your investment. If you’re installing insulation under a new roof or below a slab, XPS can be an effective solution. If your insulation needs are for sidewall applications before the siding is installed, we recommend using GPS insulation that not only adds insulation but also provides durability and lasting support to the siding panel.

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