APPLICATIONS


Below-Grade

XPS is often used in foundations because of its high, stable, long-term R-value of 5 per inch and its excellent water resistant properties.From below the ground . . . up. . . . XPS is very suitable for use.

XPS is often used in foundations because of its high, stable, long-term R-value of 5 per inch and its excellent water resistant properties. It is also unaffected by common soil acids, mildew and fungus growth, decay or corrosion — properties that make it ideal for long-term durability.

Extruded polystyrene foam (XPS) insulation is most commonly-used below-grade in poured concrete, or concrete block foundation systems. Foundations play an important role in keeping a building comfortable, moisture-resistant, and structurally sound.

Learn how XPS can help.

Insulation that comes in contact with the soil is subjected to severe conditions, including long-term exposure to water, high soil humidity and freeze thaw action. These environmental factors can diminish an insulation’s effectiveness. Therefore, insulation in contact with the ground should be inert to the action of soil and water such that its insulating properties are not diminished due to this exposure. XPS insulation is ideal for below-grade applications due to its high moisture resistance and long-term insulating performance. In "slab-on-grade" applications, shown to the left here, XPS boards are applied vertically to the inside of the foundation wall. Additionally, XPS can be used to insulate beneath the floor slab.

Freezing has little or no harmful effect on insulation that remains dry, such as XPS. Similarly, insulation that does not absorb moisture from the surroundings will benefit. Conversely, insulation that gets wet does not perform as well. This is an important consideration when specifying an insulating material where freeze-thaw cycles are common. Weather data demonstrate that many locations in North America will experience several hundred freeze thaw cycles over a 10 to 20 year period. Independent studies demonstrate that only XPS insulation is suitable for use in wet, below grade environments where freeze-thaw cycles are typical.

There are several advantages to insulating the exterior surface of foundation walls. The block or concrete wall insulated on the exterior surface is not subjected to large temperature differences and so will not act as a thermal bridge. Block walls insulated on the exterior undergo less air convection in block cavities. At nearly room temperature, the basement walls act as a heat reservoir, buffering interior temperature fluctuations. In some instances, adfreezing forces are prevented from acting directly on the basement wall.

In "slab-on-grade" applications, XPS boards are applied vertically to the inside of the foundation wall. Additionally, XPS can be used to insulate beneath the floor slab.

XPS insulation is available with varying degrees of compressive resistance from 25 psi to 100 psi. The higher compressive strength insulation should be considered in applications subjected to high loading, i.e., mechanical equipment, etc. XPS is durable and versatile, thus it stands up to the rigors of job-site handling and is available in a variety of sizes. XPS insulation for below grade applications is typically provided in standard 2’ or 4’ widths by 8’ lengths and in thicknesses ranging from 1” to 4”. XPS insulation is easily cut on the job-site to needed sizes by scoring with any common knife and snapping.

Case Study
Silver Valley Condominimum Complex, Munroe Falls, Ohio

 



 

About XPSA


The Extruded Polystyrene Foam Association (XPSA) is a trade association representing manufacturers of Extruded Polystyrene Foam (XPS) insulation products and the industry's raw material suppliers. XPSA members collectively manufacture more than 95% of all XPS destined for use in the North American market. XPSA promotes the benefits that accrue to society from appropriate use of XPS foam insulation applications.

© Copyright 2016 The Extruded Polystyrene Foam Association


XPSA Headquarters


750 National Press Building
529 14th Street, NW
Washington, DC 20045

Phone Number:
202.591.2466