Rigid foam sheeting is versatile and effective, and can be used in walls, roofs and foundations.
Rigid foam can be for retrofits or new construction. Most varieties of rigid foam have a higher R-value per inch than fiberglass, cellulose or cotton. Versatile and effective, rigid foam can be used in walls, roofs and foundations.
You’ll want to ensure you get the right type of foam sheeting for your project.
There are three main types of rigid foam insulation: expanded polystyrene (EPS), extruded polystyrene (XPS), and polyisocyanurate. Key differences are R-value per inch, water resistance, permeability to water vapor, compressive strength, facings and cost. All foam insulation products are petroleum-derived.
Call us today at (412) 875-6320 and speak with an expert foam associate at Reed Building Supply. We will provide you with a free quote and help you select the proper foam product for your project.
To learn more about foam sheeting and insulation, contact us.
The three types of foam sheeting:
Expanded polystyrene (EPS), known as beadboard, is commonly used for coffee cups and coolers. EPS is the most commonly used insulation in structural insulated panels (SIPs) and insulating concrete forms (ICFs).
EPS can be manufactured in different densities. Although higher densities of EPS have a greater compressive strength than lower densities, EPS is not as strong as XPS. EPS is more susceptible to crumbling at the edges and to other job-site damage. EPS is rarely used for wall sheathing.
The R-value of EPS depends on its density, with higher-density foams having higher R-values. The R-value range is from about 3.6 to 4.2 per inch.
Extruded polystyrene (XPS) is stronger, smoother, denser, more water-resistant, and more expensive than EPS. It’s also a better thermal insulator, rated at R-5 per in. XPS is less vapor permeable than EPS. One inch of XPS has a permeance of 1.1, while 2 inches have a permeance of 0.55, making XPS a semi-impermeable material.
Because of its high compressive strength and water resistance, XPS is often used below grade to insulate slabs and foundation walls.
For XPS sheeting, Reed Building Supply carries GreenGuard Type IV 25 psi XPS Insulation Board.
For green builders, XPS has two major strikes against it: it contains the flame retardant HBCD, and its blowing agents have a very high global warming potential. For these two reasons, most green builders try their best to avoid the use of XPS.
Polyiso has a higher R-value. Polyiso doesn’t use ozone-depleting blowing agents, but rather uses pentane.
Polyiso has higher insulating values (R-6 to R-6.5 per in.) than XPS orEPS at warm temperatures; however, when temperatures drop, the performance of polyiso worsens.
Because its manufacture doesn’t require the use blowing agents that deplete the ozone layer or contribute to global warming, polyiso board is considered the most benign type of rigid foam from an environmental perspective. However, because it can absorb water, polyiso is not recommended for use under slabs or on the exterior of foundation walls.
Foil-faced polyisocyanurate is more resistant to ignition than unprotected XPS or EPS.