Extruded polystyrene (XPS) closed-cell, rigid XPS insulation significantly improves the energy efficiency of unfinished exterior and interior walls for remodeling and new construction. In addition, the XPS boards provide thermal resistance with an R-value of 4.6 to 5.0, depending on their density, to create a comfortable indoor temperature and reduce utility bills. Moisture-resistant XPS panel insulation, with an absorption rate of 0.3 percent, resists moisture intrusion during and after application to help protect against damaging and unhealthy mold and rot.
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Lightweight, versatile, and simple to install, extruded polystyrene sheets typically come in 8-foot and 5-foot lengths, ranging from 16 inches to 4 feet wide and ¾-inch to 4-inches wide. The sheets come unfaced, and are covered with a foil facing, or laminated with plastic. The facing adds water resistance, and the lamination offers strength, but neither affects the sheets’ R-value. XPS sheets come in an array of colors (typically blue, green, and pink), based on the manufacturer, not insulating quality.
Flexible XPS boards come in various compressive strengths, making them ideal for numerous applications in all areas of the building envelope:
Manufacturing XPS insulation involves combining polystyrene crystals with special additives and a gas blowing agent. Manufacturers feed the mixture into an extruding machine that blends and melts it into a thick liquid. The liquid then gets processed through a die, which expands it into foam, shapes, cools, and trims it into standard-sized rectangular or square boards, with surfaces according to the intended use.
Specially designed machines produce XPS boards in smooth, rough, and grooved surfaces.
Demanding applications, like below-grade installation, utilize smooth XPS panels. Smooth, closed-cell XPS panels protect against absorption and diffusion due to long-term water exposure.
Rough surfaces increase the adhesion of the facade plaster.
Grooves in the XPS panel enhance wall drainage and thermal insulation for foundations.
XPS insulation offers many benefits contributing to an eco-friendly, healthy, durable, and safe building envelope.
XPS closed cell insulation, with an R-value of 4.6 and 5.0, gives it a high thermal resistance value, making it extremely energy efficient, by saving energy in buildings and reducing CO2 emissions.
100-percent recyclable XPS allows manufacturers to melt and reform the thermoplastic polystyrene resin into new XPS foam insulation.
XPS insulation’s high compressive strength allows it to withstand a high pressure of >300 kPa, so it can withstand more than lbs ft2 (30,000 kilos m2) with a maximum deformation of 10 percent, making it ideal for challenging applications:
XPS insulation provides water and freeze-thaw resistance, to protect the insulation’s thermal performance from damaging rot and unhealthy mold. In addition, the high permeability of XPS insulation makes it ideal for bathrooms and other high-moisture rooms.
Lightweight XPS insulation allows for easy application without irritating the worker’s skin.
Applying XPS insulation boards involves gluing the lightweight sheets to the substrate, which is much simpler than batts, blown-in fibers, or spray foam insulation. It is important to only use the manufacturer’s recommended foam-safe adhesive. The wrong glue can melt the foam. In addition, butt the sheets snugly together and seal joints with a manufacturer-recommended adhesive seam tape.
To insulate the stud, joist, and rafter cavities, cut the sheets to fit snug in the cavities, inserting them flush with the framing. To prevent airflow that can diminish the R-value, fill gaps along the edges with expandable insulation foam, safe for use with XPS. You can increase the R-value in two-by-six and larger dimension framing by inserting an additional layer of rigid foam insulation.
You can simply cut thin XPS sheets (less than 2-inches) by holding the straight edge of a utility knife along the cut line, scoring it about 3/4-inch deep. After scoring, lay the sheet on a table scored side up with the cut about 1-inch off the table. Firmly hold the sheet down and snap along the line. Trim the rough edges with the utility knife
For thicker sheets (greater than 2-inch), you will need a handheld drywall saw, or a table saw.
Installing 2-inch EPS boards on exterior sheathing requires additional furring strips or other structural supports. In addition, 2-inch XPS does not supply the strength needed to support the weight of the siding. Therefore, Sto strongly recommends that you check with your local building authority to determine the required type of additional support before installing 2-inch XPS as exterior sheathing.
Sto offers superior, simple-to-apply cladding solutions for applying XPS to an exterior wall system compared to XPS insulation boards: StoTherm ci XPS and StoPanel XPS ci. In addition, Sto XPS CI wall systems meet the requirements of fire, energy, and green building codes.
Sto XPS Wall Systems meets the requirements of NFPA 285 and NFPA 268 for use on non-combustible construction (Types I-IV).
Ch. 6: Energy Conservation, Efficiency and Atmospheric Quality (Section 606: Building Thermal Envelope insulation and Air Sealing) Alternative Compliance Path: ASHRAE 189.1-
Durable StoTherm® ci XPS, one of StoTherm® ci wall systems, is a drainable exterior insulation finishing system that incorporates high R-value XPS insulation into the wall system, and StoGuard® fluid-applied air and moisture barrier, with Owens Corning Foamular CI-C or Dow STYROFOAM™ Panel Core 20 insulation. StoTherm® ci XPS produces water and airtight air walls to ensure superior durability and thermal efficiency.
The unique, durable system sustains maximum curb appeal and lowers energy bills to save money. In addition, StoTherm® ci XPS can be finished with a variety of Sto textured finishes or specialty aesthetic finishes to accommodate your building’s design needs.
Lightweight StoPanel XPS ci prefabricated panels incorporate extruded insulation within the panel assembly, and create exterior wall cladding with excellent air and weather tightness, superior thermal performance, and long-lasting durability. In addition, architects and designers can choose from Sto’s numerous decorative and protective color and finish options.
StoPowerwall® ci energy-efficient stucco wall systems include StoGuard® air and water-resistive barrier, Owens Corning or Dow Type IV XPS insulation board, Sto DrainScreen, and Sto textured finishes.
StoPowerwall ci integrates continuous XPS insulation, air/moisture barrier, drainage, and Sto’s extensive collection of aesthetic surfaces in a hard coat stucco system.
Designers can use Sto’s unique Color System as a planning tool for choosing the colors for their architectural designs. The Sto Color System provides several benefits:
The Sto Color Collections include:
Sto’s extensive selection of finishes features pure white marble aggregate, acrylic polymers in various textures, and a wide range of color options to boost your design and harmonize with the surrounding environment. In addition, durable, high-performing Sto finishes resist dirt and water, protect the building’s facade, and enhance its curb appeal. Sto high-quality finishes include:
StoCast Finishes
Specialty Aesthetic Finishes
StoSignature
Sto Traditional Finishes
iQ Technology
Sto offers superior, sustainable, simple-to-apply, multiple code-compliant cladding solutions for applying XPS to an exterior wall system compared to XPS insulation boards. Drainable StoTherm® ci XPS and StoPanel XPS ci create high-performing, sustainable, and attractive cladding systems, improve indoor comfort and air quality, save both money and energy, and ensure long-term durability:
One of the most popular types of foam insulation on the market, XPS is used in many different construction applications. Knowing XPS’s strengths and weaknesses make it much clearer on when to use it versus another type of insulation. Learn more about what XPS is, how and when to use it, and when other insulation types make more sense.
Extruded polystyrene is made through an extrusion process into a rigid foam board. Blowing agents are injected into a mix of molten polystyrene before being forced through an extruder. The mix of the blowing agents and injection pressure pushing the molten mix through the extrusion die results in a foam board with tight cell spacing.
Easily recognizable by its blue, green, or pink color, XPS can be found on many job sites. This type of foam board readily accepts being faced and can be sold unfaced as a semipermeable rigid insulation board.
XPS is a closed cell foam with an R-value of around 5 per inch of thickness and is very lightweight and durable. The tight cell spacing and closed cell nature of XPS make it an excellent vapor retarder due to its low permeability, especially when faced. XPS panels also provide a great deal of compression strength and dimensional stability. During the extrusion process fire retardants can be mixed in to improve fire-resistance. XPS can even be recycled.
XPS panels are used in a variety of different applications, and the structural characteristics of the panels make them fairly easy to install.
For a cavity installation, XPS panels are fairly easy to work with. XPS panels can be scored and snapped or cut with a table saw to fit the size of the wall cavity. Spray foam is typically applied along the perimeter of the cavity. Instead of spray foam, XPS compatible adhesive can be applied to the face of the panel that will go against the exterior sheathing. The cut XPS panels can then be pushed into the cavity and sealed with the spray foam.
XPS is often installed as exterior insulation as well, especially below grade. After initial framing of the wall’s structural components, XPS panels are installed directly on the exterior of the framing members. Typically, ⅜” head galvanized nails, 1” crown galvanized staples, or equivalent fasteners long enough to penetrate at least ¾” into the framing members are used to secure the insulation.
The XPS panels are secured to the framing members using a few fasteners per board. Fasteners should not be over-driven to ensure long term stability of the installation. After the panels are secured, tape is used to seal all of the insulation joints.
XPS tends to be slightly more expensive than EPS and a bit cheaper than polyiso foam boards. While material prices can be highly volatile, XPS typically costs around $0.42 per square foot for one inch thick panels. XPS is often used in applications with tougher requirements that EPS cannot meet. Even for general insulation purposes, XPS can still be a viable alternative due to the ease of working with the material.
XPS is a strong and durable foam board with respectable thermal properties. This type of foam board typically works well in applications requiring higher strength and exposure to moisture. Common applications for XPS include:
Cold storage floors
Basement and below grade insulation
Under slab insulation
Flat roof insulation
Parking decks
The compressive strength of XPS and stability over time make it a great choice for underfloor insulation. For the same reasons, XPS is often selected for insulating foundation walls.
XPS is a great choice for insulation, and when it comes to continuous insulation applications polyiso is also the clear winner. Continuous insulation requirements are increasing and architects, designers, and specifiers must choose which type of insulation to use for their projects. Polyiso is not only a better insulator than XPS, but is also a completely different material.
Polyiso is a thermoset while XPS is a thermoplastic. The difference between these two materials can easily be seen at elevated temperatures. XPS, being a thermoplastic, softens and melts into a liquid when heated. Polyiso, however, chars and hardens.
Due to the elevated surface temperatures of exterior walls, over time XPS may not stay in place in the same way polyiso will. The elevated temperature performance coupled with the dimensional stability, moisture resistance, and superior thermal performance of polyiso make the choice easy.
For a continuous insulation material that will perform as well decades later as the day it was installed, choose Rmax polyiso! Contact our experts today to find the perfect solution for your project.