XPS vs EPS: Product Comparisons & Value Engineering

It's important to understand the differences between XPS and EPS foam board in continuous insulation (ci) exterior wall systems.

Advanced Insulated Wall Systems — Part 2

As exterior insulation wall systems gain in popularity and demand, it’s important to differentiate between the options available to building professionals. The key words that count these days are “code compliance,” “continuous insulation,” “hydrophobicity,” “compressive strength,” and “R-Value.” Other desired benefits when comparing insulation for ci systems include moisture management, durability, and reduced energy costs.

While polystyrene-based insulation board products are often specified as part of a continuous insulation (ci) wall system, and some products may appear similar on the surface, the fact is, if you drill down into the science of insulated plastic sheeting, not all foam plastic insulations are the same.

 A quick primer on the differences between XPS and EPS

Extruded polystyrene foam insulation (XPS) is a high-performance, closed-cell rigid insulation, manufactured in a proprietary process that melts plastic resin and additives into a molten material that is extruded through a die where it expands and cools into a uniform closed-cell, rigid foam insulation board with no voids or pathways for moisture to enter. It is, therefore, inherently moisture-resistant or, in scientific terms, “hydrophobic.”

Molded bead expanded polystyrene (EPS) is made from small foam beads that are placed in a mold. These beards are exposed to steam while in the mold, which causes the beads to expand and stick together. This method of manufacture can result in interconnected voids between the beads, and these gaps can potentially provide pathways for water to penetrate the insulation. It is, therefore, not nearly as moisture resistant as XPS and could lead to degradation of the insulation’s performance.

The differences in composition and structure between the two insulation types can obviously affect the ultimate long-term performance, durability and efficiency of a ci-system wall. And yes, XPS is a more expensive, up-front investment than EPS, but before you “value engineer” it out of a project, you may wish to consider the long-term savings and benefits of its molecular structure and formulation.

Is XPS insulation the right product for your next EIFS wall?

Make an informed decision. The superior water resistance and higher lifetime R-value for XPS make it a compelling product to consider, as its performance compares favorably to the more commonplace molded bead expanded polystyrene (EPS).

The cost savings for EPS can be tempting, but it is also more susceptible to moisture intrusion and therefore not as durable. Another drawback: its R-value is rated “medium” versus “high.” (R-value is the measure of thermal resistance; the higher the R-Value, the greater the energy savings.) That means higher energy costs will be required to maintain the comfort level for the building’s occupants.

While the initial cost of an XPS system needs to be considered, its attributes will pay dividends when accounting for future energy savings and protection from moisture intrusion. An XPS system is also lighter weight, which makes for a low allowable deflection value. This savings and the fact that an XPS system is installation friendly with just one installer and a single skilled trade person required, also offsets the product cost, making XPS a more competitive option.

So when you weigh the options and lean in the direction of durability and efficiency, XPS becomes the logical choice.

Advanced Insulated Wall Systems that Exceed Expectations and Code

StoTherm ci XPS is a continuous insulation system, which provides air, thermal and moisture control without the connection and compatibility challenges that characterize other systems, while also offering multiple design and finish options.

Today’s architects, specification professionals, and owners are typically looking for an insulated wall design that not only meets but exceeds the nation’s increasingly demanding code requirements. Enter the StoTherm® ci XPS continuous insulation system, which provides air, thermal and moisture control without the connection and compatibility challenges that characterize other systems, while also offering multiple design and finish options.

As the building industry adopts more stringent energy codes (Title 24, IBC, IECC, ASHRAE 90.1), the need for external insulated finish systems (EIFS) is increasing. The StoTherm ci system is highly energy efficient, minimizing heating and cooling costs while reducing greenhouse gas emissions. The components prevent thermal bridging, thus lowering the risk of heat leakage and the attendant energy loss.

Other features that make the StoTherm ci XPS system a superior alternative to other systems include:

  • Durability and impact resistance (77% higher density and 250% higher compressive resistance than EPS)
  • Low Water Absorption (due to its closed cell structure)
  • R-Value of R5/inch (the higher the R-value, the greater the resistance to heat flow)

The system is also installation friendly; one installer and a single skilled trade person can make quick work of it. The low allowable deflection value makes for lightweight construction, which reduces overall project cost and weight per square foot.  These factors make for material and labor costs that are highly competitive, if not more economical than most other options.

A wide range of decorative and protective wall finishes (StoCreativ® Brick, granite, limestone) along with unlimited color choices make StoTherm ci XPS is one of the most versatile and innovative products on the market today.

Look for the second part in this series next week, which explores other advances in durable insulation products offered by industry leaders and several case studies that demonstrate their value add for building professionals and owners.

How to Meet Today’s Building Codes with the Right Continuous Insulation

A cutaway drawing of the protective layers of StoTherm ci XPS insulation with an exterior Lotusan coating.

Many of today’s building designers and owners find themselves contending with the need for an advanced insulated wall cladding that meets the country’s increasingly rigorous IBC building codes such as Title 24, IBC, IECC and ASHRAE 90.1. What they want is efficiency, durability and a flexible range of exterior appearances. Sto’s answer? StoTherm® ci XPS continuous insulation.

StoTherm ci XPS is an integrated, continuous-insulation wall system that is air & moisture-controlled, thermally-efficient and highly durable. It helps cut energy costs, reduces maintenance expenses by extending the building life cycle and adds value by offering designers a variety of aesthetic options thanks to a wide range of decorative and protective finishes available in virtually unlimited colors. It checks all the boxes on today’s exterior specifications requirements list.

You’ll find more specification information on both ARCOM Masterspec Section 072419: Water-Drainage Exterior Insulation and Finish System (StoTherm ci Wall Systems – EIFS) and BSD Speclink-E Section 072400: Exterior Insulation and Finishing System (StoTherm ci systems).

The newly-renovated Nippert Stadium at the University of Cincinnati incorporated StoTherm ci XPS in several of the wall structures.

The newly-renovated Nippert Stadium at the University of Cincinnati incorporated StoTherm ci XPS in several of the wall structures.

StoTherm ci XPS is a highly energy-efficient system thanks to the combination of a fluid-applied StoGuard air & moisture barrier and extruded polystyrene insulation with installation-friendly components that eliminate heat-dissipating thermal bridging from mechanical fasteners and minimizes heating and cooling costs. It requires only one trade to install the entire system, which both cuts the time to build and lowers overall construction costs. And its low allowable deflection value of L/240 compared to L/360 for stucco and L/620 for brick facilitates lightweight construction and produces a lower cost per square foot.

This makes the StoTherm ci XPS system an ideal alternative to stucco and brick systems. Why? Faster, easier installation; high durability with a maintenance-friendly exterior finish that looks great and lasts. The economics are favorable, too; XPS material costs are typically lower than insulated stucco, brick or metal panel.

StoTherm ci XPS is part of StoCorp’s range of continuous insulation systems including EIFS, Stucco, Cement board stucco and Sto Panel (prefabricated) wall systems. The latest news is that the company is now partnered with two of the insulation industry’s leading vendors, Owens Corning and Dow as suppliers for a key component of the StoTherm ci XPS system. This now means that Sto customers will have two options when choosing the durable, high-R-value rigid foam insulation that resists water absorption and significantly contributes to the Sto ci wall.

This development makes it even more apparent that today’s StoTherm ci XPS is a true problem-solver. The news for architects and contractors is that the product now deserves a second look.

PACE Spurs Building Upgrades for Energy Savings

Now there's financing available to cut energy waste in buildings of all types and sizes.

PACE, which stands for Property Assessed Clean Energy, is a simple and effective mechanism for financing energy-efficiency retrofits and renewable energy upgrades that might not otherwise be affordable for commercial, residential, industrial, and agricultural buildings. PACE financing overcomes the upfront cost barrier these upgrades can pose by providing 100% of the financing for such projects.

The financing is paid back via property tax assessments that can stretch as long as 20 years. In most instances, the related energy savings more than pay for the assessment. Through the use of innovative PACE funding, new energy-efficient heating and cooling systems, insulation, solar and lighting improvements can be immediately rendered cash flow positive.

PACE funding has soared, as owners recognize the opportunity to increase their bottom line by reducing energy costs, to enhance the value of their property and do their part to offset greenhouse gas emissions. Since three quarters of the electricity generated in America is used to heat, cool, illuminate, and otherwise operate buildings, it’s not surprising that Scientific American magazine named PACE one of 20 “world changing” ideas.


Can Green Buildings Make Us Smarter?

Green is good -- outside or inside an occupied building.

A recent study published by Environmental Health Perspectives (EHP) suggests that Green Buildings create optimized conditions for health and productivity. In a series of experiments, indoor environmental quality (IEQ) factors for both “green” and “conventional” buildings were simulated in a controlled environment that included office workers, and the researchers measured variables such as carbon dioxide variation, ventilation and exposure to volatile organic compounds in the building atmosphere.

The results? On average, cognitive scores for the two groups of workers were 61% higher for those working in a building with green features than with conventional construction.  In other words, green building can potentially deliver a smarter workforce.

Energy Efficient Buildings Key to Combating Climate Change

energy efficient building

Renovating the Federal Building in Portland, Oregon cut energy usage by 45% and water consumption by 60%.

A new report from the U.S. Green Building Council and the American Sustainable Business Council concludes that energy-efficient buildings are one of the most effective and economical ways to reduce the nation’s carbon footprint in response to global warming. That’s because buildings account for more greenhouse gas emissions in the U.S. than any other source, including transportation and industry. The report probes the economics of green buildings and their value in mitigating greenhouse gas production, suggesting that brick and mortar solutions to the climate challenge make for good economics in the long run.