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.

The Changing Face of Construction

In this three-part blog series, we are going to explore how the evolution of design and construction processes have dramatically changed in the past decade, especially as they relate to prefabrication and modular construction.

We’re not talking about the prefabricated kit homes of the 20th century, but rather offsite construction that accounts for a wide range of projects today, from whole-building modular solutions, to prefabricated walls and mechanical, electrical and plumbing systems that can help contractors accelerate production schedules while employing less labor on site. In today’s labor-constrained construction environment, the prefabrication solution is being increasingly adopted where reduced costs, resource efficiency and meeting tight schedules are priorities.

Several industry reports have shed light on these big-picture industry trends, including a study by FMI, a leading investment banking and consulting firm focused on the engineering and construction infrastructure and the built environment, and the BIM (Building Information Modeling) Forum. They surveyed 156 industry leaders most of whom work in the commercial sector and whose businesses, collectively, represent approximately $38 billion in annual revenue.

Some of the findings:

  • In 2010, only 26% of the survey respondents were using prefabricated assemblies on more than 20% of their projects. By late 2016, this number more than doubled: 55% of respondents were using prefab assemblies on more than 20% of their projects.
  • Project inefficiencies and improved technologies are driving prefabrication as a way to mitigate labor shortages and improve construction schedules.
  • Contractors who use prefab on more than 50% of their projects are more productive and efficient compared to those who do less prefab.
  • While many contractors struggle to make prefab pencil out, others plan to increase their investments in prefab over the next five years.

Just how much can prefabrication impact a project’s bottom line, and can it really be a competitive differentiator? Join us next week as we delve deeper into this topic and take a look at the relatively small, fast-growing cottage industry of prefabrication innovators who are driving change and shaping the future of the industry.

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.

How Biomimicry Is Inspiring Building Innovation

The cellular construction of the lotus leaf inspired the engineering of StoCoat® Lotusan® , a coating with self-cleaning properties, from Sto.

Biomimicry is a process that employs natural organisms and systems to inspire innovation. Biomimicry has inspired technical breakthroughs for decades—one of the most often-cited examples is Velcro, which the Swiss engineer Georges de Mestral patented in 1955 after studying how burrs stuck to his clothes— but better technology and more nuanced research have enabled increasingly complex adaptions.

Take the example of the lotus leaf, which has a surface texture that is “self-cleaning,” meaning that dirt particles are unable to obtain a hold on the leaves and simply flow off with the rain droplets that fall on the plant. Researchers at Sto, the building products innovator, studied this organic structure and used it as the inspiration for an exterior coating called StoCoat® Lotusan® that possesses a highly water-repellent surface similar to that of the lotus leaf. Its microstructure has been modeled on the lotus plant to minimize the contact area for water and dirt.

You can get the facts on biomimicry at Scientific American.