ASK THE EXPERT: What differentiates one rigid foam insulation from another?

Originally posted in American School & Hospital Facility e-Newsletter, July 2014 “Ask the Expert”

Q: What differentiates one rigid foam insulation from another? Building design and construction professionals can select from several rigid foam insulations, all of which perform well in helping buildings retain or keep out heat.  Yet, there are important factors to consider when evaluating some of the primary rigid foam products, like expanded polystyrene (EPS), extruded polystyrene (XPS) and polyisocyanurate (polyiso). Beyond product chemistry and manufacturing methods, two of the key differences among these materials are:

  • Insulating performance per unit of measure, and
  • Long-term thermal resistance (LTTR).

Insulating performance per unit of measure A common way to compare various insulations is R-value per inch. While such a figure demonstrates a material’s physical ability to impede heat transfer, it is of limited use when specifying insulation since performance vs. cost is the real driver in many architectural product decisions. To use a cliché, “what’s the bang for the buck?” If one looks at the R-value obtained per dollar spent, EPS rates highest. This property becomes more important once designers realize that insulation suffers from the ‘law of diminishing returns’ – additional insulation, beyond a design optimum, results in a very small net increases in energy savings.

Long-term thermal resistance (LTTR) Specifiers often focus on an insulation’s published R-value, yet might not realize that this figure is the initial value at time of manufacture. Many insulations are subject to R-value degradation over the product’s time in service. This is crucial as a drop in performance over time means higher heating and cooling costs over the life of the building. EPS is one of the few rigid foam insulations with a stable thermal resistance throughout its life. In other words, the published R-value of EPS does not decrease over time, compared to other rigid insulations that typically lose up to 20% or more of their insulating capacity during time in service. The reason some rigid foams have declining R values is they use blowing agents that enhance the initial R-value, but diffuse over time and are replaced with air. A simple way to check for this is to review product warranties, which will confirm a stable or declining R-Value over time. EPS manufacturers warrant a stable R-value.

Other factors The degree to which an insulation absorbs water impacts its thermal performance. Compared to some other insulations, rigid foams as a class resist moisture well. However, one misconception is that EPS readily absorbs moisture. However, when one considers that the material is commonly used in food packaging, it’s clear that moisture absorption is actually quite low. This has been demonstrated in real-world and laboratory tests comparing moisture absorption rates. For example, side-by-side testing of EPS and XPS as below grade insulation on a building foundation in St. Paul, Minnesota, showed that EPS outperformed XPS. When the two insulations were removed after being buried under soil for 15 years, the EPS had 4.8% moisture content by volume compared to 18.9% for the XPS. After 30 days of drying time, the EPS moisture level dropped to 0.7%, while the XPS continued to hold 15.7% moisture. These days, design professionals are focusing more on the ‘life-cycle’ effect of moisture on insulation, namely the ability of an insulation to not only resist moisture, but also to readily release any moisture it absorbs. Over dry/moist cycles that grade-application insulations are commonly subjected to, EPS has shown to be the most optimum performing, through its ability to retain the least amount of moisture among rigid insulations. This helps EPS provide a higher R-value over moist-dry cycles that characterize below-grade applications.

Product make-up and applications EPS, XPS and polyiso can all be used throughout the building envelope – roofs, walls and below-grade – in buildings of all sizes and types. The three insulations are recognized as follows:

  • EPS is typically white and comes in blocks and panels of various sizes and can be faced or unfazed.  Facers enhance physical properties like R-value, fire and moisture protection
  • XPS products are commonly offered as pastel or primary colored foams, depending on the brand.  The product is most commonly available as board stock of fixed size and thickness.
  • Polyiso insulation panels are comprised of foam sandwiched between two facers.

Cost-saving insulation approaches As with other commercial and institutional buildings, in healthcare and educational facilities project teams can minimize rigid foam insulation material and labor costs through careful product specification. Following are two simple ways to help keep insulation costs down.

Better targeting of compressive strength

Insulation manufacturers sometimes market high compressive strength to distinguish their products. As a result, rigid foam insulation is often over-engineered in under-slab and roof applications. Readily available EPS options run up to 60 psi in compressive strength, and are strong enough for almost all building envelop applications. A testimony to EPS’s compressive strength is its use in applications in roadways and structural earthworks as geofoam, which are specified under ASTM D6817 with tighter tolerances than traditional below-grade insulation applications. The cost of using a higher strength insulation than the application requires, can be substantial. For example, specifying a 100 psi XPS product in a below-grade application when a 40 psi EPS product would suffice, can almost double the material cost.

Simplified installation with tapered roof blocks

Building professionals often create positive slopes on flat roof deck assemblies using insulation. Because they are only available in relatively thin sheets, most rigid foam insulations require stacking several layers to build up the desired slope, costing a lot of labor time and material. EPS, on the other hand, is available in individual tapered panels up to 40 inches thick. Some manufacturers have the ability to pre-cut EPS blocks into any slope 1/16 inch or greater and in virtually any custom shape to accommodate roof crickets, saddles, valleys, and ridges, along with all types of drainage systems and layouts. Since fewer separate pieces are needed, building up a slope with tapered EPS blocks requires less on-site material handling and cutting and thus installs much faster. Using tapered EPS can reduce roof insulation costs up to 30% compared to other rigid foam products.

Composite insulation

EPS and polyiso are commonly used in many roofing assemblies, and now manufacturers are producing composite panels that combine these two materials. The EPS provides a lightweight, insulating and resilient foam insulation, while the polyiso serves as an insulating cover board for enhanced durability. Some composite products, such as the InsulFoam® HD Composite panel, carry a UL Class A fire rating for both combustible and non-combustible decks, and are compatible with a range of roofing membranes – including EPDM, TPO, PVC, CSPE, and low-sloped, built-up and modified bitumen membrane systems. As many low-rise healthcare facilities and some schools have wood roof decks, such rated products provide an easy-to-install insulation for fire-rated assemblies.

EPS QUESTIONS?

Ram Mayilvahanan

Ram Mayilvahanan

Contact Ram Mayilvahanan, Insulfoam’s Product-Marketing Manager

The Dirt on Below-Grade Insulation

Originally posted online at Construction Superintendent

Understanding rigid foam insulation for foundation and under-slab applications

Contractors are increasingly called upon to install rigid foam insulation under concrete slabs and on building foundations.

Contractors are increasingly called upon to install rigid foam insulation under concrete slabs and on building foundations.

Up to one-quarter of a building’s energy loss is due to lack of insulation in below-grade areas, including the foundation and under slabs. Now that high-performance building envelopes are common above ground, the relative amount of total heat lost below grade will grow if these spaces are not addressed.

As a result, superintendents increasingly will encounter below-grade and under-slab insulation on all building types. To help increase understanding of how two common rigid-foam insulations perform in these settings, this article evaluates moisture absorption and thermal performance. It also discusses installation procedures for below-grade and under-slab insulation.

Rigid foam insulation
Two common rigid foam insulations specified for below-grade applications are expanded polystyrene (EPS) and extruded polystyrene (XPS).

EPS

An easy way to recognize EPS on the jobsite is that it is commonly white. This insulation is made of expanded polystyrene beads fused into sheet stock and blocks of various densities, compressive strengths and sizes. Historically used as a stable roof insulation, EPS has gained wide acceptance in wall, below-grade and under-slab applications due to its low-moisture absorption, strength and stable, long-term thermal performance. EPS insulation blocks can be custom-cut into a variety of shapes and sizes to meet wide ranging job specifications.

Building professionals have used EPS successfully in below-grade applications for decades. As of 2013, the International Code Council explicitly permits EPS throughout frost protected shallow foundations, under slabs and any other below-grade application.

XPS
To make XPS, manufacturers combine and melt polystyrene with blowing agents and additives, then force the liquid mixture through an extrusion die in a continuous feed, where it is shaped, cooled and trimmed to size. The product is most commonly available as boardstock of fixed size and thickness. Manufacturers often tint XPS a primary color for brand recognition.

EPS insulation absorbs significantly less moisture than does XPS insulation according to studies of real-world installations.

EPS insulation absorbs significantly less moisture than does XPS insulation according to studies of real-world installations.

Moisture absorption and thermal performance
There is much confusion in the marketplace regarding whether EPS or XPS insulation resists moisture better. This is a key point, as wet insulation has lower thermal performance. While manufacturers of both insulation types tout that their products have lower moisture absorption, in-situ tests indicate that EPS performs better in this regard.

For example, in 2008, Stork Twin City Testing – an accredited independent testing laboratory – examined sheets of EPS and XPS removed from a side-by-side installation after 15 years in service on a below-grade foundation in St. Paul, Minnesota. The XPS was significantly wetter on extraction, with 18.9 percent moisture content by volume compared to 4.8 percent for the EPS. After 30 days of drying, the XPS still had elevated moisture of 15.7 percent, while the EPS had dried to 0.7 percent.

The U.S. Department of Energy’s Oak Ridge National Laboratory also reports high moisture absorption levels for XPS. In a 2012 study, the lab reported “all samples of XPS insulation gained much more moisture during the 15 years of contact with soil moisture.” The resulting loss of energy savings performance was 10 percent for a full basement (“deep basement”) and 44 percent for a slab-on-grade installation.

By comparison, the U.S. Army Cold Regions Research and Engineering Laboratory found EPS buried in wetted soil for 1,000 days absorbed only 1.7 percent moisture by volume, which is substantially lower than the XPS rates noted above.

Installing rigid foam insulation below grade
On building foundations, the insulation (whether EPS or XPS) is installed over the damp/waterproofing, after that layer has adequately cured. Crews can use mechanical fasteners or polystyrene-compatible adhesive to attach the insulation. Applying a bead of polystyrene-compatible caulk or mastic to the top of the insulation board minimizes water infiltration behind it.

For under-slab applications, the rigid foam insulation typically should be installed over a gravel base, with a poly vapor diffusion retarder between the gravel and insulation. Additional insulation is applied along the edges of the slab, because that is a primary surface for heat loss. To avoid damage to the insulation, it is necessary to ensure removal of any jagged surfaces or irregularities in the substrate before installing the rigid foam panels.

In either case, it is important to confirm all details with the insulation manufacturer and local building department, and to ensure appropriate construction techniques to drain water away from the building.

In addition to its lower moisture absorption and better long-term thermal performance, EPS has the highest R-value per dollar among rigid insulations. As such, it provides a cost-effective way to insulate building foundations, and under slabs.

Ram Mayilvahanan is the product marketing manager for Insulfoam, which offers below-grade insulation under the Insulfoam and R-Tech brand names. For more information, visit www.insulfoam.com.

 

Ram Mayilvahanan

Ram Mayilvahanan

Contact Ram Mayilvahanan, Insulfoam’s Product-Marketing Manager

Ram.Mayilvahanan@insulfoam.com

Connect with Ram on LinkedIn  |  Follow Insulfoam on LinkedIn

Read more on Insulfoam.com

 

A Guide to Below-Grade Insulation and Moisture

Originally posted online at Buildings.com in Buildings Buzz!

OLYMPUS DIGITAL CAMERAWet insulation is ineffective insulation – rigid foams that retain high volumes of moisture lose about half of their insulating R-value. Because insulation installed on below-grade building foundations and under concrete slabs is often exposed to moist soil, it is crucial to choose an insulation that has minimal long-term moisture retention and the ability to dry quickly.

For facility professionals that are evaluating insulation for building retrofits or for new construction, paying attention to moisture performance helps ensure effective long-term thermal resistance. Because the insulation will be hidden from view, any problems with degraded materials will not be obvious, although the effect on higher energy bills will be very real.

One challenge in selecting insulation is cutting through the competing claims of insulation manufacturers. Producers of extruded polystyrene (XPS) and expanded polystyrene (EPS) – common below grade insulations – both claim that their products are superior at resisting moisture. In their own ways, each one is right, but it depends on whether one is looking at abstract, standardized tests or performance in actual installed conditions.

Claims that XPS insulation absorbs less moisture than EPS are based on ASTM 272Standard Test Method for Water Absorption of Core Materials for Sandwich Constructions. This test calls for fully submerging an insulation sample in water for 24 hours, then weighing it for moisture absorption immediately upon removal from the water.

How does this test represent reality? The truth is it doesn’t reflect real-world conditions for two reasons:

1) Unless your building is in a lake or river or subjected to severe flooding, the insulation will not be fully submerged.

2) It doesn’t account for how much an insulation dries out or does not dry out between periods of moisture exposure.

Entire marketing campaigns have been built around this test, but when it comes to what really happens on your building, it’s necessary to look at actual exposure during in-situ tests. Studies of insulation exposure to moisture in actual field conditions show that EPS outperforms XPS by a wide margin, largely because EPS dries much faster than XPS.

For example, the independent lab Stork Twin City Testing evaluated the moisture content of EPS and XPS buried side-by-side for 15 years on a building foundation in St. Paul, MN. At the time the insulations were removed, the EPS was four times drier than the XPS – the EPS had only 4.8% moisture by volume compared to 18.9% moisture content for the XPS. After 30 days of drying time, the EPS had dried to only 0.7% moisture by volume, while the XPS still contained 15.7% moisture.

The high moisture absorption of XPS is further seen in a 2012 report from the U.S. Department of Energy’s Oak Ridge National Laboratory. Researchers found that XPS insulation installed below grade for 15 years had absorbed 67% or more moisture. The resulting loss of energy savings performance for the XPS was 10% for a full basement (“deep basement”) and 44% for a slab-on-grade installation.

Insulation manufacturers are well aware of how their products will perform over the years. Evidence of this is seen in the limitations stated in warranties they offer. This is why XPS manufacturers typically warrant only 90% of the insulating R-value of their products during time in service, whereas most EPS manufacturers warrant 100% of the R-value. Some XPS manufacturers will also void warranties in case of ponding or water immersion, which runs contrary to their highlighting of 24-hour, full-immersion testing.

There are many claims in the market about whether EPS or XPS offers the best moisture resistance. When evaluating such statements, it is important to consider the basis upon which the statements are made. Does the testing involve guys in lab coats dunking insulation into a fish tank for one day, or does it replicate how insulation performs on actual buildings over many years? If facility managers are making the investment in insulation, this is an important distinction to pay attention to, otherwise the product might not perform as desired.

EPS QUESTIONS?

 

Ram Mayilvahanan

Ram Mayilvahanan

Contact Ram Mayilvahanan, Insulfoam’s Product-Marketing Manager

Ram.Mayilvahanan@insulfoam.com

Connect with Ram on LinkedIn  |  Follow Insulfoam on LinkedIn

Read more on Insulfoam.com

New Mexico Schools Save on Construction Costs with EPS Insulation

 

APS

APS Food & Nutrition Services Kitchen & Storage Warehouse, R-Tech Installation

Albuquerque Public Schools (APS) in New Mexico have been undertaking a massive classroom and educational rebuild and remodel.  All new construction has been designed using sustainable materials and energy-efficient principles with LEED certification as the end goal.

As part of new buildings under construction is a 108,000 sq. ft. central Food and Nutrition Services Kitchen and Storage Warehouse.

Originally specified XPS was replaced with Insulfoam R-Tech VI 40 psi over the sub slab freezer floor.  The project utilized 2 lifts of 3″ R-Tech instead of 3 lifts of 2″ XPS ultimately saving the  concrete contractor approximately $20,000 in material costs.

(More photos below)

Useful industry publications references on specifying EPS in below grade or under slab applications:

APS

APS Food & Nutrition Services Kitchen & Storage Warehouse, R-Tech Installation

APS

APS Food & Nutrition Services Kitchen & Storage Warehouse, R-Tech Installation

APS

APS Food & Nutrition Services Kitchen & Storage Warehouse, R-Tech Installation

PROJECT DETAILS

Questions on this project or application?

Travis Montgomery, Insulfoam Territory Manager

Travis Montgomery, Insulfoam Territory Manager

Contact Travis Montgomery, CSI, Insulfoam Territory Manager

Email: Travis.Montgomery@insulfoam.com

Connect with Travis on LinkedIn | Follow Insulfoam on LinkedIn

Read more on Insulfoam.com

 

Question & Response: XPS, EPS, and Dock Flotation

Useful references to support this article:  NEW moisture absorption data regarding XPS, moisture absorption and the effects on R-Value was released in March 2014.  Read more in the updated summary and in subsequent 2008 test program documents:

Originally posted on Construction Specifier online, Author Response to Reader Question, February 18, 2014

After the feature, “Out of Sight, Not Out of Mind: Specifying Thermal Insulation Below-grade and Under-slab” ran in our December 2013 issue, we received a letter from retired architect, Joseph S. Bond. Mr. Bond wrote that the article in question “seems to reverse the findings” from both his personal and professional experience with expanded and extruded polystyrene (EPS and XPS):

I am a retired architect, and may not have the best current information on EPS and XPS, but when these two products were mistakenly used as ‘flotation’ for lake docks and later removed, the XPS bales were like new and had no water soakage beyond the first (1/8 in.). However, I remember the EPS bales were waterlogged to the extent it took two people to even carry the bales. On top of this, the EPS bales showed a lot of disintegration due to freeze-thaw.

My observations may have been on EPS that had much less density (1-1/2 -2 #) than implied by The Construction Specifier article, but many reading will probably have the same concerns and begin to question the piece’s validity.

We asked the article’s author, Ram Mayilvahanan, to respond.

Mr. Bond raises a frequently discussed point about the long-term problems that arise when using rigid foam insulations that do not conform to ASTM standards.

Since insulation, especially below-grade, is out of sight, it can also be out of mind when it comes to ensuring the product being used at the job site matches the product that was specified.  As with other building products, there are numerous companies making rigid foam insulations, often with varying degrees of quality.  We building professionals share the responsibility in making sure the selected right-foam manufacturer can consistently deliver product that meets the specified performance.

To ensure performance on key factors, including moisture resistance, it is crucial to not only specify foam insulation that has been manufactured and tested to meet ASTM C578, Standard Specification fro Rigid, Cellular Polystyrene Thermal Insulation, but also to ensure the manufacturer supplying the foam insulation can consistently deliver quality product.  A manufacturer’s longevity and track record with past projects should help in assessing this.

As an example, the floating green on the 14th hole in the world-famous Coeur d’Alene Golf resort in Idaho – considered on the of the coolest shots in golf- was built with EPS.  It continues to be a testimony to well-engineered flotation insulation.  Projects like this help establish the ability of manufacturers to deliver quality product.

Mr. Bond’s observation is a timely reminder for us building professionals that it pays to make sure the right product gets to the job site.

EPS QUESTIONS?

Ram Mayilvahanan

Ram Mayilvahanan

Contact Ram Mayilvahanan, Insulfoam’s Product-Marketing Manager

Ram.Mayilvahanan@insulfoam.com

Connect with Ram on LinkedIn  |  Follow Insulfoam on LinkedIn

Read more on Insulfoam.com

New Below Grade Data Released: EPS vs. XPS Insulation

The EPS Industry Alliance (EPS IA) has released NEW moisture absorption data regarding XPS, moisture absorption and the effects on R-Value through the latest Technical Bulletin, EPS Below Grade Series 105:   XPS Insulation Extracted After Field Exposure Confirms High Water Absorption & Diminished R-Value, March 2014 (pdf)

EPS IA March 2014

EPS Below Grade Series 105, March 2014

A test program conducted in August 2008 evaluated the field performance of expanded (EPS) and extruded (XPS) polystyrene foam insulation in a side-by-side, below grade application following a continuous 15-year installation period.  When water and R-value retention were compared between EPS and XPS, the results demonstrated that EPS insulation outperformed XPS insulation with better R-value retention and a lower moisture absorption.

In 2013, an independent testing laboratory was again commissioned to evaluate the R-value and water absorption from XPS insulation samples extracted from several field locations and applications. A summary of the 2013 test results reconfirm there is no correlation between the results from standardized laboratory test methods and actual field exposure for XPS water absorption.  Further, the significant loss of R-value associated with XPS water absorption is shown in the summary.  

Read Full Technical Bulletin Summary (pdf)

“Studies show that as much as 25% of energy loss from a structure can be attributed to a lack of insulation. Insulation R-value is directly correlated to maximum energy efficiency in a building envelope; higher R-values translate into increased savings. It is important to understand that in-situ water absorption can diminish the thermal performance of building materials and designers must account for this when evaluating different insulation choices.”

 

Read more on the technical background expanding on the moisture resistance comparison between EPS and XPS conducted in the 2008 test program:

Insulation Choices: EPS or XPS?

Originally posted in Concrete Construction

As a specifier, architect and contractor….you must make well-informed decisions when it comes to below-grade, under slab, and cavity wall insulations in your projects.  Below are two informative articles listing the similarities and differences between both EPS (expanded polystyrene) and XPS (extruded polystyrene) insulations.

Insulation Choices:  Whether to use EPS or XPS can be a matter of cost.

Originally posted in Concrete Construction, November 2013, written by Mayilvahanan, Insulfoam’s Product-Marketing Manager

EPS insulation helps reduce heat loss through concrete foundations and floor slabs.

EPS insulation helps reduce heat loss through concrete foundations and floor slabs.

What’s the difference between XPS insulation and EPS insulation, other than a single letter? For installation on concrete foundations and under floor slabs, the rigid foam insulation you choose can make a difference of tens of thousands of dollars on a project. A careful evaluation of these materials’ performance attributes against the project’s needs can dramatically shrink labor and material costs. The savings could mean the difference between a profitable job and one you just have to chalk up to experience.

When it comes to concrete and insulation, contractors tend to be most familiar with extruded polystyrene (XPS). Yet, expanded polystyrene (EPS) performs as well or better than XPS, and at a substantially lower cost. Below are three important factors to consider when comparing these two insulations for any belowgrade or under-slab applications, read FULL article to see more side by side comparisons of EPS and EXP for these insulation factors:  1.) Compressive strength  2.) Moisture retention  3.) Insulating capability.

Full Article:  Insulation Choices

EPS vs XPS:  Insulation industry advances with EPS developments

Originally posted on Concrete Construction, February 2014, written by Frank Keisecker, ACH Foam’s VP of Sales and Marketing

There is much competition among polystyrene insulation manufacturers for the below-grade, under slab, and cavity wall insulation market. Claims made by the XPS (extruded polystyrene) industry are conflicting with that of EPS (expanded polystyrene) manufacturers. The validity of some claims is debatable. Specifiers, architects, and contractors must make well-informed decisions.

Read FULL article to thoroughly understand the similarities and differences between EPS and XPS insulations.  Key differences include: 1.) Moisture resistance 2.) Environmental impact  3.) Long-term R-value  4.) Compressive strength   5.) Panel sizes  6.) Cost per R-value.

Full Article:  EPS vs XPS

EPS QUESTIONS

Ram Mayilvahanan

Ram Mayilvahanan

Contact Ram Mayilvahanan, Insulfoam’s Product-Marketing Manager