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

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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

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Below Grade and Under-Slab Building Insulation

Originally posted in Modern Contractor Solutions Magazine, June 2014 issue

Modern Contractor Solutions Magazine, June 2014 Digital Issue

MC_june 2014

Modern Contractor Solutions, June 2014

Three tips for choosing the right material for your project

Which insulation is best for use on buried building foundations and under concrete slabs? Sales reps, naturally, will tell you that their company’s product is best. But, what does independent testing and research say?

These three tips will help your firm select a cost-effective and high-performance rigid foam insulation type for your next below-grade insulation job.

1.  CONFIRM LONG-TERM THERMAL PERFORMANCE

Two of the rigid foam insulations most commonly used below grade and under slabs are expanded polystyrene (EPS) and extruded polystyrene (XPS). Although both are closed cell insulations, they perform very differently over the long term.

XPS has a higher initial insulating R-value than does a similar thickness and density of EPS, but the R-value of XPS degrades over time. EPS does not experience such “thermal drift,” and the reported R-value remains the same throughout years of installed service.

This is a crucial point when selecting insulation, as a decreasing R-value means lower thermal performance over time, and thus increased heating and cooling energy and costs for the building owner.

Below Grade

Rigid foam insulation is increasingly common in below-grade and under-slab applications.

A simple way to confirm an insulation’s long-term thermal performance is to review the warranty. Established EPS manufacturers typically warrant 100 percent of the published R-value for 20 years. By comparison, most XPS warranties typically cover only up to 90 percent of the published R-value, to account for the R-value degradation that occurs in the field.

2.  ENSURE MINIMAL LONG-TERM MOISTURE ABSORPTION

In addition to R-value stability, rigid foam insulations differ in their rates of moisture absorption and their ability to dry. Wetted insulation provides lower thermal resistance and can degrade over time. Since insulation installed below grade frequently contacts wetted soil, rates of moisture absorption and the ability to dry is key in these applications.

Independent laboratories have conducted extensive tests of moisture absorption rates for both EPS and XPS. Although XPS often rates better in laboratory short term, fully submerged tests, real-world long term tests show that EPS performs much better. The reason is that EPS has the ability to dry much faster than XPS. This ability to dry at a fast rate helps EPS remain drier during conditions of repeated exposure to moisture.

A 15-year in-situ test of EPS and XPS dramatically demonstrated this point. 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, Minnesota. At the time the insulations were removed, the EPS was much drier than the XPS—the EPS had only 4.8 percent moisture by volume, compared to 18.9 percent moisture content for the XPS. After 30 days of drying time, the EPS had only 0.7 percent moisture by volume, while the XPS still contained 15.7 percent moisture.

The high moisture absorption rate of XPS in real-world settings is further seen in a 2012 report from the U.S. Dept. of Energy’s Oak Ridge National Laboratory (ORNL). Their researchers found that XPS insulation installed below grade for 15 years had absorbed 67 percent or more moisture.

3.  TARGET AN APPROPRIATE COMPRESSIVE STRENGTH

EPS insulation resists moisture better than XPS, including on buried foundations where it is in regular contact with wetted soil.

EPS insulation resists moisture better than XPS, including on buried foundations where it is in regular contact with wetted soil.

One of the best ways to save money on rigid foam insulation installed under concrete slabs is to ensure the material is not over-engineered. A common design assumption leads to specification of rigid foam strengths that are many orders of magnitude higher than necessary, which can double the insulation material cost.

Without getting into extensive technical details and mathematical formulas, the problem is engineers often use an overly conservative approach for insulation under concrete slabs. Many designers assume that point loads applied to a slab, such as those from the wheels of a forklift, transfer to the insulation in a triangular load path. Yet, concrete slabs distribute loads more uniformly than this, which means the insulation does not need as high of a compressive resistance as when one assumes a concentrated triangular load path.

An overly conservative design approach often results in specification of a high compressive resistance XPS product, when a more cost-effective EPS would offer sufficient strength. Since XPS typically costs more per inch than EPS, this is wasted money that comes off the contractor’s bottom line.

A simple solution for contractors is to ask the designers if they are using a formula from the Theory of Plates on Elastic Foundations, which take into account how slabs and insulation behave together. A resource to point them to for example calculations is the article “Right-sizing Under-slab Insulation,” in the April 2014 issue of Structure magazine.

CONCLUSION

With building owners’ growing desire to save money on heating and cooling costs, and increasingly stringent energy codes, contractors will be installing below-grade and under-slab insulation on more of their projects. EPS insulation out-performs XPS for both long-term thermal resistance and long-term moisture absorption, and EPS comes in a variety of compressive strengths suitable for nearly all building projects. With the highest R-value per dollar, EPS is the cost effective insulation choice.

Modern Contractor Solutions Magazine, June 2014 Digital Issue

EPS QUESTIONS?

 

Ram Mayilvahanan

Ram Mayilvahanan

Contact Ram Mayilvahanan, Insulfoam’s Product-Marketing Manager

Ram.Mayilvahanan@insulfoam.com

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Project Profile: Target Retail Store Saves 25% Cost Savings in Insulation with EPS

Target  |  King of Prussia, PA  |  View Project Profile (Pdf)

R-Tech Below Grade provided 25% cost savings in insulation on the project without sacrificing performance.

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The Target store located in King of Prussia, PA was constructed different than most and was not built as a slab on grade.  The bottom level of the building is a parking garage while the retail space is located on the second level.  Target used InsulGrade R-Tech as a between slab insulation as a way of insulating the floor of the retail space and providing a thermal barrier between the concrete planks and the floor slab.

DOW XPS was initially specified on the Target project, however; R-Tech was substituted and provided a substantial cost savings while providing both long-term stable and non-degrading R-Value.

PROBLEM & SOLUTION

Space was a challenge for this Target project as the parking garage is on the ground level and the actual retail floor is on the second level.  Concrete planks were installed as the base substrate.  R-Tech was then installed over the plank to insulate the interior of the retail space from the open parking garage underneath.  A topping slab was then poured over the R-Tech to create the retail floor.  The R-Tech insulation has a long-term stable R-Value and is eligible for an Insulfoam 20-Year Thermal Performance Warranty … a warranty that’s not prorated or limited to a percentage of the published R-Value.

InsulGrade R-Tech features a premium factory-applied laminate polymeric facer that is virtually impervious to moisture, keeps water from entering the insulation, and away from concrete foundations and slabs.  Available in 4′ x 8′ panels and thicknesses starting at 3/8″, with compressive strengths from 10-50 psi.

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View Project Profile (Pdf)

PROJECT DETAILS:

EPS vs. XPS

  • Both EPS and XPS are closed-cell insulations
  • EPS and XPS below grade insulations are covered under the same standard- ASTM C578
  • EPS has a more stable R-value and less long-term moisture retention than XPS
  • XPS is 20-40% more expensive for the same compressive strength

Cost Effective

  • Highest R-value per dollar
  • 100%, 20 year R-value warranty
  • 10-30% less than XPS insulations

Green From the Start

  • Up to 20 LEED points possible
  • 100% recyclable
  • contains up to 15% recycled content
  • Minimal job site waste
  • No thermal drift
  • Helps preserve energy and fossil fuels

R-Tech Uses

R-Tech has been used successfully for numerous commercial, industrial and residential applications:

  • Below grade insulation
  • Waterproofing protection board
  • Cavity walls
  • Interior walls
  • Cold storage & freezers
  • Sheathing
  • Concrete panel insulation
  • Concrete slabs
  • Radiant heated floors

PROJECT OR EPS QUESTIONS

Jason Myers

Jason Myers, Insulfoam Territory Sales Manager

Contact Jason Myers, Insulfoam Territory Sales Manager

Cell:  609-385-8930

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Right-sizing Under-slab Insulation

Structure Magazine, April 2014

Structure Magazine, April 2014

Originally published in Structure Magazine, Structural Economics section, April 2014

Structural Economics:  cost benefits, value engineering, economic analysis, life cycle costing and more…

Applying the Theory of Plates on Elastic Foundations to Save Material Costs.

Article (pdf)  |  Digital Edition

A common, simplifying assumption used for specifying polystyrene insulation under concrete slabs results in material costs that are significantly higher than necessary. Using a design equation based on a more rigorous analysis of the design conditions can help avoid over-engineering the insulation and save thousands of dollars on the project.

Rigid foam insulations, such as expanded polystyrene (EPS), have been used successfully under concrete slabs for more than 40 years. Such insulation helps reduce heat loss to the ground in residences, cold storage units, warehouses and other commercial, institutional and industrial structures.

The problem is that designers often do not adequately account for how the concrete slab and underlying subgrade interact. Many designers assume that a concentrated load applied to the slab transfers to the rigid foam subgrade through a triangular load path. This assumption, while not necessarily incorrect, can be very conservative.

Concrete slabs distribute loads in a more even fash- ion, which means that the insulation does not need as high a compressive resistance compared to the typical simplified approach. A more accurate approach to this problem is to use the Modulus of Subgrade Reaction (K) to determine the slab’s deflection and the resultant stress applied to the elastic insulation subgrade. The pressure beneath a given slab under a load can be determined using the following formula, found in the Theory of Plates on Elastic Foundations, as described by Timoshenko and Woinowsky-Krieger:

Pressure on the subgrade = (P/8)√(K/D) Where:

  • P = concentrated load on concrete slab in pounds
  • K = Subgrade reaction modulus of total EPS insulation in pounds per cubic inch (k/t)
  • k = Stiffness of one inch of EPS insulation in pounds per square inch
  • t = EPS insulation thickness in inches
  • D = Eh3 / 12(1-u2)
  • E = Modulus of elasticity of concrete in pounds per square inch (57000√ f’c)
  • f’c = specified concrete compressive strength in pounds per square inch
  • h = Thickness of concrete slab in inches
  • u = Poisson’s ratio for concrete (0.15)

An example illustrates the significant difference in the calculated results.

EPS insulation in an under-slab application

EPS insulation in an under-slab application

Take the case of a warehouse with a 6-inch-thick, 2,500-psi concrete slab on 2 inches of EPS insulation with a rated stiffness of 360 psi for one inch. Forklifts to be used in the building impart 8,000 pounds of force at the wheel, which has a 6-inch by 10-inch tire footprint on the slab. If the designer assumes that this load distributes at a 45-degree angle through the slab, the 8,000 pounds ends up distributed over approximately 396 square inches [(6 + 6 + 6)(6 + 10 + 6)] of the insulation’s surface, for an average pressure of 20.2 psi.

Taking into account the fact that concrete slabs distribute loads more evenly, using the Modulus of Subgrade Reaction method, the pressure on the insulation is actually much lower – approximately 1.85 psi. Since EPS insulation rated for 1.85 psi costs about 50% less than other rigid foam insulations rated for the much higher value of 20.2 psi, using the more precise method reduces insulation costs substantially. In fact, the 20.2 psi value is beyond the elastic range of the EPS material, and long-term creep effects must be taken into account when using that design approach. With:

P = 8000 pounds, h = 6 inches, f’c = 2,500 psi,

E = 57,000√ 2,500 = 2,850,000 psi, u = 0.15,

k = 360 psi for 1-inch EPS

K = 360 psi / 2 inches = 180 pci

D = Eh3/12(1-u2) = 2,850,000 (6)3/12(1–(0.15)2) = 52,480,818 lb-in

Pressure on EPS = (P/8)√(K/D) =

8000/8 √(180 / 52,480,818) = 1.85 psi.

The k value can be found by consulting the insulation manufacturer. One EPS insulation brand available throughout the U.S. has k values ranging from 360 to 1860 psi for one inch of insulation thickness. The specific value depends on the product type selected. Note that increasing the thickness of EPS insulation decreases the overall subgrade modulus.

Using the above method to determine the pressure that a slab transfers to the subgrade allows for proper specification of rigid foam insulation and avoids over-engineering the insulation for compressive strength. In the example application discussed in this article, the simplifying assumption of triangular load transfer through a concrete slab results in a compressive force on the insulation 11 times higher than the result from the more rigorous (but not much more complicated) analysis. Specifying higher compressive resistance insulation than necessary not only is overly conservative for the given design, it also does not improve the insulation’s thermal performance, and the cost to the project is excessive and unnecessary. It is a lose-lose scenario.

Article (pdf)  |  Digital Edition

ARTICLE QUESTIONS

Joe Pasma

Joe Pasma, Insulfoam Technical Manager

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800.469.8870 x104

joe.pasma@insulfoam.com

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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

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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:

Thermal Loss Thwarted

Originally printed in Architectural Products Magazine, Features Special Report, Insulation, Nov 2013

By:  Alan Weis, Contributing Writer

INSULATION- APPLIED AND INSTALLED PROPERLY- CAN BE AN INTEGRAL MEASURE IN CREATING AN EFFECTIVE AND EFFICIENT ENVELOPE.

FULL article (pdf)

Architectural Products, Nov 2013

Architectural Products, Nov 2013

When it comes to insulation, R-value- the measure of thermal resistance – seemingly rules.  In other words, the higher the R-value the better the thermal resistance.  But there’s more to the story than that according to industry experts.  “An insulation product’s R-value is only a starting point for understanding how well it works, says James Hodgson, general manager for Premier SIPS.

In fact, Hodgson says it’s crucial to evaluate the whole-wall R-value of the assembly, since the insulation is only one part of creating a tight, well-insulated envelope.  For example, he claims DOE research shows that a 4.5-in. structural insulation panel (SIP) wall rated at R-14, out-performs a 2×6 stud wall with R-19 fiberglass insulation.  “It comes down to significantly less air leakage, thermal bridging and convective looping for a better performing assembly,” says Hodgson.

Insulation, unfortunately, is too often treated as an afterthought, as Hodgson says it ends up getting fit around the structural systems instead of being an integral part of them, making it difficult to seal leaks.  SIPs, he notes, address this by incorporating both in one assembly.

NOW VS. LATER

Longevity is another consideration when it comes to R-values.  “It’s common for building professionals to look at R-value per inch at the time of installation, “says Ram Mayilvahanan, product marketing manager with Insulfoam.  “Yet, it makes more sense to evaluate insulation’s long-term thermal performance and the return on investment.”

R-tech

Insulfoam EPS insulation not only offers a high initial R-value, it also doesn’t lose R-value with time.

His company manufactures HD composite roof insulation, which bonds expanded polystyrene (EPS) foam to a high-density polyiso cover board, a combination that has high thermal efficiency and provides significant field labor savings.  Plus, Mayilvahanan says it can be used to achieve UL Class A fire ratings on combustible roof decks without the use of gypsum or other cover boards.

“Many rigid foam insulations experience thermal drift, which is a loss of R-value over time as insulating gases within them dissipate and are replaced by air,” Mayilvahanan continues.  “Some materials lose up to 20% of their insulating capacity during their time in service.”  One the other hand, EPS insulation, he explains, not only offers a high initial R-value, it also doesn’t lose R-value with time.  And, it can be used in wall, roof, below-grade and under-slab applications.

Continue to read FULL article (pdf) where further insulation consideration and types are described by industry experts.

“The push toward comprehensive green design has raised awareness that many building systems must work together for optimum performance,” says Mayilvahanan.  “It’s not just insulating the structure appropriately, but also right-sizing the HVAC systems and educating owners and occupants on how to operate the building for high energy efficiency.”

 

More info on Insulfoam:  Website  |  Read blog articles  |  Follow on LinkedIn

More info on Premier SIPs by Insulfoam:   Website  |  Read blog articles  |  Follow on LinkedIn

 

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

2012 IECC Code Changes: Insulation of Radiant Heating Systems

2012 IECC Code Changes

2012 IECC Code Changes

 

Don’t get caught out in the cold as the new 2012 IECC takes effect.  Make sure you plan for cost effective solutions to your insulation concerns.

Read more in significant code changes to the 2012 International Energy Conservation Code, Insulation of Radiant Heating Systems (pdf)

Specifying Thermal Insulation Below-Grade & Under-Slab

Originally posted in The Construction Specifier Magazine (pg 34), December 2013

The Construction Specifier, December 2013

The Construction Specifier, December 2013

Read full article (pdf)

In the push to forge more energy-prudent builders, design professionals are leaving no part of the envelope unexamined.  Walls and roofs have always presented a clear target for better thermal performance.  Somewhat less obvious are surfaces that are out of sight – below-grade foundation walls and floor slabs.  Well-engineered insulation in these locations can provide significant energy savings.

What separates below-grade insulation types from one another?  Moisture retention, R-value stability, and compressive strength are the key performance attributes to consider when evaluating and comparing different below-grade insulations.

Installing thermal insulation on below-grade foundation or perimeter walls and under slabs is important because un-insulated concrete provides a thermal and moisture bridge between the heated building interior and the relatively cooler earth surrounding the building, or through exposed slab edges to the outside air.

“While insulation strength is important consideration, erroneous design assumptions can lead to over-engineering for compressive resistance, adding unnecessary material costs.” – Ram Mayilvahanan, Insulfoam Product-Marketing Manager

Continue reading the full article, Out of Sight, NOT Out of Mind (pdf), in The Construction Specifier Magazine and learn about:

  • How installing thermal insulation on foundations help much more than just saving energy
  • How XPS and EPS compare with regard to moisture retention
  • What are the degrading effects of moisture on R-value
  • What specialty insulations for enhanced moisture protection are available

Read full article (pdf)

EPS Questions?

Ram Mayilvahanan

Ram Mayilvahanan

Contact Ram Mayilvahanan, Insulfoam’s Product-Marketing Manager

All Insulation is NOT Created Equal

EPS IN BELOW-GRADE APPLICATIONS?

Yes, when using engineered EPS products that are made in strict accordance with ASTM standards for below-grade insulation.

FACT:  All insulation is NOT created equal.  As a guide when choosing the right insulation product and manufacturer for moisture protection and thermal insulation, refer to ASTM C578. This third party standard establishes the minimum physical properties and requirements, and is the industry’s consensus standard for BOTH expanded (EPS) and extruded (XPS) polystyrene. For example, not all EPS manufacturers can produce 40 or 60 psi insulation in accordance with ASTM C578; Insulfoam does – it makes both products across its US locations.

BELOW-GRADE INSULATION PROJECT FEATURE

Starwood Hotel Finance Headquarters

Starwood Hotel Finance Headquarters

Rouser Concrete, the concrete contractor for the Starwood Hotel Finance Headquarters project in Arizona, chose Insulfoam R-Tech due to its superior performance as a durable and stable under-slab insulation which came at an economical price- great value for money.

During construction, the surrounding high-end retail stores were open for business, making it difficult for trucks to get in and out with product.  And storage space was at a premium.  Insulfoam’s Phoenix plant stepped in as a ‘local’ manufacturer with Just-In-Time, delivering however much product was needed at the jobsite at a given time.

Insulfoam R-Tech

Insulfoam R-Tech

  • Project:  Starwood Hotel Finance Headquarters
  • Location:  Scottsdale, Arizona
  • Product:  R-Tech 10, 65,000 Sq. Ft.
  • Application:  Under Slab

WHAT MAKES R-TECH EPS AN EFFECTIVE BELOW-GRADE INSULATION?

High compressive strength and engineered facers on both sides make R-Tech the most versatile combination of performance and economy.

  1. COMPRESSIVE STRENGTH- high compressive resistance that can be tailored to the loading requirements of the job
  2. MOISTURE PROTECTION- comparative study shows R-Tech has very low long-term moisture retention with no detrimental effect on its physical properties
  3. THERMAL STABILITY- long-term, stable, and warranted R-value that does not drift
  4. BEST R-VALUE PER DOLLAR- of comparable rigid insulations
  5. NATIONWIDE PRESENCE- manufacturing locations throughout the US

Visit Insulfoam for more information.

Energy Efficient Construction at World of Concrete

EVENT:  World of Concrete, Las Vegas   |   DATE:  February 5-8th   |   BOOTH:  N2915

ABOUT INSULFOAM

The future of architecture and construction is not only going to expand and grow at a rapid pace this New Year, but it is also becoming one of the r-tech_blog copybest industries in regards to saving the environment. When it comes to ultimate respectability in the industry, two names have come together to form one truly amazing ‘gift’ for all the building-owners and contractors out there. The name, Insulfoam, is synonymous with the creation of quality polystyrene-based engineered insulation products that have become even better than before. In addition,Carlisle Construction Materials has been known in all areas of architecture and construction for single-ply roof systems and waterproofing products that are unmatched in quality, durability, and savings. With Insulfoam, the largest manufacturer of expanded polystyrene in all of North America, being a part of Carlisle Construction Materials for several years now, these two powerhouses have shown the rest of the industry that they are not only still among the most respected names in construction, but are also constantly looking out for everyone from architects to building owners to contractors. With this ‘team,’ everyone has the ability to purchase and utilize energy-efficient construction products that are a ‘must-have’ in this ‘greener’ world. Insulfoam’s products insulate buildings, from the foundation to the roof and everything in-between. Versatility is a key word when it comes to these products. Not to mention the product line is 100% recyclable. Being leaders and visionaries when it comes to new product development, the latest in technology, and code approvals, the brands of InsulFoam® and R-Tech® also contribute immensely toward LEED® credit requirements, which is one of the biggest and most important issues to address nowadays. Insulfoam products, which have warranted long-term stable R-values with no thermal loss, are built upon sustainable manufacturing practices. Dye-free, free of formaldehyde and HCFCs, no toxic chemicals or heavy metals are leeched, and prevention of mold or mildew growth, are just a few of the benefits that come with these products. Offered under the InsulFoam® and R-Tech® brands, Insulfoam’sexpanded polystyrene (EPS) products for under-slab and below-grade applications insulate foundation walls, protect water and/or damp proofing, and can be used during backfilling in both commercial and residential projects.

roofing copyStudies have shown that R-Tech® below-grade insulations have some of the lowest levels of long-term water retention among below-grade insulation products. Combined with high compressive strength and long-term stable R-values, these properties make Insulfoam’s products among the most efficient in below-grade insulation. When speaking about wall installations, Insulfoam offers a variety of insulations that cover applications ranging from exterior, interior and cavity wall applications to tongue-and-groove sheathing, whole wall, and gable end applications. Not to mention, these products are extremely lightweight and have physical properties that are well ahead of their time. But below-grade and wall installations are not all that Insulfoam is renowned for. It also makes GeoFoam, a geo-synthetic structural fill that literally exceeds the requirements of ASTM D6817 Standard Specification for Rigid Cellular Polystyrene Geofoam. This is a fantastic alternative to other fill-materials, providing excellent lateral-load support and dimensional stability as a soil and slope stabilizer in various engineered applications.  And, yes, before one asks - roofing applications are also completely covered by offering roof insulation panels that help reduce overall energy consumption, and end up creating a fantastic and comforting environment for the occupants of the building. The company has a wide-range of code-approved composite roof insulations that work with fully adhered, mechanically attached and ballasted roof systems without the need for coverboards or slip sheets. Insulfoam’s high-density composite has code approval for direct-to-combustible decks without a thermal barrier, an excellent illustration that Insulfoam products work for virtually every type of roofing system. And what’s one of the most important words to hear when it comes to building and construction products? Cost-effective! Insulfoam’s products provide some of the best R-values per dollar. These products resist almost everything, which makes these products necessary for a long list of projects ranging from highway retaining walls to parking structures to foundations, loading docks, levees, underground utility protection, railways, runways, and so much more. Are you working on an entertainment construction project that will involve theater or stadium seating? This is what you need. Working on creating that pool with deck outside? …Need I say more? Even the website that is available discussing each and every one of these products proves how efficient and up-to-date this company is. Data, research, analysis, facts, figures – even instructional and technical information is offered on each one of these products, leaving absolutely nothing to doubt. And this includes questions and data regarding global warming, RA standards and the true goal that Insulfoam and Carlisle have to decrease our ‘carbon footprint and make this a healthy place where the next generation can thrive! For more information, head to this amazing website now and get to work making that next project the absolute best and ’greenest’ it can possibly be. http://www.insulfoam.com