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

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

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

What Compressive Strength Do You Really Need?

EPS:  THE FOUNDATION FOR MOISTURE PROTECTION & INSULATION
 
Many projects design & build for higher load bearing densities then are required, thus costing significantly more time and money than is necessary.  ASTM’s D6817 is the specification for rigid cellular polystyrene geofoam. Designing to this standard not only helps engineers meet technical specifications, but also helps save money and time by using EPS (expanded polystyrene) geofoam, which is listed by the standard, as a structural void fill.  Geofoam has the compressive strength to bear heavy loads like concrete slabs, soil overburden, highway trucks and even airplane traffic and has gained widespread acceptance in load-bearing applications with federal and state entities like DoTs, airports and commercial projects.  
 
Similarly referring to ASTM C578 (Specification for Rigid Cellular Polystyrene Thermal Insulation) while selecting your below-grade insulation products, not only helps you design the right product for the job, but also helps avoids unnecessary costs associated with over engineering. 
 
ASTM C578 publishes compressive strength, deformation and dimensional stability values for both EPS & Extruded Polystyrene – XPS. Insulfoam’s wide range of plain and coated-facer insulation products meet ASTM C578 specifications, providing the same compressive strengths and long-term moisture prevention as competing below-grade insulations. But Insulfoam products come at a lower cost to the building owner, helping deliver significant savings in project costs.
 
FEATURED BELOW GRADE PROJECT: 49er’s Stadium
  • Project:  San Francisco 49er’s New Football Stadium
  • Location:  Santa Clara, CA
  • Product:  Insulfoam GeoFoam 2,500 cubic feet of EPS39 and 25,000 cubic feet of EPS15
  • Application:  Below grade structural void fill to support foundation for the fan seating areas

EPS Geofoam

EPS Geofoam

The contractors (Conoco Company of Concord and Turner & Devcon Construction) chose EPS Geofoam due to it’s extremely low weight and high load-bearing capacity to support the dimensional stability required for concrete topping slabs.  Insulfoam’s multiple manufacturing locations in California and nearby states provided just-in-time deliveries direct to the job site, which was a welcome bonus.

The single largest benefit to concrete contractors when using EPS is the ability of the material to constitute half of the form and the fill simultaneously, which completely eliminates the concept of a two pour operation. Read the full project profile here:  San Francisco 49er’s Find EPS Geofoam Useful In Future Home.

 

DID YOU KNOW?

  • Geofoam is 98% lighter than traditional fill
  • Geofoam does not settle
  • Geofoam eliminates lateral stresses from retaining structures
  • Geofoam can be designed for seismic forces

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.