Insulfoam’s Regional Sales Director, Rick Canaday, joined Home Talk USA with Michael King to discuss insulation in your home, insulation properties, moisture concerns, energy leaks in and out of the home and more.
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.
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.
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.
Contact Joe Pasma, PE, Insulfoam Technical Manager
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:
- Specifying Thermal Insulation Below-Grade & Under-Slab, Construction Specifier Magazine
- New Below Grade Data Released: EPS vs. XPS Insulation, EPS Industry Alliance
- Insulation Choices: EPS or XPS? Concrete Construction
- Commercial Concrete Contractor: Cleo J. Powell, Inc.
- Insulfoam Distributor: Zia Concrete Supply Company, Inc.
- General Contractor: Gerald Martin
Questions on this project or application?
Contact Travis Montgomery, CSI, Insulfoam Territory Manager
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:
- XPS Insulation Extracted After Field Exposure Confirms High Water Absorption & Diminished R-Value, March 2014 (pdf)
- 15- Year In-Situ Research shows EPS Outperforms XPS in R-value Retention, November 2008 (pdf)
- Expanded Polystyrene Insulation: Below Grade Testing Confirms R-Value Retention, August 2008 (pdf)
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.
Contact Ram Mayilvahanan, Insulfoam’s Product-Marketing Manager
Originally printed in Today’s Facility Manager Magazine, January/February 2014
As with new construction, the insulation chosen for a reroofing project can mean a difference of tens of thousands of dollars in material and labor. With the range of rigid foam insulation products available, it is possible for facility managers (fms) to reduce costs substantially without sacrificing thermal performance. The key is understanding product options for insulation, and the physical properties of these options.
Many reroofing jobs involve a recover of an existing metal roof. While fms can save labor and disposal costs by leaving an existing metal roofing in place, the standing seams make it difficult to create a smooth surface for the recover. One solution can be found with flute-fill EPS (expanded polystyrene) insulation. A number of rigid foam insulation manufacturers offer these products to fit the spaces between a metal roof’s flanges. And an advantage of EPS over other insulations is that it can be custom cut to fit any profile or size of flute, with high compressive strength products also available for use in high traffic conditions.
As these flute-fill insulations are light-weight and fit accurately into the flute, roofing crews can readily lay such products into a metal roof’s channels, providing a stable, even base for additional roof layers. And because the flute-fill insulation fills the flutes completely, heat transfer into or out of a building is blocked.
Another common challenge of reroofing is the need to install a large quantity of smaller insulation boards over the existing roofing. This can be labor-intensive as crews must carry and place many separate boards. One way to alleviate this is to use fanfold panel bundles. Economical, code approved EPS fanfold bundles are available in accordion style sets. By working with these bundles, crews can handle more material faster.
Such products also help prevent thermal leakage by avoiding multiple joints. Further, fanfold products come with polymeric and metalized faces that provide enhanced moisture protection.
Another area where the choice of insulation can dramatically impact a reroofing budget is the conversion of a flat deck to a positive sloped roof. In such cases, the slope is often built up with insulation. Since most rigid foam insulation is available in sheets no more than a few inches thick, achieving the necessary slope can require stacking numerous sheets on top of one another. EPS insulation is available up to 40″ thick and can be pre-cut to virtually any slope. Such tapered EPS can reduce roof insulation costs up to 30% compared to other tapered rigid foam products, through material, labor, and also adhesive or fastener savings.
Insulation choice also impacts a facility’s energy efficiency year after year. Often, manufacturers report only the initial R-value, when the product comes out of the factory. However, many rigid foam insulations use blowing agents that boost initial R-value, but diffuse over time, losing up to 20% of the initial R-value while in service. Fms should look at long-term R-value to ensure there is no thermal loss. In the realm of rigid foams, EPS offers high insulating R-values. And engineered EPS is a stable non-degrading product, which leads many manufacturers to provide a long-term warranty of the product’s full R-value.
Contact Ram Mayilvahanan, Insulfoam’s Product-Marketing Manager
Originally printed in Architectural Products Magazine, On Spec, Insulation, Nov 2013
Design professionals typically want to use as much insulation as possible, not only to comply with building codes, but also to build to the highest standards. Building owners want enough insulation to keep heating and cooling costs down, without having to ‘pay through the roof’ in upfront costs. Performance vs. cost: where is the middle ground that makes sense for both parties?
To answer that question, it is important to look at how insulation is designed. For many years, the use of rigid foam insulation was based not the R-value per inch – the higher the better. Today, well-informed design professionals are cognizant of the design optimum and the realization that insulation suffers from the law of diminishing returns. Any insulation installed beyond the design optimum provides little additional energy savings, but costs a lot of money. Efficient insulation design comes down to choosing the product that balances upfront costs with the energy savings offered over the life of the building.
So, which insulation gives the best ‘bang for the buck?’ To understand performance vs. expenditure across different rigid insulations, it is important to consider the R-value per dollar spent on both materials and labor.
Because material and labor costs for insulation vary by market, specific R-value per dollar figures often shift, but EPS consistently rates highest when compared to other rigid foam insulations. Also, EPS comes in much higher thicknesses (up to 40 in.) in a single-layer than does XPS or polyisocyanurate, so higher R-values can be achieved with fewer layers, lowering on-job labor time and cost. Plus, EPS does not suffer any loss in R-value over the life of the building, so the design R-value for EPS is the long-term R-value.
With that in mind, here are some increasingly popular applications in which design professionals use EPS to comply with building codes while reducing material and labor costs for roof insulation. Read full article (pdf) to learn more about:
- Roof recovers requiring a separator board
- Metal roof recovers
- Bilt-up sloped roofs
- High-traffic areas
- Comparison of common rigid foam insulations
“In the end, the right insulation product is the one that offers the optimum balance of performance and economy. Such a product satisfies both the design professional and the building owner, leading to a building that is code compliant, built to high performance standards and economical enough to deliver lifetime energy savings that justify the upfront costs.”
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.
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.
EPS vs XPS: Insulation industry advances with EPS developments
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.
Contact Ram Mayilvahanan, Insulfoam’s Product-Marketing Manager
Originally posted in Construction Canada, July 2013
Keeping the Outside Out and the Inside In: A look at rigid foam insulations for high-performance building envelopes
By Ram Mayilvahanan, Insulfoam Product Marketing Manager
If the concept of building science could be distilled to one essential sentence, it would be the now-famous aphorism of Joseph Lstiburek, PhD, P.Eng., building science expert and adjunct professor of civil engineering at the University of Toronto.
“The perfect wall is an environmental separator- it has to keep the outside out and the inside in,” he wrote .
Lstiburek’s “perfect wall” (or roof or slab) includes four primary layers:
- rain control;
- air control;
- vapour control; and
- thermal control.
For the last category, specifiers can select from numerous insulation types; fiberglass batts to spray foam and rigid foam boards, as well as integrated systems such as structural insulated panels (SIPs). This article examines the various performance attributes and product options for expanded polystyrene (EPS) insulation in high-performance building envelopes.
Read the full article in Construction Canada’s feature article, Keeping the Outside Out and the Inside In.
We are in full swing with final preparations for Greenbuild 2012 in San Francisco Nov 14-16, the largest international conference and expo dedicated to green building. With 35,000 participants expected this will be one of the largest Greenbuild shows ever. Exciting!
1,000+ exhibitors, how do you decide what booth to go to, who to talk to? Ok, we aren’t Kohler who seems to have one of the BEST booths possible every year (and the one booth I always make sure to sneak away and visit), but we do have plenty of good information to help you with your next insulation project and meet your energy efficiency goals. Insulfoam (booth #3169N) provides insulation solutions from roof to foundation and everything in between.
High Performance. Lower Cost. Most R-Value Per Dollar.
With a broad range of insulation products available, it’s easier than ever for designers to create an energy efficient building project. InsulFoam EPS (Expanded Polystyrene) rigid foam insulation has been used for decades by smart industry professionals looking to achieve high thermal properties for a cost-effective price. In fact, EPS offers more cost savings and higher R-Values than any other rigid insulation. The benefit of lightweight EPS goes far beyond price, since it also helps contractors significantly decrease material and labor expenses. EPS is also one of the most versatile engineered insulations, making it a designer’s dream product. You tell us what you need and we make it fit within your design. Not limited by stock sizes InsulFoam blocks can be molded, cut, shaped, tapered into virtually any design need, regularly solving challenges for contractors on the jobsite.
InsulFoam EPS is the only rigid insulation that does not experience “thermal drift” (loss of R-Value over time). In fact, the R-Value is backed with a 20-year non-prorated thermal performance warranty. ISO and XPS rigid insulations don’t come close in warranty, so you can be confident that Insulfoam’s EPS products are the best rigid insulation option for your project.
The following Insulfoam product lines will be highlighted in our Greenbuild booth with specialists to talk you through technical attributes applications, projects and more. And not to mention we got some pretty great and easy to talk to guys! As you gear up for planning mode this coming week, put Insulfoam’s booth #3169N on your route.
FRAMING SYSTEMS: Premier SIPs by Insulfoam: Structural Insulated Panels are an extremely strong building panel that need no additional frame of skeleton for support. Premier’s large, pre-fabricated SIPs make the framing process faster than other building methods and enable a more airtight, well-insulated building for high energy efficiency.
BELOW GRADE INSULATION: Insulfoam’s Below Grade Insulation products are designed to insulate the foundation wall or slab and protect the waterproofing or damp proofing, especially during backfilling for both commercial and residential below-grade applications. Compressive strength, moisture protection and thermal stability.
ROOF INSULATION SOLUTIONS: Insulfoam’s roofing insulation applications are green, high-performing and economical products that help reduce overall energy consumption, create improved comfort for the building’s occupants and provide an excellent substrate for a new or retrofit roofing system.
INSULFOAM GEOFOAM: InsulFoam GF provides structural and architectural void fill applications that are lighter, easier to handle and faster than soil. Hardscapes, landscapes, soil remediation and load reduction.
For real time updates before, during and after the expo follow us on Twitter: @PremierSips @Insulfoam @InsulFoamGF. Be sure to also check out Greenbuild’s official twitter feed, @Greenbuild and conversation at #Greenbuild.