So What is the Difference between STYROFOAM™ Insulation and Rigid High Density EPS Insulation?What Does R-Value Really Mean?So is STYROFOAM™ Insulation or Spray Foam Insulation Better than High Density EPS Insulation?Spray Foam and rigid XPS foam insulation like STYROFOAM™ lose R-value over their lifetimeIs Rigid High Density EPS Insulation Better for use in Ontario or New York States?Is EPS or XPS more moisture resistant?Where do I get the Best Price for EPS Polystyrene Foam Insulation?You know Styrofoam: The flimsy white stuff that holds soda pop at picnics and Chinese takeout, right?
Wrong… STYROFOAM™ has never been used to hold food and for making beverage containers or coolers for the beach - STYROFOAM™ is actually a registered brand of the Dow Chemical company – with very few exceptions they color it light blue to differentiate it from EPS or expanded polystyrene foam, and it is a version of closed-cell extruded polystyrene foam currently made for thermal insulation and craft applications.
In the United States and Canada, the word and generic term “Styrofoam” is used incorrectly to refer to expanded (not extruded) polystyrene foam, such as disposable coffee cups, coolers, or cushioning material in packaging, which is typically white and is made of expanded polystyrene beads. The term is used generically although it is a very different material from the extruded polystyrene used for actual Styrofoam™ insulation. The Styrofoam™ brand polystyrene foam, which is used for craft applications, can be identified by its roughness and the fact that it "crunches" when cut. Additionally, it is moderately soluble in many organic solvents, cyanoacrylate, and the propellants and solvents of spray paint and Dow Chemical Company go to great lengths to point out that “There’s no such thing as a STYROFOAM cup!”
Construction Insulation is of paramount importance to reduce the energy consumption of buildings. In the summer, insulation reduces the heat flow from a hotter exterior to a cooler interior environment. In winter, insulation reduces the heat loss from a warmer interior to a colder exterior. The resistance to this heat flow through a material, including insulation is called “thermal resistance” and this thermal resistance is commonly referred to as an R-value. So first, let’s look at and understand R-Value.
The R-value is a measure of thermal resistance used in the building and construction industry. Under uniform conditions it is the ratio of the temperature difference across an insulator and the heat flux (heat transfer per unit area per unit time, \dot Q_A) through it or R = \Delta T/\dot Q_A. Thermal resistance varies with temperature but it is common practice in construction to treat it as a constant value to be able to compare building materials for particular application.
An R-value is a unit of thermal resistance for a particular material or assembly of materials (such as an insulation panel). The R-value depends on a solid material's resistance to conductive heat transfer. For loose or porous material, the R-value accounts for convective and radiative heat transfer through the material. However it does not account for the radiative or convective properties of the material's surface, which may be an important factor for some applications.
R is expressed as the thickness of the material normalized to the thermal conductivity. The unit thermal conductance of a material is the reciprocal of the unit thermal resistance. This can also be called the unit surface conductance.
In a nutshell - The higher the value of R, the better the building insulation's theoretical effectiveness.
A complete understanding of the R-value performance of insulation over its lifetime is critical to designing buildings that achieve reduced energy consumption throughout their lifetime – otherwise extrapolated as a part of their Carbon Footprint or incorporated in a LEED classification. This is especially important in areas that are subject to extreme climates with highly variable temperature swings between summer and winter or night to day – such as the climate experienced in Ontario Canada or New York, New Jersey and most of the North East of North America.
Most people understand that the higher the R-value, the greater the insulating power of an insulation. However, many people do not understand that the R-value of polyiso and XPS including STYROFOAM™ sheets is lost over the lifetime of the product. Long-term thermal resistance (LTTR) test methods have evolved considerably in the past decade and two test methods are commonly used to report R-value for materials with trapped gases other than air. The test methods are ASTM C1303 and CAN/ULC-S770. Both test methods provide a method to estimate the long-term thermal resistance or long-term R-value of insulations. Each of the methods involves cutting thin sections approximately 3/8” (10 mm) from a sample of thicker insulation. Due to the thin size of the samples, diffusion of air in and trapped gases out is quicker than for the original thicker sample and so the R-value loss of the thin sections can then be used to predict the R-value loss of the original thickness material.
It is well understood that polyiso and XPS insulations trap gas in their cells other than air and polyiso and XPS will lose the gas over time. This is a natural process of materials coming to equilibrium with the environment. As this encapsulated gas assists with providing enhanced R-value then the R-value of the insulation will consequently and inevitably drop over time. The trapped gases in the cells of polyiso and XPS foam assist to provide an initially higher R-value than that of Rigid High Density EPS Insulation, which may prove misleading when specifying which insulation board to use for maximum insulation. During the life of these foams then air from the atmosphere diffuses in and the trapped gases diffuse out with the result being that polyiso spray foam and XPS extruded polystyrene foam lose R-value over their lifetime.
Unlike polyiso and XPS, the R-value of EPS expanded polystyrene foam is permanent and the LTTR values commonly published from testing to ASTM C1303 or CAN/ULC-S770 is an estimate for the R-value of the insulation after five years. Many insulation manufacturers are promoting LTTR without providing a clear understanding that LTTR is an estimate for the R-value of the material after only five years. The concept of a five year R-value being equal to the “time-weighted 15 year average” is also often used by polyiso and XPS manufacturers. This approach assumes that the higher R-value established in years 1-4 is weighted by the inevitably lower R-value of the insulation in years 6-15. However the EPS Industry Alliance maintain that neither the five year R-value, nor the time-weighted 15 year average approach is appropriate for use in building design due to the proven fact that the R-values of polyiso and XPS continue to decline below the LTTR published five year numbers. Starting in year five and for the remaining life of the insulation, the R-values of polyiso spray foam and XPS including STYROFOAM™ sheets are below LTTR published R-values.
50 YEAR R-VALUE Most insulation users are interested in a true long-term thermal R-value for their insulations. A time period appropriate for building application is 50 years. In order to avoid confusion with the existing LTTR numbers commonly published, we recommend the use of a 50 year R-value be used for insulation specifications. A 50 year R-value is a more suitable long-term R-value for use in building design. The 50 year R-value can easily be determined using the existing protocol described in ASTM C1303 or CAN/ ULC-S770.
EPS provides a permanent lifetime R-value. The five year and 50 year R-values for EPS are the same as the initial R-value since the gas trapped in the cells of EPS is atmospheric air. Unlike polyiso and XPS, EPS does not lose R-value over time. This is one reason the National Institute of Standards & Technology (NIST) chose EPS as the Standard Reference Material for Thermal Conductivity (SRM 1453), using a lot of samples certified in 1996 that still provide the same R-value today. (See here for the Long-Term Thermal Resistance & R-Value Performance Report from the EPS Industry Alliance.)
Moisture resistance is an important issue for architects, contractors, and specifiers to consider in high humidity North Eastern American & Canadian states like Ontario, New York and New Jersey when selecting below-grade, cavity wall, and under-slab insulation. Claims by the XPS industry on moisture resistance conflict with those made by the EPS industry because one source is using controlled laboratory testing and the other is using real-life field testing.
The XPS industry prefers to quote the figures obtained during controlled underwater tests, submerging the XPS for a relatively short period of time, depending upon the type of XPS tested and the test parameters. Usually the submersion time is somewhere between 2 and 24 hours. In this scenario, XPS appears to win over EPS because it resists water absorption in the near-term quite well. However the reality is more revealing, as the XPS takes in moisture more slowly than EPS, it also releases it very slowly leading to higher retained humidity values in actual long term usage – which are also proven to impact detrimentally on XPS product’s R-Values over time.
A recent 15-year field study by a leading Polystyrene foam manufacturer demonstrates actual performance in the ground after 15 years, where the results show dramatic differences in the real world performance of Rigid Expanded Polystyrene Insulation (EPS) in comparison with Extruded Insulation (XPS) such as Styrofoam™.
EPS is the clear winner for high quality, resistant, sustainable and recyclable construction insulation products, and Forte EPS based in Ontario manufactures and ships a competitively priced range of products including FORTEFY THERMO & THERMO HD RIGID EPS INSULATION, THERMO HDS HIGH DENSITY RIGID EPS INSULATION, FORTEFY GEOFOAM EPS BILLET, THERMO FLO EXTERIOR EPS FOUNDATION INSULATION & DRAIN BOARD and Industry leading ICF Concrete Deck Forms to demanding clients in the construction industry of North East North America, Including Ontario, Quebec, New York state, New York City and New Jersey. For the best rates on Construction Grade High Density Polystyrene Sheet Insulation in Eastern Canada and USA, Contact us here.