One of the key elements of the building envelope is insulation because it can help dictate comfort for the family. Use of insulation helps create the peace of mind that comes with knowing we have made an investment that not only serves our family, but is energy and cost-efficient. A variety of plastic products may be the solution for the home, including housewraps and foams: spray polyurethane foam (SPF) and rigid foams made with polyurethane (Polyiso), extruded polystyrene (XPS) and expanded polystyrene (EPS). Learn more about how EPS reduces global warming.
Many people do not know rigid and blown foamed insulation is made of plastics or that the use of plastics in building and construction often uses less energy and creates less greenhouse gas per application than traditional materials. For a free fully documented, peer-reviewed and published “cradle-to-gate” life cycle inventory (LCI) of nine major plastic resins and two polyurethane precursors, click here. For additional LCI information on a particular product to compare environmental impacts, contact the specific product manufacturer.
The same material we use to wrap our bodies—in the form of Gore-Tex clothing—or to ship our goods—in overnight packages—can also wrap our building envelope. Plastic house wrap, coupled with insulating plastic foams and sealants, adds another layer of protection to a home. House wrap has been shown, in the Franklin Associates Study, to reduce infiltration of outside air by as much as 10 to 50 percent. By reducing air infiltration of outside air, we reduce the energy required to heat or cool a home—saving the average homeowner thousands of dollars over the life of a 30-year mortgage. House wrap insulation can also help reduce airborne pollutants that otherwise penetrate your home’s envelope.
Spray polyurethane foam (SPF) and rigid foams made with polyurethane (Polyiso), extruded polystyrene (XPS) and expanded polystyrene (EPS) are growing solutions for insulation systems.
SPF conforms to the surface to which it is applied and forms a seamless layer of insulation, thus filling energy-wasting holes and gaps around pipes, outlets, windows and more. Since SPF fills in gaps and seams during application, it is increasingly being used as an air barrier in buildings. The material—cut into sheets, slabs or any desired design, as well as sprayed to meet specific building code requirements or custom designs—serves as a durable design solution since it often arrives at the job site as a liquid, saving on transportation costs and reducing waste.
This beneficial “air barrier” effect can be achieved by rigid polyurethane (Polyiso) foams installed properly with taped seams. Structural insulated Panels (SIPs) also demonstrate this same beneficial air barrier trait. SIPs can be made from Expanded polystyrene (EPS) or Extruded polystyrene (XPS). A SIP is two layers of 5/16th inch OSB with the expanded or extruded polystyrene encased between those two layers forming a rigid wall structure without normal “studs” being needed. See the June issue of Modern Materials magazine for National Association of Home Builders wall performance tests showing how plastics building materials can outperform typical “stick and batt” construction under real-world windy conditions.
Can SPF and rigid plastic foam insulations (SIPs, Polyiso, EPS and EPS) exhibit green characteristics? Yes. By inhibiting heat flow and helping create air barriers, plastic building products can help save energy heating and cooling the structure over time. This lessens the environmental “footprint” of the building over time. Savings in manufacture of plastic building products have been validated as well, to show that plastic materials save approximately 467.2 trillion BTU of energy a year as compared to alternative materials. The energy saved is enough to meet the average annual energy needs of 4.6 million U.S. households.
According to a 2000 study by Franklin Associates, for the entire country, the annual savings in energy cost would be $2.58 billion or $128.6 billion over 50 years if all houses were insulated with plastic foam insulation.
In commercial applications, SPF is typically applied over existing roof systems, which avoids scrap and waste while the product also provides exceptional energy savings through high R-values with no seams, longevity, resistance to leaks, and little degradation due to UV rays.
See Details From a New Study on Polyurethane Insulation in Europe:
- Low Thermal Conductivity
- Mechanical Properties
- Resistance to Moisture
- Reaction to Fire
- Stability Temperature Resistance
- Chemical Stability
The Energy Efficient Foam Coalition’s mission is to promote the benefits of foam insulation products and to provide factual information that brings a credible, science-based perspective to discussions surrounding the use of flame retardants in rigid foam insulation.
Polyiso, XPS, and EPS Board
Polyisocyanurate (polyiso) insulation is an excellent choice for a variety of renovation applications because of its excellent energy conserving qualities. It has a high R-value per inch, which helps reduce energy costs for the homeowner over the life of the building—an especially important factor considering the expected sustained rise in fuel costs.1
Polyisocyanurate (polyiso) insulation is a thermoset, closed-cell, rigid foam plastic insulation manufactured in board form. Via a continuous lamination process, liquid raw materials that expand and become light (yet strong) are applied between engineered facing materials. These facings provide strength, improve rigidity, and enhance thermal performance. Polyisocyanurate (polyiso) is most commonly supplied as 1.2-x-2.4-m or 1.2-x-2.7-m (4-x-8-ft or 4-x-9-ft) sheets in various thicknesses.
The boards are available in a range of compressive strengths, meeting various marketplace requirements. Compressive strength refers to the ability of a rigid foam plastic board to resist deformation and maintain its shape when subjected to a force or load. Common construction applications require compressive strengths adequate for polyisocyanurate (polyiso) to maintain its shape during installation, as well as during use. ASTM International C 1289, Specification of Polyiso Insulation, mandates all polyisocyanurate (polyiso) products have a minimum stated compressive strength of 110 kPa (16 psi).
XPS Sheathing From Manufacture to Installation
Extruded polystyrene (XPS) foam begins as a solid granule of polystyrene resin. The plastic granules are fed into an extruder, where they are melted and mixed with critical additives to form a viscous fluid. Next, a blowing agent is injected to enable the plastic product’s expansion. Under carefully controlled heat and pressure conditions, the plastic mixture is forced through a die into the desired shape. The rigid foam plastic is then trimmed to the final product dimensions and is usually recognized as boards.
This continuous process produces a closed-cell structure that looks like a mass of uniform bubbles with common walls between them. A continuous smooth skin on the top and bottom also forms.
The closed-cell structure of extruded polystyrene (XPS) foam imparts excellent long-term strength and durability. Products are available in a range of compressive strengths to suit varied application needs. Due to its inherent physical properties, this strength does not depend on the use of facers or laminates, which can sometimes be compromised during installation. However, extruded polystyrene (XPS) foam faced-products are available to add extra strength when specified for a particular application. Extruded polystyrene plastic also comes in a wide variety of sizes, and up to a thickness of 102 mm (4 in.) to suit many applications.
Properly installed extruded polystyrene (XPS) foam can also improve a building’s energy efficiency by providing a complete layer of insulation on the wall. This reduces air movement through the wall that can rob energy. Insulation between studs does not necessarily offer complete insulation value because wood studs and other framing members are not insulated. This phenomenon is called thermal bridging and can dramatically decrease thermal performance of the building.
Since residential wood framing typically makes up about 25 percent of the wall area (taking into account window and door framing), a quarter of the wall is uninsulated when only cavity insulation is used. As such, extruded polystyrene (XPS) foam sheathing can provide insulating value to the entire wall area. Aside from its inherent insulating performance, extruded polystyrene (XPS) foam sheathing, when properly installed and seams taped, can also greatly reduce air leakage through walls, which can improve energy efficiency and comfort.
An essential attribute for sustainable building products, especially insulation, is the ability to function properly over its useful life without physical property performance degradation. In fact, good long-term insulation performance is needed to correctly design a building’s heating and air-conditioning systems.
Extruded polystyrene (XPS) foam can also have advantages due to its ability to assist with moisture management, resisting both water absorption and freeze/thaw cycles. When traditional insulation absorbs water, its thermal performance can be compromised over time.
EPS begins as a polystyrene bead or pellet. The pentane-loaded bead is then exposed to pressurized steam, which causes the polystyrene to expand and mold into the desired shape and density needed. Manufacturing EPS does not involve the use of ozone depleting chlorofluorocarbons or hydrochlorofluorocarbons (CFCs or HCFCs). The final product is a moisture-resistant, closed-cell structure consisting of 90-percent air, yet can possess a compressive strength of up to 276 kPa (40 psi). It is available in varying densities, usually from 14.4 kg/m3 to 28.8 kg/m3 (0.90 pcf to 1.8 pcf), depending on the intended application. (Higher densities can be manufactured for custom projects.)
EPS possesses ideal physical and mechanical properties for most insulating needs. As a result of its manufacturing process, aging does not effect the long-term thermal resistance (LTTR) of EPS. Due to its flexibility and versatility, it can be cut into sheets, slabs, or any desired design to meet specific building code requirements, as well as customized designs. EPS is used as insulation in walls, roofs, and foundations, and serves as an integral component of structural insulated panels (SIPs), insulated concrete forms (ICFs), and exterior insulation and finish systems (EIFS). From humble beginnings, EPS has grown into one of the most versatile insulating materials in construction today.