Insulation

Insulation is one of the most important components of any environmentally responsible building because it reduces energy consumption and the pollution that usually results. In this sense, any insulation material is a “green” product. Good design and appropriate levels of insulation can minimize, or even eliminate, the need for central heating and cooling in many buildings.

Insulation is a key part of the building envelopeExterior components of a house that provide protection from colder (and warmer) outdoor temperatures and precipitation; includes the house foundation, framed exterior walls, roof or ceiling, and insulation, and air sealing materials. and an important element in the entire building as an integrated system. Choosing an insulation material should include considering how it works with the rest of the wall, roof, and floor system—and what additional functions, such as air-sealing, the material might serve.

A few guidelines and issues to consider when pairing insulation materials and structural elements for maximum efficiency:

• Different types of insulation also have varying impacts in terms of their raw materials and manufacture. These life-cycle impacts should be considered along with factors such as R-valueMeasure of resistance to heat flow; the higher the R-value, the lower the heat loss. The inverse of U-factor. , air-sealing ability, and cost.
• The quality of installation also makes a big difference in how well insulation performs. If insulation is not installed properly, it will not achieve the energy savings its rated R-value would suggest. A California study concluded that a 4 percent void in fiberglass batts resulted in a 50 percent decrease in insulation effectiveness.
• The type of structural framing also affects the performance of insulation. Steel studs conduct heat much more readily than wood studs, so they create thermal bridgingHeat flow that occurs across more conductive components in an otherwise well-insulated material, resulting in disproportionately significant heat loss. For example, steel studs in an insulated wall dramatically reduce the overall energy performance of the wall, because of thermal bridging through the steel. that can bypass insulation installed in the cavities. Steel-framed exterior walls should have insulative sheathingMaterial, usually plywood or oriented strand board (OSB), but sometimes wooden boards, installed on the exterior of wall studs, rafters, or roof trusses; siding or roofing installed on the sheathing—sometimes over strapping to create a rainscreen. installed over the framing members to reduce this problem—in fact, the U.S. Department of Energy recommends that insulative sheathing should be used with steel framing in all U.S. climates.
• Fiberglass insulation is the standard in the industry today. High-density fiberglass makes the same wall cavity 15 to 20 percent more effective in reducing heat loss. Most fiberglass manufacturers now incorporate at least 30 percent recycled material, and some products are third-party certified for their recycled-glass content.
• The potential for health problems due to fiber shedding is controversial. Loose fill is a greater risk than batts in this regard. While concern has been expressed that airborne fibers might be carcinogenic, those concerns have been allayed to some extent in recent years. Most fiberglass batts are manufactured with phenol formaldehydeChemical found in many building products; most binders used for manufactured wood products are formaldehyde compounds. Reclassified by the United Nations International Agency for Research on Cancer (IARC) in 2004 as a “known human carcinogen." as a binderGlue used in manufactured wood products, such as medium-density fiberboard (MDF), particleboard, and engineered lumber. Some binders are made with formaldehyde. See urea-formaldehyde binder and methyl diisocyanate (MDI) binder. , though some products use alternative binders or no binder at all.
• Cellulose insulationThermal insulation made from recycled newspaper or other wastepaper; often treated with borates for fire and insect protection. is primarily made out of recycled newspaper, though not always from post-consumer sources. When it is damp-sprayed into open cavities, or blown into closed cavities at relatively high density, it forms a good infiltration barrier that adds to the airtightness of the house—and it‘s less contractor-dependent for quality control in filling voids than fiberglass batts.
• Rigid foam insulation applied to framing yields added infiltration resistance, reduced frame conductionMovement of heat through a material as kinetic energy is transferred from molecule to molecule; the handle of an iron skillet on the stove gets hot due to heat conduction. R-value is a measure of resistance to conductive heat flow. losses, and higher overall wall R-value. Extruded polystyrene (XPSExtruded polystyrene. Highly insulating, water-resistant rigid foam insulation that is widely used above and below grade, such as on exterior walls and underneath concrete floor slabs. In North America, XPS is made with ozone-depleting HCFC-142b. XPS has higher density and R-value and lower vapor permeability than EPS rigid insulation.) and polyisocyanurate (polyiso) rigid foam insulation used to be made with ozone-depleting CFC blowing agents, but when ozone depletion was identified as a major environmental problem, the CFCs were replaced with HCFCs through international agreement. HCFCs were eliminated from polyiso insulation as of 2003, but they are not scheduled to be totally eliminated from XPS until 2020. Polyiso is currently produced with hydrocarbon blowing agents.
• Expanded polystyrene (EPSExpanded polystyrene. Type of rigid foam insulation that, unlike extruded polystyrene (XPS), does not contain ozone-depleting HCFCs. EPS frequently has a high recycled content. Its vapor permeability is higher and its R-value lower than XPS insulation. EPS insulation is classified by type: Type I is lowest in density and strength and Type X is highest.) rigid foam has long been made with non-ozone-depleting pentane rather than HCFCs.

Insulation is one of the most important components of any environmentally responsible building because it reduces energy consumption and the pollution that usually results. In this sense, any insulation material is a “green” product. Good design and appropriate levels of insulation can minimize, or even eliminate, the need for central heating and cooling in many buildings.

Insulation is a key part of the building envelope and an important element in the entire building as an integrated system. Choosing an insulation material should include considering how it works with the rest of the wall, roof, and floor system—and what additional functions, such as air-sealing, the material might serve.

Insulation Subcategories

Products in Insulation

Our guide lists products from the Greenspec® Online Directory of environmentally preferable building products. Manufacturers and/or their representatives should visit this page to learn more about suggesting their products for inclusion.