Glossary

This is the air leakage rate, defined as the number of air changes per hour that occur in a building. This is determined with a blower door with a 50 pascal pressure difference between the inside and outside of a building and then extrapolated for the natural building pressures that occur annually.

Just like it sounds, an air barrier is any physical barrier that physically prevents the movement of air and doesn’t have holes, crack, penetrations, etc. in it.

Short version: Insulation is all about preventing this. Long version: Air infiltration refers to either the process of unconditioned air entering a conditioned space (like outside air getting into a building) or conditioned air migrating to an unconditioned space (like heated air escaping to an attic or to the outdoors.) Air drives change with the seasons, and are affected by things like air pressures and wind. As a rule, however, air will move from the hot side to the cold side. That means during the winter, air is more likely to move from the inside to the outside, while the reverse is true in the summer. Air infiltration is a direct result of several factors, including unsealed penetrations (joints, cracks, and holes), insulation materials of insufficient density to effectively limit or prevent infiltration, poor installation, lack of air sealing, etc. Air infiltration is one of the four ways that heat moves through a structure.

Short version: It’s how you plug stuff up, and  you should do it before your insulate. Long version: The process by which very small holes, cracks, penetrations and joints which could allow the passage of air from the interior to the exterior, or vice versa, or between areas of a building (such as living space to attic space) are sealed or closed off, using caulking, canned foams, etc. Proper air sealing should precede any insulation job.

An inorganic salt often used to reduce the amount of borate needed to achieve a Class A fire rating in cellulose insulation. Ammonium sulfate may, in the presence of sufficient moisture, produce ammonia smells and lead to the corrosion of metal pipes, fasteners, etc. GreenFiber produces several products, including Cel-Pak, that are an all-borate formulation and which do not include any ammonium sulfate in them in their manufacture.

Short version: Places to install insulation. Long version: In terms of structures and insulation, these words refer to any enclosed space that can effectively contain insulation. For example, a stud bay in a wall will be bounded by a top and bottom plate, wall studs on the left and right, sheathing on the exterior and wallboard on the interior, forming an assembly. The same would hold true for a rafter bay in a cathedral ceiling. Both of these would be referred to as “assemblies.”

American Society for Testing and Materials - ASTM International is one of the largest voluntary standards development organizations in the world and a source for technical standards for materials, products, systems, and services.

A test method using flame spread and smoke-developed densities, which is designed to measure the relative burning behavior of a material. Materials with lower flame spread and smoke-developed values are considered more “fire safe” since they would give occupants a better chance of escaping a fire.

Plain speak version: Sunlight is attenuated by dark glasses, X-rays are attenuated by the metal lead, and sound is attenuated by dense packed cellulose insulation. Technical version: The gradual loss in intensity of any kind of flux, or rate of flow, through a medium.

A blower door is a tool used by an Energy Auditor which lowers the air pressure inside a building, allowing outside air to flow in through all unsealed cracks and openings.

Blower doors consist of a frame and flexible panel that fits in an exterior doorway, a variable-speed fan, a pressure gauge to measure the pressure differences inside and outside the home, and instruments for measuring airflow.

Blower doors are either calibrated or uncalibrated. The latter can only locate leak paths in a home, but can’t measure the overall tightness of the building, expressed in air exchanges per hour. Use of a calibrated blower door is preferred, and will provide data that quantifies the amount of air leakage and the effectiveness of air-sealing.

An unfilled assembly. (See Assembly). May also refer to an open assembly before the application of interior wallboard, paneling, etc.

As it concerns cellulose insulation, coverage refers to either a) the square footage of an open area, such as an attic floor, that can be covered to a specified depth by a single bag of material or b) the cubic footage of a cavity or assembly that can be dense packed, typically to 3.5 lbs. of material per cubic foot, by a single bag of material.

An ASTM E-84 fire test used to determine the fire performance in wall and roof / ceiling assemblies. Class A or Class 1 ratings pertain to those products that have a flame spread of 25 or less and a smoke developed rating of 450 or less. A Class A or 1 rating is considered the most 'fire safe'. These fire ratings also influence the code decisions on what materials can be left exposed without the need for a 15 minute thermal barrier such as drywall.

The standard unit for measuring air leakage in buildings with a blower door. These are expressed in Cubic Feet of air per Minute at a pressure differential of 50 pascals, typically between the inside of the building and the outside.

Conduction (or heat conduction) is the transfer of thermal energy between neighboring molecules in a substance due to a difference of temperature. It always takes place from a region of higher temperature to a region of lower temperature, and acts to equalize temperature differences. Conduction is one of the four ways heat moves through a structure.

Refers to airborne heat carried through a structure or building assembly, one of the four ways in which heat moves through a structure.

The Consumer Product Safety Commission

Damp sprayed cellulose refers to cellulose insulation to which a small amount of moisture is added during application. It is most often applied in new construction where cavities are open, just before the application of interior coverings such as wallboard, drywall or paneling. The moisture serves to activate starches in the cellulose, allowing it to adhere both to itself and to the surfaces of the cavity.

'Dense packed' refers to cellulose insulation installed in a cavity or assembly, either dry-blown or damp-sprayed, to a density of 3.2-3.5 lbs. of material per cubic foot of space, or approximately twice the settled density of the material. The process by which a space is dense packed is referred to as "dense packing".

An acronym for 'Do-It-Yourself'.

Embodied energy is a measurement of the energy that it takes to manufacture something, and one way to quantify a product's environmental impact. Simply put, if it takes less energy to manufacture one product versus another, it means that product has less negative impact on the environment - sometimes a lot less - and that's good for everyone. Greenfiber is especially stingy in this regard, when compared to the alternatives. Relative to cellulose insulation, fiberglass and foam insulations take much more energy to produce.


A more comprehensive approach to embodied energy is to look at the Global Warming Potential and Life Cycle Analysis measurements relative to energy usage. According to the University of Minnesota's 'Minnesota Sustainable Housing Initiative' research, by these measures, when compared to cellulose insulation, the life cycle of fiberglass batts feature:


  • 683% greater energy consumption
  • 728% greater global warming potential (in lbs. of CO2) and an
  • 1,850% higher air pollution index

That's not good. Sprayed foams? They take far more energy to produce than fiberglass, which means they have far worse environmental effects.


If you want to save money on energy and take it easier on the environment over time, Greenfiber cellulose is a great choice! Insulating your home or business with our cellulose insulation products is an opportunity to do well (save money) by doing good (lessening your environmental impact)!

An Energy Audit is a comprehensive evaluation of a structure to determine its relative efficiency, the efficiency of its systems and the need for air sealing. It typically is performed by a trained professional, who prepares a list of recommendations or upgrades to be considered in lowering a structures total energy usage.

When referring to cellulose insulation, 'fiberized' or 'fully fiberized' refers to the reduction of the paper raw material to the original state of long cellulose fibers, bearing no resemblance to the source material. Proper and complete fiberization is key to both the insulating and fire resistance capabilities (after the addition of mineral borate) of cellulose insulation.

Fire blocking refers to both the component and the process of installing a physical barrier, called a 'fire block' and typically made out of wood, in a cavity, the purpose of which is to slow the progression of fire and/or flame in the event that a cavity is compromised during a fire. Fire blocking can be either eliminated or greatly reduced through the use of cellulose insulation, due to its inherent capability to prevent the spread of flames.

In construction, a firewall is a wall assembly with a code-rated fire resistance intended to slow the spread of fire from one side to the other.

Greenwashing is a negative term and has a meaning similar to that of 'whitewashing'. It is most often used to describe efforts by corporations to portray themselves or their products as more environmentally friendly or responsible than is the actual case. From a marketing standpoint, it is considered an exaggeration of environmental benefit without discussing environmental downsides.

Refers to the paper making process in which 10% or more or the wood pulp is produced from mechanical means such as grinders.

The transfer of thermal energy by conduction, convection and radiation from areas of higher energy intensity, or warmer areas, to lower energy intensity, or cooler areas.

Resistant to water, non-absorptive. Glass fiber and sprayed foam insulations are typically hydrophobic, that is, they do not readily absorb and manage moisture, but rather provide possible condensing surfaces.

Readily take up and/or retain moisture. When referring to cellulose insulation, the hygroscopic properties of cellulose allow it to manage the natural humidity drives that occur in all structures, allowing assemblies to gradually transmit airborne moisture.

International Building Code

Impact Insulation Class refers to how well impact noise is transmitted through a floor system. Unlike airborne sound transmission, impact noise is primarily transmitted through the floor joists and therefore needs to be separated with resilient channel. The higher the value, the better the floor isolates the sound.

These are the open spaces or pathways that exist and interconnect in buildings between the walls and ceilings. These offer pathways for fire, heat, odor, insects and vermin to travel and remain hidden from the building occupants.

International Residential Code

A term used to describe installation in an unrestrained space or cavity, such as in an attic, where cellulose would be loose-blown over the attic floor.

The National Fire Protection Association

Particularly when referring to indoor air quality, is the slow release from a material, over a period of time, of a gas or chemical that was previously contained in or trapped in that material, either by design or use in the manufacturing process.

Over-issue or over-issued newsprint refers to newspapers that are printed but not purchased by consumers. For example, the Boston Globe may produce and distribute 1,000,000 newspapers on a given day, and have 250,000 returned unpurchased. These are over-issue newsprint and Greenfiber purchases them in bulk for upcycling into cellulose insulation.

A measurement used to determine how fast water vapor is able to move through the pores of a material. A material with a perm rating of less than one, as defined by ASTM E-96, is commonly referred to as a vapor barrier.

Thermal radiation is one of the four ways by which heat moves through a structure. Thermal radiation is electromagnetic radiation emitted from the surface of an object, due to the object's temperature. Infrared radiation from a household radiator or electric heater, or the light emitted from a typical incandescent light bulb, are common examples of thermal radiation.

R-Value is a measure of a material's thermal conduction (see conduction). Unfortunately, R-Value has taken hold in the consumer's mind as a universal method for comparing insulations - the higher the R-Value, the better the insulation performance, which isn't the case. R-Value measures only thermal conduction, just one of the factors that determine how an insulation product will perform in the real world.

R-value is a measure of resistance to heat flow through a given thickness of material. While R-Value is one way of comparing insulations — the higher the R-Value, the better the insulation performance, it is just one of the factors that determine how an insulation product will perform in the real world. Insulation is, first and foremost, meant to stop the movement of heat. The problem with using R-Value as the sole yardstick of an insulation's effectiveness is that heat moves out of your home or office in four ways: by conduction (which R-value measures), and by convection, radiation, and air infiltration (none of which R-value measures).

Retrofitting refers to the process of installing insulation in a finished, presumably older, structure. The process involves, typically, removing a band of exterior siding for each story, drilling holes to allow access to stud bays, installing dense-packed cellulose insulation, sealing the holes and replacing the siding.

Settled density refers to the final density of a material after a period of time, allowing for natural settlement, vibration, the effects of gravity, etc. It is the density of a material after these natural settlement processes have concluded. Cellulose insulation has a settled density of app. 1.5 lbs. per cubic foot.

Open cell/Low Density, Closed Cell/High Density

Cellulose insulation that contains additional amounts of starch or binders that when activated with moisture allows the cellulose, in theory, to be applied in an attic loose-fill application and not experience any settling.

Stabilized insulation reduces settling and decreases the amount of cellulose needed. This can prove advantageous at reducing the overall weight on the ceiling drywall helping prevent possible sag.

Stack effect is the movement of air into and out of buildings, chimneys, flue gas stacks, or other containers, driven by buoyancy. Buoyancy occurs due to a difference in indoor-to-outdoor air density as a result of temperature and moisture differences. The result is either a positive or negative buoyancy force. The greater the thermal difference and the height of the structure, the greater the buoyancy force, and thus the stack effect. The stack effect is also referred to as the 'chimney effect', and it helps drive natural ventilation and infiltration.

The Sound Transmission Class (STC) rating is a single-number rating of a material's ability to resist airborne sound transfer at the frequencies 125-4000 Hz. In general, a higher STC rating indicates better airborne sound attenuation performance than the same or similar material with a lower rating. Dense-packed cellulose insulation has a higher STC rating than either glass fiber or sprayed foam insulations.

An agent that reduces the surface tension of liquids so that the liquid spreads out, rather than collecting in droplets.

A thermal bridge is a component or series of components (an assembly) in a building envelope through which heat transfers at a substantially greater rate than the surrounding area. Another way to picture a thermal bridge is as a chain of low-R-Value materials that provide a direct path from the exterior of a building to the interior, uninterrupted by any air space or traditional insulating material.

For example, the assembly consisting of interior drywall, the stud that it is in contact with, the sheathing that contacts the stud, and the siding that contacts the sheathing, represents a direct thermal 'bridge' from the exterior to the interior of a structure. Because these materials have substantially lower R-Values, or resistance to heat conduction, than cellulose insulation, they represent a 'faster" or 'more direct' path for heat to exit the building in winter or enter it in summer.

The thermal envelope of a structure consists of the structure's foundation, walls, roof, windows, and doors, considered as a system. The thermal envelope of a structure controls the flow of energy between the interior and exterior of that structure.

Thermal radiation is one of the four ways by which heat moves through a structure. Thermal radiation is electromagnetic radiation emitted from the surface of an object, due to the object's temperature. Infrared radiation from a household radiator or electric heater, or the light emitted from a typical incandescent light bulb, are common examples of thermal radiation. Thermal radiation is one of the four ways heat moves through a structure.

Thermography, relative to assessing the insulation and/or air leakage in a structure, measures surface temperatures through the use of an infrared still camera. These cameras see light, invisible to the naked eye, in the heat spectrum. The images record the temperature variations of the building's surfaces, where white typically indicates warmer regions and black indicates colder areas. These images are useful in determining the need for air sealing and insulation, 'before and after' assessments, distinguishing air leakage from moisture leakage, etc.

An unvented roof assembly is a sealed component of a roof, such as a rafter bay, that has no mechanical means of ventilation, such as soffit vents or ridge vents. It is often seen in the construction of cathedral style ceilings.

Similar to recycling, upcycling is the practice of taking something that is disposable and transforming it into something of greater use and value.

In terms of insulation, any material that prevents the transmission of moisture from one side of a cavity or assembly to another. Vapor barriers are typically required by insulations that do a poor job of managing air infiltration and/or airborne moisture, such as glass fiber batts. Vapor barriers can create their own problems in a structure, especially in the Northeast, as the temperature and vapor drives shift dramatically with the seasons. In effect, a vapor barrier installed in a New England home will effectively be on the 'wrong side' of the cavity for a substantial period in any given year.

In the typical installation, cellulose insulation requires no vapor barrier and, in fact, use of a vapor barrier is not recommended for the vast majority of situations.

The process in which water moves through the pores of building materials, driven by changes in vapor pressure as a result of temperature or moisture concentration.

Ventilation refers to the introduction of fresh air into a structure. A properly air-sealed and insulated building will typically require some form of mechanical ventilation, in compliance with building codes, to assure an adequate supply of air for its occupants and for its mechanical systems, e.g., stoves, fireplaces, dryers, etc.

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