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 the case of National Fiber's Cel-Pak and NuWool, over-issue newsprint is upcycled into cellulose insulation.

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 fiberglass 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.