Term Description
Intensive (deep) vegetative roof system

Vegetative roof system with a growth medium greater than 10 inches deep.
Interlayment

A felt, metal or membrane sheet material used between courses of steep-slope roofing to improve the weather- and water-shedding characteristics of the primary roof covering during times of wind-driven precipitation; typically used with wood shakes.
Interlocking shingles

Individual shingles that mechanically attach to one another to provide enhanced wind resistance without reliance on sealing strips.
IRC

International Residential Code; a model building code published by the International Code Council; applies to detached one- and two-family dwellings and townhouses.
ISANTA

International Staple, Nail & Tool Association.
Isocyanate

A highly reactive organic chemical containing one or more isocyanate groups. A basic component in spray polyurethane foam systems and some polyurethane coating systems. See "A-component (A-side)" and "methylene diphenyl diisocynate (MDI)."
Joist

Any of the small timbers, metal or wood beams arranged parallel to one another and spanning from wall to wall to support a floor, ceiling or roof of a building.
Joule

A unit of energy or work in the SI system; equals the work done by a force of 1 newton, which acts over a distance of 1 meter in the direction of the force.
K or k-value

See "thermal conductivity (k)."
KEE

See ‚"ketone ethylene ester.‚"
Ketone ethylene ester (KEE)

A high molecular weight thermoplastic copolymer of ethylene, containing carbon monoxide and either vinyl acetate or acrylate monomer, which are incorporated to provide softness and polarity.
Kick-out

A lower downspout section used to direct water away from a wall.
Kick-out flashing (diverter)

A metal flashing detail installed at the eave end of a roof-to-wall transition designed to direct runoff away from the wall or wall cladding.
Laitance

A weak layer of cement and aggregate fines on a concrete surface that is usually caused by an over-wet mixture, overworking the mixture, improper or excessive finishing, or combination thereof.
Laminate

To join layers of materials together using fusion; the process of joining layers of materials together using adhesion.
Laminated shingles

See "dimensional shingles."
Lap

That part of a roofing, waterproofing or flashing component that overlaps or covers any portion of the same or another type of adjacent component.
Lap cement

An asphalt-based roof cement formulated to adhere overlapping plies or asphalt roll roofing.

Lap seam

Occurs where overlapping materials are seamed, sealed or otherwise bonded.
Launderability

The ability of a reflective coating to resist dirt pickup and the ease with which it can be cleaned, especially by natural means such as ordinary rain events.
Leaching

(1) The action of removing soluble constituents from a solid into a solution; (2) the dissolving out of soluble substances when water seeps through a roof system.

Lead

A soft, malleable, naturally weathering heavy metal; has low melting point and a high coefficient of thermal expansion.

Leeward

The direction opposite that from which the wind is blowing. The side sheltered from the wind. For comparison, see "windward."
Life-cycle assessment (LCA)

A method of evaluating a product or system by reviewing the ecological effect over its entire life. Life stages include extraction of raw materials, processing and fabrication, transportation, installation, use and maintenance, and reuse, recycling and disposal. At each stage, the product or system and its components are evaluated based on materials and energy consumed and the pollution and waste produced. LCA is an environmental review methodology.
Life-cycle cost analysis

A technique of economic evaluation that sums up the costs of a product or system during its entire life, including raw materials extraction, processing and fabrication, transportation, installation, use and maintenance, and reuse, recycling or disposal. At each stage the product or system and its components are evaluated based on the costs of materials and energy consumed and pollution and waste produced.

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