| La Nina | La Nina is an extensive cooling of the central and eastern Pacific Ocean that occurs less frequently than El Nino and is its climatic opposite. It occurs when easterly trade winds in the tropics strengthen, intensifying the up-welling of cold waters off the coast of Peru and Ecuador. The effects of La Nina are strongest during the Northern Hemisphere winter, and include abundant snowfall from the interior of British Columbia to the Great Lakes region |
| Laminate | A product made by bonding together two or more layers (laminations) of material or materials. |
| Laminate, Paper-Based | A multilayered panel made by compressing sheets of resin-impregnated paper together into a coherent solid mass. |
| Laminated Timbers | An assembly made by bonding layers ofveneer or lumber with an adhesive so that the grain of all lamina-tions is essentially parallel. (1) Horizontally Laminated Timbers—Laminated timbers de-signed to resist bending loads applied perpendicular to the wide faces of the laminations. (2) Vertically Laminated Timbers—Laminated timbers designedto resist bending loads applied parallel to the wide faces of the laminations. |
| Laminated Veneer Lumber (LVL) | A structural lumber manufactured from veneers laminated into a panel with the grain of all veneer running parallel to each other. The resulting panel is normally manufactured in 19- to 38-mm (3/4- to 1-1/2-in.) thicknesses and ripped to common lumber widths of 38 to 290 mm (1-1/2 to 11-1/2 in.) or wider. |
| Lap Joint | A joint made by placing one member partly over another and bonding the overlapped portions. |
| Latewood | The portion of the growth ring that is formed after the earlywood formation has ceased. It is usually denser and stronger mechanically than earlywood. |
| Latex Paint | A paint containing pigments and a stable water suspension of synthetic resins (produced by emulsion polymerization) that forms an opaque film through coalescence of the resin during water evaporation and subsequent curing. |
| Lathe Checks | In rotary-cut and sliced veneer, the fractures or checks that develop along the grain of the veneer as the knife peels veneer from the log. The knife side of the veneer where checks occur is called the loose side. The opposite and log side of the veneer where checking usually does not occur is called the tight side. |
| Layup | The process of loosely assembling the adhesive-coated components of a unit, particularly a panel, to be pressed or clamped. |
| Lbs/MSGL | Abbreviation for rate of adhesive application in pounds of adhesive per 1,000 ft2 of single glueline (bondline). When both faces of an adherend are spread as in some plywood manufacturing processes, the total weight of adhesive applied may be expressed as Lbs/MDGL (pounds per 1,000 ft2 double glueline). |
| LCA | Life Cycle Assessment. An examineation opf all aspects opf a produts life from cradle to grave. |
| LEED® | The Leadership in Energy and Environmental Design rating system. It represents the U.S. Green Building Council's effort to provide a national standard for what constitutes a "green building". (www.usgbc.org) |
| LEED® - Leadership in Energy and Environmental Design | This is a building performance rating system administered by the US Green Building Council and the Canadian Green Building Council. (See USGBC and CaGBC) |
| LEED® Accredited Professional (LAP) | A professional who has successfully passed the LEED® Accreditation exam and is knowledgeable in green building design practices. |
| Life Cycle Cost Analysis | The total cost of a product of material including the initial cost and the long term maintenance costs. This approach can often be used to justify more expensive and energy efficient systems which save money over the life of the product. |
| Light Pollution | Stray light that escapes off site and affects nocturnal ecosystems. Light pollution can also cause glare, compromise astronomical research and is an inefficient use of energy. |
| Lignin | The second most abundant constituent of wood, located principally in the secondary wall and the middle lamella, which is the thin cementing layer between wood cells. Chemically, it is an irregular polymer of substituted propylphenol groups, and thus, no simple chemical formula can be written for it. |
| Living Machine | Living Machine systems use aquatic plants, algae, etc. as reactors to clean different waste water streams by mimicking natural processes. |
| London Dispersion Forces | Intermolecular attraction forces between nonpolar molecules that result when instantaneous (nonpermanent) dipoles induce matching dipoles in neighboring molecules. London forces also exist between polar molecules. |
| Longitudinal | Generally, parallel to the direction of the wood fibers. |
| Loose Knot | A knot that is not held firmly in place by growth or position and that cannot be relied upon to remain in place. |
| Low-E | Low emissivity glazing has a thin metallic coating applied to glass or plastic. It reduces heat loss and solar heat gain through glazing. |
| Lumber | The product of the saw and planing mill for which manufacturing is limited to sawing, resawing, passing lengthwise through a standard planing machine, crosscutting to length, and matching. Lumber may be made from either softwood or hardwood. |
| Lumber for Dimension | The National Dimension Manufacturers Association defines both hardwood and softwood dimension components as being cut to a specific size from kiln-dried rough lumber, bolts, cants, or logs. Dimension components include Flat Stock (solid and laminated) for furniture, cabinet, and specialty manufactures. This term has largely superceded the terms "hardwood dimension" and "dimension parts." |
| Lumber Nominal Size | As applied to timber or lumber, the size by which it is known and sold in the market (often differs from the actual size). |
| Lumber, Boards | Lumber that is less than 38mm (2" nominal) thick and 38mm ( 2" nominal) or more wide. |
| Lumen | In wood anatomy, the cell cavity. |