Eave—The line along the sidewall formed by the intersection of the planes of the roof and wall.

Eave height—The vertical dimension from finished floor to the eave.

Eave strut—A structural member at the eave to support roof panels and wall panels. It may also transmit wind forces from roof bracing to wall bracing.

Edge stripping—Application of felt strips cut to narrower widths than the normal felt roll width to cover a joint between flashing and built-up roofing.

Edge venting—The practice of providing regularly spaced protected openings at a roof perimeter to relieve water vapor pressure in the insulation.

Efflorescence—A deposit or encrustation of soluble salts, generally white and most commonly consisting of calcium sulfate, that may form on the surface of stone, brick, concrete, or mortar when moisture moves through and evaporates on the masonry. Often caused by free alkalies leached from mortar, grout, or adjacent concrete.

Elastic design—A design concept utilizing the proportional behavior of materials when all stresses are limited to specified allowable values.

Elasticity—The property of matter by virtue of which it lends to return to its original size and shape after removal of the stress which caused the deformation.

Elastomer—A macromolecular material that returns rapidly to its approximate initial dimensions and shape after subsequent release of stress.

Electric charge—A physical phenomena caused by an isolated imbalance between the number of protons and electrons in a substance.

Electric force field—The invisible forces created by electric charges of opposite polarity.

Electrode potential—The potential of a half cell as measured against a standard reference half cell.

Electrolyte—A liquid, most often a solution, that will conduct current.

Electron-volts (eV)—An extremely small unit used in measuring the energy of nuclear constituents. It is the energy developed by an electron falling through a potential difference of 1 volt.

Embedment—(1) The process of pressing a felt, aggregate, fabric, mat, or panel uniformly and completely into hot bitumen or adhesive to ensure intimate contact at all points; (2) The process of pressing granules into coating in the manufacture of factory prepared roofing, such as shingles.

Emissivity—A quantity characterizing the radiant emittance of a substance equal to the ratio of power of its radiation to the power of radiation of a black body at the same temperature, area, and solid angle of emission. The ratio of radiant energy emitted from a surface under measurement of that emitted from a black body (the perfect emitter and absorber) at the same temperature.

Emulsion—A dispersion of fine particles or globules of a liquid in a liquid. Asphalt emulsions consist of asphalt globules, an emulsifying agent such as bentonite clay and water.

End frame—A frame at the endwall of a building to support the roof load from one-half the end bay.

End lap—The overlap where one panel or felt nests on top of the end of the underlying panel or felt.

Envelope—A continuous edge seal formed by extending one ply of felt beyond the edge of the assembly. After other plies or insulation are in place, the extended ply is turned back and adhered.

E/P (Elastoplastic)—Pertaining to polymeric materials, including thermoplastic and elastomeric categories.

EPDM—A synthetic elastomer based on ethylene, propylene, and a small amount of a non-conjugated diene to provide sites for vulcanization. EPDM features excellent heat, ozone and weathering resistance, and low temperature flexibility.

Epichlorohydrin rubber—This synthetic rubber includes two epichlorohydrin-based elastomers which are saturated high molecular weight, aliphatic polyethers with chloro-methyl side chains. The two types include a homopolymer (CO) and a copolymer of epichloro-hydrin and ethylene oxide (ECO). These rubbers are vulcanized with a variety of reagents that react difunctionally with the chloromethyl group, including diamines, urea, thioureas, two mercaptoimidazoline, and ammonium salts. Excellent oil resistance.

Equilibrium moisture content—(1) The moisture content of a material stabilized at a given temperature and relative humidity expressed as percent moisture by weight; (2) The typical moisture content of a material in any given geographical area.

Erection—The on-site assembling of fabricated components to form a complete structure.

EVA—Family of copolymers of ethylene and vinyl acetate used for adhesives and thermoplastic modifiers. They possess a wide range of melt indexes.

EVT (Equiviscous Temperature)—The temperature at which the viscosity of an asphalt is appropriate for application. Viscosity units are generally expressed in centipoise or centistokes. Tolerance on EVT is usually ± 25°F (± 14°C).

Exotherm—Heat generated in a chemical reaction.

Expansion joint—A structural separation between two building elements that allows free movement between the elements without damage to the roofing or waterproofing system.

Expected total error—Where different portions of a testing procedure have measurement errors, this refers to the accumulated effects of these individual errors.

Exposure—(1) The transverse dimension of a roofing element not overlapped by an adjacent element in any roofing system. The exposure overlapped by an adjacent element in any roofing system. The exposure of any ply in a membrane may be computed by dividing the felt width minus 51 mm (2 in.), by the number of shingled plies; thus, the exposure of 914 mm (36 in.) wide felt in a shingled, four ply membrane should be 216 mm (8-1/2 in.); (2) The time during which a portion of a roofing element is exposed to the weather.

Exposure limits—The established maximum exposure to a health hazard, usually expressed in units per unit time.

Extension—The increase in length produced in the gage length of a test specimen during a creep test.

Extra steep asphalt—See Super steep asphalt

Extractables—Components or substances removable from a solid or liquid mixture by means of an appropriate solvent.

Extruder—A machine with a driven screw that forces ductile or semisoft solids through a die opening of appropriate shape to produce continuous film, strip, or tubing.