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Replacement window glossary letter "R"
R-value. A measure of the resistance of a
glazing material or fenestration assembly to
heat flow. It is the inverse of the U-factor (R
= 1/U) and is expressed in units of hr-sq
ft-°F/Btu. A high-R-value window has a greater
resistance to heat flow and a higher insulating
value than one with a low R-value.
Radiation. The transfer of heat in the
form of electromagnetic waves from one separate
surface to another. Energy from the sun reaches
the earth by radiation, and a person's body can
lose heat to a cold window or skylight surface
in a similar way. Rail. Horizontal member of a window
sash. Reflectance. The ratio of reflected
radiant energy to incident radiant energy. Reflective glass. Window glass coated
to reflect radiation striking the surface of the
glass. Refraction. The deflection of a light
ray from a straight path when it passes at an
oblique angle from one medium (such as air) to
another (such as glass). Relative humidity. The percentage of
moisture in the air in relationship to the
amount of moisture the air could hold at that
given temperature. At 100 percent relative
humidity, moisture condenses and falls as rain.
Retrofitting. Adding or replacing
items on existing buildings. Typical retrofit
products are replacement doors and windows,
insulation, storm windows, caulking,
weatherstripping, vents, landscaping. RESFEN. A computer program used to
calculate energy use based on window selection
in residential buildings. Roof window. A fixed or operable
window similar to a skylight placed in the
sloping surface of a roof. Rough opening. The opening in a wall
into which a door or window is to be installed.
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