Interior Lighting for Designers

R lamps
Inreflector(R) lamps, the bulb is shaped into
a reflecting contour; the inner surface is
coated with vaporized silver. The lamps are
available in spot or flood beam-spreads.
Spot lamps have a light frost on the inside
front of the bulb; flood lamps have a heavier
frosting to increase the spread of the beam.
As with nondirectional and semi-direc-
tional incandescent lamps, the glass bulbs
of most R lamps are made of blown lime
glass. This “soft” glass is intended only for
indoor use. Some wattages are available in a
“hard,” heat-resistant glass for areas where
contact with moisture is a possibility, but
these lamps still require protection from
rain.
All R lamps emit a substantial percent-
age of light outside the principal beam.
Unless intercepted by an auxiliary reflector,
this light is usually lost due to absorption
within the luminaire; in most luminaires, R
lamps are inefficient.

AR and MR lamps
See low-voltage lamps, pages 75 to 77.

PAR lamps
Parabolic aluminized reflector(PAR) lamps
are made of low-expansion, heat-resistant
borosilicate glass that is pressed rather than
blown. This method of construction allows
great precision in shaping the reflector of the
bulb and in the configuration of the lens, as
well as in the positioning of the filament. The
combined precision of these factors
accounts for the superior beam control and
greater efficacy that are characteristic of
PAR lamps (figure 6.8).
PAR lamps were originally designed for
outdoor applications and are sometimes still
referred to as “outdoor” lamps because they
are weather-resistant. Over the years their
use indoors has grown rapidly wherever effi-
cacy and precise beam control are desired.

PAR lamps are available with beam-

spreads that range from 3° (very narrow

spot, or VNSP) to 60° (very wide flood, or

VWFL). The initial beam is formed by the

shape of the reflector and the position of the

filament. The configuration of the lens modi-

fies that beam: a light stipple smoothes the

narrow beam for a spot lamp; “prescription”

lenses similar to those of car headlights pro-

vide the wider beam distributions of flood

lamps.

Incool-beamPAR lamps, a reflective

dichroic coating replaces the bright alumi-

num used on the reflector surface of stan-

dard PAR lamps. Visible wavelengths (light)

are reflected forward into the beam while

infrared wavelengths (heat) pass through the

back of the bulb. About two-thirds of the

heat energy in the beam is removed; light

output and distribution are unchanged.

These lamps were originally developed to

light perishable foods (figure 6.9).

EPACT

The U.S. Energy Policy Act of 1992 (EPACT)

established minimum average efficacy stan-

dards for certain incandescent R and PAR

lamps that operate at 115 to 130 V and

have medium bases and diameters larger

than 2¾ in. Most incandescent R30, R40,

and PAR38 lamps do not meet the criteria;

tungsten-halogen PAR lamps do. Colored

lamps and rough- and vibration-service

lamps are exempt from the efficacy stan-

dards. The act does not prescribe standards

for other kinds of incandescent lamps.

As of 31 October 1995, the following

lamps are prohibited from manufacture or

sale in the United States: 75R30; 75-, 100-,

120-, and 150R40; and 65-, 75-, 85-, 120-,

and 150PAR38. These efficacy standards,

measured in lumens per watt, were estab-

lished according to lamp wattage. This

approach ignores the function of the

luminaire, however: an inefficient, incandes-

INTERIOR LIGHTING FOR DESIGNERS