Degree day. A
unit that represents a
one-degree Fahrenheit
deviation from some
fixed reference point
(usually 65° F) in the
mean, daily outdoor
temperature.
See also
heating degree day.
Desiccant. An
extremely porous
crystalline substance
used to absorb moisture
from within the sealed
air space of an
insulating glass unit.
Dewpoint. The
temperature at which
water vapor in air will
condense at a given
state of humidity and
pressure.
Divided light.
A window with a number
of smaller panes of
glass separated and held
in place by muntins.
DOE-2.1E. A
building-simulation
computer program used to
calculate total annual
energy use.
Double glazing.
In general, two
thicknesses of glass
separated by an air
space within an opening
to improve insulation
against heat transfer
and/or sound
transmission. In
factory-made double
glazing units, the air
between the glass sheets
is thoroughly dried and
the space is sealed
airtight, eliminating
possible condensation
and providing superior
insulating properties.
Double-hung
window. A window
consisting of two sashes
operating in a
rectangular frame, in
which both the upper and
lower halves can be slid
up and down. A
counterbalance mechanism
usually holds the sash
in place.
Double-strength
glass. Sheet glass
between 0.115" and
0.133" (33.38 mm)
thick.
Drip. A
projecting fin or a
groove at the outer edge
of a sill, soffit, or
other projecting member
in a wall designed to
interrupt the flow of
water downward over the
wall or inward across
