perpendicular to a surface. It determines the percentage of direct sunshine
intercepted by that surface.
Solar azimuth. The horizontal angle between the sun's bearing and a
north-south line projected on a horizontal plane. The sun passes the horizon
at a different point each day. The arc of the sun is smaller in winter,
larger in summer.
Stack effect. The movement of air into and out of a space due to temperature
differences. When the temperature is higher inside, differences in air
density produce a negative inside pressure and inward air flow at low levels
within the space, and a positive inside pressure and outward air flow at high
levels within the space.
Structural cooling. Cooling of the building structure directly rather than
the body of the occupant. Structural cooling by natural ventilation involves
directing air flow across the building's interior surfaces to remove heat
stored in the building. This in turn can cool occupants indirectly.
Summary of Metereological Observations, Surface (SMOS). A weather summary
distributed by the National Climatic Center containing detailed summaries of
numerous weather variables for numerous weather station worldwide.
Thermal comfort. A state in which the human body is in thermal equilibrium
with its surroundings. Major factors are. air temperature, surrounding
surface temperatures, humidity, solar radiation, air movement, clothing level
and activity level.
See Heat Capacity.
Thermal mass. The heat capacity of a given mass or volume of material.
Commonly used to describe the heat absorption and retention of massive
Turbulence. The fluctuating component of wind velocity.
Experienced as gusts
or passing eddies.
Ventilation. Airflow through and within an internal space stimulated by two
means: 1) the distribution of wind pressure gradients around a building and
2) pressure differences caused by temperature gradients between indoor and
Wake. The area of turbulent air directly to the leeward side of an
Wet-bulb temperature. The temperature of a thermometer bulb covered with a
wet wick and exposed to moving air. It is a measure of the moisture content
of the air. On the psychrometric chart it is plotted as lines sloping
downward from left to right and labelled at the upper left.
Wingwall. A projection from the building facade that may act to direct wind
or provide shading.