Originally Posted By: CR94
Originally Posted By: ZeeOSix
Yep, it's common to get ice on the top of cars on a clear night if there's moisture on them due to the direct view factor and heat loss to space, even though the ambient air temperature is above freezing.
There doesn't have to be moisture on them, other than moisture that condenses from the air (aka, dew) due to the same radiative cooling to space on a clear night. Basic Heat Transfer!
Yep, if the air humidity is high enough the cold sheet metal from losing heat to space on a clear night will condense moisture from the air and it may also freeze. Similar to an iced drink in a glass condensing moisture from humid air.
Originally Posted By: CR94
For related reasons, a white roof can not only be less hot than a black roof on a sunny day, but also less hot than a shiny metal one.
Now you're talking about solar absorption properties of surfaces along with their radiative and conductive losses. If the roof was chromed like a car bumper it would absorb less solar radiation than some white paints. Here's a quick search that shows a table of different surfaces ... chromium plate (I assume very shiny chrome surface) is only 0.20 absorption.
http://www.engineeringtoolbox.com/radiation-surface-absorptivity-d_1805.html
Here's another table showing solar absorption properties. Aluminum foil (which is pretty shiny) is alpha 0.15, and white paint ranges from 0.23 - 0.49 depending on what is is exactly.
http://www.solarmirror.com/fom/fom-serve/cache/43.html