"Lloyd E. Sponenburgh" lloydspinsidemindspring.com wrote in message
. 3.70...
"Jim Wilkins" fired this volley in
:

Trouble is, they don't radiate infrared and the heated air from the
ballast stays near the ceiling.

Not _quite_ true.

It's true that most of the heat stays near the ceiling, because most of
it is conducted away from the housing by convection. However... (It's
SCIENCE!) ALL objects warmer than their surrounds also radiate in the
infrared. (Hint... infrared IS "heat". Radiation is one of the three
ways heat moves)

G
LLoyd

When I told my Ph.D. boss about my 4-layer insulated windows he calculated
the radiant heat flux through them in his head. It was essentially
irrelevant above freezing, considering the 10-micron infrared behavior of
older iron-bearing window glass. However I made curtain liners from
aluminized cloth just for good measure.

http://en.wikipedia.org/wiki/Stefan%...3Boltzmann_law
http://hyperphysics.phy-astr.gsu.edu...mo/grnhse.html

I had an undergrad summer research grant that involved quite a lot of
infrared spectroscopy using NaCl and KBr optics and sample holders. The
wavelengths I've worked with in long-wave infrared optics and microwave
electronics nearly meet.

jsw