Eeyore wrote in
:



dizzy wrote:

Eeyore wrote:

If the central heating is on, then you are, by definition, needing
extra heat. The heat output from lighting will mean that the room
thermostat (or radiator valves) will turn off that bit sooner.

Not really.

The heat from most lamps hangs around at ceiling level. It does sod
all to warm a room.

Wrong.

Not wrong.

Graham



Yes it is. Most of the heat is radiant. Just because the intensity falls
off fourfold per unit distance doesn't mean the energy vanishes. Even if
you consider the ceiling covering nearly half of the volume through which
heat tries to radiate through, the shallow angle of incidence means that
most of that reflects to join the rest to warm the walls and anything else
it can reach. The small amount of heat above the lamp is from convection,
and keeping the bulb clean will help to let the heat radiate more
efficiently and usefully.

Cieling heat isn't useless in heating a room anyway. While I think it IS a
bit daft, I remember a house I visited a few times as a kid, it had a low
temperature heater in the entire ceiling of one room. It was very low-grade
heat, but it still warned the room. I felt it on my face when I looked up
at it. Less so while sitting, but not much, because the area was so large.
Similarly, a lightbulb radiating across a ceiling adds heat usefully to the
whole room. More in fact (proportionally), because more of it is radiated
than conducted away above.