"pete" wrote in message
...
: On Wed, 16 Sep 2009 16:25:27 +0100, Jerry wrote:
: "pete" wrote in message
: ...
: : On Wed, 16 Sep 2009 15:24:10 +0100, Jerry wrote:
: : "pete" wrote in message
: : ...
: :
snip
:
: : As you say, you may get some small improveent from that heat
: adding to
: : the temperature gradient in the room, but it won't be
anything
: like the
: : 100Watts the bulb is putting out. You'd be far better off
: putting in a
: : CFL (or 6) and installing a small fan to move the warm air
off
: the ceiling
: : if only temporarily, so that it can usefully warm the room's
: occupants.
:
: No you would not, the fan will actually cause the ambient
: temperature to fail, due to the air movement, you will
actually
: need to use more heat to keep to the same ambient
temperature!
: Only use a fan if you have to either distribute heated (or
cooled
: air) or need air movement for other reasons.
:
: And that's precisely what you're trying to acheive (distribute
the
: heat - in this case from the warm ceiling area to the cooler
lower
: parts fo the room).

Only if you have 6ft ceilings! There is absolutely no need to
keep the ceiling level to the same temp as mid height, there is
*possibly* an argument for wanting to keep the lower 1/4 or 1/3
to the same level as the middle quarters or third hence why
people tend to put radiators (and as you suggested elsewhere,
make use of radiator shelves) at the lower height or even use UF
heating.

Rooms don't have a single temperature. Even if
: you remove all the draughts, you still have the heat in a room
rising
: to the top of the room.

Exactly but, like a shop doorway [1], a buffer zone exists (in
this case vertical rather than horizontal as in a doorway), use a
room fan - and you destroy that buffer and make the whole room
the same temp that then requires a greater amount of heat to get
to an over all even temp.

[1] for either of two reasons, heating or air conditioning,
keeping warm air in or out depending on climate

: Whereas the people occupy the lower (and therefore cooler) part
of
: the room. Typically 0 - 3 feet if they're seated, 0 - 6 if they
are
: standing. There's nothing to be gained from heating the air
higher up
: than that - which is one reason modern houses have lower
ceilings.

No they no not have lower ceiling to reduce heating costs, they
have them to make houses cheaper, when we lived in our Victorian
area house (complete with 12ft ceilings) the cost of heating
wasn't that much different to that of the modern brand new house
we then moved into that had 8ft ceilings (adjusted figures to
take into account different fuels and inflation etc.). Of course
if we were careless as to how we used the heating in that
Victorian house, such as allowing the house fabric to cool down,
it cost a fortune to reheat or keep to the constant 68 deg C we
desired. I would also point out that the upper 3rd floor was
heated solely by convection from the lower floors, only in the
depth of winter did we need to boost the heating in those rooms
with an alternate heat source.

: Using a fan assists convection (as does having a shelf above a
radiator)
: in getting the warm air off the ceiling and down to where it
can

You will always heat the ceiling, unless you live on a different
planet with different laws of physics... :~)

: usefully warm the occupants - without the need to add extra
heat into
: the room.

Impossible with our laws of physics.
--
Regards, Jerry.