Ah, sorry, there's another unstated assumption of mine - that the pot has
a Hole in the middle of the "base" (base when used as pot, top when used

Are you also assuming that the pot doesn't have a plant in it?

Colin

(Lobster) wrote in message . com...
Having installed some LV halogen lights in the bathroom, I need to
protect them against overheating or causing a fire by buring them
under 250mm of Rockwool.

Interesting thread, this.

My own plan (not implemented yet) is to use old biscuit tins to cover each
lamp.
My thoughts are to line the rim of a normal-way-up rectangular biscuit
tin with draught-proof strip, to help seal the tin to the plasterboard.

Then simply invert the tin over the lamp.

I've been pestering friends and relatives to retain their biccy tins from
Christmas time (it seems a common gift up here in Scotland) - I've tried
to munch many biscuits to help the collection! :-)

I'm thinking that a biscuit tin is quite a big volume of air, hence it ought
to dissipate the heat better.
And tin doesn't burn that well, does it?

Any flaws in the plan?

Mungo

wrote in message ...
wrote:
Chris, David -

neither of you seem to have bothered stating what you're assuming
happens
*around* the flowerpot. And it seems from the side as if one of you
thinks
it's "totally obvious" that the flowerpot is *instead* of the rockwool,
i.e. that the top and sides of the inverted flowerpot are open to the
surrounding air - in which case the lamp will indeed run a lot cooler,
since
the pot itself will be able to dissipate a fair proportion of the heat
produced by the lamp to the free air around it by both radiation and
convection. The other of you seems to assume the pot is
covered/surrounded
by the rockwool, and under this assumption quite correctly points out
that
once the air around the lamp and the pot have risen to pretty much the
temperature of the lamp fitting (which they will, since the surorunding
rockwool prevents nearly all the heat from going anywhere useful), the
temperature of the lamp under the pot under the rockwool will be no
different from the temperature of the lamp directly under rockwool.

Have I got the source of the divergent views right? (And will I regret
piping up at all? ;-)

Yes, I think you may well be right. I'm assuming the flowerpot is
buried in the mineral wool insulation, otherwise what is the point?

The flower pot when sealed with silicon keeps the house air-tight. Air
laden with moisture is not what you want in the loft. Far from it.

"mark" wrote in message
...
In message ,
writes
You are probably also doing something awful to the fire proofing.

fire proofing???

I meant that the hole in the ceiling, unless dealt with somehow,
reduces the fire barrier created by a plasterboard ceiling.

So the open tube/chimney idea makes this worse as it gives a path for
the flames as opposed to the sealed pot

As a builder this point has worried me for some time.
Everyone seems to want down lighters in their new houses/extensions.
Installed in floor void they make holes in the half hour fire protection
(plasterboard) and I have been told that a study (not seen it) claimed
that the blow lamp effect through the holes might actually accelerate
the destruction of the floor structure. For this reason I have been
making boxes around the down lighters from a fireproof board sealed up
with intumescent mastic; so far so good.

Use large cheap ceramic plantpots. Just silicon them around the base.
Insulation can directly on top of the pots. Quicker and probably cheaper.

Mains downnlighters are hotter than LV. As mains is superseding LV in most
downlighter applications, fire may become a problem. Transformers must be
above the insulation screwed to the rafters, or on an MDF board screwed to
the joists with the xformer above the insulation.

In a loft space they make holes in the insulation and make a mockery of
the regulations brought in regarding cold bridging through timber
joists. For this reason we have been making plasterboard boxes to give a
foot square space around the fitting to allow the heat to dissipate
while putting insulation over the box to complete the necessary
insulation requirement.
I am aware that the insulation probably mucks up the heat dissipation
but again; so far so good.

Foot square box; too small? I've been asked to install them in much
smaller available spaces between floor joists so I don't know...
I'd be very interested in other peoples comments and experiences as I
was on the verge of refusing to install them for all the above reasons
and I was worried about being sued

I believe dedicated boxes are for sale.

snipped question - subject says it all

Hi,

How about using compact fluorescent spotlights?

I bought one recently - the light is very very nearly as good as a
halogen, it only uses 7W instead of 50 so excessive heat isn't a
problem so you could insulate fully and save even more money.

Only downsides are that they are a tenner a pop and aren't dimmable.
They will of course, pay for themselves many times over during their
life.
Hopefully they will bring out a dimmable version.

Alan.