"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.