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.

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


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