"RichardS" wrote in message
...

Well, I'm running a sadistic hardware experiment at the moment, running 2
pcs and an ultrasparc in the loft. Despite my long-standing must-do job
of
putting insulation in the loft it remains unstarted, so I think now is as
good a time as any. (If I have a burst of energy tonight I will probably
cave in and bring the poor machines back down into the office).

It's a victorian terraced house with standard roof construction (the name
escapes me at the moment, but they're not trusses).

My plan is to install as thick kingspan or celotex between the rafters as
I
can get away with, whilst leaving a ventilation gap of 50mm between the
insulation and the sarking/tiles. At the apex I will sacrifice a little
headroom and fix some insulation horizontally so that there is a
ventilation
route connecting both sides and all gaps betwen the rafters. At the edges
I'll leave a small gap & install vertical insulation so that there is no
airgap underneath & into the loft, but ventilation is maintained from any
gaps in the soffits up to the rafter ventilation space. Everything will
be
sealed as far as is possible.

There are 2 air vents per roof face, about 1m from the apex.

Does anyone see any fault with this plan, and do I need to install any
additional vents (if so, how - I really don't fancy climbing on the roof)?

we provided vents for my loft conversion (after some argument with the BCO
who gave way eventually), by pushing pieces of treated timber roof battens
between the layers where one sheet of roofing felt/sarking overlays the next
and stapling in place. this opens up a ventilation gap between the two
layers. You have to ensure the piece of wood isn't so long that it emerges
from beneath the edge of the top layer (otherwise it may get wet and rot).


--
Bob Mannix