On Wed, 21 Jan 2004 18:28:07 +0000, Dean Richard Benson
wrote:

On Wed, 21 Jan 2004 16:29:12 +0000, Christian McArdle wrote:

Yes. The law of diminishing returns says that 350mm is the best
environmentally speaking. Any more and the environmental cost of
manufacturing and transporting the insulant is higher than the energy saved.
100mm is definitely on the low side. 200mm would be better. The difference
between 200mm and 350mm isn't that great.

Some useful info in there. Leads me to even more questions....

- with currently having a 100mm joist height, should i either increase the
joist height (cross joists) or just cross-lay the insulation over the top
of the 100mm.

It depends on whether you want to board over the top.


- If you insulation up to 350mm, how are you meant to ever reach places in
your loft without falling through the ceiling ;P

It may not matter, since you won't be putting many other things there
anyway :-)

Before you get over-excited by this idea, take a look at how much heat
is going out through the walls and windows.......



- You mention the recommended above, based on diminishing returns, but
what insulation material is that based on - as I understand it, different
manufacturers produce insulation to different values. So my thought was,
that maybe 200mm of rockwool, might equal 300mm of crown or something?

If you want a better compromise between thickness and U value, then
you could use polyisosyanurate board such as Celotex or Kingspan which
have about 4x the insulating property of glass fibre.

However, it costs £15-18 for a 2440x1220 sheet........



Thanks again

Dean

..andy

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