Mike Barnard wrote:
On Sat, 29 Dec 2007 13:51:04 +0000, Mike Barnard
wrote:

Hi.

I need a basic chart showing the heat losses through a loft area if
there is no insulation, 50mm, 100mm up to the 265mm nominal 'perfect'
insulation. Anyone know where there is one or the facts (validated)
so I can draw one up for myself?

Along the lines of...

One sq metre of uninsulated plasterboard has a U value of... ?
Ditto with 50 mm standard rolled fibre insulation.
Ditto with 100 mm, 150 mm etc.

It's so I can show someone a comparison so she can decide just when
enough is enough compared with keeping spending more and more on more
materiels.

I am googling, and it's ongoing, but all I find so far is detailed
tech guides or company ads. I'll bet someone on here has a link
already!

Thanks.

Interesting answers, thanks. All I really need to know is whether
adding another 150mm of insulation will make a big difference to the
existing 125mm. So If I had a chart as described I'd have an idea of
a 'typical' heatloss for various depths. At what point does it become
pointless (oops, bad english) to add more? Is it worth 300mm? 500MM?
Where does one reasonably stop?


Where the loses from other sources exceed the losses from the bits you
are insulating.

In a house to modern standards, it is in fact the trickle ventilation
that sets an upper limit on how much its worth insulating.

That and unavoidable 'cold bridges' around window and door frames.