RJH wrote
Rod Speed wrote
RJH wrote

I've read a few articles now from the peer reviewed scientific press on
the environmental impact of insulation materials.

While useful and doubtless scholarly (on my lay reading) in the sense
of seeing which materials work, in what quantity and why, reported wider
environmental benefits are misleading.

Nope.

Not a single one even mentions the 'CO2 cost' of production, only
effects post-fit -

That's because the CO2 cost of the production of the
insulation is a trivial part of the dramatic reduction
in the CO2 produced when heating the place.

Well, a very rough calculation taking my house and insulating just floors
and roof with Celotex would suggest that it would take about 5 years to
offset the CO2 used in the manufacture of the insulation material (Celotex
160kgCO2e/m3,

Where are you getting that number from ?

gas 0.2kg/kW/hr).

And even if your calculation is correct, 5 years is a reasonable
payback period for house insulation. The house is obviously
going to be heated for a lot longer than that with most houses.

And factor in building life,

That is almost always going to be a lot more than 5 years.

installation errors, use, ventilation

Those arent going to make a lot of difference
to the 5 years and will in fact reduce it.

- I find the science just lacking.

I dont.

It obviously gets more complicated with walls - payback may be quicker due
to high heat loss.

No maybe about it.

Worth it in the long haul,

Less than 5 years isnt the long haul with a house.

but not trivial. Especially to those who do things for 'green' reasons -
the papers I've read are environmentally inclined.

Sure, but clearly insulation does pay for
itself CO2 costs wise with a normal house.

Money saved is a different matter - depends a great deal on installation
costs. Far and away the best value thing I've done here - two alcoves,
about a day, less than £100. But it'd still take some yeasr to repay the
materials costs.

Sure, but with a new house, hardly ever doesnt the cost of
insulation pay for itself quite quickly when done properly.