Andy Hall wrote:
On 2006-12-26 13:15:04 +0000, "Clive" said:

Hi,

I hope to buy a late-Victorian end-of-terrace house sometime in the
new year.
snip
If the walls are cavity, then insulation in the cavity is a possible
option and will pay back fastest of all, even more so than loft
insulation.

If they are not, then you could insulate them internally with Celotex.
You could use 50mm sheet and make an enormous difference to overall
loss from the building. This would entail losing approximately 75mm
or possibly a little more from room widths,, however, and if they are
already small, may not be acceptable. You could always choose a
subset of rooms, of course. However, ventilation is then even more
important than normal since moisture from the air will tend to condense
on cooler surfaces.

You only lose 75mm, if there is no internal plasterboarding, or if it's
touching the existing walls.

snip
You could do something about the windows, although that will be
restricted if the house is in a conservation area.
If it isn't, then horrible plastic DG units can be used, or there are
wooden framed units that should be in better keeping with the period of
the house. Heat loss through windows is normally third after walls
and an uninsulated loft.

But...
Taking as an example my house.
It's got 15m^2 of window, in 12 windows.
Under very pessimistic assumptions, this costs maybe a couple of hundred
quid a year to heat, this takes a long time indeed to pay back if new
windows cost 3 grand. (of course, it is possible to DIY reterofit for a
fraction of this, and comfort factors may be important)

Compared to 25mm+12mm of kingspan +plasterboard, over 1/2 of the walls,
that should be the one done first, if at all possible. (and 25mm only if
you are really pushed for space).

snip
All of the above are places where you can make a major difference,
assuming that they are architecturally and economically possible. In
comparison, energy generating schemes such as windmills and solar
panels and alleged saving schemes such as fluorescent bulbs are either
not worth doing or pale into insignificance.

I'd _sligtly_ disagree on energy saving schemes - currently 3 rooms in
the house are lit. With non-CF bulbs, I'd be using 150W or so.
With CF bulbs, I can properly light the rooms, using 50W or so, saving
100W of electricity.
Even if I need to heat at the moment, and neglecting the poor heating
position, that's still a saving of 40 quid a year or better.

IMO - you should first do everything with a short payoff time.
Even if this is only draughtproofing the front door letterbox, and CF
lights.