(Wed 02:00 23/Feb/05)Most likely insufficient or total lack of insulation. This is especially important in the ceiling areas...
hopalong
(Wed 09:49 23/Feb/05)Could be draughts.
woofgang
(Wed 10:03 23/Feb/05)
large single glazed windows? damp? exposure to cold winds? poorly placed central heating? radiators the wrong shape (small and thick instead of larger and flat?)
smudge
(Wed 10:23 23/Feb/05)Our house has full central heating, but we have two open fireplaces for burning coal/logs. No matter how long the heating is on for, we'll always get down draughts from these chimneys!