Pete Cross wrote:
Thanks for your reply Phil L, the firm that did the job did exactly
as you said, as it turned out only two holes where needed as the orig
back door opening ( now inside but 1mtr from the new outside wall )
meant they could fill one section from the outside edge. The holes in
the outer walls are now almost invisible. I know it's warmer weather
now but I'm sat here at nearly midnight having had the heating
switched off for two days and its really warm inside, the drafts are
def reduced if not gone altogether ! they also replaced the airbricks
under the suspended wood floor areas with sleeeved one's and put what
looks like a 20ft long loo brush vertically in the cavity between our
half and the neighbours ( 1930's semi ) so it didn't spill over into
their walls. We paid £75 and Powergen paid the rest ( or prob the
government paid Powergen ) but so far it looks like the heating bill
for next winter will be lowered.

Pete

The long brush is called a barrier and sometimes they are a royal PITA to
get in.

The underfloor vents are almost always replaced, given that builders around
that time hadn't heard of sleeving the vent off from the rest of the cavity,
which may also what had been causing your draughts (the vents were open to
the cavity...the upstairs floor joists also go through to the cavity, and
very often there were gaps around the joist ends, meaning that outside air
was flowing not only underneath your downstairs floor, which is required to
prevent rot, but also your upstairs floors), under baths where pipes go
through and hundreds of other tiny holes all over the place - these have all
now been filled with fibreglass.

Next winter you will notice that your CH boiler only stays on for a fraction
of the time to get the house up to temp, that it takes less time for the
house to reach a comfortable temp, and also that it stays warmer for longer
after the CH has switched off.

£75 is a bargain, 15 years ago the firm I worked for charged £300 for a
semi.