On 20 Dec, 12:31, Jim wrote:
I plan to redirect our ground floor front room next year.

Currently, the walls are unplastered, and we've rewired so floorboards
are loose, so any option is possible at this point.

My question is what, if anything to do about draughts from under the
floor.

We live at a T junction, with a road running off our road straight in
front of our house. This road is a bit of a wind tunnel, and the room
we plan to decorate gets the brunt of it.

The house is Victorian, and slightly raised with large cavities under
the floor-boards. There is also a metal decorated air-grill at the
front of our house which ventilates the space under this room.

Net result is that it is seriously cold and draughty at the moment,
and I can feel quite strong cold draughts if I put my hands over the
floorboard gaps in this room.

When we've decorated the room, I plan to get an underlayed berber
style carpet, which should prevent the draughts, but I'd like it to be
as cosy as possible for my children.

Is there anything else I can do to improve insulation/carpet warmth?

I presume blocking up the air vent completely would be a bad thing? Is
it worthwhile attempting any other sort of under-floor insulation?

Thanks for your input.

There has been an awful lot of misinformation and with some small
amount of good corrections.
It is best to insulate. Do so such that the timber remains warm and
thus not at risk of condensation. If it is warm it does not need
ventilation of the sub-floor airvents but they should be left in
regardless for keeping moisture levels low in the abutting masonry and
oversite.
This is what I would recommend on our pro bono terms.
lift all fbs labelling so they go back in same places
use a proper floorboard lifter if you can hire or or borrow one
if not use long long levers with flat iron heads
glue any that split

When lifting use a hammer and fulcrum to knock them out with the nails
rather than trying to lift the nailed boards up direct (like knocking
the other end of a see saw)
Put in polythene sheeting on the oversite and put on some sand to keep
it down in place (reduces water vapour entry into void)

put in PU 4" foam with a careful cut filling any gaps with foam gun
get under and put one or two inches of foil-backed PU under the lot
cross ways using large plastic washers and long enough nails (or
battens) and leave just a small hole for you to get up back inside and
then put the last bit in and hold it up with string or whatever from
the inside
fill the last gap between FBs
put on a vapour check such as thin poly
Fbs back down either in right places or cramped together with a
replacement to take up the slack

Job done Wall plates not at risk if on a DPC joists all warm - you
warm as toast

can have boards or carpet as you wish
U Value probably (guess) 0.25 bobs yer uncle

no decay risk from oversite

chris