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.

I'm in a similar position and this is what I plan to do.

I sanded and varnished several of my downstairs floors last year, and
am now kicking myself for not taking the opportunity to take all or
most of the boards up and insulate underneath first. Not only are the
boards cold under foot (even through rugs), but despite the greatest
care I have gaps and draughts where boards have had to come up for
plumbing and electrics (someone said in a similar thread in an other
place that they'd totted up all the gaps and holes in their floor, and
if they were all in once place they'd amount to an eight inch square
hole).

I have one more room to do, and I'm going to start by lifting all the
boards. It's a job, but a job you only have to do once. I might cut
the tongues out first, to get them up easier, as once I've insulated,
tongues won't matter.

What you need to do is insulate between the joists, putting the
floorboards into the warm zone of the room.

The easiest way to insulate is probably to use space blanket, which is
a roll insulation encapsulated in plastic to avoid mess. It is rolled
out between the joists and supported on netting or similar. My problem
with this is that the standard size is 370mm wide, and assumes that
your joists are at 400 centres, whereas mine, annoyingly, are at 430
centres, so I'd have a gap. This leaves me the option of using
messier, unencapsulated roll insulation, or what I'll probably do
which is buy seconds of 50mm Kingspan, cut to size and fix in place
with PU foam.

Where my previously-sanded floors are concerned, I had a plan to lift
a couple of floorboards in four or five places across the floor, and
pull space blanket through, under the floor, between the joists,
supporting it where I could. Unfortunately I have this width issue so
I'm not sure what approach I'll take to that now - possibly pull up a
lot more boards than I had intended, and use Kingspan again.

Important issues are electric cabling and central heating pipes -
cable should not be buried in insulation as it can theoretically
overheat and become a fire hazard, so it needs to run above it. I also
need access to my central heating pipework (in case I want to
reconfigure the radiators or access the Speedfit connectors, so I need
to make sure that's abpve the insulation too - which has an obvious
other benefit).

As people have said, on no account block up your air bricks, as air
circulation to the bottom of the joists is essential for the avoidance
of rot. I think worrying about the floorboards is unnecessary, as Tim
Watts says.

I've had three winters here now and dealt with a lot of the other
insulation issues that the house has - I'm convinced now that a major
part of the cold feel that is left is down to the floors. Especially
when outside is minus fifteen. I've yet to hear anyone say they
insulated their floor, but considered it a waste of time. You can't
build anything new without insulating the floor...

Cheers
Richard