Hello all,


I have got some spare 40mm Celotex sheets left from a previous project
and was wondering if there would be any benefit gained in using them for
the stud walls in the converted loft.

The said walls are already insulated with 100mm mineral wool in between
the studs and I'd prefer to leave that in place.

The Celotex would have to go on top of the existing insulation/over the
studs provided there is nothing wrong with doing this? Is this a
reasonable thought or have I gone completely mad?

Cheers,

--
Dawood

In article , gremlin_95
writes
Hello all,


I have got some spare 40mm Celotex sheets left from a previous project
and was wondering if there would be any benefit gained in using them for
the stud walls in the converted loft.

The said walls are already insulated with 100mm mineral wool in between
the studs and I'd prefer to leave that in place.

The Celotex would have to go on top of the existing insulation/over the
studs provided there is nothing wrong with doing this? Is this a
reasonable thought or have I gone completely mad?

No problem, that's a perfectly normal way to do it, particularly if
there is a need for extra high insulation where insulating over the
studwork avoids the problem of cold bridging due to heat passing through
the studs.

Prob easiest to tack the Celotex in place using the odd screw with a
penny washer under the head to stop it putting through, screwed just
flush, then you'll need plasterboard over the top to get a decent
finish. Fix the PB through the celotex into the studs using extra long
plasterboard screws as they wont tear up the PB paper like normal
screws. Easier to find the studs first and draw a line down the celotex
and a little over at the ends to still be visible when you offer up the
PB.

--
fred
it's a ba-na-na . . . .

On 25/11/2013 11:56, fred wrote:
In article , gremlin_95
writes
Hello all,


I have got some spare 40mm Celotex sheets left from a previous project
and was wondering if there would be any benefit gained in using them for
the stud walls in the converted loft.

The said walls are already insulated with 100mm mineral wool in between
the studs and I'd prefer to leave that in place.

The Celotex would have to go on top of the existing insulation/over the
studs provided there is nothing wrong with doing this? Is this a
reasonable thought or have I gone completely mad?

No problem, that's a perfectly normal way to do it, particularly if
there is a need for extra high insulation where insulating over the
studwork avoids the problem of cold bridging due to heat passing through
the studs.

Prob easiest to tack the Celotex in place using the odd screw with a
penny washer under the head to stop it putting through, screwed just
flush, then you'll need plasterboard over the top to get a decent
finish. Fix the PB through the celotex into the studs using extra long
plasterboard screws as they wont tear up the PB paper like normal
screws. Easier to find the studs first and draw a line down the celotex
and a little over at the ends to still be visible when you offer up the PB.


Hi Fred, thank you for your reply.

Perhaps I should have made it clear that this stud wall is pre-existing
and it already has PB covering the insulation. I was thinking of fixing
the Celotex above this PB and then boarding it again but I can't really
afford to lose that much space and it would be quite a lot of upheaval.

There is access *behind* the stud walls so the plan was to put the
Celotex over the studs/insulation from behind.

--
Dawood

In article , gremlin_95
writes
On 25/11/2013 11:56, fred wrote:
In article , gremlin_95
writes
Hello all,


I have got some spare 40mm Celotex sheets left from a previous project
and was wondering if there would be any benefit gained in using them for
the stud walls in the converted loft.

The said walls are already insulated with 100mm mineral wool in between
the studs and I'd prefer to leave that in place.

The Celotex would have to go on top of the existing insulation/over the
studs provided there is nothing wrong with doing this? Is this a
reasonable thought or have I gone completely mad?

No problem, that's a perfectly normal way to do it, particularly if
there is a need for extra high insulation where insulating over the
studwork avoids the problem of cold bridging due to heat passing through
the studs.

Prob easiest to tack the Celotex in place using the odd screw with a
penny washer under the head to stop it putting through, screwed just
flush, then you'll need plasterboard over the top to get a decent
finish. Fix the PB through the celotex into the studs using extra long
plasterboard screws as they wont tear up the PB paper like normal
screws. Easier to find the studs first and draw a line down the celotex
and a little over at the ends to still be visible when you offer up the PB.


Hi Fred, thank you for your reply.

Perhaps I should have made it clear that this stud wall is pre-existing
and it already has PB covering the insulation. I was thinking of fixing
the Celotex above this PB and then boarding it again but I can't really
afford to lose that much space and it would be quite a lot of upheaval.

I did wonder :-)

There is access *behind* the stud walls so the plan was to put the
Celotex over the studs/insulation from behind.

Yes, that will work but the difficulty may be in getting the rigid board
behind without chopping them into tiny pieces, they wont bend. Get some
foil tape (cheap at toolstation) to re-tape the joints when
reassembling. Make absolutely sure that you can't get any draughts
circulating on the room side of the celotex between it and the
fibreglass or it will be a wasted effort. Less risk of this if the
fibreglass is filled to full depth or you can hand stuff a bit of extra
fibreglass in at the edges or use foam but the gaps may be a bit large,
say at the bottom where the joists meet the studs.
--
fred
it's a ba-na-na . . . .

In article , fred writes

Yes, that will work but the difficulty may be in getting the rigid board
behind without chopping them into tiny pieces, they wont bend. Get some
foil tape (cheap at toolstation) to re-tape the joints when
reassembling. Make absolutely sure that you can't get any draughts
circulating on the room side of the celotex between it and the
fibreglass or it will be a wasted effort. Less risk of this if the
fibreglass is filled to full depth or you can hand stuff a bit of extra
fibreglass in at the edges or use foam but the gaps may be a bit large,
say at the bottom where the joists meet the studs.

Sorry, forgot to mention that the screw with penny washer under the head
is again the easiest way to fix.
--
fred
it's a ba-na-na . . . .

On 25/11/2013 22:35, fred wrote:
In article , gremlin_95
writes
On 25/11/2013 11:56, fred wrote:
In article , gremlin_95
writes
Hello all,


I have got some spare 40mm Celotex sheets left from a previous project
and was wondering if there would be any benefit gained in using them
for
the stud walls in the converted loft.

The said walls are already insulated with 100mm mineral wool in between
the studs and I'd prefer to leave that in place.

The Celotex would have to go on top of the existing insulation/over the
studs provided there is nothing wrong with doing this? Is this a
reasonable thought or have I gone completely mad?

No problem, that's a perfectly normal way to do it, particularly if
there is a need for extra high insulation where insulating over the
studwork avoids the problem of cold bridging due to heat passing through
the studs.

Prob easiest to tack the Celotex in place using the odd screw with a
penny washer under the head to stop it putting through, screwed just
flush, then you'll need plasterboard over the top to get a decent
finish. Fix the PB through the celotex into the studs using extra long
plasterboard screws as they wont tear up the PB paper like normal
screws. Easier to find the studs first and draw a line down the celotex
and a little over at the ends to still be visible when you offer up
the PB.


Hi Fred, thank you for your reply.

Perhaps I should have made it clear that this stud wall is pre-existing
and it already has PB covering the insulation. I was thinking of fixing
the Celotex above this PB and then boarding it again but I can't really
afford to lose that much space and it would be quite a lot of upheaval.

I did wonder :-)

There is access *behind* the stud walls so the plan was to put the
Celotex over the studs/insulation from behind.

Yes, that will work but the difficulty may be in getting the rigid board
behind without chopping them into tiny pieces, they wont bend. Get some
foil tape (cheap at toolstation) to re-tape the joints when
reassembling. Make absolutely sure that you can't get any draughts
circulating on the room side of the celotex between it and the
fibreglass or it will be a wasted effort. Less risk of this if the
fibreglass is filled to full depth or you can hand stuff a bit of extra
fibreglass in at the edges or use foam but the gaps may be a bit large,
say at the bottom where the joists meet the studs.


There is actually quite a lot of room behind the stud walls which is
used for storage, the boards are not the 2400x1200 size; they are 1200 x
450 so getting behind in one piece isn't a problem. I have plenty of
tape and expanding foam left over from the previous project so I
*should* be OK.

OOI, could I insulate the roof part of a bay window from the inside? The
whole house has external wall insulation but the front lounge with the
bay window is still a bit cooler.




--
Dawood

In article , gremlin_95
writes

OOI, could I insulate the roof part of a bay window from the inside? The
whole house has external wall insulation but the front lounge with the
bay window is still a bit cooler.

I don't see why not but the ceiling may not be the most significant loss
and so may not be worth the effort. Maybe calculate the area of glass,
area of wall under the glass and compare it to the area that you will
insulate. I'd expect you to be losing more through the glass.

In IR thermometer would be a good toy to play with to see what is the
coldest surface around there as that will likely be losing most. You can
measure the surface temp of the glass by adding a bit of insulating tape
to the pane and then targeting that. A 20mm sq piece is fine if you
place the lens hole in contact with it.

If you do go ahead then you will need some sort of surface finish under
the insulation (PB or ply). I tried cutting corners in putting up some
celotex in a utility and not plasterboarding it over and despite taking
great care to get all the joints smooth and level it is very noticeable
(to me) that it is a bodge.
--
fred
it's a ba-na-na . . . .

In message , fred writes
In article , gremlin_95
writes

OOI, could I insulate the roof part of a bay window from the inside? The
whole house has external wall insulation but the front lounge with the
bay window is still a bit cooler.

I don't see why not but the ceiling may not be the most significant
loss and so may not be worth the effort. Maybe calculate the area of
glass, area of wall under the glass and compare it to the area that you
will insulate. I'd expect you to be losing more through the glass.

.

I think it's one of those jobs that's worth doing as part of something
else, but not necessarily otherwise.

So I did ours in our old house when they we being skimmed, as I was
overboarding the ceiling anyway. worth looking at the walls as well. Our
downstairs one was single skin brick IIRC (certainly solid anyway) and
the upstairs was tile hung over a wodden frame, lathe and plaster
inside
--
Chris French

On 25/11/2013 23:30, fred wrote:
In article , gremlin_95
writes

OOI, could I insulate the roof part of a bay window from the inside? The
whole house has external wall insulation but the front lounge with the
bay window is still a bit cooler.

I don't see why not but the ceiling may not be the most significant loss
and so may not be worth the effort. Maybe calculate the area of glass,
area of wall under the glass and compare it to the area that you will
insulate. I'd expect you to be losing more through the glass.

In IR thermometer would be a good toy to play with to see what is the
coldest surface around there as that will likely be losing most. You can
measure the surface temp of the glass by adding a bit of insulating tape
to the pane and then targeting that. A 20mm sq piece is fine if you
place the lens hole in contact with it.

If you do go ahead then you will need some sort of surface finish under
the insulation (PB or ply). I tried cutting corners in putting up some
celotex in a utility and not plasterboarding it over and despite taking
great care to get all the joints smooth and level it is very noticeable
(to me) that it is a bodge.


Cheers, I will get some reading with my IR thermometer this weekend.

--
Dawood

On 26/11/2013 20:00, chris French wrote:
In message , fred writes
In article , gremlin_95
writes

OOI, could I insulate the roof part of a bay window from the inside? The
whole house has external wall insulation but the front lounge with the
bay window is still a bit cooler.

I don't see why not but the ceiling may not be the most significant
loss and so may not be worth the effort. Maybe calculate the area of
glass, area of wall under the glass and compare it to the area that
you will insulate. I'd expect you to be losing more through the glass.

.

I think it's one of those jobs that's worth doing as part of something
else, but not necessarily otherwise.

I can imagine, wish I had thought of it when it was being decorated.


So I did ours in our old house when they we being skimmed, as I was
overboarding the ceiling anyway. worth looking at the walls as well. Our
downstairs one was single skin brick IIRC (certainly solid anyway) and
the upstairs was tile hung over a wodden frame, lathe and plaster inside

The walls are 9 inch solid walls, the whole house used to be quite cool
and require the heating to be on for ages to keep it warm, however the
whole house has been insulated externally with 90mm EPS boards and this
has made the place a lot warmer and allowed me to run the CH at lower
temperatures