OK, stupid time.

Accidently bought 6 sheets of ordinary 9.5mm PB in 3x6' sheets. Need to use
vapour barrier PB for the ceilings on some bay window ceilings which will
be insulated with celotex above. I don't even think the use of vapour
barrier PB is that critical as there's a huge void over half the bay
ceiling as the pitched roof meets the lead flat roof of the bay, but vapour
barrier was suggested.

Any harm in using normal PB together with a vapour barrier or either plastic
or perhaps even bacofoil (turkey sized) stuck on the back of the board.

Seems a pointless waste to dump the board as I can't use it elsewhere.

Cheers

Tim

On Jul 15, 8:47*am, Tim S wrote:
OK, stupid time.

Accidently bought 6 sheets of ordinary 9.5mm PB in 3x6' sheets. Need to use
vapour barrier PB for the ceilings on some bay window ceilings which will
be insulated with celotex above. I don't even think the use of vapour
barrier PB is that critical as there's a huge void over half the bay
ceiling as the pitched roof meets the lead flat roof of the bay, but vapour
barrier was suggested.

Any harm in using normal PB together with a vapour barrier or either plastic
or perhaps even bacofoil (turkey sized) stuck on the back of the board.

Seems a pointless waste to dump the board as I can't use it elsewhere.

Cheers

Tim

ali foil is a more effective VB than plastic, and sticks well with
PVA. VB PB is only ali foil coated anyway.


NT

Tim S wrote:
OK, stupid time.

Accidently bought 6 sheets of ordinary 9.5mm PB in 3x6' sheets. Need to use
vapour barrier PB for the ceilings on some bay window ceilings which will
be insulated with celotex above. I don't even think the use of vapour
barrier PB is that critical as there's a huge void over half the bay
ceiling as the pitched roof meets the lead flat roof of the bay, but vapour
barrier was suggested.

Any harm in using normal PB together with a vapour barrier or either plastic
or perhaps even bacofoil (turkey sized) stuck on the back of the board.

Seems a pointless waste to dump the board as I can't use it elsewhere.

I can't see a separate barrier being a problem - just because its not
glued to the board does not stop it working.

--
Cheers,

John.

/================================================== ===============\
| Internode Ltd - http://www.internode.co.uk |
|-----------------------------------------------------------------|
| John Rumm - john(at)internode(dot)co(dot)uk |
\================================================= ================/

NT wrote:

ali foil is a more effective VB than plastic,

Is that so? Plastic would be easier

Stuart Noble coughed up some electrons that declared:

NT wrote:

ali foil is a more effective VB than plastic,

Is that so? Plastic would be easier

Thanks all,

That's settled.

I thought foil would be a good possibility, because a) I can buy it readily
in the supermarket, b) it's vapour proof and durable, c) I can probably
lightly stick it with either PVA or some spray on evo-stick I happen to
have a can of. Sticking it, even very lightly would ensure it stays put as
I install the board.

Just glad I don't have to waste it

Cheers

Tim

On 15 July, 08:47, Tim S wrote:
OK, stupid time.

Accidently bought 6 sheets of ordinary 9.5mm PB in 3x6' sheets. Need to use
vapour barrier PB for the ceilings on some bay window ceilings which will
be insulated with celotex above. I don't even think the use of vapour
barrier PB is that critical as there's a huge void over half the bay
ceiling as the pitched roof meets the lead flat roof of the bay, but vapour
barrier was suggested.

Any harm in using normal PB together with a vapour barrier or either plastic
or perhaps even bacofoil (turkey sized) stuck on the back of the board.

Seems a pointless waste to dump the board as I can't use it elsewhere.

Cheers

Tim

Tim
There is a BG wall board "paint on" vapour barrier - ? wall board top
coat or the like
any oil based paint will do
chris

On Jul 15, 10:46*am, John Rumm wrote:
Tim S wrote:
OK, stupid time.

Accidently bought 6 sheets of ordinary 9.5mm PB in 3x6' sheets. Need to use
vapour barrier PB for the ceilings on some bay window ceilings which will
be insulated with celotex above. I don't even think the use of vapour
barrier PB is that critical as there's a huge void over half the bay
ceiling as the pitched roof meets the lead flat roof of the bay, but vapour
barrier was suggested.

Any harm in using normal PB together with a vapour barrier or either plastic
or perhaps even bacofoil (turkey sized) stuck on the back of the board.

Seems a pointless waste to dump the board as I can't use it elsewhere.

I can't see a separate barrier being a problem - just because its not
glued to the board does not stop it working.


Yes, normally. Cooking foil comes in narrow strips though, and this
will need to be glued to avoid gaps between strips.


NT

NT wrote:
On Jul 15, 10:46 am, John Rumm wrote:
Tim S wrote:
OK, stupid time.
Accidently bought 6 sheets of ordinary 9.5mm PB in 3x6' sheets. Need to use
vapour barrier PB for the ceilings on some bay window ceilings which will
be insulated with celotex above. I don't even think the use of vapour
barrier PB is that critical as there's a huge void over half the bay
ceiling as the pitched roof meets the lead flat roof of the bay, but vapour
barrier was suggested.
Any harm in using normal PB together with a vapour barrier or either plastic
or perhaps even bacofoil (turkey sized) stuck on the back of the board.
Seems a pointless waste to dump the board as I can't use it elsewhere.
I can't see a separate barrier being a problem - just because its not
glued to the board does not stop it working.


Yes, normally. Cooking foil comes in narrow strips though, and this
will need to be glued to avoid gaps between strips.

You could use the ali foil tape to stick em together if you really want.
;-)


--
Cheers,

John.

/================================================== ===============\
| Internode Ltd - http://www.internode.co.uk |
|-----------------------------------------------------------------|
| John Rumm - john(at)internode(dot)co(dot)uk |
\================================================= ================/

On Jul 15, 3:20*pm, Rad wrote:
On 15 July, 08:47, Tim S wrote:



OK, stupid time.

Accidently bought 6 sheets of ordinary 9.5mm PB in 3x6' sheets. Need to use
vapour barrier PB for the ceilings on some bay window ceilings which will
be insulated with celotex above. I don't even think the use of vapour
barrier PB is that critical as there's a huge void over half the bay
ceiling as the pitched roof meets the lead flat roof of the bay, but vapour
barrier was suggested.

Any harm in using normal PB together with a vapour barrier or either plastic
or perhaps even bacofoil (turkey sized) stuck on the back of the board.

Seems a pointless waste to dump the board as I can't use it elsewhere.

Cheers

Tim

Tim
There is a BG wall board "paint on" vapour barrier - ? wall board top
coat or the like
any oil based paint will do
chris

I assume a coat of oil based paint is significantly less effective
than foil though, and less effective than plastic film. May be good
enough though.


NT

NT wrote:
On Jul 15, 3:20 pm, Rad wrote:
On 15 July, 08:47, Tim S wrote:



OK, stupid time.
Accidently bought 6 sheets of ordinary 9.5mm PB in 3x6' sheets. Need to use
vapour barrier PB for the ceilings on some bay window ceilings which will
be insulated with celotex above. I don't even think the use of vapour
barrier PB is that critical as there's a huge void over half the bay
ceiling as the pitched roof meets the lead flat roof of the bay, but vapour
barrier was suggested.
Any harm in using normal PB together with a vapour barrier or either plastic
or perhaps even bacofoil (turkey sized) stuck on the back of the board.
Seems a pointless waste to dump the board as I can't use it elsewhere.
Cheers
Tim
Tim
There is a BG wall board "paint on" vapour barrier - ? wall board top
coat or the like
any oil based paint will do
chris

I assume a coat of oil based paint is significantly less effective
than foil though, and less effective than plastic film. May be good
enough though.

You can get paint on DPC products if you want. Used before laying
screeds etc.

--
Cheers,

John.

/================================================== ===============\
| Internode Ltd - http://www.internode.co.uk |
|-----------------------------------------------------------------|
| John Rumm - john(at)internode(dot)co(dot)uk |
\================================================= ================/

NT wrote:
On Jul 15, 3:20 pm, Rad wrote:
On 15 July, 08:47, Tim S wrote:



OK, stupid time.
Accidently bought 6 sheets of ordinary 9.5mm PB in 3x6' sheets. Need to use
vapour barrier PB for the ceilings on some bay window ceilings which will
be insulated with celotex above. I don't even think the use of vapour
barrier PB is that critical as there's a huge void over half the bay
ceiling as the pitched roof meets the lead flat roof of the bay, but vapour
barrier was suggested.
Any harm in using normal PB together with a vapour barrier or either plastic
or perhaps even bacofoil (turkey sized) stuck on the back of the board.
Seems a pointless waste to dump the board as I can't use it elsewhere.
Cheers
Tim
Tim
There is a BG wall board "paint on" vapour barrier - ? wall board top
coat or the like
any oil based paint will do
chris

I assume a coat of oil based paint is significantly less effective
than foil though, and less effective than plastic film. May be good
enough though.


NT
Both foil and plastic film are 100% impervious

John Rumm wrote:
NT wrote:
On Jul 15, 3:20 pm, Rad wrote:
On 15 July, 08:47, Tim S wrote:



OK, stupid time.
Accidently bought 6 sheets of ordinary 9.5mm PB in 3x6' sheets. Need
to use
vapour barrier PB for the ceilings on some bay window ceilings which
will
be insulated with celotex above. I don't even think the use of vapour
barrier PB is that critical as there's a huge void over half the bay
ceiling as the pitched roof meets the lead flat roof of the bay, but
vapour
barrier was suggested.
Any harm in using normal PB together with a vapour barrier or either
plastic
or perhaps even bacofoil (turkey sized) stuck on the back of the board.
Seems a pointless waste to dump the board as I can't use it elsewhere.
Cheers
Tim
Tim
There is a BG wall board "paint on" vapour barrier - ? wall board top
coat or the like
any oil based paint will do
chris

I assume a coat of oil based paint is significantly less effective
than foil though, and less effective than plastic film. May be good
enough though.

You can get paint on DPC products if you want. Used before laying
screeds etc.


Probably not as effective on a porous surface though. IIRC paraffin wax
is the vital ingredient in water resistant PB

Stuart Noble wibbled:


Probably not as effective on a porous surface though. IIRC paraffin wax
is the vital ingredient in water resistant PB

Ah - but aren't there two distinct products: vapour barrier *and* moisture
resistant?

The former is useful to me to prevent excessive vapour getting to cold bits
of wood. The latter would be of more use perhaps in a bathroom?

Cheers

Tim

In article
,
NT wrote:
I can't see a separate barrier being a problem - just because its not
glued to the board does not stop it working.


Yes, normally. Cooking foil comes in narrow strips though, and this
will need to be glued to avoid gaps between strips.

What do you do with the gaps between boards? Just curious.

--
*Acupuncture is a jab well done*

Dave Plowman London SW
To e-mail, change noise into sound.

On Jul 15, 8:47*am, Tim S wrote:
OK, stupid time.

Accidently bought 6 sheets of ordinary 9.5mm PB in 3x6' sheets. Need to use
vapour barrier PB for the ceilings on some bay window ceilings which will
be insulated with celotex above. I don't even think the use of vapour
barrier PB is that critical as there's a huge void over half the bay
ceiling as the pitched roof meets the lead flat roof of the bay, but vapour
barrier was suggested.

I'm interested in why a vapour barrier is needed. is it because there
are no ventilation points into the void?

Robert

RobertL wrote:
On Jul 15, 8:47 am, Tim S wrote:
OK, stupid time.

Accidently bought 6 sheets of ordinary 9.5mm PB in 3x6' sheets. Need to use
vapour barrier PB for the ceilings on some bay window ceilings which will
be insulated with celotex above. I don't even think the use of vapour
barrier PB is that critical as there's a huge void over half the bay
ceiling as the pitched roof meets the lead flat roof of the bay, but vapour
barrier was suggested.

I'm interested in why a vapour barrier is needed. is it because there
are no ventilation points into the void?


Normally its to prevent condensation on the far side of e.g. porous
rockwool insulation.

Robert

RobertL coughed up some electrons that declared:

On Jul 15, 8:47*am, Tim S wrote:
OK, stupid time.

Accidently bought 6 sheets of ordinary 9.5mm PB in 3x6' sheets. Need to
use vapour barrier PB for the ceilings on some bay window ceilings which
will be insulated with celotex above. I don't even think the use of
vapour barrier PB is that critical as there's a huge void over half the
bay ceiling as the pitched roof meets the lead flat roof of the bay, but
vapour barrier was suggested.

I'm interested in why a vapour barrier is needed. is it because there
are no ventilation points into the void?

Robert

I think in this case it is to reduce the risk of condensation on cold
bridges, the rafter faces. And to reduce the amount of warm vapour leaking
into the cold side. These will be nominally air tight but there's no way to
make it 100% so - too many bits of random wood to seal every interface.

I have no way to overlay insulation on these, only between them.

The cold side has the requisite 50mm air gap.


Cheers

Tim

On Jul 15, 10:14*pm, The Natural Philosopher
wrote:
NT wrote:
On Jul 15, 3:20 pm, Rad wrote:
On 15 July, 08:47, Tim S wrote:

OK, stupid time.
Accidently bought 6 sheets of ordinary 9.5mm PB in 3x6' sheets. Need to use
vapour barrier PB for the ceilings on some bay window ceilings which will
be insulated with celotex above. I don't even think the use of vapour
barrier PB is that critical as there's a huge void over half the bay
ceiling as the pitched roof meets the lead flat roof of the bay, but vapour
barrier was suggested.
Any harm in using normal PB together with a vapour barrier or either plastic
or perhaps even bacofoil (turkey sized) stuck on the back of the board.
Seems a pointless waste to dump the board as I can't use it elsewhere..
Cheers
Tim
Tim
There is a BG wall board "paint on" vapour barrier - ? wall board top
coat or the like
any oil based paint will do
chris

I assume a coat of oil based paint is significantly less effective
than foil though, and less effective than plastic film. May be good
enough though.

NT

Both foil and plastic film are 100% impervious

not quite, hence some medical & food products need to be in glass
jars, and some plastic piping needs a foil layer in it. I assume its
good enough though.


NT