I am about to start dividing off my extended garage to create a man cave. This involves a studded dividing wall which along with the other three outer walls need insulating. Incidentally the garage is a timber framed structure with CLS roughly 4x2 frames with 18mm shiplap over a breathable membrane and lined behind with plywood. The plan is to fill up the spaces in the framework with either Celotex or Kingspan foam panels.

So the question is, can the foil coating do as a vapour barrier using sealing tape across the framework as I did when insulating the kitchen floor or do I need to add a polythene sheet over before boarding the inner wall?

I have been watching some YouTube of people doing similar things and have been left confused. The following video is a compilation of a number of videos of a professional build of a garden room.

https://youtu.be/S92rEaAj188

The guy insulates the bays between frames with foil coated foam panels before adding a rock wool bat sound deadening layer and then a vapour barrier before plaster boarding but then cuts holes in the PB for sockets destroying the vapour barrier behind?

Got to admit some of the work looks rough and some to my mind over engineered. See what you think the relative insulation is towards the end of the video or you can look at the daily video record of 15 daily videos.

Richard

On 24/05/2021 10:58, Tricky Dicky wrote:
I am about to start dividing off my extended garage to create a man
cave. This involves a studded dividing wall which along with the
other three outer walls need insulating. Incidentally the garage is a
timber framed structure with CLS roughly 4x2 frames with 18mm shiplap
over a breathable membrane and lined behind with plywood. The plan is
to fill up the spaces in the framework with either Celotex or
Kingspan foam panels.

So the question is, can the foil coating do as a vapour barrier using
sealing tape across the framework as I did when insulating the
kitchen floor or do I need to add a polythene sheet over before
boarding the inner wall?

The foil will act as a vapour barrier if any joints are taped up with
foil tape.


I have been watching some YouTube of people doing similar things and
have been left confused. The following video is a compilation of a
number of videos of a professional build of a garden room.

https://youtu.be/S92rEaAj188

The guy insulates the bays between frames with foil coated foam
panels before adding a rock wool bat sound deadening layer and then a
vapour barrier before plaster boarding but then cuts holes in the PB
for sockets destroying the vapour barrier behind?

Got to admit some of the work looks rough and some to my mind over
engineered. See what you think the relative insulation is towards the
end of the video or you can look at the daily video record of 15
daily videos.

ok not had a chance to look at the videos.

However, the general rule for vapour barriers is that they need to be in
a position where they can prevent warm moist air reaching a cold
surfaces - especially if those are in voided off parts of a building
(aka interstitial spaces).

So in the case of the rigid Kingspan et al boards (aka Polyisocyanurate
foam (PIR)) with a foil cover, there is a barrier on the warm side of
the insulation. With something like rockwool there is no "built in"
barrier, and the insulation itself is also air permeable - so there is
some logic in preventing the warm wet air reaching the warm side of the
insulation since that (and its moisture) can permeate the insulation and
migrate toward the cold surface.

Where you have rockwool over PIR boards, its probably less critical
since the warm side of the PIR boards will likely be above the dew point
anyway.


--
Cheers,

John.

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On 24/05/2021 10:58, Tricky Dicky wrote:
I am about to start dividing off my extended garage to create a man
cave. This involves a studded dividing wall which along with the
other three outer walls need insulating. Incidentally the garage is a
timber framed structure with CLS roughly 4x2 frames with 18mm shiplap
over a breathable membrane and lined behind with plywood. The plan is
to fill up the spaces in the framework with either Celotex or
Kingspan foam panels.

So the question is, can the foil coating do as a vapour barrier using
sealing tape across the framework as I did when insulating the
kitchen floor or do I need to add a polythene sheet over before
boarding the inner wall?

yes it can


I have been watching some YouTube of people doing similar things and
have been left confused. The following video is a compilation of a
number of videos of a professional build of a garden room.

https://youtu.be/S92rEaAj188

The guy insulates the bays between frames with foil coated foam
panels before adding a rock wool bat sound deadening layer and then a
vapour barrier before plaster boarding but then cuts holes in the PB
for sockets destroying the vapour barrier behind?


First of all making a you tube video is no guarantee of competence.
Secondly vapour barriers are not about perfection as much as a 90%
reduction in humidity etc

I have foil backed plasterboard and rockwool insulation. Vapour barrier
is not perfect, but its *good enough*





--
WOKE is an acronym... Without Originality, Knowledge or Education.

In message , John
Rumm writes
On 24/05/2021 10:58, Tricky Dicky wrote:
I am about to start dividing off my extended garage to create a man
cave. This involves a studded dividing wall which along with the
other three outer walls need insulating. Incidentally the garage is a
timber framed structure with CLS roughly 4x2 frames with 18mm shiplap
over a breathable membrane and lined behind with plywood. The plan is
to fill up the spaces in the framework with either Celotex or
Kingspan foam panels.
So the question is, can the foil coating do as a vapour barrier
using
sealing tape across the framework as I did when insulating the
kitchen floor or do I need to add a polythene sheet over before
boarding the inner wall?

The foil will act as a vapour barrier if any joints are taped up with
foil tape.


I have been watching some YouTube of people doing similar things and
have been left confused. The following video is a compilation of a
number of videos of a professional build of a garden room.
https://youtu.be/S92rEaAj188
The guy insulates the bays between frames with foil coated foam
panels before adding a rock wool bat sound deadening layer and then a
vapour barrier before plaster boarding but then cuts holes in the PB
for sockets destroying the vapour barrier behind?
Got to admit some of the work looks rough and some to my mind over
engineered. See what you think the relative insulation is towards the
end of the video or you can look at the daily video record of 15
daily videos.

ok not had a chance to look at the videos.

However, the general rule for vapour barriers is that they need to be
in a position where they can prevent warm moist air reaching a cold
surfaces - especially if those are in voided off parts of a building
(aka interstitial spaces).

So in the case of the rigid Kingspan et al boards (aka Polyisocyanurate
foam (PIR)) with a foil cover, there is a barrier on the warm side of
the insulation. With something like rockwool there is no "built in"
barrier, and the insulation itself is also air permeable - so there is
some logic in preventing the warm wet air reaching the warm side of the
insulation since that (and its moisture) can permeate the insulation
and migrate toward the cold surface.

Where you have rockwool over PIR boards, its probably less critical
since the warm side of the PIR boards will likely be above the dew
point anyway.

How much moisture are you planning to put in a *man cave* anyway?
I suppose it might convert to a micro-brewery:-)

Small point on foil taping (in my case Celotex) there is a release agent
on the foil surface and I found tape peeling off after appearing to
stick securely. Meths. worked well.



--
Tim Lamb

On 25/05/2021 09:24, Tim Lamb wrote:
In message , John
Rumm writes
On 24/05/2021 10:58, Tricky Dicky wrote:
I am about to start dividing off my extended garage to create a man
cave. This involves a studded dividing wall which along with the
other three outer walls need insulating. Incidentally the garage is a
timber framed structure with CLS roughly 4x2 frames with 18mm shiplap
over a breathable membrane and lined behind with plywood. The plan is
to fill up the spaces in the framework with either Celotex or
Kingspan foam panels.
Â*So the question is, can the foil coating do as a vapour barrier using
sealing tape across the framework as I did when insulating the
kitchen floor or do I need to add a polythene sheet over before
boarding the inner wall?

The foil will act as a vapour barrier if any joints are taped up with
foil tape.


I have been watching some YouTube of people doing similar things and
have been left confused. The following video is a compilation of a
number of videos of a professional build of a garden room.
Â*https://youtu.be/S92rEaAj188
Â*The guy insulates the bays between frames with foil coated foam
panels before adding a rock wool bat sound deadening layer and then a
vapour barrier before plaster boarding but then cuts holes in the PB
for sockets destroying the vapour barrier behind?
Â*Got to admit some of the work looks rough and some to my mind over
engineered. See what you think the relative insulation is towards the
end of the video or you can look at the daily video record of 15
daily videos.

ok not had a chance to look at the videos.

However, the general rule for vapour barriers is that they need to be
in a position where they can prevent warm moist air reaching a cold
surfaces - especially if those are in voided off parts of aÂ* building
(aka interstitial spaces).

So in the case of the rigid Kingspan et al boards (aka
Polyisocyanurate foam (PIR)) with a foil cover, there is a barrier on
the warm side of the insulation. With something like rockwool there is
no "built in" barrier, and the insulation itself is also air permeable
- so there is some logic in preventing the warm wet air reaching the
warm side of the insulation since that (and its moisture) can permeate
the insulation and migrate toward the cold surface.

Where you have rockwool over PIR boards, its probably less critical
since the warm side of the PIR boards will likely be above the dew
point anyway.

How much moisture are you planning to put in a *man cave* anyway?
I suppose it might convert to a micro-brewery:-)

So long as you refrain from exhaling you should be fine :-)

Small point on foil taping (in my case Celotex) there is a release agent
on the foil surface and I found tape peeling off after appearing to
stick securely. Meths. worked well.

Interesting - not seen that before, but then again I have not often used
genuine Celotex. (and for that matter have usually ended up covering up
the taped areas fairly shortly after anyway)

--
Cheers,

John.

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

Thanks for all the advice, put my mind at rest. Now just a few jobs to complete and it is on with the mancave.

Richard

In message ,
Tricky Dicky writes
Thanks for all the advice, put my mind at rest. Now just a few jobs to
complete and it is on with the mancave.

Breaking news!

Post lunch international call enquiring after our loft insulation.
Nicely spoken English voice.

After a few opening gambits, it became clear she was hoping to arrange
some sort of follow up to the *green deal*? loft insulation we had
fitted to the farmhouse some years back.

She confided that both Rockwool and Glass fibre absorb moisture leading
to degradation and less effective insulation due to compaction!

At this stage I decided to be merciful and said we were no longer at the
farmhouse but had retained our landline number. Undeterred she moved on
to the loft insulation at the cottage. However, became totally flummoxed
at the idea a modern construction would have a vapour barrier....
--
Tim Lamb