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Default qu about insulation of outside wall

I plan to insulate the walls of my still-to-be-built 'garden office'
as well as I can, and wondered whether someone could help on a couple
of questions...

I understand about a vapour barrier having to be on the warm side of
the insulation; and about the difference between the conduction,
convection, and radiation of thermal energy i.e. heat.

What I am confused about is what can be next to the said vapour
barrier, which will be foil.

Going from the outside, I plan to have:

1) weather-resistant paint as used on houses in Sweden
2) 10mm timber
3) a thick layer of polystyrene, probably XPS, probably 2 x 100mm
4) plasterboard
5) common-or-garden internal silk emulsion paint

(I won't mention the studs. These will prob be in two layers, one
perpendicular to the other).

My questions a

a) should there be an air gap between the polystyrene and the
plasterboard?
b) if so, where should the foil layer be? I.e. should I use foil-
backed polystyrene or foil-backed plasterboard?
c) as well as 1-5 and the foil, and not counting the studs, should
there be a layer of anything else in there?

(I'm aiming for an inside-to-outside R-value in excess of about 4.5
RSI x 8 inches, giving R 36).

Thanks for any help with this.

John
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Default qu about insulation of outside wall

John Nagelson wrote:
I plan to insulate the walls of my still-to-be-built 'garden office'
as well as I can, and wondered whether someone could help on a couple
of questions...

I understand about a vapour barrier having to be on the warm side of
the insulation; and about the difference between the conduction,
convection, and radiation of thermal energy i.e. heat.

What I am confused about is what can be next to the said vapour
barrier, which will be foil.

Going from the outside, I plan to have:

1) weather-resistant paint as used on houses in Sweden
2) 10mm timber
3) a thick layer of polystyrene, probably XPS, probably 2 x 100mm


Way too much - the walls are to be 225mm thick? - are you planning on using
8 inch timber framing?

4) plasterboard
5) common-or-garden internal silk emulsion paint

(I won't mention the studs. These will prob be in two layers, one
perpendicular to the other).

My questions a

a) should there be an air gap between the polystyrene and the
plasterboard?


No - you can purchase PB with polystyrene already affixed to the back of
it....come to think of it, there's no vapour barrier in it neither.

b) if so, where should the foil layer be? I.e. should I use foil-
backed polystyrene or foil-backed plasterboard?
c) as well as 1-5 and the foil, and not counting the studs, should
there be a layer of anything else in there?

(I'm aiming for an inside-to-outside R-value in excess of about 4.5
RSI x 8 inches, giving R 36).

Thanks for any help with this.

John


If it were mine, I'd buy 3X2 scant and 75mm jablite (polystyrene) and a roll
of visqueen.....it's only ever going to be a temporary structure anyway, and
there'll be little difference between using 75mm and 200mm of polystyrene,
inthat it's still going to be a cold shed.

And don't forget that you'll also need underfloor and loft insultaion
otherwise insulating the walls will be a waste of time.


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Default qu about insulation of outside wall

On Feb 28, 5:48*pm, "Phil L" wrote:
John Nagelson wrote:


Going from the outside, I plan to have:


1) weather-resistant paint as used on houses in Sweden
2) 10mm timber
3) a thick layer of polystyrene, probably XPS, probably 2
x 100mm


Way too much - the walls are to be 225mm thick? - are you
planning on using 8 inch timber framing?


Two lots of 4 inch. Over the top by some people's standards, I
realise. Call it a folly or a waste of capital investment, but I want
something very warm and with very low running costs.

4) plasterboard
5) common-or-garden internal silk emulsion paint


My questions a


a) should there be an air gap between the polystyrene and
the plasterboard?


No - you can purchase PB with polystyrene already affixed to
the back of it....come to think of it, there's no vapour
barrier in it neither.


How would you get a vapour barrier onto the warm side? Use vinyl paint
facing into the room or...?

If it were mine, I'd buy 3X2 scant and 75mm jablite
(polystyrene) and a roll of visqueen.....it's only ever going
to be a temporary structure anyway, and
there'll be little difference between using 75mm and 200mm
of polystyrene, in that it's still going to be a cold shed.

And don't forget that you'll also need underfloor and loft
insultaion otherwise insulating the walls will be a waste of
time.


Sure; it will be very warm once I've finished with it! As for
temporary, well true in the planning sense but it will be similar to
many buildings classified as permanent in Scandinavia.

What would you put on top of the visqueen?

I'd value your opinion on which is preferable, if I do it my way, i.e.
from outside:

1) polystyrene/foil, gap, plasterboard
2) polystyrene, gap, foil/plasterboard
3) just forget about the gap, in which case it doesn't matter what the
foil is stuck to

I'm told that when foil gets dusty, it stops reflecting so much
radiant heat. And various places say you need a gap by it; but I'm not
sure why.

Cheers,

John

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Default qu about insulation of outside wall

On 29 Feb, 10:42, John Nagelson wrote:
On Feb 28, 5:48 pm, "Phil L" wrote:

John Nagelson wrote:
Going from the outside, I plan to have:


1) weather-resistant paint as used on houses in Sweden
2) 10mm timber
3) a thick layer of polystyrene, probably XPS, probably 2
x 100mm


Way too much - the walls are to be 225mm thick? - are you
planning on using 8 inch timber framing?


Two lots of 4 inch. Over the top by some people's standards, I
realise. Call it a folly or a waste of capital investment, but I want
something very warm and with very low running costs.

4) plasterboard
5) common-or-garden internal silk emulsion paint
My questions a


a) should there be an air gap between the polystyrene and
the plasterboard?


No - you can purchase PB with polystyrene already affixed to
the back of it....come to think of it, there's no vapour
barrier in it neither.


How would you get a vapour barrier onto the warm side? Use vinyl paint
facing into the room or...?

If it were mine, I'd buy 3X2 scant and 75mm jablite
(polystyrene) and a roll of visqueen.....it's only ever going
to be a temporary structure anyway, and
there'll be little difference between using 75mm and 200mm
of polystyrene, in that it's still going to be a cold shed.


And don't forget that you'll also need underfloor and loft
insultaion otherwise insulating the walls will be a waste of
time.


Sure; it will be very warm once I've finished with it! As for
temporary, well true in the planning sense but it will be similar to
many buildings classified as permanent in Scandinavia.

What would you put on top of the visqueen?

I'd value your opinion on which is preferable, if I do it my way, i.e.
from outside:

1) polystyrene/foil, gap, plasterboard
2) polystyrene, gap, foil/plasterboard
3) just forget about the gap, in which case it doesn't matter what the
foil is stuck to

I'm told that when foil gets dusty, it stops reflecting so much
radiant heat. And various places say you need a gap by it; but I'm not
sure why.

Cheers,

John


It would be more usual to use celotex/kingspan, which is a better
insulator than polystyrene (but more expensive also). Taped with foil
tape to give a vapour barrier.
Simon.
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Default qu about insulation of outside wall


"John Nagelson" wrote in message
...
I plan to insulate the walls of my still-to-be-built 'garden office'
as well as I can, and wondered whether someone could help on a couple
of questions...

I understand about a vapour barrier having to be on the warm side of
the insulation; and about the difference between the conduction,
convection, and radiation of thermal energy i.e. heat.

What I am confused about is what can be next to the said vapour
barrier, which will be foil.

Going from the outside, I plan to have:

1) weather-resistant paint as used on houses in Sweden
2) 10mm timber
3) a thick layer of polystyrene, probably XPS, probably 2 x 100mm
4) plasterboard
5) common-or-garden internal silk emulsion paint

(I won't mention the studs. These will prob be in two layers, one
perpendicular to the other).

My questions a

a) should there be an air gap between the polystyrene and the
plasterboard?
b) if so, where should the foil layer be? I.e. should I use foil-
backed polystyrene or foil-backed plasterboard?
c) as well as 1-5 and the foil, and not counting the studs, should
there be a layer of anything else in there?

(I'm aiming for an inside-to-outside R-value in excess of about 4.5
RSI x 8 inches, giving R 36).

Thanks for any help with this.

John


Don't forget about building in some thermal inertia unless you are going to
provide a heating source which is on 24/7. A shed with intermittent heating
and very little thermal inertia will show rapid changes of temperature
causing condensation on the colder bits. Ideally I would have a very well
insulated shell as you are proposing and have some material with a high
specific heat inside. eg Concrete blocks.
Don





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Default qu about insulation of outside wall

On Feb 29, 11:04*am, sm_jamieson wrote:
On 29 Feb, 10:42, John Nagelson
wrote:


It would be more usual to use celotex/kingspan, which is a
better insulator than polystyrene (but more expensive also).
Taped with foil tape to give a vapour barrier.
Simon


Thanks - I will have a look at this. Seems to have very high
resistivity. I've seen it with foil both sides. I guess this is for
manufacturing reasons?

John
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