aluminium foil
 

Hi I have recently moved into a new house (to me anyway) and am going to be
doing some improvements. One of which is to insulate the attic as the
present insulation material is woefully inadequate. I was told that before I
lay the new insulation I should put down a layer of aluminium foil before
laying the insulation between the joists, as this will reflect heat back
down into the rooms below. Is this correct or his the person giving me this
advice talking a load of ********. Also the house is a upstairs downstairs
type and I have discovered that there is no insulation of any type between
the floors. Just a gap. Should I put any insulation in there? It would have
to be a type that could be put in without lifting the flooring but there is
some access from a cupboard under the stairs. Would it be worth while or
would the hassle involved outweigh the advantages? Or is this not normally
insulated?

I hope that I can get some correct advice from this group as the person who
is giving me advice at the moment seems to make it up as he goes along. I
think he may be for the chop.

Thanks Karen

Karen wrote:

I was told that before I
lay the new insulation I should put down a layer of aluminium foil before
laying the insulation between the joists, as this will reflect heat back
down into the rooms below. Is this correct or his the person giving me this
advice talking a load of ********.

While it's technically correct, the amount of energy it will reflect
will be negligible, so for all intents and purposes they are talking
********.


Also the house is a upstairs downstairs
type and I have discovered that there is no insulation of any type between
the floors. Just a gap. Should I put any insulation in there? It would have
to be a type that could be put in without lifting the flooring but there is
some access from a cupboard under the stairs. Would it be worth while or
would the hassle involved outweigh the advantages? Or is this not normally
insulated?

Why would you insulate the floor? Any heat lost from downstairs will
simply end up upstairs - so overall you lose nothing.


I hope that I can get some correct advice from this group as the person who
is giving me advice at the moment seems to make it up as he goes along. I
think he may be for the chop.

Good plan. His name isn't IMM/Drivel, is it?


--
Grunff

"Grunff" wrote in message
...
Karen wrote:

I was told that before I lay the new insulation I should put down a layer
of aluminium foil before laying the insulation between the joists, as
this will reflect heat back down into the rooms below. Is this correct
or his the person giving me this advice talking a load of ********.

While it's technically correct, the amount of energy it will reflect will
be negligible, so for all intents and purposes they are talking ********.

But, the foil will act as a vapour barrier, all be it an imperfect one,
which is a worthwhile reason to do it.

--
73
Brian, G8OSN
www.g8osn.org.uk

On Wed, 05 Oct 2005 16:17:42 GMT, "Brian Reay"
wrote:



"Grunff" wrote in message
.. .
Karen wrote:

I was told that before I lay the new insulation I should put down a layer
of aluminium foil before laying the insulation between the joists, as
this will reflect heat back down into the rooms below. Is this correct
or his the person giving me this advice talking a load of ********.

While it's technically correct, the amount of energy it will reflect will
be negligible, so for all intents and purposes they are talking ********.

But, the foil will act as a vapour barrier, all be it an imperfect one,
which is a worthwhile reason to do it.

Where is the 'vapour' coming from Brian? I would have *thought* you
wouldn't want to trap vapour in the room but let it permeate out
through the walls / ceilings etc and if there was a vapour trap above
the ceiling it would keep the plasterboard damp?

All the best ..

T i m

T i m wrote:
snip
Where is the 'vapour' coming from Brian? I would have *thought* you
wouldn't want to trap vapour in the room but let it permeate out
through the walls / ceilings etc and if there was a vapour trap above
the ceiling it would keep the plasterboard damp?

Nope.
Plasterboard isn't an insulator.
It'll be at essentially the same temperature as the room.
However, it's essentially porous to water vapour, and what that means
is that you get warm damp air on the far side of the insulation, shortly
after you start breathing or cooking in a room.
It then permeates through insulation, cooling as it goes.
If you are unlucky, it cools to below the dew-point, and you get
condensation in the insulation, which can cause whatever's touching it
to rot rapidly.

The right way to insulate nearly all structures is to have the inside
a vapour-tight box, with air entry and exit done through ventilators,
not a porous structure.
Otherwise, if you try to insulate highly, you're likely to get condensation
where you don't want it.

"Karen" wrote

I was told that before I lay the new insulation I should put down a layer
of aluminium foil before laying the insulation between the joists, as this
will reflect heat back down into the rooms below. Is this correct or his
the person giving me this advice talking a load of ********.

I hope that I can get some correct advice from this group as the person
who is giving me advice at the moment seems to make it up as he goes
along. I think he may be for the chop.


Did this person also advise you to wrap the tinfoil around your head to stop
aliens reading your mind?
If so definitely give him the chop. Also run away quite quickly.........

hth
Neil

On 05 Oct 2005 16:52:36 GMT, Ian Stirling
wrote:

T i m wrote:
snip
Where is the 'vapour' coming from Brian? I would have *thought* you
wouldn't want to trap vapour in the room but let it permeate out
through the walls / ceilings etc and if there was a vapour trap above
the ceiling it would keep the plasterboard damp?

Nope.
Plasterboard isn't an insulator.
It'll be at essentially the same temperature as the room.

Ok ..

However, it's essentially porous to water vapour, and what that means
is that you get warm damp air on the far side of the insulation, shortly
after you start breathing or cooking in a room.

That's what I thought ...

It then permeates through insulation, cooling as it goes.
If you are unlucky, it cools to below the dew-point, and you get
condensation in the insulation, which can cause whatever's touching it
to rot rapidly.

Ah .. not a good thing then.

The right way to insulate nearly all structures is to have the inside
a vapour-tight box, with air entry and exit done through ventilators,
not a porous structure.

Understood, so anything non permeable 'above' the ceiling plasterboard
and between the joists could cause moisture to collect and via
capilary action wet the roof timbers? Even of it didn't get *through*
the plasterboard to 'cool to the dew point' where would it go?

Otherwise, if you try to insulate highly, you're likely to get condensation
where you don't want it.

And that's what I thought ... something to be said for draughty sash
windows then ;-)

All the best

T i m

"T i m" wrote in message
...

Understood, so anything non permeable 'above' the ceiling plasterboard
and between the joists could cause moisture to collect and via
capilary action wet the roof timbers? Even of it didn't get *through*
the plasterboard to 'cool to the dew point' where would it go?


If it doesn't "cool to the dew point", then it stays as vapour.

Either the "damp air" then gets circulated out of the house or, if the more
vapour is added, you reach the point where the air at the ambient
temperature can't 'hold' the all vapour and it condenses out.

In fact, if this didn't happen in the wider world, we'd not need umbrellas
;-)

Foil under new insulation isn't as good as a proper vapour barrier (new
houses should have foil backed plasterboard for ceilings) but it is better
than nothing.

--
73
Brian, G8OSN
www.g8osn.org.uk

T i m wrote:
Where is the 'vapour' coming from Brian? I would have *thought* you
wouldn't want to trap vapour in the room but let it permeate out

They're quite right. The warm air absorbs water vapour from breathing,
plants, laudry, cooking, etc.. People generally prefer Rh around 50%,
so it's an advantage. It's not a problem whilst the warm air stays in
the heated space. If it can get into the loft it will condense in the
insulation & can waterlog it and reduce it's efficiency. It rarely
causes problems in the UK, for some reason. In colder climates you can
find the insulation saturated and frozen.

You can often get rot/damp problems above the airing cupboard, where
great holes are usually hacked for small pipes and where damp laundry
is dried.

Aidan wrote:

PS
Where I have seen problems with no/defective vapour barriers is on
chilled water pipes. The chilled water is generally run at 6 degC and,
if mineral/glass fibre insulation is used, it WILL get waterlogged
unless there is a continuous vapour barrier. The water vapour condenses
from the atmosphere. The BS on pipe insulation goes into great detail
about having a continuous vapour barrier and the pipe supports/clips
outside the insulation & vapour barrier.

This is relevant, in that 6 degC is quite warm compared with the winter
temperatures you might expect in most loft spaces and the same
mechanism is causing the condensation.

In article ,
"Brian Reay" writes:

But, the foil will act as a vapour barrier, all be it an imperfect one,
which is a worthwhile reason to do it.

It's not.
The permiability of the plasterboard is very much lower than
the rate moisture escapes from even a poorly ventilated loft.
If the amount of moisture in the loft is an issue, then you
need to ventilate the loft, and it's much more likely to be
comming from a roof leak or header tanks, or holes punched in
the ceiling for recessed lamps, loft hatches, etc.
Forget about the tin foil.

--
Andrew Gabriel

Gripper wrote:

Did this person also advise you to wrap the tinfoil around your head to stop
aliens reading your mind?
If so definitely give him the chop. Also run away quite quickly.........

What if he advised earth bonding the foil?

--
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In article , Grunff
writes
Karen wrote:

I was told that before I
lay the new insulation I should put down a layer of aluminium foil before
laying the insulation between the joists, as this will reflect heat back
down into the rooms below. Is this correct or his the person giving me this
advice talking a load of ********.

While it's technically correct, the amount of energy it will reflect
will be negligible, so for all intents and purposes they are talking
********.

Gggggrn not the right answer, foil will only reflect heat where the transfer
mechanism is radiation, when in direct contact with any material, the heat
transfer mech will be conduction so it wont help at all. It'll only help it's
adjacent to an air gap and even then the efficiency will be reduced as the
foil tarnishes.

I agree with the end result tho', ******** was spake . . .
--
fred

fred wrote:

Gggggrn not the right answer, foil will only reflect heat where the transfer
mechanism is radiation, when in direct contact with any material, the heat
transfer mech will be conduction so it wont help at all.

I was taking that into account, which is why I said negligibl (honest!).
The foil won't be in direct contact with the plasterboard right across -
there will be a proportion of the area, maybe 10% or more, where the
foil is sitting there with a gap between it and the pb. In tose areas,
the heat transfer between the pb and the foil will be convective and
radiative.

:-P


--
Grunff

""Pet @ www.gymratz.co.uk ;¬)"" wrote

Gripper wrote:

Did this person also advise you to wrap the tinfoil around your head to
stop aliens reading your mind?
If so definitely give him the chop. Also run away quite quickly.........

What if he advised earth bonding the foil?


then he is a "Competent Person" with regards to Part P of the regs: not
only must the OP follow his advice to the letter, she must pay him great
wodges of cash, and not run away at all.

:-

In article , Grunff
writes
fred wrote:

Gggggrn not the right answer, foil will only reflect heat where the transfer
mechanism is radiation, when in direct contact with any material, the heat
transfer mech will be conduction so it wont help at all.

I was taking that into account, which is why I said negligibl (honest!).
The foil won't be in direct contact with the plasterboard right across -
there will be a proportion of the area, maybe 10% or more, where the
foil is sitting there with a gap between it and the pb. In tose areas,
the heat transfer between the pb and the foil will be convective and
radiative.

:-P

Yeah right, was just bringing you back down to earth after my unbridled
praise in the solder thread :-).
--
fred

"Andrew Gabriel" andrew@a17 wrote in message
.. .
In article ,
"Brian Reay" writes:

But, the foil will act as a vapour barrier, all be it an imperfect one,
which is a worthwhile reason to do it.

It's not.
The permiability of the plasterboard is very much lower than
the rate moisture escapes from even a poorly ventilated loft.

So why do building regs now specify foil backed plasterboard?

--
73
Brian, G8OSN
www.g8osn.org.uk

On Wed, 05 Oct 2005 19:50:31 GMT, fred wrote:

foil will only reflect heat where the transfer
mechanism is radiation, when in direct contact with any material, the heat
transfer mech will be conduction so it wont help at all.

Like the guy in the camping shop that said 'put some of that foil they
use for emergency blankets on top of your airbed and under your
sleeping bag to keep you warm ..." shakes head

All the best ..

T i m

On Wed, 05 Oct 2005 20:59:54 +0000, Brian Reay wrote:



"Andrew Gabriel" andrew@a17 wrote in message
.. .
In article ,
"Brian Reay" writes:

But, the foil will act as a vapour barrier, all be it an imperfect one,
which is a worthwhile reason to do it.

It's not.
The permiability of the plasterboard is very much lower than
the rate moisture escapes from even a poorly ventilated loft.

So why do building regs now specify foil backed plasterboard?

There are plenty of regs which have only a marginal impact of the quality
of the end result, but make significant cost implications for compliance.
This problem is not confined to the BRs.



--
Ed Sirett - Property maintainer and registered gas fitter.
The FAQ for uk.diy is at http://www.diyfaq.org.uk
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