Foam backed board?

On (the inside of) an external wall, is there much benefit to foam backed boards? Construction is stone in places, brick in others.

What about party walls?

Generally speaking of course.

Reply to
R D S
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What are the wall constructions?

Any insulation already in them?

Jim K

Reply to
JimK

yes. If the stone has no other insulation.

Probably not, since the temperature differential across them will be small.

Reply to
The Natural Philosopher

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Reply to
meow2222

Yes, but beware interstitial condensation (with any form of internal insulation).

Short version: The air inside a house usually has more water vapour (measured in grams / cubic meter) than the air outside. The vapour level through the thickness of the wall will gradually fall to the level outside. If you insulate inside, the temperature will fall steeply to the outside level, so the temperature may fall below the dew-point in the middle of the wall.

Solutions are: A really vapour-tight vapour barrier. Using an insulation that can wick the condensate away.

Unlikely to be worth it. The other side of the wall will be pretty warm anyway (and no wind on it).

Reply to
Martin Bonner

/ Short version: The air inside a house usually has more water vapour (measured in grams / cubic meter) than the air outside. The vapour level through the thickness of the wall will gradually fall to the level outside. If you insulate inside, the temperature will fall steeply to the outside level, so the temperature may fall below the dew-point in the middle of the wall/q

And?.........

Jim K

Reply to
JimK

... and you get condensation. Regular soaking in liquid water is damaging for most building materials (particularly wood and lime mortar.)

(I had mistakenly assumed that didn't need saying).

Reply to
Martin Bonner

- show quoted text - ... and you get condensation. Regular soaking in liquid water is damaging for most building materials (particularly wood and lime mortar.)

(I had mistakenly assumed that didn't need saying). /q

Mmm I believe the jury is still out on all this.

France has, so I've read, internally insulated millions of houses with no apparent interstitial ill effects according to their equivalent of our BRE.

Jim K

Reply to
JimK

not really

trivial to do

NT

Reply to
meow2222

/> Mmm I believe the jury is still out on all this.

not really

trivial to do

NT/q

Gee definitive stuff there...

Jim K

Reply to
JimK

If the foam has a closed cell sructure it is not a problem. If it is air permeable, there may well be a problem. Many foams are aluiminium foil covered to prevent interstitial condensation.

Reply to
harryagain

/If the foam has a closed cell sructure it is not a problem. If it is air permeable, there may well be a problem. Many foams are aluiminium foil covered to prevent interstitial condensation/q

Indeed.

It's hard to imagine a habitable solid walled room that would not 'suffer' interstitial condensation according to the definitions promulgated here.

Jim K

Reply to
JimK

Maybe you'd had a few too many when you (mis)read those 'definitions promulgated here.'

Reply to
meow2222

/Maybe you'd had a few too many when you (mis)read those 'definitions promulgated here.' /q

Er.., no dear....

Anything constructive to add today?

Jim K

Reply to
JimK

I think its pretty much covered already. Troll on.

NT

Reply to
meow2222

/I think its pretty much covered already. Troll on.

NT /q

I'll take that as a 'no' then (once again).

Why do you bother posting? you don't add anything?

Who's the real troll?

Oh and f*ck off, feel better now?

Jim K

Reply to
JimK

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Reply to
harryagain

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