>Is this actually proven Jon?<<

There's evidence that it does Keith. For instance, damp environments accelerate the deterioration of wall ties (particularly older types common before 1990) and increase the probability of rot: The rate of deterioration found in older types of cavity wall building may be one of the reasons for moving over to stainless from galvanised. In older cavity buildings, it may also create a damp point around the timbers that sit on the inner leaf (another vulnerable detail that building regulations have changed in the last 30 years or so). Just read Tony's note: Yes, spalling is another decay mechanism that would be accelerated by internal insulation. Also, of top of head.. in some buildings where a vapour barrier has been installed, by internally insulating, one might be putting the frame into a condition where this barrier becomes on the 'cold side' and thus helping condensation to form at the interface (which again might impact on the vulnerable connections to external structure)

Edit: lower temperatures do lower humidity (% by volume or mass) but this condition would cause higher relative humidity (% of maximum possible relative to temperature): So by lowering the temperature and not having driving energy to help evaporation, you're creating a condition where condensation is more likely to occur because in cooling cycles the relative humidity is at 100%: The lower absolute humidity would be a result of condensation.

There are some building types that internal insulation wouldn't impact on at all.

However, I couldn't state with certainty the CO2 impact of internally insulating versus increased demolition rates: I ran it through the model and got, for a sample timber building, a worst case impact of 10kg so it would probably be environmentally good to do this (if not financially good).

If the mortgage and insurance companies realise that this is going on and the potential impact of doing it, there may be a problem, (in disposing of a building to which a detrimental refurb has been undertaken), in the future.

I agree with your comment above: This is what I would do if there was even the remote possibility that the local planning department would allow it. For most people, there would be no chance of getting planning for external insulation: There may be some advantages in waiting until the Government sorts out its priorities regarding existing stock.

I've got some sketches on my desk for this thread which I need to turn into drawings but I'm held up on the spring edition of green Building mag at the moment.

Any body ever look for and/or find insulated joist hangers ? I have looked but not found . When dry lining continuity of insulation is important - and whilst it is possible to insulate in between joists of intermediate floors - how can you at the joist ends ? The worst place for interstitial condensation to arise

Compromises occur such as - use pressure impregnated joists + fingers crossed ?
Or firstly anchor a hardwood joist bearer along the wall and hang the joists off it

Anybody else cracked this one ?

So that's a no then Tony

which type of insulation did they eat?!

There are a series of reports from SPAB where real life research seems to address several of concerns raised in the initial questions. There are a number of approaches being tested out in real time and in real life - and the results are re-assuring (and even a little surprising!)

Here's a link;

http://www.spab.org.uk/downloads/Courses%202014/SPAB_BPSReport%202013Final.pdf

I too have an old rubble built house and there is no acceptable way to add External Wall insulation. So it has to be internally insulated where this is possible.

The solution which seems to fit the bill is Woodfibre boards plus lime internal plastering (or PIR board).

I think I'll go for the woodfibre option (but probably more like 100mm) plus lime and see how things go .....

Cheers

Y

Posted By: NoyersI'm struggling to find a solution that doesn't involve plastic foams

The worries you rightly point to, about lifetime exposure to low level cocktails of toxins, vanish completely with MHRV.

Far from the conventional 'I wouldn't want to live in an airtight box', everyone who's lived with MHRV reports a wonderful 'mountain fresh' indoor environment because all the headachey sleepy toxins we think are 'normal', are swept away - radon too.

That being the case, feel free to use plastic insulants - no more beneficial, eco-friendly use of petrochemicals could be imagined.