I recently reviewed this report into the effectiveness of cavity insulation in modern structures. It is rather disturbing to see that BBA were quite easily able to reproduce wet walls within a cavity, as part of their testing. They claim this was due to the severity of the test rig, and under normal atmospheric conditions this might not occur - but a 15 day test, as opposed to years of normal exposure, is not really a valid test in my view. Their tests do not reproduce the effects of moisture degradation of mortars - and consequent water penetration as salts form, and degrade mortar beds. What is disturbing is the very clear evidence that moisture penetration was happening in many of the tests - and no follow up work appears to have been done to find out why.
BBA report into Cavity Insulation problems
This report was ONLY done using modern materials - and does not accurately reproduce any of the conditions found in older buildings with cavities - lime mortars, degraded mortar beds because of cement render trapping condensation and so on.
NO assessment was made of temperature differences, of condensation potential, moisture levels externally, internally, and within the room.
A poor report overall in my opinion - which leaves a LOT of unanswered questions, and throws serious doubt on the use of blown fibre - note the comments they make about blown fibreglass being wet.