Cavity Wall insulation is associated with increased indoor humidity which is a risk factor for condensation and mould. Home owners suffering from black mould are told by installers and CIGA inspectors that humidity and condensation is the cause of their damp, yet home owners are also told that 'disturbing the insulation' which includes installing through wall vents apparently invalidates the 25 CIGA guarantee.  The industry need to stop blaming home owners and guarantees should be fit for purpose.  Occupiers instinctively know that living in a dwelling with visible mould has health implications. With the recent publication of the PAS2035 standards for retrofit  ventilation has been promoted to a 1st class citizen which must be addressed in any retrofit. Ventilation is incredibly important for the management of humidity, controlling mould growth and expelling various particulates from the room. The sort of particulates that are thought to be detrimental incl...

I'm slowly getting there in this long saga documenting the poor standard of CWI installed into our 1930s property. But over a year later and I'm still finding very basic examples of poor workmanship. This one is somewhat subtle but demonstrates why pumping in installation with minimal understanding of the building fabric is utterly reckless.  It has become apparent that the external DPC protrudes into the cavity and it does so in all the walls of the old part of house as illustrated in the diagram below. The DPC has a mortar bed on top of it which makes it very rigid and acts as a pinch point capable of snagging large pieces of bricks and mortar as they drop into the cavity, holding them against the internal wall above the DPC level. The impact of CWI on a protruding DPC The presence of such debris causes a thermal bridge (condensation spot risk) to the internal wall quite a few bricks up from the internal DPC and so any moisture that enters the cavity has ...