Cavity insulation and vents

[ronedwards]

Hello

Have just had cavity wall insulation installed on my 1950's detached house and the installers have knocked out all of the 9X3 terraccotta vents above the DPC and replaced them with new plastic ones. I asked them why they did this and they said that it was because the vents filled up so they had to knock the vents out to clear the insulation and put a sleeve inside so that air flow could still get in and air my floor otherwise my floor would rot over time. Now, I have a solid floor and the vents are ABOVE the dpc, so surely they are just cavity vents that could have been left alone? Or do solid floors still need air flow? it is not a suspended solid floor, just a normal one. But there are about 10 of these vents, just above the dpc.

can anyone shed any light?

cheers in advance