Cavity wall insulation failure can cause serious hardship to vulnerable households who believed it would help keep their homes warmer and fuel bills lower.
Gall methiant inswleiddio wal geudod arwain at galedi difrifol i bobl sy'n agored i niwed ac a oedd dan yr argraff y byddai inswleiddio'n cadw eu tai'n gynnes ac yn gostwng eu biliau ynni.