Doing testing of existing homes it is typical to see mottled patterns of surface temperatures with the FLIR Infrared Thermal Imager during Blower Door Testing.
Part of the problem is air sealing and the other part of the problem is poorly installed fiberglass insulation.
This is not a rant against fiberglass insulation (I am a fan of both Rock Wool/Roxul and dense packed cellulose) for retrofit projects. Fiberglass batt or blown insulation can perform fine, if it is installed properly and the air sealing details are paid proper attention.
How successful have some of you folks been with going into a sloppy fiberglass insulated house and doing dense pack cellulose into the wall cavity?