Painting & Wallpapering/paint blistering on outside walls
I have a 40+ year old colonial home located in New Hampshire that I purchased approximately 12 years ago. The pine clapboard siding had never been repainted by the original owners.
The siding was in bad shape. I had to replace many cracked boards. I hired a painter to paint over the original stained paint with tinted water base primer and one coat of Latex. It looked great but only lasted a couple of years before it started to blister on all exterior walls of the house and garage.
I have been scrapping, priming and repainting one side of the house and garage every year and the blistering continues. I have been using expensive oil base primer and quality water base paint.
The exterior walls are framed with 2x6 construction, 6" of fiberglass insulation with a polyethylene vapor barrier between the interior sheetrock and insulation.
I am also experiencing the same issues on my attached garage which has no insulation or inside finish.
The problem is that you are still getting moisture through your finish either by condensation or vapors created by humidity. Your primers especially the waterbased ones are not getting the surface sealed adequately prior to finish. Prior to applying a good oil primer (Benj.-Moore) I would strip all of the problem areas and apply a 2 part clear epoxy. You can google local merchants for a product called Restor-it. This has worked wonders for me on exposed wood walls.