I wish to take your last post item by item so we are clear in our understanding of each other. First I am not acting on behalf of the USDA Forest Products Laboratory, though I am a committee member there, and rely almost totally on their unbiased expert advice. I am attempting to show the causes of the problems and Dis-satisfaction with the products I represent on such issues, namely Western Red Cedar Lumber.
You could not be more wrong about the scientists who do this work. They constructed a new house 4 years ago at the FPL just to study numerous issues, and they did not tell the contractor how to build it. As to old homes and such issues the many branches of the FPL around the US provide a limitless supply of data about restorative issues. You need to remember that any nationally notable structures turn to the lab, as did Howard Hughes for building his 'Spruce Goose' and other agencies like the U.S. Park Service that maintains many old, even ancient homes and buildings. All of these experiences feed the scientist at the FPL, and they travel extensively as part of their work. They are most definitely NOT just lab workers, far from it. Take New Orleans, they were there before the hurricane studying what is ground zero for the worst termite threat in the nation, the Formosan Subterranean Termite. The old homes are subject for study on many levels. If you have paint or stain issues on older existing homes there is no one better to advise on the planet.
The advice to back prime was their advice, learned from years of dealing with such issues on wood sided structures. They know the old siding can't be back primed, they have advice on remedial actions in such cases anyway, like putting small wedges under old clapboards to allow the water vapor an easy 'out'.
Architects are learning from seminars held in 6 different cities each year arranged by the Canadian Wood Council, 2 in Canada, and 4 in the states. I did Pittsburgh just last month. R.Sam Williams Ph.D. from the lab, and senior scientist responsible for this area, Wood Surface Chemistry, held two, well attended seminars filled with hundreds of architects. I speak to architects myself on these issues, and they call my office (800 266 1910) all day long for advice and recommendations on just such topics. The architects know how to specify paint on Western Red Cedar, and many have seen the photo's of the paint that still hasn't peeled at the FPL test fence in Wisconsin, after 23 years of exposure.
As to the paint vs, stain issue I will continue to disagree. The modern pigments in each are trans oxide, and the acrylic formualtions are not hardened, they remain flexible, which is precisely why the FPL doesn't care which you choose to apply over the prime coat. ( the FPL says both opaque(solid ) stains and paint form paint films and therefore MUST be primed) Semi-Solid is OK to apply unprimed, BUT one coat only or you'll create the paint film.
The FPL and you and I agree about 'Film-Forming' finishes like paints and solid stains being problematic on all wood decks.
Decades of bad advice on paint cans, and yes, no input from the lumber side of the industry on coatings issues, and bogus terms like Mill Glaze to excuse what the paint companies never understood all helped mis-inform painters, homeowners, contactors and architects. Untold millions in wasted materials, labor and coatings inflicted on American and Canadian homeowners over my entire 40 year career. It is about time the facts were known, understood, and disseminated. I appreciate the help.