Is the front in the shade? More shade means more mildew but less peeling because the direct sun is what makes paint peel faster. I don't think the linseed oil is a factor because you painted over that with a primer and two latex topcoats. Mildew just grows where it grows though it does grow faster on top of oil based coatings. You can add a mildewcide to the paint or buy a coating with mildewcide in it already....I doubt that Sears weatherbeater has it in there.

My own experience is exactly the same. I painstakingly stripped, sanded and did the turp/linseed oil thing that is generally recommended to conscientious old house owners. Then I oil primed, and used SW best exterior paint. Paint has held up just fine, but I have the same need to wash the mildew away every year. I do it just before it gets too cold up here in northern NY, so it's on my list for next week.

And, yup, I think the linseed oil is the culprit. I lived in this house for a decade before I did my painting project, and ever since, but never before, I have had to wash off the mildew annually.

Of course, linseed oil was a traditional component of paint on our old houses (mine is 160+ yo), but the other components of the paint are very different from modern coatings. On my own house I have quite a bit of heavy aligatored, very chalky paint that is completely different from the side which I painted (which happens to be the northern exposure, but not in shade otherwise). And the rest of the paint never mildews, even in shady and protected areas. It's just the exposure where I did the painting. It's very frustrating!

There has been quite a bit of discussion of this phenomenon on Old House websites, both here on GW and on others

So the recommendation to use linseed oil and turps as a "feeding" undercoat has been abandonned, as far as I can tell. Though it still shows up in books on old house restoration/conservation.

There is another kind of linseed oil, made by the Solvent Free Paint people. Their linseed oil is organic (whoo-eee!) and processed in a different way. I have used it (and am testing it further) in a couple of projects started this year. So far I am not seeing mildew on surfaces where I used the SF Organic product, but they have only been up for about six months, or so. The stuff is quite a bit more expensive, but has a significant advantage in being much nicer to work with. The company makes a line of solvent free paint, which I am also testing on my barns.

I am not sure if you could substitute the SF linseed oil in the same recipes, but it would be interesting to find out how that works out, if you do.

You can find Solvent Free Paint by googling them, but I think it's solventfreepaint.com

HTH,

Molly~