Hardiplank siding that sweats 2

[swthwdy]

Why Does horizontal Hardiplank siding develop vertical sweaty appearance on so many houses in the Houston TX area.
These sweaty areas turn green and appear to be a type of algae, which has to be removed by pressure washing every year.
Does this have something to do with lack of moisture barrier paper or something to do with the studs?

 

[MOB1]

Here in Australia Hardiplank horizontal siding was and is used extensively. We have many areas of high humidity. I have noticed that a similar green algal growth occurs on this material particularly on the shaded side of buildings.
I believe that it has something to do with the relative porosity of the material and acrylic paint combination.
A solution may be to seal before painting with a suitable waterproof sealer and/or use oil based paint rather than acrylics (which allow moisture to pass through them).

 

[btrueblood]

I wasn't going to reply to this, because I'm no expert. But I do have LP siding on my house ... It too has this green crud growing on it. One of the problems that the original LP siding installations had is that the lower edge of the siding wasn't getting sealed well, and LP made the recommendation that extra attention paid to getting paint onto the bottom edge would help prevent moisture migration into their product.

Me, I'm going to invest in vinyl. The homeowner's association will fine me for doing so, but it will be money well spent, IMO.

Good luck
Ben T