Hawaii house with exterior black substance only at rafter venting bays

[Frazier Jeffery]

Ok I will start again because of the misunderstanding Sorry
The house is located in Hawaii has a metal roof with rafter bay ventingThe attic roof sheeting is black only whee the vents are located

Any thoughts
THANKS

[Dom D'Agostino]

Hawaii house with clean attic but exterior black substance only at rafter bay vents ?

Is that a question? Is this a riddle?:D

Bats, maybe...

[Jim Luttrall]

Hawaii house with clean attic but exterior black substance only at rafter bay vents ?

Wow, that must be some commute. :p

Seriously, what is a "Hawaii house"? I googled it but came up dry.

[Jerry Peck]

The house is located in Hawaii has a metal roof with rafter bay ventingThe attic roof sheeting is black only whee the vents are located

Are there areas in Hawaii that are not close enough to the ocean so that they don't have ocean mist?

Could it be caused from the roof sheathing being 'continuously' dampened?

[Gunnar Alquist]

I am going to try and decipher here, but we are going to need more information.

1) Seems like you live somewhere in the state of California; but for some reason, you inspected a home in Hawaii and are not completely familiar with local conditions.

2) When you refer to "rafter bay venting", are you talking about ventilation baffles at the eaves to hold back the insulation and provide a space for air to enter from eave vents or are you referring to eyebrow/dormer vents? Are there both lower (eave/soffit) and upper (gable/ridge/dormer/turbine) vents too?

3) You mention the attic roof sheeting is discolored near the vents. Do you see the discoloration on the underside of the roof sheathing from the attic above, below, or alongside the vent openings? What type of material is the roof sheathing? Did you see stains adjacent to all of the vent openings or just on one side?

4) What about the home's location in reference to prevailing winds and storms. Is this home sheltered, near the coast, far from the coast, up on a mountain?

5) Could this be "blow-by" (wind-driven rain that enters through vent openings)?

A more complete explanation, pictures and punctuation would help. Otherwise, we are shooting blind.

[John Kogel]

It sounds like the black stain is on the underside of the roof sheathing.
We get that here and it is due to condensation from moist air as it enters the attic. The moisture collects on the cooler sheathing which promotes fungus or mold to grow there on the wood. The mold often turns from a green fuzz when fresh to a black stain.
I imagine this occurs in other climates when the conditions are right.
There is no simple solution as we need the ventilation and can't control the climate. We could put a heat source in the attic but nobody is doing that AFAIK.

Inspecting while on vacation, yes, it's a curse we have to live with. ;)

[ATInspections]

Did you ever figure out what it was?