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Where is the black coming from?

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OK this might be easy for you old timers but a young buck like myself got tripped up. Interior of outside walls are showing darkness on the corners and appears to follow the studs down the wall; drywall nials are also slighly visible. Paint appears to be very thin and they have never been repainted. No moisture appears to be coming from the roof to saturate the studs. Sheetrock does not act water damaged. Almost looks like smoke damage...customers say no candles or other reason for smoke damage. Any ideas? Thanks guys!

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The black staining is commonly called Ghosting. It is generally caused by soot deposits. Typically, when the deposits follow studs or ceiling joists, the deposits are caused by a phenomenom known as thermophoresis where soot particals deposit along a thermal gradient. Because there is less insulation at the stud it is cooler than the surrounding surface and that is where black soot and dust is being deposited. Anything that forms soot will contribute to ghosting. Common sources are candles, smoking, improperly operating gas appliances, pilot lights and cooking greases.

Home Energy did an article on Ghosting back in 1998. You can read the article on their web site at http://homeenergy.org/archive/hem.dis.a ... 80109.html


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