Two years ago, we installed a new roof with ridge vents. Recently, we have noticed shadows on our ceilings in places where the roof trusses run. The house has cathedral ceilings as well as flat ceilings, and these “shadows” show up in all rooms. Also, along an exterior wall in our kitchen, we can see (from end to end) the outline of the roof truss, as well as vertical markings of studs. The markings in the ceiling and the walls look like someone lightly penciled in shadows of the trusses and studs. Can this be a result of the ridge vent that was cut in the roof?
What you are describing is textbook “shadowing” or “ghosting ” from candle soot. Does someone in your family burn those nice aromatic candles in glass jugs? Those are great soot producers.
Candle soot is about as heavy as air. It moves throughout your home, aided by the forced air furnace. Outside walls and attic ceilings have plenty of insulation, but there is much less insulation on the framing edges. As a result, framing edges and fasteners are slightly cooler than the surrounding drywall.
When the air moves across the cooler surfaces, it slows slightly and deposits soot. The dark soot stains outline the framing with a shadowy or ghostly appearance.
So, stop burning candles! Or at least burn only very high-quality candles, and keep the wicks trimmed to 1/4 inch or less. Don’t burn candles in jugs – their combustion is starved of oxygen, so it produces lots of soot. You can find more information at misterfix-it.com in the Free Articles section; look for the article, Soot, Ghosts and Ugly Stains.