new yellow insulation in attic is now black - why?

Several weeks ago a contractor building an addition on my home installed R-30 insulation in an attic space, right above a ceiling. The ceiling has now been sheetrocked but I can still see the insulation in some holes cut for speakers and in the ceiling of an unfinished untility closet.
The original color of the insulation was bright yelllow.
Above the speaker holes the insulation is now solid black. And in the ceiling of the utility closet, behind a plastic moisture barrier that is stapled to the bottom of trusses, the insulation is streaked with black.
Is this right? Why would the yellow insulation turn black?
mh
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Mike wrote:

Dust?
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Is the roof solid plywood or planks and what sort of roofing went on after the insulation was installed? Could it be crap from the roofing job?
Do you have any chimneys/flues going through the ceiling that might be broken and dumping soot into the attic?
Do you have an attic fan that's pulling dirty air through the attic?
Mike wrote:

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Dust: I suppose it it possible. Since the insulation has gone in the work in the area has consistent of sheetrocking and now skim coat plastering. How could this get dust above the closet moisture barrier?
Roof: the roof is T&G plywood covered with bituthane. No real roof yet.
Attic fan: there is none.
Chimney: one exists but has never been used (the chase was built a month ago and a metalbestos chimney went in a Friday. It will eventually vent a wood stove but there is no stove yet in the house.
Could the insulation rot in a period of weeks?
mh
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Any opening will cause a chimney effect, drawing air up and into the attic. This will carry dust, construction smoke and moisture up with it. Possibly, gas or oil heaters were installed if the temperature dropped and caused smoke soot to carry up and into the insulation. It is one of two things, either dust and/or dirt OR it is mould caused by water or dampness. Insulation does not rot (possibly cellulose would, but not in that short time). Normally all cracks or breaks in the vapor barrier will have a dirty stain in the insulation right behind the opening. If the speaker holes have been left open they are ripe for the dirt to be carried into the insulation, especially from the construction activities.

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I'll bet this is it: a kerosene heater has been used to keep the temperature in the addition around 50 F at night (so the drying plaster does not freeze). The heater throws off a lot of carbon when it runs low on kerosene, as it does around 6am.
Now we have an extra layer of dust on the instulation. Any reason to think that this is a problem?
Thanks,
mh
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The layer of dust on the insulation is not a problem. What is a potential problem is your lungs. If it got onto the insulation, it also got into your lungs if you were there when the heater was running. If is was used during construction it is probably not that big a deal, but be sure to keep it in the unoccupied space
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Mike wrote:

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What kind of heat do you have?
Do you know if it is black everywhere, or only in the holes that are open. They may be chimneys for hot air from the rooms below.

Remove NOPSAM to email me. Please let me know if you have posted also.
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