Strange "tar" smell in my home
	
	
		I have lived in my home for eight years.  It was new construction.  We have a basic shingle roof.  About 3 months ago, we had a warm snap and I noticed when the sun would hit the roof (I'm guessing it's the roof), there is a strange smell that fills my house.  It smells like tar.  It only happens when the windows are open and the sun heats up the roof.  I have had several people in my home to check it out.  It remains a mystery to everyone that has come in. 
Suggestions have been:
A Dead Animal:  The smell doesn't seem organic to me.  Also its intermittent and if I close the house up you can't smell it.
It's coming from a nearby roofing project:  negative. Can't smell it outside... only inside.
It's mold:  Negative, again, not an organic smell and why would you not smell mold when the windows are shut?
Anyone?  Suggestions?  I need to get to the bottom of it.[/LIST]