The bigger the difference between the inside and outside temperature the easier it is to detect heat leaks.

Is it temperature zone or cost or ?

For one, PVC has a rather low maximum operating temperature.

Not that its lack of temperature eliminates opportunities, but don't fall into that whole illusion of the "right" time to get in.

(personally, if I had to *guess*, I would think average temperatures are increasing, but it has nothing to do with anything we've done, it's just a natural planetary cycle, but who knows)...

If there is/was little insulation in the attic (the ceiling joists are exposed above the insulation), you would have cooler/warmer temperature along the bottom of the joists which could both cause moisture issues and may have affected how the smoke particulate stuck to the ceiling.If you take the pointed tip of a knife or {one blade} of a pair of scissors and {gently} press into the drywall along one of those lines, is the drywall hard or does the knife tip slid in fairly easily?  

http://www.refinisherswarehouse.com/refinishing_coatings_glaz_weld.htm "The Advanced Molecular Bonding System Found Exclusively at Refinishers Warehouse.Current (now outdated) methods of preparing bathroom and kitchen surfaces for re-coloring by etching with acids and sanding are dangerous, time-consuming, expensive . . .and they can lead to microscopic pores in the prepared surfaces that virtually guarantee eventual failure of the new surfaces due to blistering and loss of adhesion.Refinishers Warehouse Glaz-Weld is a molecular bonding agent.

They have one at my office, and it has vents on the sides of course so it can read temperature, and they take bent paper clips to push the little levers when they get cold.

It is certainly a humidity and temperature issue cause all mold issues are!

The changes in water saturation and temperature throughout the year makes the foundation heave and settle, if only by a fraction.