Most new houses in Edmonton insulate the attic with blown in fiberglass, a light fluffy insulation not too dissimilar from the poplar fluff that will blankets our streets and yards in early summer. In some instances, when inspecting new homes I have found that the blown in fiberglass can be blown around inside the attic, creating insulation voids.
The wet spot on this ceiling occurred the morning after a late night thunderstorm with high winds and blowing rain.
The insulators forgot to install one of the cardboard baffles fitted between the trusses. The baffle allows air to move from the eaves to the underside of the roof sheathing, essential for good attic and roof ventilation while holding the insulation in place. The high winds blew the insulation off the soffits and also allowed water to enter the roof and collect on the ceiling where it leaked through the vapor barrier and created a wet spot on the ceiling.
In this new home the thermograph indicated there was little or no insulation in various spots on the ceiling. The inspection revealed that parts of the attic were bare, and insulation piled up in fiberglass drifts in other spots.
Talking to the builder revealed that the insulation had been installed before the soffits were covered, a wind storm had blown the insulation from one end of the roof to the other.
In the next picture, in this newly built home the roofers mistakenly installed an extra gooseneck ventilator for a bathroom exhaust.
There was no exhaust required here, so the gooseneck was left open, allowing the wind to blow into the attic, dispersing the insulation underneath it. A truss had been uncovered, if left, the wind would eventually blow away all the insulation underneath the gooseneck, exposing the ceiling.