Updated: Feb 27
When it's cold and frosty in the morning, and I'm out walking the dog contemplating the different methods to assess the impacts of thermal bridging (it's a thing), I often notice how the frost melts at different rates in different areas on different roofs around my neighbourhood.
Vertical striping on the roof is telling me that we've got some thermal bridging going on. Not sure why - could be a cathedral ceiling in there? Maybe the roof has been insulated during recent re-roofing? Not sure exactly why, but it can be dramatic.
Horizontal frost lines on a gable roof suggests we've got a difference in insulation level between the cathedral (sloping) portion of the roof and the area behind the knee-walls. Or maybe some air leakage into the "lower attic" behind the knee-wall?
Way less frost on one roof than it's neighbour is a good indication that the less frosty house:
has a less insulated attic
has air leakage or ventilation issues in the attic (like a bathroom fan that isn't properly vented through a roof vent)
is way warmer inside
Weird patchiness is a head scratcher. My intuition says air leakage but I'm not totally sure.
Lots of melt at the peak of a hip or gable and less lower down (but not as far down as the eaves) suggests some air leakage induced melting, as that warmer air rises within the attic space.