On 6 Jan 2007 22:34:23 -0800, "m35603" wrote:


The frost/snow is where it is the coldest. In
other words, all of the roof is colder than the
are where the frost is. The area where the frost
is either the area of best insulation or most
ventilation. Your neighbor should wish that all
of his roof look like what you call wet spots.

It *is* a wet spot when it's not below feezing. It is obvious that the
shingles are wet in this one spot in the morning. They dry durig the
day, but the next morning they are wet again.

Angie

Whether wet or frosted the area in question is cooler than the rest
of the roof. When this section gets cooler than the dewpoint then
either dew or frost will form. The majority of the roof usually never
gets cold enough for frost or dew to form because the majority of the
roof is warmed by the escaping heat from the house.

The area in question does no receive as much escaping heat as the
majority of the roof. This small section is insulated or sealed from
the rest of the house better than the majority of the roof.