This all depends on the style of construction of said homes.
In standard construction, the insulation is in the ceiling joist bay, and
the attic space is allowed to ventilate to the outside.
Like a tea pot, moisture builds up in the attic inbetween the roof and the
Allowing it to ventilate prevents mold, moisture, condensation.
Some people decide to turn their home into a "cathedral ceiling" take out
the ceiling joist, and leave the roof rafter as the ceiling.
They insulate the rafter. What happens is that moisture builds up under the
plywood roof sheathing, having no place to go, weeps down.
I have replaced many a rafter and roof construction due to this error.
Now a person can "tight" insulate a ceiling, and use a rigid insulation
product, but leaving no air space for moisture to condense.
This way a person can have a cathedral type ceiling.
Some use a larger rafter, say a 2x10 or 2x12 and allow a 1" to 2" air space
under the plywood roofing and allow the moist air to leave via
a ridge vent or some other means.
Look up Cora Ridge for roofing solutions and insulation factors.
There are many articles on this.
Especially the idea of snow on a roof.
"richard" wrote in message
According to Mike Holmes, HGTV show Holmes on Homes, when there is no snow
on the roof, and your neighbors have snow, that indicates heat loss.
But isn't that a good thing? Do you want snow buildup on the roof which
will cause damage in the long run, or do you want no snow?
Once he got into the attic, you could see why.
Proper insulation on the ceiling, improperly installed.
No insulation on the roof itself.
A hell of a good show. Watch it if you can. You may learn a few things.