Re: Exterior Wall Heat Loss
I would agree with the information about this being common -- for one.
The exterior surfaces reaching dewpoint with night time cooling and thermal bridging --- second.
Interupted method of insulating between studs and rafters actually has a less R value averaged over the entire wall or roof assembly. --- third.
However, the comments about an air gap between the batts of insulation ( within the stud bay ) and the exterior wall sheathing is incorrect. There should never be a gap of any sort throughout the entire cavity. Fiber glass batts will have initmate contact with both the exterior and interior walls in order to completely fill the cavity. Any gaps will allow air movent ( stack effect ) within the space which has a negative impact on fiber glass insulation by reducing it's R value .
The main point of insulating a wall cavity --- in this case -- for preventing heat loss and condensation issues is to raise the temperature within the space. Having the insulation in direct ( intimate ) contact with the exterior wall provides the seperation barrier between the colder outside and the warmer inside. If you leave a gap from the exterior you allow the cold zone to move further into the wall cavity defeating the the intention of raising the temperature with the wall. Moving the cold zone in further means more heat loss and condensation potentials.
"" an ounce of perception -- a pound of obscure "