Relevant observations 3
Continuing ice dam thoughts.
After a lot more snow and a lot more cold, a more refined pattern has emerged.
Factoring out individual variations of shade, materials and insulation, the BEST type of house is a plain Cape Cod with occupied attic and roof >= 45 degrees.
The WORST is the abovementioned low hip rancher.
[Both pictures are obviously Googlestreet pics taken in summer, but both of these actual houses fit the pattern as of this morning.]
Cape Cods with occupied attic never held more than an inch or two. They stayed UNLOADED all the time, thus avoiding both dams and stress. This is intuitively obvious. Warm is good, steep is good.
Those low-hip ranchers are still firmly dammed and heavily loaded. No relief at all.
There was a theory several years ago that you should keep the entire roof cold. The advocates of this theory specifically recommended a hip roof with wide overhangs. I went along with the theory until I started to observe houses by type. Now it's clear that the theory is EXACTLY WRONG. The champion dambuilders are EXACTLY what the theory recommends. I wrote an item about the theory
a couple years ago. I was thinking about trying to buy a house of that type. Lucky I didn't follow through. My house loves to build dams, but at least it's paid for. If I'd bought a better house, I'd have ice dams AND a mortgage payment.
March 10 update: Now that nearly
all the snow is gone, the abovepictured Poster House For Bad Theory has a brand-new tarp over most of its roof, and the bottom row of shingles has been removed pending repair. Clearly there was significant leakage. /// And March 12: Now another house of the same species is newly tarped. /// March 19: And one more.