Ice dam risk in Cadillac, MI
Ice dams in Cadillac, MI: how often
38.5 dam days a winter
Severe risk. On an ordinary house in Cadillac, conditions for an ice dam come on about 38.5 days in a normal winter, mostly in January and February.
Cadillac averages 74 inches of snow a year and about 109 days with snow on the ground. Snow that lies that long is what turns a little attic heat into a ridge of ice at the eave. The conditions that make a dam need all three at once: snow, cold at the eave and heat above it.
What your attic does to that number in Cadillac
| Attic | Dam days | Risk |
|---|---|---|
| Air-sealed and well insulated | 17.3 | High |
| Typical, some insulation, not air-sealed | 38.5 | Severe |
| Older or poorly insulated, warm attic | 65.1 | Severe |
Sealing and insulating a typical attic takes out about 21.2 days a winter here. It drops the risk from severe to high. An older house with a warm attic should expect closer to 65.1 days.
Preventing ice dams on a Cadillac roof
- Air-seal the attic floor: the gaps around the hatch, light fixtures, plumbing stacks and the top plates of interior walls. This is the fix that removes the cause, and it usually costs less than a season of contractor ice removal.
- Rake the bottom three or four feet of roof after any storm that leaves more than about six inches, from the ground with a roof rake.
- At the next reroof, ask for ice-and-water membrane under the shingles from the eave to at least 24 inches inside the wall line. It does not stop a dam; it stops the leak when one forms.
- Heat cable is worth pricing here even on a sealed house, along the eave and in the gutters and downspouts it drains into.
Running 60 feet of 5 W/ft cable whenever snow lies below freezing would use about 382 kWh a winter in Cadillac, roughly $65 at 17 cents a kWh.
Which to spend on first: air sealing or heat cable.
Cadillac winter, month by month
| Month | Snow (in) | Days on ground | Dam days |
|---|---|---|---|
| January | 18.7 | 28.5 | 11.9 |
| February | 13.9 | 27.2 | 10.6 |
| March | 9.4 | 21.0 | 6.0 |
| April | 5.2 | 3.8 | 0.6 |
| May | 0.3 | 0.1 | 0.0 |
| October | 1.4 | 0.5 | 0.1 |
| November | 9.0 | 7.3 | 1.7 |
| December | 16.1 | 21.0 | 7.6 |
Cadillac next to nearby towns
Cadillac ranks 3 of 90 Michigan cities here for ice-dam days, behind Sault Ste. Marie at 48.8 days.
- Traverse City, MI 36 mi, 35.2 days
- Mount Pleasant, MI 55 mi, 24.7 days
- Midland, MI 73 mi, 21.6 days
- Muskegon, MI 82 mi, 22.2 days
- Norton Shores, MI 85 mi, 22.2 days
Where these numbers come from
NOAA 1991–2020 climate normals from Lake City Exp Farm, 12.0 miles from Cadillac. A dam day is a day with snow on the roof and freezing at the eave while heat or sun melts the snow above it. This describes a normal winter, not this one.