Ice dam risk in Minot, ND
Ice dams in Minot, ND: how often
42.0 dam days a winter
Severe risk. On an ordinary house in Minot, conditions for an ice dam come on about 42.0 days in a normal winter, mostly in January and December.
Minot averages 45 inches of snow a year and about 113 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 Minot
| Attic | Dam days | Risk |
|---|---|---|
| Air-sealed and well insulated | 16.7 | High |
| Typical, some insulation, not air-sealed | 42.0 | Severe |
| Older or poorly insulated, warm attic | 73.5 | Severe |
Sealing and insulating a typical attic takes out about 25.2 days a winter here. It drops the risk from severe to high. An older house with a warm attic should expect closer to 73.5 days.
Preventing ice dams on a Minot 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 454 kWh a winter in Minot, roughly $77 at 17 cents a kWh.
Which to spend on first: air sealing or heat cable.
Minot winter, month by month
| Month | Snow (in) | Days on ground | Dam days |
|---|---|---|---|
| January | 9.8 | 27.9 | 11.9 |
| February | 5.4 | 23.8 | 9.7 |
| March | 6.1 | 15.5 | 4.8 |
| April | 4.5 | 5.3 | 0.8 |
| May | 0.7 | 0.1 | 0.0 |
| September | 0.1 | 0.0 | 0.0 |
| October | 1.2 | 1.6 | 0.2 |
| November | 9.2 | 14.7 | 4.6 |
| December | 8.1 | 24.4 | 10.0 |
Minot next to nearby towns
Minot ranks 4 of 9 North Dakota cities here for ice-dam days, behind Jamestown at 45.7 days.
- Mandan, ND 99 mi, 33.8 days
- Bismarck, ND 101 mi, 33.8 days
- Williston, ND 109 mi, 36.3 days
- Dickinson, ND 117 mi, 23.8 days
- Jamestown, ND 151 mi, 45.7 days
Where these numbers come from
NOAA 1991–2020 climate normals from Minot International Airport, 1.2 miles from Minot. 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.