Ice dam risk in Alexandria, MN
How often ice dams form in Alexandria
40.8 dam days a winter
Severe risk. On an ordinary house in Alexandria, conditions for an ice dam come on about 40.8 days in a normal winter, mostly in January and February.
Alexandria averages 46 inches of snow a year and about 112 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 Alexandria
| Attic | Dam days | Risk |
|---|---|---|
| Air-sealed and well insulated | 17.0 | High |
| Typical, some insulation, not air-sealed | 40.8 | Severe |
| Older or poorly insulated, warm attic | 70.4 | Severe |
Sealing and insulating a typical attic takes out about 23.7 days a winter here. It drops the risk from severe to high. An older house with a warm attic should expect closer to 70.4 days.
What to do about ice dams in Alexandria
- 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 427 kWh a winter in Alexandria, roughly $73 at 17 cents a kWh.
Which to spend on first: air sealing or heat cable.
Alexandria winter, month by month
| Month | Snow (in) | Days on ground | Dam days |
|---|---|---|---|
| January | 10.6 | 27.5 | 12.1 |
| February | 8.9 | 26.1 | 10.5 |
| March | 7.6 | 20.2 | 5.6 |
| April | 2.9 | 4.8 | 0.7 |
| October | 0.6 | 1.1 | 0.1 |
| November | 5.3 | 9.1 | 2.5 |
| December | 10.4 | 22.8 | 9.2 |
Alexandria next to nearby towns
Alexandria ranks 12 of 103 Minnesota cities here for ice-dam days, behind Hermantown at 52.9 days.
- Fergus Falls, MN 44 mi, 47.3 days
- Willmar, MN 54 mi, 37.6 days
- Sartell, MN 59 mi, 39.1 days
- Sauk Rapids, MN 62 mi, 38.6 days
- St. Cloud, MN 63 mi, 38.6 days
Where these numbers come from
NOAA 1991–2020 climate normals from Glenwood 2WNW, 15.4 miles from Alexandria. 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.
- Snow-on-the-ground counts come from a second, nearby station, because the closest one does not record them.