Ice dam risk in Red Wing, MN
Will your roof get ice dams in Red Wing, MN?
36.2 dam days a winter
Severe risk. On an ordinary house in Red Wing, conditions for an ice dam come on about 36.2 days in a normal winter, mostly in January and February.
Red Wing averages 44 inches of snow a year and about 101 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 Red Wing
| Attic | Dam days | Risk |
|---|---|---|
| Air-sealed and well insulated | 15.2 | High |
| Typical, some insulation, not air-sealed | 36.2 | Severe |
| Older or poorly insulated, warm attic | 62.4 | Severe |
Sealing and insulating a typical attic takes out about 21.0 days a winter here. It drops the risk from severe to high. An older house with a warm attic should expect closer to 62.4 days.
Preventing ice dams on a Red Wing 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 378 kWh a winter in Red Wing, roughly $64 at 17 cents a kWh.
Which to spend on first: air sealing or heat cable.
Red Wing winter, month by month
| Month | Snow (in) | Days on ground | Dam days |
|---|---|---|---|
| January | 10.5 | 27.3 | 11.9 |
| February | 9.5 | 26.4 | 10.2 |
| March | 6.2 | 18.3 | 4.7 |
| April | 3.3 | 3.0 | 0.4 |
| May | 0.5 | 0.1 | 0.0 |
| October | 0.6 | 0.4 | 0.0 |
| November | 3.0 | 4.8 | 1.1 |
| December | 9.9 | 20.6 | 7.8 |
Red Wing next to nearby towns
Red Wing ranks 48 of 103 Minnesota cities here for ice-dam days, behind Hermantown at 52.9 days.
- Hastings, MN 16 mi, 32.6 days
- River Falls, WI 19 mi, 38.8 days
- Cottage Grove, MN 22 mi, 32.4 days
- Rosemount, MN 25 mi, 32.6 days
- Hudson, WI 27 mi, 38.8 days
Where these numbers come from
NOAA 1991–2020 climate normals from Zumbrota, 19.7 miles from Red Wing. 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.