Ice dam risk in Bellevue, WI
Ice dams in Bellevue, WI: how often
29.3 dam days a winter
High risk. On an ordinary house in Bellevue, conditions for an ice dam come on about 29.3 days in a normal winter, mostly in January and February.
Bellevue averages 56 inches of snow a year and about 82 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 Bellevue
| Attic | Dam days | Risk |
|---|---|---|
| Air-sealed and well insulated | 12.1 | Moderate |
| Typical, some insulation, not air-sealed | 29.3 | High |
| Older or poorly insulated, warm attic | 50.8 | Severe |
Sealing and insulating a typical attic takes out about 17.2 days a winter here. It drops the risk from high to moderate. An older house with a warm attic should expect closer to 50.8 days.
Preventing ice dams on a Bellevue 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.
Which to spend on first: air sealing or heat cable.
Bellevue winter, month by month
| Month | Snow (in) | Days on ground | Dam days |
|---|---|---|---|
| January | 14.3 | 24.3 | 10.2 |
| February | 12.0 | 23.5 | 9.1 |
| March | 8.1 | 13.0 | 3.4 |
| April | 4.7 | 2.3 | 0.2 |
| October | 0.3 | 0.1 | 0.0 |
| November | 3.1 | 2.5 | 0.5 |
| December | 13.1 | 16.7 | 5.9 |
Bellevue next to nearby towns
Bellevue ranks 29 of 98 Wisconsin cities here for ice-dam days, behind Wausau at 41.6 days.
- Allouez, WI 4 mi, 29.3 days
- Green Bay, WI 4 mi, 29.3 days
- De Pere, WI 6 mi, 31.4 days
- Ashwaubenon, WI 7 mi, 29.3 days
- Howard, WI 9 mi, 29.3 days
Where these numbers come from
NOAA 1991–2020 climate normals from Green Bay, 8.1 miles from Bellevue. 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.