Ice dam risk in De Pere, WI
How often ice dams form in De Pere
31.4 dam days a winter
High risk. On an ordinary house in De Pere, conditions for an ice dam come on about 31.4 days in a normal winter, mostly in February and January.
De Pere averages 61 inches of snow a year and about 86 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 De Pere
| Attic | Dam days | Risk |
|---|---|---|
| Air-sealed and well insulated | 12.5 | Moderate |
| Typical, some insulation, not air-sealed | 31.4 | High |
| Older or poorly insulated, warm attic | 55.0 | Severe |
Sealing and insulating a typical attic takes out about 18.9 days a winter here. It drops the risk from high to moderate. An older house with a warm attic should expect closer to 55.0 days.
Preventing ice dams on a De Pere 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.
De Pere winter, month by month
| Month | Snow (in) | Days on ground | Dam days |
|---|---|---|---|
| January | 13.3 | 24.1 | 10.2 |
| February | 15.1 | 25.0 | 10.1 |
| March | 7.9 | 13.6 | 3.4 |
| April | 5.3 | 2.1 | 0.2 |
| May | 0.1 | 0.1 | 0.0 |
| October | 0.4 | 0.2 | 0.0 |
| November | 2.1 | 1.4 | 0.3 |
| December | 17.1 | 19.1 | 7.2 |
De Pere next to nearby towns
De Pere ranks 15 of 98 Wisconsin cities here for ice-dam days, behind Wausau at 41.6 days.
- Ashwaubenon, WI 3 mi, 29.3 days
- Allouez, WI 4 mi, 29.3 days
- Hobart, WI 6 mi, 31.4 days
- Bellevue, WI 6 mi, 29.3 days
- Green Bay, WI 8 mi, 29.3 days
Where these numbers come from
NOAA 1991–2020 climate normals from Green Bay Wfo, 4.9 miles from De Pere. 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.