Ice dam risk in Elkhorn, WI
Will your roof get ice dams in Elkhorn, WI?
19.2 dam days a winter
High risk. On an ordinary house in Elkhorn, conditions for an ice dam come on about 19.2 days in a normal winter, mostly in January and February.
Elkhorn averages 40 inches of snow a year and about 60 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 Elkhorn
| Attic | Dam days | Risk |
|---|---|---|
| Air-sealed and well insulated | 9.2 | Moderate |
| Typical, some insulation, not air-sealed | 19.2 | High |
| Older or poorly insulated, warm attic | 31.8 | High |
Sealing and insulating a typical attic takes out about 10.0 days a winter here. It drops the risk from high to moderate. An older house with a warm attic should expect closer to 31.8 days.
Preventing ice dams on a Elkhorn 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.
Elkhorn winter, month by month
| Month | Snow (in) | Days on ground | Dam days |
|---|---|---|---|
| January | 13.9 | 22.4 | 8.7 |
| February | 8.1 | 15.6 | 4.8 |
| March | 4.8 | 5.3 | 1.1 |
| April | 2.6 | 1.3 | 0.1 |
| October | 0.2 | 0.1 | 0.0 |
| November | 3.4 | 3.6 | 0.6 |
| December | 7.1 | 12.0 | 3.8 |
Elkhorn next to nearby towns
Elkhorn ranks 79 of 98 Wisconsin cities here for ice-dam days, behind Wausau at 41.6 days.
- Burlington, WI 13 mi, 20.2 days
- Whitewater, WI 15 mi, 21.9 days
- Salem Lakes, WI 23 mi, 20.1 days
- Fort Atkinson, WI 23 mi, 22.2 days
- Janesville, WI 24 mi, 20.5 days
Where these numbers come from
NOAA 1991–2020 climate normals from Lake Geneva Wwtp, 7.5 miles from Elkhorn. 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.