Ice dam risk in Norfolk, NE
Ice dams in Norfolk, NE: how often
16.1 dam days a winter
High risk. On an ordinary house in Norfolk, conditions for an ice dam come on about 16.1 days in a normal winter, mostly in January and February.
Norfolk averages 26 inches of snow a year and about 49 days with snow on the ground. Most of it comes and goes within a few days. 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 Norfolk
| Attic | Dam days | Risk |
|---|---|---|
| Air-sealed and well insulated | 8.7 | Moderate |
| Typical, some insulation, not air-sealed | 16.1 | High |
| Older or poorly insulated, warm attic | 25.4 | High |
Sealing and insulating a typical attic takes out about 7.4 days a winter here. It drops the risk from high to moderate. An older house with a warm attic should expect closer to 25.4 days.
Preventing ice dams on a Norfolk 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.
Norfolk winter, month by month
| Month | Snow (in) | Days on ground | Dam days |
|---|---|---|---|
| January | 6.4 | 17.2 | 6.3 |
| February | 5.7 | 12.9 | 4.4 |
| March | 3.8 | 4.8 | 1.1 |
| April | 1.2 | 0.7 | 0.1 |
| May | 0.1 | 0.0 | 0.0 |
| October | 0.5 | 0.3 | 0.0 |
| November | 2.2 | 2.7 | 0.6 |
| December | 6.4 | 10.4 | 3.6 |
Norfolk next to nearby towns
Norfolk ranks 2 of 16 Nebraska cities here for ice-dam days, behind South Sioux City at 19.2 days.
- Columbus, NE 41 mi, 12.5 days
- Vermillion, SD 58 mi, 23.8 days
- Yankton, SD 60 mi, 18.8 days
- South Sioux City, NE 60 mi, 19.2 days
- Sioux City, IA 62 mi, 19.2 days
Where these numbers come from
NOAA 1991–2020 climate normals from Norfolk 4W, 3.0 miles from Norfolk. 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.