Ice dam risk in Portage, IN
Will your roof get ice dams in Portage, IN?
14.1 dam days a winter
Moderate risk. On an ordinary house in Portage, conditions for an ice dam come on about 14.1 days in a normal winter, mostly in January and February.
Portage averages 40 inches of snow a year and about 46 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 Portage
| Attic | Dam days | Risk |
|---|---|---|
| Air-sealed and well insulated | 6.8 | Moderate |
| Typical, some insulation, not air-sealed | 14.1 | Moderate |
| Older or poorly insulated, warm attic | 23.2 | High |
Sealing and insulating a typical attic takes out about 7.3 days a winter here. It does not move the risk band, but it shortens every dam. An older house with a warm attic should expect closer to 23.2 days.
What to do about ice dams in Portage
- 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.
Which to spend on first: air sealing or heat cable.
Portage winter, month by month
| Month | Snow (in) | Days on ground | Dam days |
|---|---|---|---|
| January | 16.0 | 17.2 | 6.1 |
| February | 9.7 | 12.9 | 4.1 |
| March | 6.0 | 4.9 | 0.9 |
| April | 0.6 | 0.3 | 0.0 |
| November | 0.7 | 1.4 | 0.2 |
| December | 7.3 | 9.6 | 2.7 |
Portage next to nearby towns
Portage ranks 20 of 88 Indiana cities here for ice-dam days, behind Plymouth at 15.9 days.
- Lake Station, IN 4 mi, 14.1 days
- Chesterton, IN 6 mi, 14.1 days
- Hobart, IN 7 mi, 14.0 days
- Gary, IN 9 mi, 14.1 days
- Valparaiso, IN 10 mi, 14.6 days
Where these numbers come from
NOAA 1991–2020 climate normals from Indiana Dunes Np, 5.6 miles from Portage. 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.