Ice dam risk in Berwyn, IL
Will your roof get ice dams in Berwyn, IL?
12.8 dam days a winter
Moderate risk. On an ordinary house in Berwyn, conditions for an ice dam come on about 12.8 days in a normal winter, mostly in January and February.
Berwyn averages 39 inches of snow a year and about 44 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 Berwyn
| Attic | Dam days | Risk |
|---|---|---|
| Air-sealed and well insulated | 6.3 | Moderate |
| Typical, some insulation, not air-sealed | 12.8 | Moderate |
| Older or poorly insulated, warm attic | 20.9 | High |
Sealing and insulating a typical attic takes out about 6.5 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 20.9 days.
Preventing ice dams on a Berwyn 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.
Which to spend on first: air sealing or heat cable.
Berwyn winter, month by month
| Month | Snow (in) | Days on ground | Dam days |
|---|---|---|---|
| January | 12.5 | 17.5 | 6.0 |
| February | 10.1 | 12.0 | 3.5 |
| March | 5.7 | 4.3 | 0.7 |
| April | 1.0 | 0.5 | 0.0 |
| October | 0.1 | 0.1 | 0.0 |
| November | 1.5 | 1.1 | 0.1 |
| December | 7.9 | 8.9 | 2.4 |
Berwyn next to nearby towns
Berwyn ranks 124 of 225 Illinois cities here for ice-dam days, behind Arlington Heights at 21.5 days.
- Cicero, IL 2 mi, 12.8 days
- Forest Park, IL 2 mi, 13.3 days
- Lyons, IL 3 mi, 12.8 days
- Oak Park, IL 3 mi, 13.3 days
- Brookfield, IL 3 mi, 12.8 days
Where these numbers come from
NOAA 1991–2020 climate normals from Chicago Midway Airport 3SW, 7.4 miles from Berwyn. 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.