Ice dam risk in Bourbonnais, IL
Ice dams in Bourbonnais, IL: how often
10.8 dam days a winter
Moderate risk. On an ordinary house in Bourbonnais, conditions for an ice dam come on about 10.8 days in a normal winter, mostly in January and February.
Bourbonnais averages 21 inches of snow a year and about 35 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 Bourbonnais
| Attic | Dam days | Risk |
|---|---|---|
| Air-sealed and well insulated | 5.7 | Moderate |
| Typical, some insulation, not air-sealed | 10.8 | Moderate |
| Older or poorly insulated, warm attic | 17.2 | High |
Sealing and insulating a typical attic takes out about 5.1 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 17.2 days.
What to do about ice dams in Bourbonnais
- 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.
Bourbonnais winter, month by month
| Month | Snow (in) | Days on ground | Dam days |
|---|---|---|---|
| January | 8.1 | 14.7 | 5.2 |
| February | 3.4 | 9.9 | 3.0 |
| March | 3.0 | 3.3 | 0.6 |
| April | 0.3 | 0.2 | 0.0 |
| November | 0.6 | 0.7 | 0.1 |
| December | 5.3 | 6.4 | 1.8 |
Bourbonnais next to nearby towns
Bourbonnais ranks 172 of 225 Illinois cities here for ice-dam days, behind Arlington Heights at 21.5 days.
- Bradley, IL 2 mi, 10.8 days
- Kankakee, IL 6 mi, 10.8 days
- Manhattan, IL 17 mi, 8.8 days
- Richton Park, IL 22 mi, 14.7 days
- Frankfort, IL 22 mi, 14.7 days
Where these numbers come from
NOAA 1991–2020 climate normals from Kankakee Metro Wastewater, 3.3 miles from Bourbonnais. 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.