Ice dam risk in Brookfield, WI
How often ice dams form in Brookfield
18.2 dam days a winter
High risk. On an ordinary house in Brookfield, conditions for an ice dam come on about 18.2 days in a normal winter, mostly in January and February.
Brookfield averages 40 inches of snow a year and about 58 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 Brookfield
| Attic | Dam days | Risk |
|---|---|---|
| Air-sealed and well insulated | 9.0 | Moderate |
| Typical, some insulation, not air-sealed | 18.2 | High |
| Older or poorly insulated, warm attic | 29.6 | High |
Sealing and insulating a typical attic takes out about 9.2 days a winter here. It drops the risk from high to moderate. An older house with a warm attic should expect closer to 29.6 days.
What to do about ice dams in Brookfield
- 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.
Brookfield winter, month by month
| Month | Snow (in) | Days on ground | Dam days |
|---|---|---|---|
| January | 11.0 | 20.3 | 7.5 |
| February | 9.9 | 16.5 | 5.4 |
| March | 5.3 | 7.0 | 1.5 |
| April | 1.5 | 0.6 | 0.0 |
| November | 2.0 | 1.6 | 0.3 |
| December | 9.8 | 11.5 | 3.5 |
Brookfield next to nearby towns
Brookfield ranks 89 of 98 Wisconsin cities here for ice-dam days, behind Wausau at 41.6 days.
- Wauwatosa, WI 4 mi, 18.2 days
- West Allis, WI 6 mi, 18.9 days
- Pewaukee, WI 6 mi, 21.4 days
- New Berlin, WI 6 mi, 21.4 days
- Menomonee Falls, WI 7 mi, 24.6 days
Where these numbers come from
NOAA 1991–2020 climate normals from Mt Mary College, 4.5 miles from Brookfield. 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.