Ice dam risk in Dubuque, IA
Will your roof get ice dams in Dubuque, IA?
23.9 dam days a winter
High risk. On an ordinary house in Dubuque, conditions for an ice dam come on about 23.9 days in a normal winter, mostly in January and February.
Dubuque averages 36 inches of snow a year and about 71 days with snow on the ground. Snow that lies that long is what turns a little attic heat into a ridge of ice at the eave. 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 Dubuque
| Attic | Dam days | Risk |
|---|---|---|
| Air-sealed and well insulated | 10.9 | Moderate |
| Typical, some insulation, not air-sealed | 23.9 | High |
| Older or poorly insulated, warm attic | 40.2 | Severe |
Sealing and insulating a typical attic takes out about 13.0 days a winter here. It drops the risk from high to moderate. An older house with a warm attic should expect closer to 40.2 days.
Preventing ice dams on a Dubuque 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.
Dubuque winter, month by month
| Month | Snow (in) | Days on ground | Dam days |
|---|---|---|---|
| January | 11.7 | 23.3 | 9.4 |
| February | 8.6 | 20.9 | 7.3 |
| March | 3.7 | 8.4 | 1.8 |
| April | 0.9 | 0.4 | 0.0 |
| October | 0.1 | 0.1 | 0.0 |
| November | 1.2 | 2.7 | 0.5 |
| December | 9.9 | 14.8 | 4.9 |
Dubuque next to nearby towns
Dubuque ranks 6 of 41 Iowa cities here for ice-dam days, behind Mason City at 28.7 days.
- Platteville, WI 20 mi, 28.8 days
- Clinton, IA 51 mi, 16.6 days
- Marion, IA 55 mi, 18.4 days
- Monroe, WI 55 mi, 24.4 days
- Freeport, IL 57 mi, 19.2 days
Where these numbers come from
NOAA 1991–2020 climate normals from Dubuque L&d 11, 4.2 miles from Dubuque. 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.