Ice dam risk in Bangor, ME
Ice dams in Bangor, ME: how often
29.5 dam days a winter
High risk. On an ordinary house in Bangor, conditions for an ice dam come on about 29.5 days in a normal winter, mostly in February and January.
Bangor averages 75 inches of snow a year and about 88 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 Bangor
| Attic | Dam days | Risk |
|---|---|---|
| Air-sealed and well insulated | 14.3 | Moderate |
| Typical, some insulation, not air-sealed | 29.5 | High |
| Older or poorly insulated, warm attic | 48.5 | Severe |
Sealing and insulating a typical attic takes out about 15.2 days a winter here. It drops the risk from high to moderate. An older house with a warm attic should expect closer to 48.5 days.
What to do about ice dams in Bangor
- 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.
Bangor winter, month by month
| Month | Snow (in) | Days on ground | Dam days |
|---|---|---|---|
| January | 18.6 | 24.1 | 9.7 |
| February | 17.5 | 24.7 | 9.0 |
| March | 15.2 | 16.8 | 4.5 |
| April | 3.7 | 2.9 | 0.4 |
| October | 0.6 | 0.1 | 0.0 |
| November | 4.3 | 3.0 | 0.6 |
| December | 14.7 | 15.9 | 5.3 |
Bangor next to nearby towns
Bangor ranks 5 of 11 Maine cities here for ice-dam days, behind Waterville at 40.9 days.
- Waterville, ME 47 mi, 40.9 days
- Augusta, ME 58 mi, 30.3 days
- Lewiston, ME 85 mi, 33.3 days
- Auburn, ME 89 mi, 31.3 days
- Portland, ME 108 mi, 22.4 days
Where these numbers come from
NOAA 1991–2020 climate normals from Bangor International Airport, 2.6 miles from Bangor. 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.