Ice dam risk in Elmira, NY
Ice dams in Elmira, NY: how often
17.2 dam days a winter
High risk. On an ordinary house in Elmira, conditions for an ice dam come on about 17.2 days in a normal winter, mostly in January and February.
Elmira averages 42 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 Elmira
| Attic | Dam days | Risk |
|---|---|---|
| Air-sealed and well insulated | 9.6 | Moderate |
| Typical, some insulation, not air-sealed | 17.2 | High |
| Older or poorly insulated, warm attic | 26.8 | High |
Sealing and insulating a typical attic takes out about 7.6 days a winter here. It drops the risk from high to moderate. An older house with a warm attic should expect closer to 26.8 days.
Preventing ice dams on a Elmira 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.
Elmira winter, month by month
| Month | Snow (in) | Days on ground | Dam days |
|---|---|---|---|
| January | 8.4 | 16.6 | 5.8 |
| February | 9.5 | 15.9 | 5.2 |
| March | 11.2 | 11.2 | 2.7 |
| April | 1.5 | 1.0 | 0.1 |
| October | 0.1 | 0.0 | 0.0 |
| November | 2.7 | 2.6 | 0.4 |
| December | 8.4 | 10.2 | 2.9 |
Elmira next to nearby towns
Elmira ranks 40 of 90 New York cities here for ice-dam days, behind Utica at 46.1 days.
- Corning, NY 13 mi, 24.0 days
- Ithaca, NY 29 mi, 22.7 days
- Endicott, NY 38 mi, 26.0 days
- Johnson City, NY 43 mi, 26.0 days
- Binghamton, NY 46 mi, 26.0 days
Where these numbers come from
NOAA 1991–2020 climate normals from Elmira, 1.4 miles from Elmira. 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.