Ice dam risk in Essex Junction, VT
How often ice dams form in Essex Junction
33.5 dam days a winter
High risk. On an ordinary house in Essex Junction, conditions for an ice dam come on about 33.5 days in a normal winter, mostly in January and February.
Essex Junction averages 86 inches of snow a year and about 101 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 Essex Junction
| Attic | Dam days | Risk |
|---|---|---|
| Air-sealed and well insulated | 16.3 | High |
| Typical, some insulation, not air-sealed | 33.5 | High |
| Older or poorly insulated, warm attic | 55.1 | Severe |
Sealing and insulating a typical attic takes out about 17.2 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 55.1 days.
Preventing ice dams on a Essex Junction 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.
- Heat cable is worth pricing here even on a sealed house, along the eave and in the gutters and downspouts it drains into.
Running 60 feet of 5 W/ft cable whenever snow lies below freezing would use about 310 kWh a winter in Essex Junction, roughly $53 at 17 cents a kWh.
Which to spend on first: air sealing or heat cable.
Essex Junction winter, month by month
| Month | Snow (in) | Days on ground | Dam days |
|---|---|---|---|
| January | 20.4 | 26.9 | 10.6 |
| February | 19.2 | 25.6 | 9.4 |
| March | 16.5 | 20.5 | 5.6 |
| April | 4.4 | 3.2 | 0.4 |
| October | 0.3 | 0.2 | 0.0 |
| November | 5.8 | 4.8 | 0.9 |
| December | 19.3 | 19.7 | 6.6 |
Essex Junction next to nearby towns
Essex Junction ranks 1 of 4 Vermont cities here for ice-dam days, the worst in the state.
- South Burlington, VT 5 mi, 29.2 days
- Burlington, VT 6 mi, 29.2 days
- Plattsburgh, NY 22 mi, 27.0 days
- Rutland, VT 61 mi, 28.5 days
- Lebanon, NH 73 mi, 30.4 days
Where these numbers come from
NOAA 1991–2020 climate normals from Essex Junction 1 N, 1.2 miles from Essex Junction. 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.