Ice dam risk in South Burlington, VT
Ice dams in South Burlington, VT: how often
29.2 dam days a winter
High risk. On an ordinary house in South Burlington, conditions for an ice dam come on about 29.2 days in a normal winter, mostly in January and February.
South Burlington averages 88 inches of snow a year and about 89 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 South Burlington
| Attic | Dam days | Risk |
|---|---|---|
| Air-sealed and well insulated | 13.4 | Moderate |
| Typical, some insulation, not air-sealed | 29.2 | High |
| Older or poorly insulated, warm attic | 48.9 | Severe |
Sealing and insulating a typical attic takes out about 15.8 days a winter here. It drops the risk from high to moderate. An older house with a warm attic should expect closer to 48.9 days.
Preventing ice dams on a South Burlington 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.
South Burlington winter, month by month
| Month | Snow (in) | Days on ground | Dam days |
|---|---|---|---|
| January | 21.1 | 25.3 | 9.8 |
| February | 19.3 | 23.9 | 8.7 |
| March | 17.5 | 17.1 | 4.6 |
| April | 4.1 | 2.2 | 0.2 |
| October | 0.3 | 0.1 | 0.0 |
| November | 5.7 | 4.1 | 0.7 |
| December | 19.5 | 16.6 | 5.2 |
South Burlington next to nearby towns
South Burlington ranks 3 of 4 Vermont cities here for ice-dam days, behind Essex Junction at 33.5 days.
- Burlington, VT 5 mi, 29.2 days
- Essex Junction, VT 5 mi, 33.5 days
- Plattsburgh, NY 22 mi, 27.0 days
- Rutland, VT 58 mi, 28.5 days
- Lebanon, NH 72 mi, 30.4 days
Where these numbers come from
NOAA 1991–2020 climate normals from Burlington International Airport, 2.7 miles from South Burlington. 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.