Ice dam risk in Worcester, MA
Ice dams in Worcester, MA: how often
22.1 dam days a winter
High risk. On an ordinary house in Worcester, conditions for an ice dam come on about 22.1 days in a normal winter, mostly in January and February.
Worcester averages 73 inches of snow a year and about 75 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 Worcester
| Attic | Dam days | Risk |
|---|---|---|
| Air-sealed and well insulated | 11.5 | Moderate |
| Typical, some insulation, not air-sealed | 22.1 | High |
| Older or poorly insulated, warm attic | 35.4 | Severe |
Sealing and insulating a typical attic takes out about 10.6 days a winter here. It drops the risk from high to moderate. An older house with a warm attic should expect closer to 35.4 days.
Preventing ice dams on a Worcester 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.
Worcester winter, month by month
| Month | Snow (in) | Days on ground | Dam days |
|---|---|---|---|
| January | 18.2 | 20.9 | 7.6 |
| February | 21.2 | 18.7 | 6.2 |
| March | 13.7 | 15.2 | 3.5 |
| April | 1.9 | 2.0 | 0.1 |
| October | 1.1 | 0.1 | 0.0 |
| November | 1.9 | 2.5 | 0.3 |
| December | 14.9 | 15.1 | 4.4 |
Worcester next to nearby towns
Worcester ranks 6 of 58 Massachusetts cities here for ice-dam days, behind Pittsfield at 31.3 days.
- Marlborough, MA 14 mi, 13.0 days
- Leominster, MA 17 mi, 29.3 days
- Southbridge Town, MA 19 mi, 14.9 days
- Framingham, MA 19 mi, 13.0 days
- Fitchburg, MA 23 mi, 29.3 days
Where these numbers come from
NOAA 1991–2020 climate normals from Worcester, 3.3 miles from Worcester. 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.
- Snow-on-the-ground counts come from a second, nearby station, because the closest one does not record them.