Ice dam risk in Greensburg, PA
Will your roof get ice dams in Greensburg, PA?
9.2 dam days a winter
Moderate risk. On an ordinary house in Greensburg, conditions for an ice dam come on about 9.2 days in a normal winter, mostly in January and February.
Greensburg averages 30 inches of snow a year and about 34 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 Greensburg
| Attic | Dam days | Risk |
|---|---|---|
| Air-sealed and well insulated | 5.3 | Moderate |
| Typical, some insulation, not air-sealed | 9.2 | Moderate |
| Older or poorly insulated, warm attic | 14.0 | Moderate |
Sealing and insulating a typical attic takes out about 3.9 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 14.0 days.
Preventing ice dams on a Greensburg 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.
Which to spend on first: air sealing or heat cable.
Greensburg winter, month by month
| Month | Snow (in) | Days on ground | Dam days |
|---|---|---|---|
| January | 9.0 | 14.2 | 4.2 |
| February | 7.5 | 9.1 | 2.6 |
| March | 5.6 | 2.7 | 0.5 |
| April | 0.3 | 0.2 | 0.0 |
| October | 0.1 | 0.0 | 0.0 |
| November | 0.9 | 0.8 | 0.1 |
| December | 6.4 | 6.6 | 1.8 |
Greensburg next to nearby towns
Greensburg ranks 28 of 68 Pennsylvania cities here for ice-dam days, behind St. Marys at 26.9 days.
- Murrysville, PA 11 mi, 8.8 days
- Monroeville, PA 14 mi, 8.8 days
- McKeesport, PA 16 mi, 8.8 days
- Plum, PA 17 mi, 8.8 days
- West Mifflin, PA 19 mi, 8.8 days
Where these numbers come from
NOAA 1991–2020 climate normals from Mt Pleasant, 7.0 miles from Greensburg. 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.