Ice dam risk in Murrysville, PA
How often ice dams form in Murrysville
8.8 dam days a winter
Moderate risk. On an ordinary house in Murrysville, conditions for an ice dam come on about 8.8 days in a normal winter, mostly in January and February.
Murrysville averages 25 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 Murrysville
| Attic | Dam days | Risk |
|---|---|---|
| Air-sealed and well insulated | 5.5 | Moderate |
| Typical, some insulation, not air-sealed | 8.8 | Moderate |
| Older or poorly insulated, warm attic | 12.9 | Moderate |
Sealing and insulating a typical attic takes out about 3.3 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 12.9 days.
Preventing ice dams on a Murrysville 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.
Murrysville winter, month by month
| Month | Snow (in) | Days on ground | Dam days |
|---|---|---|---|
| January | 10.2 | 14.2 | 4.2 |
| February | 5.6 | 9.1 | 2.5 |
| March | 3.0 | 2.7 | 0.5 |
| April | 0.2 | 0.2 | 0.0 |
| November | 0.7 | 0.8 | 0.1 |
| December | 5.3 | 6.6 | 1.5 |
Murrysville next to nearby towns
Murrysville ranks 31 of 68 Pennsylvania cities here for ice-dam days, behind St. Marys at 26.9 days.
- Monroeville, PA 6 mi, 8.8 days
- Plum, PA 6 mi, 8.8 days
- Lower Burrell, PA 10 mi, 9.6 days
- New Kensington, PA 10 mi, 8.8 days
- Greensburg, PA 11 mi, 9.2 days
Where these numbers come from
NOAA 1991–2020 climate normals from Murrysville 2 SW, 4.1 miles from Murrysville. 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.