Ice dam risk in Hackettstown, NJ
Ice dams in Hackettstown, NJ: how often
12.4 dam days a winter
Moderate risk. On an ordinary house in Hackettstown, conditions for an ice dam come on about 12.4 days in a normal winter, mostly in January and February.
Hackettstown averages 23 inches of snow a year and about 47 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 Hackettstown
| Attic | Dam days | Risk |
|---|---|---|
| Air-sealed and well insulated | 8.6 | Moderate |
| Typical, some insulation, not air-sealed | 12.4 | Moderate |
| Older or poorly insulated, warm attic | 17.1 | High |
Sealing and insulating a typical attic takes out about 3.8 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 17.1 days.
Preventing ice dams on a Hackettstown 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.
Hackettstown winter, month by month
| Month | Snow (in) | Days on ground | Dam days |
|---|---|---|---|
| January | 9.9 | 14.5 | 4.5 |
| February | 5.2 | 14.5 | 4.0 |
| March | 3.5 | 9.1 | 1.8 |
| April | 0.3 | 0.4 | 0.0 |
| November | 0.4 | 0.7 | 0.1 |
| December | 4.0 | 7.8 | 1.9 |
Hackettstown next to nearby towns
Hackettstown ranks 3 of 116 New Jersey cities here for ice-dam days, behind Hopatcong at 14.7 days.
- Hopatcong, NJ 11 mi, 14.7 days
- Dover, NJ 14 mi, 5.7 days
- Morristown, NJ 19 mi, 5.7 days
- Phillipsburg, NJ 22 mi, 10.6 days
- Madison, NJ 22 mi, 5.7 days
Where these numbers come from
NOAA 1991–2020 climate normals from Belvidere Brg, 13.6 miles from Hackettstown. 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.