Ice dam risk in Greenfield, IN
Ice dams in Greenfield, IN: how often
7.7 dam days a winter
Moderate risk. On an ordinary house in Greenfield, conditions for an ice dam come on about 7.7 days in a normal winter, mostly in January and February.
Greenfield averages 20 inches of snow a year and about 27 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 Greenfield
| Attic | Dam days | Risk |
|---|---|---|
| Air-sealed and well insulated | 4.2 | Low |
| Typical, some insulation, not air-sealed | 7.7 | Moderate |
| Older or poorly insulated, warm attic | 12.0 | Moderate |
Sealing and insulating a typical attic takes out about 3.5 days a winter here. It drops the risk from moderate to low. An older house with a warm attic should expect closer to 12.0 days.
Preventing ice dams on a Greenfield 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.
Greenfield winter, month by month
| Month | Snow (in) | Days on ground | Dam days |
|---|---|---|---|
| January | 7.4 | 10.8 | 3.5 |
| February | 5.4 | 7.3 | 2.1 |
| March | 1.8 | 2.3 | 0.4 |
| April | 0.1 | 0.1 | 0.0 |
| November | 0.7 | 0.7 | 0.1 |
| December | 4.8 | 6.1 | 1.6 |
Greenfield next to nearby towns
Greenfield ranks 53 of 88 Indiana cities here for ice-dam days, behind Plymouth at 15.9 days.
- McCordsville, IN 11 mi, 8.1 days
- Lawrence, IN 13 mi, 8.1 days
- Fishers, IN 16 mi, 8.1 days
- Shelbyville, IN 17 mi, 4.0 days
- Beech Grove, IN 18 mi, 7.0 days
Where these numbers come from
NOAA 1991–2020 climate normals from Greenfield, 0.8 miles from Greenfield. 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.