Ice dam risk in Laramie, WY
Ice dams in Laramie, WY: how often
32.6 dam days a winter
High risk. On an ordinary house in Laramie, conditions for an ice dam come on about 32.6 days in a normal winter, mostly in January and December.
Laramie averages 64 inches of snow a year and about 106 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 Laramie
| Attic | Dam days | Risk |
|---|---|---|
| Air-sealed and well insulated | 18.7 | High |
| Typical, some insulation, not air-sealed | 32.6 | High |
| Older or poorly insulated, warm attic | 50.0 | Severe |
Sealing and insulating a typical attic takes out about 13.9 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 50.0 days.
Preventing ice dams on a Laramie 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.
- Heat cable is worth pricing here even on a sealed house, along the eave and in the gutters and downspouts it drains into.
Running 60 feet of 5 W/ft cable whenever snow lies below freezing would use about 250 kWh a winter in Laramie, roughly $43 at 17 cents a kWh.
Which to spend on first: air sealing or heat cable.
Laramie winter, month by month
| Month | Snow (in) | Days on ground | Dam days |
|---|---|---|---|
| January | 5.5 | 25.5 | 9.1 |
| February | 7.2 | 21.6 | 7.4 |
| March | 9.4 | 12.3 | 3.2 |
| April | 13.4 | 6.8 | 1.3 |
| May | 6.0 | 1.8 | 0.1 |
| June | 1.0 | 0.1 | 0.0 |
| September | 0.7 | 0.5 | 0.0 |
| October | 7.2 | 3.6 | 0.5 |
| November | 6.4 | 10.3 | 2.6 |
| December | 7.3 | 23.1 | 8.2 |
Laramie next to nearby towns
Laramie ranks 3 of 11 Wyoming cities here for ice-dam days, behind Jackson at 50.0 days.
- Cheyenne, WY 44 mi, 10.3 days
- Wellington, CO 53 mi, 11.6 days
- Fort Collins, CO 60 mi, 10.5 days
- Timnath, CO 63 mi, 11.6 days
- Severance, CO 68 mi, 11.6 days
Where these numbers come from
NOAA 1991–2020 climate normals from Laramie 4SE, 4.3 miles from Laramie. 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.