Ice dam risk in Denver, CO
How often ice dams form in Denver
10.4 dam days a winter
Moderate risk. On an ordinary house in Denver, conditions for an ice dam come on about 10.4 days in a normal winter, mostly in December and January.
Denver averages 49 inches of snow a year and about 43 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 Denver
| Attic | Dam days | Risk |
|---|---|---|
| Air-sealed and well insulated | 8.2 | Moderate |
| Typical, some insulation, not air-sealed | 10.4 | Moderate |
| Older or poorly insulated, warm attic | 13.2 | Moderate |
Sealing and insulating a typical attic takes out about 2.2 days a winter here. It does not move the risk band, but it shortens every dam.
Preventing ice dams on a Denver 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.
Denver winter, month by month
| Month | Snow (in) | Days on ground | Dam days |
|---|---|---|---|
| January | 6.4 | 10.0 | 2.8 |
| February | 7.6 | 9.3 | 2.5 |
| March | 8.8 | 3.9 | 0.8 |
| April | 6.2 | 2.0 | 0.2 |
| May | 1.4 | 0.2 | 0.0 |
| September | 0.8 | 0.2 | 0.0 |
| October | 3.9 | 1.5 | 0.1 |
| November | 7.3 | 5.4 | 1.2 |
| December | 6.6 | 10.0 | 2.8 |
Denver next to nearby towns
Denver ranks 27 of 53 Colorado cities here for ice-dam days, behind Steamboat Springs at 51.0 days.
- Aurora, CO 9 mi, 10.4 days
- Commerce City, CO 10 mi, 9.4 days
- Englewood, CO 10 mi, 7.2 days
- Federal Heights, CO 10 mi, 7.7 days
- Greenwood Village, CO 10 mi, 7.2 days
Where these numbers come from
NOAA 1991–2020 climate normals from Denver-Stapleton, 0.6 miles from Denver. 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.