Ice dam risk in Laconia, NH
Will your roof get ice dams in Laconia, NH?
29.5 dam days a winter
High risk. On an ordinary house in Laconia, conditions for an ice dam come on about 29.5 days in a normal winter, mostly in January and February.
Laconia averages 62 inches of snow a year and about 91 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 Laconia
| Attic | Dam days | Risk |
|---|---|---|
| Air-sealed and well insulated | 15.7 | High |
| Typical, some insulation, not air-sealed | 29.5 | High |
| Older or poorly insulated, warm attic | 46.7 | Severe |
Sealing and insulating a typical attic takes out about 13.8 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 46.7 days.
What to do about ice dams in Laconia
- 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 248 kWh a winter in Laconia, roughly $42 at 17 cents a kWh.
Which to spend on first: air sealing or heat cable.
Laconia winter, month by month
| Month | Snow (in) | Days on ground | Dam days |
|---|---|---|---|
| January | 18.8 | 26.9 | 10.3 |
| February | 16.9 | 25.4 | 8.9 |
| March | 9.4 | 18.9 | 4.9 |
| April | 1.6 | 2.2 | 0.3 |
| October | 0.3 | 0.1 | 0.0 |
| November | 2.1 | 2.4 | 0.4 |
| December | 12.8 | 14.9 | 4.6 |
Laconia next to nearby towns
Laconia ranks 3 of 11 New Hampshire cities here for ice-dam days, behind Claremont at 34.6 days.
- Concord, NH 24 mi, 28.7 days
- Rochester, NH 32 mi, 18.6 days
- Somersworth, NH 37 mi, 18.6 days
- Sanford, ME 38 mi, 29.0 days
- Lebanon, NH 39 mi, 30.4 days
Where these numbers come from
NOAA 1991–2020 climate normals from Lakeport 2, 2.1 miles from Laconia. 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.