Stopping ice dams is simple, in principle: Just keep the entire roof the same temperature as the eaves. You do that by increasing ventilation, adding insulation, and sealing off every possible air leak that might warm the underside of the roof, as shown in the illustration below. By taking care of these trouble spots, listed here in order of priority, you should enjoy a winter free of dams and use less energy to boot.
The Truth About Ice Dams
How Ice Dams Form
Preventing Ice Damming
Ventilate With A Ridge Vent and or Gable End Vents
Dam-free winters start off like this: a ridge vent paired with two gable end vents, thus promoting ventilation. How does this work, you ask? It allows the fan to exhaust air through one vent while pulling in cooler air from the opposite vent.
Cap the Hatch
After properly ventilating, this would be your next step thus far. By capping the hatch, you ensure no heat escapes. An unsealed attic hatch or whole-house fan is a massive opening for heat to escape, and by following what comes next, you avoid that. How do you do this? By covering them with weather stripped caps made from foil-faced foam board held together with aluminum tape.
And Make Sure the Exhaust Goes to the Outside
Make sure that the ducts connected to the kitchen, bathroom, and dryer vents all lead outdoors through either the roof or walls, but never through the soffit. You want the exhaust to go outside, well, because, no one wants to smell what comes out of your dryer, right?
More insulation on the attic floor keeps the heat where it belongs. So you definitely don’t want to skip this one. To find how much insulation your attic needs, check with your local building department. However, you can apply the alternative: open or closed cell foam to the underside of the roof will also eliminate all ice dams.
Install Sealed Can Lights
Old-style recessed lights give off great plumes of heat and can’t be insulated without creating a fire hazard; you, therefore, are going to want to update them. Replace them with sealed “IC” fixtures, fixtures that hence can be covered with insulation.
Flash Around Chimneys
Bridge the gap between chimney and house framing with L-shaped steel flashing held in place with unbroken beads of a fire-stop sealant. This, therefore, can provide safety, eliminating the need for canned spray foam or insulation, which isn’t fire safe.
Seal and Insulate Ducts
Spread fiber-reinforced mastic on the joints of HVAC ducts and exhaust ducts. Cover them entirely with R-5 or R-6 foil-faced fiberglass.
Seal around electrical cables and vent pipes with a fire-stop sealant. Also, look for any spots where light shines up from below or the insulation is stained black by the dirt from passing air.