What Are Ice Dams?

An Ice Dam is a build-up of frozen snow and ice that forms on your roof. This solid build-up of ice prevents the water produced by snow melting from being able to flow down and off of your roof. Just above and behind these ice dams a trough of water forms, and this water sitting on your roof can then find its way into your house by seeping underneath your shingles.

How Do Ice Dams Form?

Ice Dams form when the snow on your roof melts while the outside air temperature is still below freezing. This is caused from excess heat in your attic or rafter bays prematurely melting the snow on your roof. When this snow melts, it travels down your roof, and re-freezes when it gets to an area that is at the ambient freezing temperature of the outside air, usually along your roofs eves or in valleys.

Why does My Roof Get Warm?

The most common reason your attic or rafter bays may become warmer than the outside air in winter is due to heat loss from inside your house. This heat can travel through your ceiling, through the attic floor, and up to the underside of the roof, warming it to above freezing and causing the snow to melt before it would do so naturally in warmer weather. The addition of extra insulation can often guard against this type of premature roof warming, but there are always places where heat can sneak through into your attic or rafter bays; like attic stairs, recessed lights, and ductwork openings. Sometimes, adding more insulation just isn't ideal if you currently use your attic for storage or have HVAC equipment already installed.

Another way your roof gets warmed is by a southern-facing roof having it's snow melted off in the sunlight, and this now exposed roof gets warmed up in the daylight, and that heat radiates into the attic space, warming the ambient air throughout the space. No amount of attic floor insulation can prevent this type of premature roof heating.

How Can I Keep My Roof Cold?

The best way to make sure that your roof stays cold in the winter at the same temperature as the outside ambient air is to allow for fresh outside air to travel up through your rafter bays, keeping the underside of your roof as cold as it is outside. The best way for you to ensure that there is plenty of outside ambient air flow through your rafter bays is by having RafterDrafterTM installed.