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Ice damming is a major source of water damage to many homes....


Sometimes known as ice dams, these giant icicles hanging from the eaves are not only dangerous to people walking underneath, they are often a sign of serious problems with the roof and/or in the attic.

In a well designed and constructed home, the attic has its own dry and cool environment, quite separate from the living space. If your attic is not isolated from the rest of the house with proper air sealing and insulation, it can become warm and moist. Warm attics can help melt the bottom layer of snow on the roof and the water runs down to the gutter where it refreezes. This is the beginning of an ice dam.



There are several sources, both exterior and interior. If the roof is old and leaking, obviously that is an exterior source. But lets talk about interior sources that are often overlooked, but are not too difficult to correct.

Interior sources include air leaks from the house into the attic. Moisture is carried by air movement from the warm home into the cold attic, where the moisture in the air condenses and wets cold surfaces, such as the roof sheathing and rafters. Over time, chronic moisture causes mold and mildew.


The largest "holes" leading directly from the house to the attic are the attic access and the whole house fan.

When an attic access is a fold-down stairway, it was difficult to control moisture and heat loss. The Battic Door Attic Stair Cover is a low-cost, easy-to-install solution to this common problem.

When a whole house fan is installed in the home, it was difficult to control moisture and heat loss. The Battic Door Whole House Fan Cover and Battic Door Whole House Fan Shutter Seal provide two low-cost, easy-to-install solutions to this common problem.   


Form the experts at University of Minnesota:

What is an ice dam?


ice dam diagram

What causes ice dams?




Nonuniform roof surface temperatures lead to ice dams.

What causes different roof surface temperatures?









Photograph 1 shows a single story house with an ice dam. The points of heat loss can be clearly seen as those areas with no snow. The ceiling below this area needs to be examined for air leakage (often through an attic stair and/or whole house fan), missing or inadequate insulation, leaky or poorly insulated ductwork, and the termination of a kitchen or bathroom exhaust into the attic space.

ice dam photo
Photograph 1. A single-story house with an ice dam. The areas without snow are the points of heat loss.


ice dam photo
Photograph 2. The unusually high heat loss on this roof has caused both an ice dam and icicles.



Here are several documents written by Zerodraft (an expert and manufacturer of sealants and foams) that describe other sources of air leaks.


Ice dams in low-rise townhouses (36 kb)
Seal party walls (544 kb)
Seal recessed light fixtures (138 kb)
Seal the attic hatch (306 kb)
Seal the baseboards (127 kb)
Seal electrical outlets (111 kb)
Seal the attic (167 kb)


Here is a recent article written by Mark Tyrol, Owner of Battic Door, and published Nationwide!

Got Attic Mold? Lets Talk Energy Conservation!
By Mark D. Tyrol, P.E., Battic Door Energy Conservation Products

It happens to countless homeowners around the end of the year – you make the annual visit to your attic to collect the holiday decorations and what do you find? Spots and blotches covering the bottom of the roof sheathing. Worse yet – it turns out to be attic mold!

What does energy conservation have to do with mold in the attic? Well if you take a step back and consider how the house behaves as system, they are often directly related.

Building science experts have long been using the “house as a system” approach to diagnose the cause and origin of building defects.



But how about that attic mold? How did it get there?


Possibly the moisture came from indoors. During the heating season, the interior of the house frequently has high moisture levels, especially bathrooms and kitchens. A quick check shows that all bathroom fans, kitchen vents, etc. are properly ducted completely outdoors and not into the attic. The amount of insulation looks good and the attic is well ventilated.

Don’t give up – you are almost there! Remember the house as a system? You know that warm, moist air is in the house, but how is it getting into the attic?

By air leaks! Air leaks are the leading source of energy loss in most houses, and a frequent source of chronic moisture that can cause attic mold. Most homeowners are well aware of air leaks around windows and doors (especially old ones), but many overlook the numerous gaps leading directly into the attic!

Have a look around the attic and you may find large gaps around recessed lights and fans, holes where wires or pipes are installed, even large gaps around the chimney. And don’t overlook the whole house fan and especially the folding attic stair - a big, uninsulated hole in your ceiling that is often overlooked!

These gaps can add up to a large hole that allows warm, moist air from the house to flow right into the cold attic. The warm moist air condenses on the cold roof sheathing, creating chronically damp conditions that can lead to attic mold growth. And the energy loss – it can be like leaving a window open all winter long!

