Jerry Ludwig: Warm air in attic is main cause of ice damming

Last week, I addressed short-term options for dealing with ice build-up at the eaves, which many homeowners have experienced this winter. Although the cold and snowy weather has temporarily subsided, more is on the way. As I noted in my last column, cleaning snow off the roof and/or cutting through ice dams are both potentially hazardous, and they are temporary measures. This week, Id like to offer some longer-term solutions.

Icicles, per se, are not necessarily bad, nor are they always cause for alarm. However, if you notice that you have ice that is tea-colored, or that is forming on the side of the house, it is cause for concern. And, if ice is present below siding or the soffits, or you discover that water is leaking into the structure, then it is also cause for concern. If ice forms over doorways or is a threat to pedestrians, steps should be taken to ensure that it does not harm anyone or anything.

If ice does not pose a threat, the best solution is to leave it alone and let it melt naturally. I know this violates the basic instinct of we have to do something, but in the long run its probably the best and safest policy.

However, if your home is experiencing water infiltration due to ice damming, then you should take steps to either partially eliminate the ice or, at the least, control its effects. Some of these measures include removal of snow from the roof and trying to contain any water that enters the house, as I discussed last week. Major roof repairs will likely have to wait until spring or summer.

One additional safe step you can take is to assess the insulation and ventilation in the attic. If there are areas missing or with substandard insulation, adding more as soon as possible makes obvious sense. One exception to this rule is if the existing insulation is wet or may become wet due to the leaking roof.

Plugging any gaps between the attic and the heated envelope of the house is also important since it is warm air escaping into the attic that is the main cause of ice-damming problems in the first place. Plumbing stacks, chimneys, bath fans, open areas over attic stairways and doors, etc., are all routes where warm air can move into the attic. Once the attic is warmed, the heat will escape through the roof and start to melt the snow above. Spray foam around gaps in the attic floor can help isolate the attic from the heated portion of the house.

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One step beyond this is to install a layer of foam between the unheated attic and the heated rooms below. This will likely mean the removal of existing insulation, the application of the foam (typically an inch or so) and then the installation of as much additional insulation as is practical. The ideal total amount of insulation would be to a minimum R-value of 38, however, the architectural design of the house may limit the available space to install that amount.

Please note that I do not recommend installing foam over the attic roof sheathing. This can conceal potential roof leaks and the layer of foam applied directly under the roof shingles can shorten their life.

If youve insulated the attic and closed potential air passages into the attic, one last option is to vent the attic so that it remains as close to the exterior temperature as possible. The addition of roof or ridge vents, or gable vents combined with free-flowing soffit vents (if your homes architecture allows for them) will help keep the attic cool enough so that snow does not melt in the first place. Some of these modifications may be able to be done during the winter months.

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Jerry Ludwig: Warm air in attic is main cause of ice damming