Ice damming is a phenomenon that occurs when snow accumulates on the roof at the point where the warm side of the roof meets the cold side of the roof. The area I am describing is where the outside wall meets the attic space or just beyond where the soffit ends.
The snow higher on the roof will melt and run down the roof with part of it refreezing just a couple of feet above the eaves trough, creating a dam effect. The water just above the dam may then work its way under the shingles.
This issue may present itself as just a stain or dripping at the ceiling near the wall edge or at an exterior door or window on the top floor.
Most newer houses will have an Ice and Water Shield for the first few feet above the roof edge, that may help keep water from entering the home. The only problem is that the ice and water shield tends to end at the area where the problem may occur.
Ice Damming may occur higher up on the roof when certain conditions exist:
- Inadequate or inconsistent insulation.
- Poor attic ventilation.
- Air leakage from the house into the attic.
There are also roofs that may be more susceptible to ice damming, such as low slope roofs or roofs that have poorly designed valleys. Your Canspec inspector will inform you of vulnerable designs when inspecting a home.
Many products exist that may help to alleviate symptoms of ice damming:
- A roof rake.
- Heating coils (use a lot of energy).
- Ice melting chemicals.
- Shoveling the roof (high risk of injury).
Using axes and shovels and even rakes to break up ice dams can cause a lot of damage to the shingles. I have heard of someone having success putting ice melting chemicals in their eaves trough (in a nylon material).
None of these solutions really gets to the root cause of the problem and will not be as reliable as just solving the problem.
When investigating an ice damming issue the first place to start is in the attic above where the water is presenting itself. How is the insulation, and ventilation in the area?
The single biggest factor in elimination of ice damming is ensuring that warm air from the house is not entering the attic. Warm air can enter the attic from improperly sealed attic hatch, pot lights, plumbing vents, chimneys etc…..
Ice damming can be corrected by a home owner, but you have to be aware of things like how to walk in the attic and how to spot design issues and poorly sealed areas.
If in doubt I would always encourage a home owner to contact a specialist.
The snow higher on the roof will melt and run down the roof with part of it refreezing just a couple of feet above the eaves trough, creating a dam effect. The water just above the dam may then work its way under the shingles.
This issue may present itself as just a stain or dripping at the ceiling near the wall edge or at an exterior door or window on the top floor.
Most newer houses will have an Ice and Water Shield for the first few feet above the roof edge, that may help keep water from entering the home. The only problem is that the ice and water shield tends to end at the area where the problem may occur.
Ice Damming may occur higher up on the roof when certain conditions exist:
- Inadequate or inconsistent insulation.
- Poor attic ventilation.
- Air leakage from the house into the attic.
There are also roofs that may be more susceptible to ice damming, such as low slope roofs or roofs that have poorly designed valleys. Your Canspec inspector will inform you of vulnerable designs when inspecting a home.
Many products exist that may help to alleviate symptoms of ice damming:
- A roof rake.
- Heating coils (use a lot of energy).
- Ice melting chemicals.
- Shoveling the roof (high risk of injury).
Using axes and shovels and even rakes to break up ice dams can cause a lot of damage to the shingles. I have heard of someone having success putting ice melting chemicals in their eaves trough (in a nylon material).
None of these solutions really gets to the root cause of the problem and will not be as reliable as just solving the problem.
When investigating an ice damming issue the first place to start is in the attic above where the water is presenting itself. How is the insulation, and ventilation in the area?
The single biggest factor in elimination of ice damming is ensuring that warm air from the house is not entering the attic. Warm air can enter the attic from improperly sealed attic hatch, pot lights, plumbing vents, chimneys etc…..
Ice damming can be corrected by a home owner, but you have to be aware of things like how to walk in the attic and how to spot design issues and poorly sealed areas.
If in doubt I would always encourage a home owner to contact a specialist.
- Article Submitted by James Waters, Canspec Home Services
*When purchasing my own home, I entrusted the services of Canspec to carry out the Home Inspection and was 100% satisfied with their work and communication as a Buyer!
How To Diagnose The Causes of Attic Mold and Ice Dams
ReplyDeleteIt 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.
For example, ice dams. These are often caused by warm air seeping into the attic which causes the snow and ice on the roof to melt. The water drains to the edge of the roof (which is colder than the rest of the roof because it is an overhang and not warmed by the attic), freezes and creates an ice dam. As this process is repeated daily, the ice dam grows larger. Eventually water is forced under a shingle where it can seep into the house.
Understanding how the house behaves as a system and the various causes and effects is necessary to diagnose most building related problems.
But how about that attic mold? How did it get there?
Mold requires chronic moisture to form and to thrive, so source(s) of moisture must be present. Possibly the moisture came from outdoors. The roof is newer and a quick check of the roof shows no obvious damage or leaks.
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!
Seal these air leaks and you stop a significant moisture source. And just think of all the energy you can save and the cold drafts you can stop!
Mark D. Tyrol is a Professional Engineer specializing in cause and origin of construction defects. He developed several residential energy conservation products including an attic stair cover and a fireplace draftstopper. To learn more visit www.batticdoor.com
Another major cause of ice damming in inadequate attic ventilation. I work for a manufacturer in the US called DCI Products (www.dciproducts.com) we receive throughout the winter with question regarding this issue. Our President and Chief Engineer developed SmartVent to aleviate this issue on homes that do not have proper intake.
ReplyDeleteGreat article!
David Kurtz
DCI Prodcuts
800-622-4455