What I learned about ice dams this year - December 2007.

Having lived in many different, mostly more temperate climates, I had not been privvy to that phenomenon known as ice damming. In the past, pictures I had seen of houses up north showed quaint iclicles hanging down, portraying the very essence of a “winter scene”. Little did I know the grief that they can cause a homeowner.

Being in the business of home performance and energy efficiency, I learned that they are caused by heat escaping through the roof, melting the snow above and then re-freezing at the eaves, causing a dam that backs the water up. Until this winter however, ice dams were mostly an academic problem that happened to houses with “problems”. The thing is that the winter conditions that cause severe ice dams are relatively rare. Just the right combination of snowfall and temperature changes have to happen to cause the water to back up far enough to cause an actual leak. Because of this, I was not often asked about the problem.

After a number of icicles had formed on our house, and I had emailed pictures of the resulting Christmas card perfection to my out-of-state relatives, I still did not think about the slow advance (is an advance uphill still an advance?) of water towards the wall cavities. Then one day I returned from work and found the kitchen counter covered in water. That academic problem had instantly become a mopping up problem. Talk about frustrating! Some of the new plaster finish on the kitchen ceiling was stained and the water was running down the wall, behind the cabinets and onto the counter.

Most of our kitchen is under the second floor but part of it is bumped out with a flat roof on top. Climbing out onto the flat roof I saw that the regular roof above had a huge amount of ice on it. More disturbing was the fact that the short wall below it had icicles coming out of the siding! There was definitely some water inside the wall which explained how it was making its way down into the kitchen ceiling area. At the same time, I found a leak up at the front of the house where we had recently enclosed the old front porch. Seems as though conditions were coming together perfectly to cause water to back up and action was called for.

I spent over 3 hours chipping and scraping the snow and ice away, breaking my good shovel in the process, but I learned a great deal while doing it. The way the ice had formed under the snow had a significant impact on how easy or difficult it was to remove it. Some ice would flake away easily but some would need beating with a hammer and sometimes levering up with a pry bar. I fairly trashed the shingle surface in some places but we are planning on replacing the roof in the near future anyway. Besides, I figured it would be easier to repair a few shingles than to have to repair the drywall and insulation inside.

Once the ice was clear I used an infra red camera to look at the heat pattern of the house. Looking at the house in this “new light” really opened my eyes but confirmed what I had suspected all along. Even though the house had been insulated in the walls and attic a number of years back, there were some areas that had not been reached. The camera showed several hot spots, especially the sloped ceilings of the small bedroom closets as well as the area behind and above the bathtub (especially when someone was showering). The intersections of the dormer walls to the roof framing were also hot, indicating that there may be physical air leakage there.

Another thing I noticed was that some of my neighbor’s homes seemed to have much fewer icicles despite the fact that I knew they were not insulated as well. This mystified me until I turned the camera onto their homes. I saw that, unlike our house, theirs were radiating heat in a much more even pattern. It seems as though a house that has a mostly well-insulated attic, but with a few hot areas, will fare worse than a house that is overall less insulated but has a more even heat loss pattern. I'm planning on looking into this further to find out why this is so.

As it happens, I had the good fortune to have signed up to attend a seminar this week put on by a gentleman by the name of Joe Lstibrick who is a leader in the field of building performance. He actually addressed the topic of ice damming and showed some pictures demonstrating how it can be traced to poor building performance. I asked him how best to tackle the problem, bearing in mind that our house, like many others of a similar style in the area, does not have any soffits and hence, no ventilation at the bottom. I felt that this type of roof is a special case and may need a different technique than a normally constructed and vented roof.

The fix? Well, come Springtime, I will be up in the attic going at it. As with any attic, it is important to seal up any penetrations in the ceiling below including electrical boxes, around plumbing pipes, holes for wiring etc. Spray foam is usually the best for larger gaps but smaller ones can be filled with caulk so I'll use a combination of these materials where needed. The attic hatch is pretty leaky so I’m going to install a foam gasket around the opening and glue some rigid insulation to the hatch itself. Because there is no soffit and therefore no air passages up to the attic, I’m going to make sure that the intersection of the roof, ceiling and wall is completetly air sealed and well insulated. Spray foam is just the ticket for this job.

The top of the wall in the attic should be at least as insulated as the wall itself otherwise heat migrates up and heats up the roof deck (melting the snow). Commercial applicators are the most economical way to do this as opoosed to cans of “Great Stuff” from the big-box store (which would be futile and wasteful). These big units come with two tanks containing separate ingredients which are mixed in a specially designed gun. This system is great because it prevents the foam from hardening in the delivery hoses. Once the spray foam is in place I’m going to have a contractor come in and spray dense-packed cellulose in the sloped ceilings over the closets. These areas have no insulation in them even though the rest of the attic was insulated previously. Once that’s done, I’ll have another 8 to 10” sprayed in the attic space to bring the overall amount to about R50. This will be comparable to a typical energy star home.

I’ll be monitoring the performance of the house closely to see if there are any significant energy savings. Stay tuned for updates! There should be some improvement in that department but I’m more concerned about eliminating (or greatly reducing) the likelihood of ice damming. Although roofers often get blamed for the water damage caused by damming, the issue really is with the performance of the house and not with the roof itself. When I replace the roof, I will install snow and ice sheild "just in case", but doing only this would merely fix the symptom not the actual problem.

Since I’ve been involved in the Focus on Energy program, I’ve noticed that most clients I help are initially motivated by a specific problem with their home. and mine was no exception. Be it cold or drafty areas, condensation or moisture issuse, unusually high utility bills or just something that doesn’t seem to be working correctly, they all are tied to the performance of the house as a whole. Sometimes several things need to be taken care of to fix one individual problem. Overall, the house will work more efficently and some energy will always be saved by addressing the performance issues outlined above.

If you have any questions or comments don't hesitate to call (920 723 8255) or email mark@gradingspaces.com

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