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Case Study

Roof Ice Dam Remediation for Northeast Ski-Area Condominiums

Part IV

by Henri C. Fennell
President, H. C. Fennell, Inc. & FOAM-TECH
North Thetford, Vermont, USA.


Following the Phase II repairs, a final round of scans and melt pattern reviews was made. Conversations with the builder, the management group, and the owners in conjunction with this review provided feedback and data about the performance of the buildings and the roofs through the end of the winter season. The snow melt patterns showed significant reduction of roof surface warming, especially above the party wall and in the valleys below the crickets. Only a few melt spots were visible in the two middle units above chimney boxes – presumed from their location to be caused by exhaust gases rising from the boiler’s through-wall vent up along the wall and into the soffit vents above. There was an apparent reduction in ice dam formation compared to adjacent unmodified units.

The results of the Phase I and Phase II procedures were the elimination or significant reduction of the major causes of roof warming and the subsequent ice dam formation. The improvements accomplished in an already existing and complex group of buildings without major demolition and cost were significant. The per-unit cost of the repairs was less than the original proposals for new roofing and flashing; it promises a short payback from energy and maintenance savings2. The ice formation has been reduced to a level that eliminates the need for the annual routine of raking snow, installing eave heaters, and repairing water and shingle damage. The information gathered and the understanding of the root causes of many of the building problems will be useful in the planning of future improvements throughout the rest of the condominium community.

Significance for Future Projects

This project demonstrates that it is possible to create solutions to ice dam formation and the related water infiltration damage by using energy conservation measures involving minimal disruption to the interior and exterior finishes of the building. This conservation-oriented approach has the additional benefit of being extremely cost effective.

The earlier proposals, which addressed the ice dam leakage by improving the roofing, all were targeting the symptoms of the problem. The fact that none of these reputable contractors proposed to address the root causes of the ice dams underscores the need for promoting a more energy conscious approach to the industry. Many building owners misunderstand the source of their problems and fail for consider the potential payback of repairing the thermal envelope rather than the roof.

This study indicates the need for proper planning and implementation of the thermal envelopes in new construction. It is far less expensive to install the effective thermal envelope components during the original construction than to properly install them in a retrofit situation. It is hoped that the examples identified in this case study might help designers and builders avoid similar problems in their own work and encourage them to use performance-based quality assurance techniques at the time of construction when it is easy and inexpensive to fine-tune the integrity of the thermal envelope. This study may also serve as a useful process outline for trouble-shooting existing buildings with related problems.

Using this as a model, Condominium Association owners and operators can see that the root causes for this common problem can be identified and eliminated with a proven team approach. The photographic essays in this document can serve as examples of frost and snow melt patterns that are the visual manifestations of flaws in the thermal envelopes of their buildings. The project has also demonstrated that pursuing an energy conservation approach can be a better investment for the homeowners than implementing damage control measures.


This case study demonstrates that for a specific project, remediation of the existing thermal envelope was the most cost-effective way to avoid ice-dam related damage. It presents a viable approach for building owners to utilize in the assessment and repair of conditions that lead to ice dam formation and its related water damage. The feasibility of successfully preventing damage caused by ice dams through the means of a science-based approach has been proven. This approach did not resort to major reconstruction, nor did it rely only on waterproofing solutions to roof leakage. It conserves fuel, is environmentally sound, and can be less expensive than replacing the roof and installing infiltration-proof membranes.

None of the test units has experienced failures (leaks) since the Phase I modifications were performed two years ago. Even though the final improvements were not completed until late in the second winter, these units have functioned successfully, realizing lower operating costs through two winter seasons.

In addition to achieving the original goal, the owners have attested to the fact that their units are quicker to warm up, have not had any frozen pipes, are more comfortable, and use less energy.


Fennell, H. C., Knee wall Performance Test Report, 1998.

Fennell, H. C., Financial Analysis – Northeast Ski-Area Condominium Association Ice Dam Remediation Project, 1998.

Janssens, A., H. Hens, A. Silverstein, and J. Boulant, 1992. The Influence of Underroof Systems on the Hygrothermal Behavior of Sloped Insulated Roofs. Thermal Performance of the Exterior Envelopes of Buildings V. Clearwater Beach, FL: American Society of Heating, Refrigerating and Air-Conditioning Engineers, Inc.

Wilkes, K. E., Ph.D., P.E. 1992. Thermal Performance of Fiberglass and Cellulose Attic Insulations. Thermal Performance of the Exterior Envelopes of Buildings V. Clearwater Beach, FL: American Society of Heating, Refrigerating and Air-Conditioning Engineers, Inc.

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