I read your comments in the paper on Sunday. I have a problem with air leaks at my skylights. Either they are not insulated properly or I have vapour barrier problems. There are 3 of them side by side and I get quite an ice build up on shingles, which last winter I chipped off. Previous winters, dripping would occur in the kitchen with water appearing to run down the poly and then find its way down the wall. Any suggestions for insulating my skylights better or poly details at the perimeter of skylights?
As an amendment to the old saying about death and taxes being a certainty, I would like to add a third item to the list. Skylights leak. In our climate, it is inevitable that at some time in the course of the lifetime of these roof-mounted windows that a leak will occur. It may be caused by deteriorated roofing or flashing, condensation inside or around the skylights, or failure of the units themselves. Your problem may be due to one or more of these issues and I will provide some insight into diagnosing your problem.
The first issue is the location of the skylights, themselves. You have stated that 3 of them were installed in close proximity, one beside the other. This positioning will make insulating and air sealing very difficult and may require very creative roofing installation around the skylights. The fact that you are experiencing major ice damming around the skylights tells me that you are having a problem with air and heat leakage through or around the skylights. This warm air is melting the snow in this area and causing the ice dams. It is this melted ice and snow that you are most certainly seeing dripping into your kitchen. I have seen this same issue several times in the last few years, particularly in areas where there are multiple skylights with little space between. The simple answer to your problem is to remove one or more of these units to allow better installation of roofing & insulation and prevent excessive ice damming in a concentrated area.
If removing some of the skylights is not practical or desirable, the alternative may much more labour intensive. The solution to this will largely depend on the installation method of the skylights and the style of ceiling and attic around these units. If these were installed in a typical sloped roof with a flat ceiling below, there may be enough room to enter the attic and do repairs that may help minimize the ice damming and leakage. If the skylights are installed in a vaulted ceiling, as in a couple of recent cases I have seen, repairs will be much more difficult. If only a small attic space, or none, is provided then repairs may have to be completed primarily from the exterior after removing the roofing and sheathing around the skylights. In this scenario, I would strongly advise removal of at least one of the skylights to allow easier repairs and installation of a higher level of insulation
Even with properly done flashing and roofing after initial skylights installation, ice damming can occur. The excessive ice may deteriorate the roofing very quickly and may cause lifting of the flashing. Both of these issues can cause small leaks, which will only become worse as time progresses. The key to stopping the leakage is minimizing the air and heat loss around the skylights.
There are two approaches to preventing the above problems in any insulated attic or roof system, and normally a combination of both is attempted. The first method is proper ventilation of the attic space, to allow easy removal of warm moist air that leaks into this area from the heated living space below. This works well in a straight forward attic where there is sufficient room for a poly air-vapour barrier and insulation above the ceiling and air movement below the pitched roof. If your skylights are installed in this type of roof system, then the boxes around the base of the skylights must also be well insulated and air sealed to prevent condensation, as well. If this is poorly done, repairs with rigid foam insulation, caulking and poly may help considerably. This will only be possible if there is sufficient room around the skylights for proper repairs, as stated earlier.
The second approach to preventing the ice damming situation is the complete insulation/air sealing method. This will be your only option if you have a vaulted ceiling or minimal attic space in the area around the skylights. The most practical repair in this situation is to fill the entire cavity and area around the skylights with blown-in foam insulation. This material will not only provide good insulation, it will completely seal any small areas of possible air leakage in this area where proper ventilation is difficult or impossible to achieve. This may have to be completed from the exterior, as mentioned, or from the interior with complete removal and replacement of existing drywall in and around the skylights. Also, sheathing on the roof or around the skylight boxes may also require replacement if moisture damaged.
Whatever the style of roofing system your skylights are installed in, repairs will not be simple or cheap. Brace yourself for major repairs, due to the possibility of major rot or moisture damage due to the prolonged leakage. In the mean time, carefully clear excess snow from the area above and around the skylights to prevent excessive ice damming.