COMMERCIALRESIDENTIAL

Revised 6/21/07

Skylight FAQS

Skylights, at best, are a necessary evil in the roofing profession. Customers love them but roofing contractors in this area hate them because, for the most part, they are not designed for the winter climate in our area and are the single biggest cause of non shingle related overhead water problems.

Homeowners like the idea of skylights to brightening up a dark room with few windows without the energy cost of electric lighting. Homeowners also like the opportunity to see more of the outside environment with some skylights.

Hopefully, the following will help you understand some of the unavoidable problems caused by skylights:

Why do skylights cause so many problems?
Skylights divert and rechannel the flow of water off your shingle roof which is OK in warm weather. The problem occurs when snow and ice accumulate on you roof and around your skylight which stops or impedes the flow of water off your roof. The most popular low profile skylights do not have curbs or flashing details that can handle this type of impeded water flow without leaking.

Another major problem is that most skylights will allow condensation to occur on the underside surface of the skylight in cold weather especially in houses with humidifiers or other sources of inside water vapor in the winter. When that occurs, this water can drip to the outside edges of the skylight, staining and saturating the adjoining walls or ceilings, and look just like a roof leak.

What causes this condensation?
There are many sources that add water vapor to the inside air of your house. Many forced hot air heating systems may include humidifiers that add water to the heated air coming from you furnace to make you house more comfortable in the winter. Many homeowners do not maintain or adjust these humidifiers properly and may even want to crank them up to create a high elative humidity inside the house to an unsafe, but comfortable level.

Another source of typical water vapor sources are heavy use of showers without venting the humid air outside. Frequent cooking can sometimes create high inside humidities if the cooking area is not properly vented outside.

Improper ventilation of moisture producers is a main contributor. Some homeowners decide not to vent their clothes driers outside to keep the exhaust heat inside the house. This is a no-no and can introduce very damaging excessively high inside relative humidities.

Wet basements can also be a source of unusually high inside humidities.

Are there other skylight problems?
Yes! Some skylights are simply glass or plastic panels caulked or sealed into a metal or wood frame. These caulks and sealants dry out over time and need to be reglazed on a frequent basis. If metal frames are used, they expand and contract with temperature changes and can break the seal of the glazing.

Can skylights be installed without problems?
It is possible but it will probably be more than you are willing to spend and the appearance may not be what you would prefer. One of the keys is to assure that the skylight curb extend well above the surface of the roof. For shingle roofs in this area and climate, the minimum curb height our company is comfortable with would be 16″ minimum. The shingle roof surrounding the sides and the top of the curb should have at least 3″ of ice backup membrane and that membrane should be installed up the vertical walls of the skylight curbs. You also want to make sure you are installing the most energy efficient skylight possible to reduce the condensation problems.

Is there anything else I should consider?
Yes. The interior finish of the skylight well is of prime concern. The expense to finish off the interior ceiling area below the skylight can involve extensive and expensive work.

It sounds like BSR does not recommend installing skylights?
That is correct. In our experience, it is only a very small percentage of skylights that problem free. If we lived in Florida, our feelings would be different. The only ceiling stains I have in my own home have been caused by the one skylight in our house, and those stains were caused by condensation.

In light of the above, if you are still interested in skylights and are willing to choose the proper curb, the proper skylight, the proper installation, the proper inside ceiling work, and the resultant expense, we can provide you with the best chance to have a problem free unit.

Does BSR guaranty skylights?
No! Even with the best properly designed and installed skylight, we cannot eliminate the problems discussed above.

Charles Griffiths, President