Both the supporters of skylight installations and those that think they are a bad idea have their arguments. Sometimes they might be the only practical way to get natural light into a space.
I am more in the negatory camp. Windows are terrible at heat loss/gain and air infiltration/exfiltration, now take that window and put it in your roof. It simply must compound the issues.
None of this discussion addresses the reality that there are lots of them out there in the real world and people are installing them every day—even in “green” houses with an endless list of certifications and designations.
But the focus of this post is more about current skylight installations and a very common problem with them that most people never think of.
Everyone knows they leak and if they aren’t now it is only a matter of time—right? I personally don’t agree with that analysis. As often as not, the “leaking” we encounter can often be attributed to condensation due to inadequate or non-existent ventilation—especially for skylights located in bathrooms. Of course the type of skylight, and poor installation details, can result in actual leaks as well.
Broken seals are another common issue, but for the most part that is cosmetic—does anyone ever actually look out of skylights anyway?
Problems with modifications of the structure to accommodate a skylight, as in a remodel, are also common.
Perhaps the single most common skylight defect that I encounter is that they are just sitting there—not attached to the roof structure at all. Small ones, and especially the plastic ones, are very light weight and can easily be lifted. Under the right wind conditions they can literally be sucked off the roof under negative pressure.
If you have skylights on your home, it is a good idea to check and make sure they are properly attached.
Charles Buell, Real Estate Inspections in Seattle
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WA State, Home Inspector Advisory Licensing Board