Six Risks You Should Know Before Putting Skylights on Your Roof

Skylights are popular for a reason. They add an extra dash of beauty to any commercial building, and they’re a great source of free lighting. But there are also drawbacks, and, if you’re not aware of them, the costs can end up being far greater than the benefits. Whether you already have a skylight or are considering adding one to the design of a new roof, make sure you’re prepared to deal with the downsides:

  • 1. Leaks
    Skylights are famous—or maybe that should be infamous—for leaking. Over time, the seals and flashing can deteriorate, providing an opportunity for water to penetrate your roof. Things like rain, snow and debris can accelerate the process. Modern skylights are less prone to leaks than older versions, but even the best skylight can leak if it isn’t installed properly.

    There’s an additional leak risk, too: ice dams. Skylights transfer heat to the surrounding roofing material, causing any accumulated snow to melt. That, in turn, can contribute to ice dams, eventually causing even more leaks and adding to the cost of roof maintenance.

  • 2. Breakage
    Even standard roofs are vulnerable to the elements, particularly wind and storm damage, but skylights are even more so. Hail and flying debris, for in-stance, can easily crack a skylight. And, when it comes to snow loads, skylights can be the weakest part of the roof. If you calculate the maximum weight load based on the rest of the roof, your sky-light could fail from the excess weight of a heavy snowfall.

  • 3. Falls
    For workers performing roof maintenance, skylights pose a risk for serious injury, or even death. Some workers simply assume skylights are designed to bear their weight and will intentionally stand or sit on them. Tripping and falling onto a skylight presents yet another risk. That’s why the Washington, D.C.-based Occupational Safety and Health Administration puts skylights in the same category as other open holes and requires that each one is protected by a screen or guard rail that meets OSHA’s regulations.

    However, guard rails aren’t 100 percent safe either. Depending on the quality of the safety net or the weight of the victim, roof-maintenance professionals can fall through just as easily as they would through a skylight.

  • 4. Light Exposure
    While access to free natural light is one of the primary benefits of skylights, there’s also a drawback. Depending on the placement, skylights can actually let in too much light, contributing to glare and excess UV exposure. Not only can that be hard on employees, it can cause preventable damage to furniture, carpeting, art and more valuable items.

  • 5. Energy Loss
    In stark contrast to the lure of free lighting, skylights can have a significant negative impact on heating and cooling costs. Skylights simply don’t present the same barrier to heat transfer that more traditional roofing materials do. In the winter, heat escapes. In the summer, heat seeps into the building—and sun-light and glare only add to that effect. According to the National Fenestration Rating Council Inc., Greenbelt, Md., skylights can cause a building’s interior temperature to fluctuate by more than half the difference between the exterior temperature.

  • 6. Space Constraints
    Skylights take up rooftop space that could be used for equipment or other purposes. To get the maximum benefit of free natural lighting, you need to dedicate 7 to 10 percent of your roof to skylights. That’s space that can’t be used for things like rooftop equipment and supports. It also claims space that might be needed for workers to perform roof maintenance. And if you have a small roof, that is going to be a problem!

There’s no doubt that skylights contribute to a building’s aesthetic appeal, and they can also reduce the cost of electrical lighting. But they have drawbacks, too, and building managers have to consider both aspects to make an informed decision. When considering skylights as part of your building’s future, remember to think about the hidden costs, like increased roof maintenance, heating and cooling, and safety precautions.

About the Author

Marion McKnight
Marion McKnight is vice president of Operations at Houston-based PHP Systems/Design. He has been responsible for overseeing core business and operational functions for more than 20 years.

5 Comments on "Six Risks You Should Know Before Putting Skylights on Your Roof"

  1. I disagree with a lot of the points made in this article, but to each their own. If you come across this article because you are considering having skylights installed, please don’t let this article change your mind. There are a lot of great benefits that you will see with skylights as well, just do your research!

  2. My name is Arthur J Valentz, 26 years ago I founded PHP Systems and Design. While on a roof in west Texas with my father in law, I saw a 4” gas line supported by a wooden sleeper that had penetrated a new roof because of the pipe’s weight and thermal expansion. I was asked if I could solve this problem and I said yes. My theory is if you hang the pipe, you isolate the movement to the pendulum, none of that movement transfers to the base, a large enough foot print and you have solved the problem. With that theory, PHP was born.

    Twelve years later I was asked to solve another serious problem. I was asked if I had a solution for skylights that leak and fall protection. Again I said yes. For 26 years I have had the opportunity to observe and make notes on the rate of decay of Acrylic and Polycarbonate materials used in the manufacturing of skylights. It is for this reason I embarked on the creation of a better skylight. That journey lead to the creation of the patented VTech Skylight – a one piece, solid state skylight that is designed not to meet state and local standards but to exceed them. All across the country, whether its hail, pounding rain, or falling debris, VTech has performed flawlessly. Most warranties for skylights today only cover frame and glazing components but I strongly believe a skylight warranty should encompass the entire system, which is why all VTech products are guaranteed for 20 years.

    To reiterate Mr. McKnight’s response, we are fully aware that the risks presented in this article are not absolutes that come with every skylight. But, they are valid concerns a discerning buyer should be sure to address. I would like to take a minute and specifically address the first three points.

    For over 26 years I have had the opportunity to hear from consultants the reasons skylights leak and they are many. In almost every case the first thing to fail was the sealant, with neoprene gaskets being the second most common. It is for these reasons that skylights utilize drip pans. Mr. Magnuson does make a valid point, that most quality skylights today have drastically improved and, if installed correctly, will not lead to leaks. But that is exactly Mr. McKnight’s point, the buyer needs to ensure that if they plan to install skylights, that they are installed correctly to avoid leaks.

    Whether the Acrylic or Polycarbonate is new or five years old, it is my opinion that they are the most dangerous thing we put on the roof today. The inherent lack of durability of skylights contributes to OSHA regulation 1926.500-503 referring to skylights as “open holes.” OSHA’s Dr. Nigel Ellis, a leading authority on fall protection, believes so much in the bolstering of skylight safety standards that he has introduced a draft, ASTM standard EO6.51.25, that mandates a three drop test of 300 pounds, measured 36” from the top of the dome, frame, and corner (not from the roof itself, as some manufacturers will try to do). Currently, VTech is the only skylight that has documented passing this test.

    If you ask skylight manufacturers how they feel about fall protection, they will tell you it’s not their problem. I believe it is our problem. From 2004-2010 there were 20-35 reported deaths per year directly connected to skylight related falls. If this isn’t an indication that skylights represent a danger to people on a rooftop, I don’t know what is. It is my opinion that a fall protection system should be the responsibility of the skylight manufacture to provide, not the third parties.

    For more information about VTech Skylights, please visit
    For our AIA Accredited presentation on why skylights fail, please contact

    Art Valentz
    Owner, PHP Systems/Design
    President, VTech Skylights

  3. Thank you both for your comments. We always welcome and appreciate feedback from industry experts such as yourself.

    We understand that the issues cited above are not absolutes that occur with the installation of any and all skylights. We did not title the article, “6 Reasons to Not Have Skylights,” we titled it, “Six Risks You Should Know Before Putting Skylights on Your Roof.” While you are both correct that all of the points we made do not reflect every skylight manufactured, and that there are regulations to specifically avoid some these issues, not every manufacturer and installer follows all regulations and best practices. The fact that these regulations and standards even exist suggests that at some point these were all issues that the product in question faced.

    The goal of this article is to raise awareness for professionals in the industry we serve. The intent was not to discourage the use of skylights, but to point out certain issues so that the buyer can be sure to avoid them when considering a purchase, even if there is only a small chance that they could occur.

    On a related side note, the owner of PHP Systems/Design also owns the skylight manufacturing company, VTech Skylights, which produces AAMA Gold Label Certified products. Our skylights are the first and only Solid-State Skylight that exceed all required codes (including Miami-Dade County).

    Experience with flaws in the skylight industry drove the creation of our innovative technology and it is our familiarity with these flaws that lead to us writing this article. We are not speaking based on unfounded assumptions, we are speaking from experience.

    Best Regards,
    Marion McKnight
    Vice President of Operations, PHP Systems/Design

  4. There are counterpoints that should be noted for this article. In addition to skylights adding “an extra dash of beauty to any commercial building…[and serving as] a great source of free lighting” (as the author points out), skylights also offer health and productivity benefits that can far outweigh quantifiable energy savings. As the Vice President of the Skylight/Sloped Glazing Council of the American Architectural Manufacturers Association (AAMA), I would like to address each of the six risks identified in the article.

    1. Leaks
    The risk identified for leaks is “old-school” information which may have been accurate 25 or 30 years ago, but certainly does not hold true today. Current skylight designs use silicon sealants and neoprene or EPDM gaskets to ensure the skylights maintain a high level of performance and longevity. Current skylights are also tested to the industry standard, AAMA/WDMA/CSA 101/I.S.2/A440, for air infiltration, water penetration, and structural loading (as required by code) and are labeled to verify the performance and quality level.

    Any penetration in an opening has a leak potential. Leaks from skylights (and other envelope openings) are an installation and maintenance issue, not necessarily a problem with the product itself. Regarding the “additional leak risk” of ice dams. Insulated curbs and above-deck insulation should minimize this issue. Those in colder climates should consider this option.

    2. Breakage
    The second risk of breakage alluded to skylights being the weakest part of the roof is obvious, just as a window is weaker than the wall it is installed in. Skylights are tested and certified to meet specific impact resistance levels and hail impact and are designed to meet the International Building Code requirements for the specific applications. It is important to choose products that can withstand design loads of the particular area; some high performing products will be as strong as the roof, if not stronger.

    3. Falls
    OSHA fall protection requirements indicate that the responsibility for workers on a roof lies with the roofing contractor who has placed workers on the roof. OSHA-compliant fall arrest or restraint systems are required for these workers to prevent the risk of a fall or injuries. Any roofing contractor who does not provide OSHA Fall-protection is negligent. Additionally, making a statement that guard rails are not 100 percent safe is irresponsible without providing actual documentation.

    Roofing professionals should protect themselves from falls from or through a roof by using proper fall safety equipment and practices. Skylights also have clear warning labels indicating proper safe use of the products.

    4. Light Exposure
    IECC requirements for haze factor, solar heat gain and U-Values all address the majority of the concerns outlined by the writer. Additionally, if damage to furniture, carpeting, etc., is a concern, there are specific acrylics as well as glass options, which will eliminate up to 99 percent of the damaging UV rays. The same applies for other fenestration products, such as windows and doors. Again, proper design and selection are vital.

    5. Energy Loss
    ASHRAE has performed numerous studies on the benefits of skylights, accumulating specific performance criteria based on the numerous climate zones throughout the U.S. The International Energy Conservation Code (IECC) also has required energy performance data, which skylights must meet to satisfy the local energy code performance criteria. Stating the obvious that skylights don’t present the same barrier to heat transfer as traditional roofing materials does not negate the value of bringing natural daylighting into interior spaces, reducing the amount of energy usage by utilizing natural daylighting to illuminate interiors and reducing the heat loads in the space by turning off electric lights, which generate more heat than a skylight.

    The writer should have noted the code requirements for skylights both in the International Building Code (IBC) and ASHRAE. Educating professionals on what the codes require will also educate them on the reasons why skylights are required in the code. California Title 24 includes a mandatory requirement for the installation of skylights in single story commercial buildings 5000 sq. ft. or larger in conjunction with an automatic daylight control system.

    There are many ways to minimize the negative effects of the light/heat connection, including specifying the control elements when the skylight is purchased. This will allow desired comfort levels to be maintained.

    6. Space Constraints
    The writer’s comment that to maximize the benefits of natural daylighting it would be required to dedicate “7 to 10 percent of the roof to skylights” is completely inaccurate and is not allowed by code. Current software, such as SkyCalc or EQuest to name a few, clearly demonstrate the benefits of natural daylighting through skylights utilizing a range of 2 to 5 percent of the roof area.

    Additionally, to state that skylights take away space from rooftop equipment indicates the writer’s opinion that designers are incapable of doing a roof layout to incorporate the equipment requirements on the roof, as well as providing roof maintenance space. Though this is not an issue, Tubular Daylighting Devices take up even less space while continuing to offer the benefits of natural daylighting.

    As with all products incorporated into a building, it is important to balance energy savings with occupant comfort, while adhering to building codes. The AAMA Skylight/Sloped Glazing Council’s mission is to act as an information provider and promoter of skylights and sloped glazing in the building products industry, by providing technical, regulatory, legislative, marketing and certification support to ensure that the appropriate standards are established, maintained and communicated for the benefit of the users and suppliers of these products. The Council sees itself as a partner to roofing professionals, offering industry resources, including tips on fall protection, which can be viewed online.

    Christian Magnuson
    Vice President of the AAMA Skylight/Sloped Glazing Council
    President, Wasco Products, Inc.

  5. I was in disbelief as I read all the reasons not to use skylights on a roof written by a pipe support manufacturer. As a manufacturer of skylights, not only do I take offense to the insinuation that skylights will create “hidden costs, like increased roof maintenance, heating and cooling, and safety precautions”, but also to an author who does not claim to have any expertise in the field in which he is writing. His list of “downfalls” are not only inaccurate, they are in many respects blatantly false.

    1. Leaks: The author states skylights are “infamous – for leaking”, but also states “even the best skylight can leak if not installed properly”. Is this not true for any roofing product that is installed improperly?
    2. Breakage: Skylights are required to meet or exceed minimum performance standards that will comply with local and nation codes for snow loads but also minimum pressure loads. In coastal areas of the US, the codes are clearly written with extreme protocols in place to insure the glazing meets large and small missile impact resistance and tested to negative pressures that well exceed most storm events. I suggest the author research Miami-Dade County HVHZ protocols to learn more about impact resistance and extreme pressures.
    3. Falls: The author misinterprets the OSHA standard as “a screen or guard rail that meets OSHA’s regulations” is not a requirement and is inaccurate. OSHA does not approve products, they set standards and these can be met in many other ways all while putting rooftop worker safety as the paramount concern. While the so called leaders of the skylight industry have been working on a fall through protocol, they have been embarrassingly slow to create an industry standard but ASTM has stepped up with a forthcoming standard. This protocol will finally eliminate the option of cheap non-impact acrylic thermoplastics that in fact are a dangerous glazing option and should not be used on a roof.
    4. Light Exposure: The author fails to mention daylight harvesting, or any knowledge thereof, and that skylight manufacturers actually can provide light transmission levels to suit different building types based on use, occupancy and specific requirements. Additionally, glare is easily controlled with translucent glazing options and UV transmission is controlled by using proper glazings of which polycarbonate inherently will block 99.9% of UV transmission. IR blocking thermoplastics are more common today and U values and SHGC are improving to provide energy efficiency not thought possible a few years ago.
    5. Energy Loss: I agree that skylights are not equal to the performance levels of the finished roof, but neither are the windows or doors. As with windows and doors, properly glazed skylights can offer the EXACT thermal and optical performance.
    6. Space Constraints: this is just such a senseless comment it does not deserve a response.

    This article is poorly written by a person who has not acknowledged any experience or knowledge in the field that he writes about. Roofing Magazine should request a retraction as these are inaccurate, inflammatory and false comments.

    David Thornton
    President, Maxim Skylights – Dallas, Texas & Lake Worth, FL

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