Types of Rooftop Skylights – PART II

Following up from the previous entry on surveying the various types of skylights, today we continue looking at a variety of different types of skylights.

The skylight shown in the photo below is very similar to one shown in the previous entry, but the one below also has an integral passive vent that is just a small part of the overall skylight, as most skylights are mainly intended for luminescence and fenestration. This particular skylight stands as another examples in which skylights which can also provide additional functions.

You can see that this skylight has likely leaked in the past because you can see that some contractor has gone and painted aluminum paint around the perimeter of each glazing panel. It’s very unlikely that anyone would have ever done that if there were never concerns or suspicions of a potential leakage. (This is NOT an appropriate solution, but the somewhat typical of stuff done to try to fix something cheap if a contractor doesn’t know how to do proper repairs.)

painted aluminum-skylight-hack-fix

The photo below shows an example of an acrylic dome skylight. This particular skylight happens to be clear. Skylights of this type are available in a variety of different colors and varying degrees of energy resistance through solar illuminations.  For example, instead of clear acrylic as shown in the photo below, opaque acrylic is also available which can offer greater privacy. In cases where low buildings are built in proximity to higher buildings, clear skylights like this do not provide privacy from neighbors in higher buildings looking inside the private space of the adjacent building.

Looking at each type of skylight, it’s not certain that one particular skylight is necessarily better than another type of skylight. In fact almost all of these skylights have a list of contrastable criteria and characteristics.  Here as well, the acrylic skylight category or subgroup has advantages and disadvantages.   Acrylic skylights are susceptible to ultraviolet rays over time and can both crack and discolor from exposure.

This skylight is set on a curb, generally skylights built on flat roofs are required to have a curb built around the perimeter of the opening for the skylight to be mounted and installed. The curb is a framed construction assembly that sits above the plane of the low slope roof. In this particular case, this a curb is extremely low and leaves the frame of the skylight within a few inches of the low slope roof membrane. Generally, skylights should be set at least several inches above the planar (aka, low slope or flat) roof system. However, there is an increased cost for retrofitting skylights to a greater height.  That retrofit would, in most cases require both reconstruction of the opening curb and reroofing that area of the perimeter and surrounding area of the curb.   In historic times, skylights were not manufactured with an integral self-rimming lapping flashing and curbs over an inch or two were uncommon.

acrylic dome skylight

The next picture below shows a different type of skylight that is actually operable. This type of skylight can open and close to an extent. Generally operable skylights have a limiting range which only allows the skylight to open a few inches for safety, but still allows ventilation.


The photo below shows an entirely different type of skylight, much larger in scale, set into a grid frame. This type of skylight looks a little bit like the lofts-style converted warehouse aesthetic of downtown Manhattan or a former industrial city. These types of skylights are very uncommon in Washington DC but are terrific because they can really light up an otherwise dark cavernous space of Washington, DC row homes.   You will probably notice, in the photo below, the glass in this particular skylight is tinted a darker color. Clear glass will allow almost unfiltered light to enter a building and can be extremely hot during the summer season. That unfiltered light can also have some degree of ultraviolet rays which can discolor walls and/or mounted art work and/or other elements in the building. The same is common with almost all types of window light but some window glass and skylight glass as well will include Low E or Low E2 glass which can also reduce the entry of ultraviolet rays.

grid frame-skylight

The final type of skylight, shown in the picture below is one of the most common of all, it is a glass skylight. Many types of glass skylights are engineered and permitted to be installed at a very low grade as low as flat or 0゚. We generally recommend against installing a skylight perfectly flat though because even skylights designed for such type of installation can leak over time as the synthetic seals are exposed to ultraviolet rays.   Here, this picture also is a good example of a field built curb, built higher than original skylight, in this case either as a retrofit or an upgrade or additional element built into the building in the years after original construction. The skylight itself is modern and the roof membrane is a single ply flat roof, a modified bitumen single-ply roof membrane. It’s likely that this skylight included or built as part of the original building construction.

glass skylight

Smart proactive replacement, construction, upkeep and maintenance of low slope roof systems requires an enthusiastic interest and understanding of waterproofing principles and building science.   Here in Washington DC, historic and modern residential and commercial buildings are extremely expensive and the roof and related systems provide the shield that preserves the building.

We encourage all of our clients, and all readers of this article and to our blog in general, to prioritize the value of quality construction and building maintenance, and develop a relationship with our company.  You can learn a lot more on our blog.  Feel free to check it out.  If you have questions about the roof and related systems of your building in Washington DC, fill out the webform below and drop us a line.  We will be in touch if we can help.

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