How Does Skylight Installation Work?

Getting adequate natural light in a living or working space is one of the best ways to positively impact your mental health.

Skylight installation, in turn, is one of the best ways to get natural light into your living or working space. Natural light is superior because it has all the visible spectrum of light, instead of only a small segment of it. Only one of the benefits that natural light gives you is by helping to regulate your circadian rhythm.

But how does installing a skylight work? Skylight installation varies widely depending on the roofing material and a number of other factors.

Keep reading to learn about installing a skylight in a typical shingle roof and other factors to know before you start.

Factors That Affect Skylight Installation

The materials roofs are made of and the types of roofs available are diverse. Each one poses unique challenges and opportunities when it comes to installing skylights. Let’s consider a few of the more common and pressing factors that affect your skylight installation.

• Commercial or residential roofing
• The slope of your roof
• The type of ceiling in the room you’re installing the skylight
• Whether you have trusses or rafters supporting your roof
• The regional climate
• Glazing types
• Insulation from heat and cold

Commercial or Residential?

Both commercial and residential roofs get skylights installed in them. However, you have to go about it differently for every type of roof.

An important thing to remember is the type of roof that the skylight is getting installed on. Residential and commercial roofs are often quite different, from the slope to the materials used. The design of every roof varies, too, which will also change the way you’re planning to integrate a skylight into your building.

Common materials on shallow-slope or flat roofs in commercial roofing are:

• BUR (built-up roofing)
• Torch-down roofing
• Rubber membrane (Thermoset or EPDM)
• Standing seam metal roofs
• “Green” garden roofs
• Thermoplastic (PVC or TPO) membranes
• Modified bitumen roofing

If you’re repairing your commercial roof it might be a good time to add a skylight. You might also want to think about checking for any common commercial roof issues.

Residential roofs are usually sloped roofs using:

• Architectural shingles
• Ceramic (clay or concrete) tiles
• Slate
• Metal shingle or standing-seam roofing
• Wood shake shingles
• Solar tiles

Uncommonly, you also come across an older home with flat or marginally sloped roofs using BUR.

Flat Roof or Pitched?

Skylights work best when they’re between five and 15 degrees higher than the latitude of your house. California has between 32.5° and 42° of latitude. The typical home has a slope of 4:12 or 18.4° and 8:12 or 33.7°.

The lower range isn’t at all close to even the low end of California’s latitude. This means you’ll have two main options. You can install a domed or bubble skylight on a higher curb. You could also use a slanted curb at an additional 3:12 or 14°.

The important thing to remember is that even with almost flat roofs like BUR on residential and commercial roofs, there are options for skylights. Having your skylight lower isn’t ideal, but it doesn’t mean you can’t have one.

Flat Ceiling or Vaulted?

Vaulted ceilings are a very traditional look incorporated using rafters. Retrofitting a vaulted or cathedral ceiling in a home is difficult and expensive. Vaulted ceilings are incorporated into scissor trusses or parallel chord trusses built specifically for this purpose.

That said, even a flat ceiling can benefit from skylights. Workers will build an enclosure of drywall and paint it to match. There’s more time involved, but the main process is the same until they enclose the skylight.

With a flat ceiling, you’ll lose attic space, though. For vaulted ceilings, it’s unlikely you had any attic space, to begin with. Undoubtedly, it’s a faster, easier job on a vaulted or cathedral ceiling.

Rafters or Trusses?

It’s much easier to mount skylights between rafters than to work with a building that uses trusses. Trusses are engineered, prefabricated assemblies designed to take a certain amount of load. It’s never recommended to cut into a truss, as it will degrade its integrity.

The reason you might need to cut into a truss is that many have between 12 inches or two feet between them.

Rafters, on the other hand, often have larger spans between them, up to four feet. This allows you to have more skylights more often, with better placement inside the home.

This isn’t to say that rafters are better than trusses or vice versa. Trusses are engineered to handle more weight than rafters, yet have more triangular webs to support them. Rafters are an older style of building, built on-site, and provide a very open attic space.

Lofted rooms very frequently have a roof that’s beneath rafters, rather than trusses. That being said, attic-style rooms can get engineered into a plan that utilizes trusses.

Climate Factors and Insulation

Low-E glass is a possibility on glass skylights that you can’t yet replicate on acrylic or polycarbonate. While polycarbonate and even acrylic are unlikely to break, they will scratch and discolor easily.

Very little UV light is blocked by the plastics skylights use, but something special happens with a low-E coating. The type of low-E coating on your skylight could block up to 56% of the light entering while barely touching the visible spectrum.

Low-E coatings reduce the IR and UV spectrum dramatically using a nanometer-scale layer of silver, which is invisible to our eyes. This layer will increase the reflection of infrared waves, which causes heat, and UV, which causes biological damage. At the same time, some coatings don’t appear as reflective when it comes to the visible light spectrum.

All things considered, low-E coatings will keep out light spectrums you don’t want, and allow in the light you do. They also keep heat or cool temperatures in and help with insulation.

If the skylight is double glazed, with argon noble gas between them, this is going to help reduce your heating and cooling costs even more.

You’ll be happy to know that skylights are also sealed from snow and rain. Even units that are designed to open, allowing fresh air in, are fully sealed and guaranteed not to leak as long as they’re installed correctly.

That said, it’s always good to get an inspection done on your skylights before the monsoon season starts in California.

Deciding on How to Mount Your Skylight

All these things considered, to optimize your skylight, you’ll need to remember the main points from these factors.

• You want between 5° to 15° greater slope than your region’s latitude
• Glass glazed low-E coatings will give you the best insulation
• Two-foot-wide skylights are best for truss-supported roofs
• Rafters can usually allow better placement
• Roofing material must be considered before installation
• If you have a commercial building, make sure your roof wasn’t built on top of another one

Skylights can get mounted on a curb, or relatively flush to the roof deck. This is deck-mounting or curb-mounting.

Curb-mounting a skylight may be one of the more common ways to mount your skylight. This is especially true since so many get mounted on flat roofs.

The benefit to curb-mounting a skylight isn’t only to adjust the angle, but also to give you an option to replace older skylights without reflashing everything (including roof material). After the first installation, much of the labor required won’t have to get redone on a new skylight or an upgrade.

On the other hand, more recent designs allow for better insulation and aesthetics through deck-mounted skylight installations. Many skylight manufacturers have designed for newer construction methods such as trusses, which helps the process along greatly.

Additionally, the lower profile increases energy efficiency. Manufacturers have even integrated the flashing and curb into the skylight itself in some designs. They’re the more common choice for new construction that’s been designed into the building plan for the home or business.

What Kinds of Skylights Are Available?

Speaking of curb-mounted and deck-mounted skylights isn’t giving a full idea of what’s available, though. Skylights are available in almost any shape you can imagine, although standard sizes and shapes will be less costly.

Often there are skylights, roof windows, and skylight tunnels that you have as options. Some have motorized blinds.

Common materials are glass and plastic. Glass is more durable and doesn’t scratch as easily. Glass is a larger upfront investment for a reason.

Not only can you get a glass that’s double-glazed and low-E as we already mentioned, but you have more options for coatings. Plastic yellows over time and scratches, but is more shatter-proof.

Flared light shafts offer a greater range of light paths as the sun moves throughout the day, maximizing the utility of your skylight.

Fixed skylights don’t open, but reduce moving parts and the possibility of leakage while increasing insulation efficiency. Vented skylights allow more ventilation and open manually or have a motorized option.

Tubular skylights, or light tunnels as they’re sometimes called, is an adjustable or fixed reflective tube attached to a dome. It directs light into a place that otherwise wouldn’t be able to receive natural light with a skylight. They’re fairly easy to install and an ideal fit in tight or enclosed places like hallways, foyers, pantries, and closets.

General Skylight Installation Process

Ready to get your skylight installed? You should have an experienced roofer make sure that you’re not missing something critical. Any time you put a pinhole in your roof you need to make sure everything is as it should be — all the more so with a two-foot by four-foot hole.

That said, the general process for installing a skylight goes something like this:

1. Locating and cutting the opening
2. Flashing the sill with membrane material
3. Inserting the skylight
4. Sealing up the sides with roofing membrane
5. Sill-flash the edge on the bottom
6. Step-flash the sides
7. Counterflashing on the sides
8. Install the saddle flashing and lay down the shingles

The trickiest part of any skylight installation isn’t putting it in, but keeping it watertight and “snow-tight,” so to speak. In that case, the steps where you’re laying down membrane and flashing are the most important.

To get proper placement, you might drive nails from below through the deck above. From there you can snap a line on the deck for the proper dimensions.

With a helper below to take care of the cutout, you can ensure it won’t damage anything below. Again, you’ll need a helper below to get the skyline into place and aligned correctly.

Also, don’t forget that overlapping membrane and flashing prevents penetration of water into places you don’t want it to go. A small leak can and will cause far more serious problems than you can imagine.

Skylight Installation in California

Skylight installation is a job that you can DIY, but it’s best left to the professionals.

Speaking of professionals, Reliance Roofing has more than 30 years of experience as a family-owned business. We work on commercial and residential roofs as well as roof inspection and skylight installation.

Entrusting your roof to anyone less than the best, whether it’s commercial or residential, isn’t the way you want to go. We handle new and old roofs, roof removal and replacement, framing, and more.

Reliance Roofing is your expert partner for an inspection of your roof for skylight installation, old skylight repair, or skylight replacement. Contact us today for your roofing needs!