Designing Effective Skylight Solutions

The most sustainable form of indoor lighting doesn’t rely on electricity—it comes directly from the sun. Daylighting, a technique that dates back to ancient architecture like the Pantheon in Rome, remains one of the most energy-efficient and cost-effective ways to illuminate interior spaces. Despite its long-standing value, skylights are often overlooked in today’s low-rise commercial building projects, usually due to perceived costs or a misconception that they are difficult to install.

In reality, with thoughtful design and modern tools, skylights can be seamlessly integrated into a building’s architecture to provide far more than just light. A well-executed skylight system offers substantial energy savings by reducing the need for artificial lighting—especially during daylight hours.

Why Skylights Matter

Sunlight does more than just brighten a space. It enhances mood, supports mental health by increasing serotonin levels and creates a welcoming, vibrant environment. From a facility management perspective, natural daylighting contributes to lower electricity bills and reduced HVAC loads. 

However, achieving these benefits depends on strategic planning and attention to key performance metrics:

• Solar Heat Gain Coefficient (SHGC): This metric measures how much solar radiation is admitted through a skylight. In warmer climates, a better SHGC repels unwanted heat.
• U-Factor: The U-Factor indicates the rate at which heat transfers through the skylight. Lower values are better in cooler climates, as they help retain indoor heat.
• Visible Light Transmittance (VLT): VLT measures how much visible light passes through the lens. 

A higher VLT allows for more daylight and less dependence on artificial lighting. Beyond these metrics, skylight design must also meet building energy code requirements. The International Energy Conservation Code (IECC) Section C402.4 provides specific thermal performance standards for fenestrations, including skylights. While the table is focused on limits to SHGC and U-Factor in specific climate zones to ensure a high-performing building envelope, smart design that yields consistent effective daylight in a space must be paired with responsive daylight controls to get any benefit from offsetting artificial light. The code is actually written to encourage this systematic approach with exclusions that promote higher VLT ratings by offsetting the layers necessary to meet the SHGC and U-Factor requirements:

• C402.4.3.1 allows increased SHGC values up to 0.60 in climate zones 0 through 6 where skylights are located in areas with responsive daylight controls.
• C402.4.3.2 provides flexibility for increased U-Factor up to 0.90 in climate zones 0 through 3 and 0.75 in zones 4 through 8 when paired with responsive daylight controls.

Understanding these allowances helps architects and engineers balance efficiency, comfort  and code compliance. Rather than defaulting to more light switches or thermostats, consider how intelligent daylighting design can eliminate reliance on such systems.

Tools for Smarter Design

Skylights are particularly impactful in buildings with daytime occupancy, including schools, retail stores, industrial facilities and agricultural operations. Planning their placement used to involve guesswork or general rules of thumb. Today, however, advanced software and manufacturer-provided tools make it easy to model optimal skylight configurations.

These tools incorporate geographic data, weather patterns and building layouts to calculate the most effective skylight sizes, types and placements. This allows designers to avoid common pitfalls like uneven lighting, glare or excessive heat. Think of it as daylight modeling—akin to how HVAC systems are now precisely engineered for airflow and energy use. By using these digital resources early in the design process, teams can fine-tune skylight integration to achieve targeted lighting levels, reduce strain on HVAC systems and improve the indoor experience for building occupants.

Materials Matter

Choosing the right skylight material is as important as its placement. For commercial low-rise buildings, polycarbonate dome style skylights with a prismatic layer are among the most efficient and popular options. These domes scatter and diffuse incoming sunlight, reducing glare and eliminating concentrated hot spots. They also limit UV exposure, which can damage furnishings and finishes over time.

Other options, such as transparent glass panels, may be used in certain architectural designs, but they require careful planning. Without diffusion properties, these panels can create overly bright concentrations of light or shadowed areas. For skylight layouts, designers should calculate the daylight zone created by the fenestration. Understanding that light travels at a 35-degree angle, and applying the size of the skylight and ceiling height allows an effective layout to be achieved with consistent overlapping natural light within a building.

Safety and Integration

Incorporating skylights involves more than just daylight performance—it also involves safety. According to OSHA regulations, workers exposed to roof skylights must be protected from potential fall hazards. 

Yet not all skylight materials or assemblies inherently meet fall protection standards. To address this, designers should include internal or external safety cages that prevent accidental falls without compromising light quality. These safety components are essential for maintenance crews and contractors who may work on the roof during or after installation.

Additionally, don’t underestimate the importance of roof curb selection. Curbs are the frames that hold the skylight in place and must integrate with insulation, waterproofing, roofing material, and the structural components. The wrong curb can lead to leaks, heat loss or incompatible connections. While membrane roof curb styles are simple to source, metal roof curbs require custom design to integrate with the panels via flange connection details that seal the major and minor panel ribs via industry specific sealants, fasteners, and closures like panel splice and eave termination details. 

Compatible materials and construction science must be applied for determining curb minimum heights, flange dimensions, cricket size and connection placement as the prolonged exposure to precipitation and typical weather effects can rapidly degrade the spliced connections if proper curb design is not employed. On the interior, special attention should be applied to the finished appearance of the interior cladding for occupants which includes trimming the hole in the ceiling with supplemental materials or an inclusive sub-framing system from the curb manufacturer, so the insulation remains encapsulated for an appealing aesthetic. 

When procuring a skylight, a total systems approach bundles all critical skylight components—curbs, skylights, safety systems and mounting hardware—into a turnkey system engineered for compatibility and long-term performance. This minimizes field coordination issues, reduces installation risks, and ensures all parts work together as a cohesive unit.

Built to Last

A common concern with skylights is the risk of leaks. Historically, roof penetrations were avoided for this reason. But today’s skylight systems, when professionally installed and properly flashed, offer long-lasting, weather-tight solutions. Modern sealing materials, advanced flashing systems, and durable domes ensure skylights remain secure and effective for years to come.

Additionally, skylights contribute to broader sustainability goals. They lower building energy use, reduce lighting system wear and tear, and provide natural light that enhances both visual comfort and indoor air quality. Skylights are no longer considered luxury features. They are practical, high-performance tools that contribute to healthier, more efficient buildings. With thoughtful design, code-aware planning, and modern materials, skylights can turn rooftops into powerful assets.

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ABOUT THE AUTHOR: Clifton Reasor is vice president of business development at Roof Curb Systems, Trenton, Ga. For more information, email [email protected] or go to www.roofcurb.com.