Skylight, Molde, Norway (C) Daniel Friedman Roof Skylights: Best Practices Guide to Selecting & Installing Skylights

  • SKYLIGHTS, GUIDE - CONTENTS: Best Practices guide to selecting & installing skylights - Skylights: choosing, installing, design issues, energy efficiency, Skylight options & choices, Skylight window sizes, Skylight window controls, Skylight shades & screens to control solar gain, heat, light, glare
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Skylight installation & repair guide: this article series discusses the selection and installation of skylights, including choosing a skylight, how to install the skylight, constructing the skylight well or chute, skylight controls, and skylight shades or screens. We also discuss skylight condensation and special skylight products such as light tubes.

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SKYLIGHTS, Guide to Choosing & Installing

Skylight, Molde, Norway (C) Daniel FriedmanOur photo (page top) shows how even a small skylight can bring light into a tight space, in this case, in a roof in Molde, Norway -DF.

[Click to enlarge any image]

In this article series we discuss the selection and installation of windows and doors, following best construction and design practices for building lighting and ventilation, with attention to the impact on building heating and cooling costs, indoor air quality, and comfort of occupants.

Article Contents

We review the proper installation details for windows and doors, and we compare the durability of different window and door materials and types.

Our photo (above left) shows how even a small skylight can bring light into a tight space, in this case, in a roof in Molde, Norway -DF.

This article includes excerpts or adaptations from Best Practices Guide to Residential Construction, by Steven Bliss, courtesy of Wiley & Sons.

See WINDOWS & DOORS our home page for window and door information, and also see WINDOW TYPES - Photo Guide for a photographic guide to window and door types and architectural styles.

A well-positioned skylight can help transform a dreary interior room into a pleasing sunlit space with a feeling of connection to the outdoors.

In addition, venting skylights can play a significant role in exhausting hot, moist air from kitchens and bathrooms, and can enhance ventilation in any room with limited cross ventilation.

However, skylights can also be a source of problems, such as roof leaks in winter and overheating in summer, if the installer does not pay attention to glazing type, installation, and flashing details.

Skylight Options

Like windows, skylights come in a wide variety of shapes, sizes, frame materials, and glazing options. In addition, they have an ever increasing variety of screens, shades, and motorized, automated, and computerized controls, providing convenience and good energy performance in almost any situation.

Skylight Glazing Types

Many lower-cost skylights use acrylic or polycarbonate glazing in single or double layers instead of glass. In general, plastic glazings resist breakage, but they can become scratched or brittle over time and are prone to yellowing. Unless specially coated to block UV transmission, plastic glazings allow high levels of UV radiation, which causes fading with many interior furnishings and finishes.

Most higher-end units use sealed insulated glass. Codes require the glass to be either tempered or laminated safety glass. When laminated glass is broken, the plastic interlayer holds the pane together. Tempered glass is harder to break, but it breaks into small, rounded fragments rather than dangerous shards.

Double-glazed skylights with safety glass typically have the safety glass on the interior and tempered glass on the outside, combining high impact resistance on the exterior with protection from falling glass below.

Skylight Window Sizes

Most manufacturers offer a wide variety of sizes, including narrow models designed to fit 24-inch rafter spaces. At least two manufacturers, Roto and Pella, make a 14-inch-wide model designed to fit between 16-inch on center framing. Many standard widths are designed to fit in a double 16- or 24-inch bay.

For narrow spaces, such as a short section of attic roof above a knee wall, Andersen offers several units wider than they are tall, measuring either 16 or 24 inches high by 38 to 72 inches wide. Some manufacturers are tooled up to offer custom sizes for a moderate up-charge.

Skylight Window Controls

Operable skylights use either metal arms that swing out or a concealed chain that unrolls and stiffens as the sash is cranked open. How many turns it takes to open the sash and how wide it opens vary considerably among units. For out-of-reach skylights, all manufacturers offer either extension poles or motorized controls. Some extension poles can be challenging to engage in the crank mechanism, making it a chore to open and close the skylight.

Motorized controls simplify the task, and manufacturers have been refining their offerings in this area. Some need hard wiring from the controller to skylight, while others need only a power connection and are controlled by a convenient hand-held remote. Other options include a battery backup, which could be useful during a power outage, and a rain sensor that automatically closes the skylights at the first drops of rain.

Guide to Skylight Shades and Screens

The tendency of south- and west-facing skylights to cause summer overheating can be greatly moderated with the new spectrally selective glazing (SHGC below .40) (Spectrally Selective Low-E Windows). Still, shades and screens can be used to further reduce heat gains and UV radiation and to provide more diffused light with less glare. Numbers vary from one manufacturer to another, but typical shading effectiveness is as follows:

  • Exterior solar screens can reduce heat gain by 40% or more.
  • Light-colored interior shades can reduce heat gain by 15 to 20%, depending on the density and reflectivity of the material.
  • Interior blinds reduce heat gain typically by 10 to 15%, depending on reflectivity.

In a bedroom, a client might also want shades for room darkening. Manufacturers offer a wide variety of shades, mini blinds, and solar screens, most of which can be controlled by the same motors that control the skylights. Pella’s between-the-glass shades and blinds offer better energy performance than interior shades and never need cleaning, a big advantage with out-of-reach units.


Skylight Light Tubes

(C) J Wiley, S Bliss

Introduced in the early 1990s, light tubes consist of a small plastic rooftop dome that conducts light to the interior through a rigid or flexible tube with a reflective interior.

On a sunny day, the diffuser at ceiling level provides about as much light as a bright electrical ceiling fixture (see Figure 3-18 at left).


Skylight Light Tubes range from 10 to 22 inches in diameter, and one manufacturer, Sun-Tek, offers a multi tube model that supplies up to four tubes from a more conventional looking skylight panel.

Used primarily in remodeling where it is too difficult or expensive to install a skylight, light tubes offer an economical way to bring daylight into bathrooms, walk-in closets, and other small interior spaces.

Skylight Manufacturers & Product Sources

  • Andersen Windows and Doors Skylights and roof windows with exterior sash clad with glass-fiber-reinforced material
  • Milgard Windows and Doors Skylights with aluminum frames (thermal break optional) with vinyl subframes on operable models; optional motorized controls with rain sensor
  • Pella Windows and Doors Wood interior, aluminum exterior, optional motorized controls, and manual or motorized fabric-pleated shades
  • Roto Frank of America Wood interior, aluminum exterior, optional motorized controls, and manual or motorized fabric-pleated shades; Sweet16 model fits 16 in. o.c. framing
  • Velux America Inc. Skylights and roof windows with wood interior and aluminum-clad exterior. Options include insect screens, blinds, motorized controls and shades with rain sensor, electrochromatic glass, and flashing kits for metal and tile roofs and mulled units
  • Skylight Light Tube Manufacturers & Sources
  • SolaTube Light tubes from 10 to 21 in. in diameter; options include electrical lighting, daylight dimmer, and integral bath fan
  • Sun-Tek Skylights Light tubes from 10 to 21 in. in diameter; options include electrical lighting and multitube Spyder skylight
  • Velux America Inc. Sun Tunnel light tubes from 14 to 22 in. in diameter with flexible or rigid tubes

Industry Associations for Windows & Doors

  • American Architectural Manufacturers Association (AAMA)
  • Efficient Windows Collaborative
  • National Fenestration Rating Council (NFRC) Sustainable by Design
  • Shareware calculators for sun angles, solar heat gain, and shading
  • Window and Door Manufacturers Association (WDMA)

-- Adapted and paraphrased, edited, and supplemented, with permission from Best Practices Guide to Residential Construction.


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SKYLIGHT LEAK DIAGNOSIS & REPAIR at - online encyclopedia of building & environmental inspection, testing, diagnosis, repair, & problem prevention advice.

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