Adding a Roof Light

Should it be a roof light or a tubular skylight to open up your roof and bring daylight and sunshine inside? Here are things to consider before cutting a hole in your roof.

By Gene And Katie Hamilton

Adding a Roof Light

A skylight installed in a roof is a good choice to bring daylight into a room in an otherwise dark area without losing wall space. It brightens dark interior spaces with warm, natural sunlight. They come in a variety of rectangular shapes as fixed or inoperable units; some open and close like a window to remove hot air during the summer.

A tubular skylight is a smaller version that's a new solution for a room that isn't directly below a convenient roof space. These ingenious units capture natural light through a roof dome and direct the light to interior areas-even into areas not directly below a roof-through a highly reflective "tunnel" that can bend and snake around framing obstructions.

Where a skylight make good sense
  • To brighten a kitchen where wall space is taken up with cabinets and appliances and there's little room for a window
  • To bring natural light into a small bathroom or hallway without an exterior wall
  • To add daylight in an attic room
  • To add daylight where wall space is at a premium or a window would opens to an unattractive view

You'll find skylights with a variety of options. Some offer sunscreening accessories like roller or pleated shades and venetian blinds that add protection from damaging strong sunlight. These shades and screens can be opened and closed manually or operated by remote control or a wall-mounted keypad.

Improvements on the flashing systems of new skylights make them less likely to leak, an all-too-often problem with older units. The new skylights are also more energy-efficient and those with insulated glazing options will lower heating and cooling costs. Choose a skylight with a low U-value, which measures the heat flow of the glass and frame; the lower the number, the better it is. In a cold climate, choose a U-value of .45 or lower. For warmer climates choose units with glass that has a solar-heat-gain coefficient between .35 and .5, that translates to less solar heat gain, but plenty of visible light.

You'll get the best advice about the types and sizes of window and accessories from a local window installer who knows the range and power of sunlight throughout the seasons where you live. For instance, if you live in a warm weather climate, the window expert knows that too large of a skylight or too many of them translate to an over-heated room and sun-damaged furnishings, especially in the summer months.

The Department of Energy's Energy Efficiency and Renewable Energy Network offers these suggestions about the placement of skylights:

  • Skylights on roofs that face north provide fairly constant but cool daylight.
  • Skylights on south-facing roofs provide the most heat gain, especially in warmer climates.
  • Skylights on east-facing roofs give maximum light and solar heat gain in the morning.
  • Skylights on west-facing roofs provide afternoon sunlight but can increase heat gain, especially in warmer climates.
What's Involved

Installing a skylight involves several steps. Inside the room the wallboard or ceiling is removed to create the rough opening. Then the roof rafters and sheathing are cut. Up on the roof, the frame of the skylight is set in place and the sash is passed through the opening. The unit is fastened to the framing and the flashing is installed underneath the roof shingles and secured. Back inside the room, the final framing is installed for structural support and the wall is finished with trim.

Related Job Costs: