Measure 8.3.1 Install skylights or light pipes.

ECONOMICS

SAVINGS POTENTIAL: In the most favorable cases, skylights can provide a majority of lighting needed during the daytime. However, skylights increase heating cost. In mild climates, the heating cost penalty is not serious if the skylights are sized properly. Skylights may increase cooling cost, but this penalty should be minor if the skylights are sized and laid out properly.

COST: The major cost components are the skylights themselves, the roof penetrations, framing for the skylights, and electric lighting modifications. Molded plastic, double-glazed skylights cost $15 to $30 per square foot, depending on size. Large, self-supporting skylights with plastic composite glazing typically cost from $30 to $60 per square foot. Double-glazed glass skylights with safety glazing may cost up to $100 per square foot. Small, simple light pipes can be installed for less than one thousand dollars, even in retrofit. See Measure 9.5.3 for the cost of the electric lighting controls.

PAYBACK PERIOD: Up to several years, in new construction. Several years or longer, in retrofit.

TRAPS & TRICKS

MAKING THE COMMITMENT: Skylights do not disappear if you decide not to use them. They can create serious permanent problems, including glare, uncomfortable heat gain, heat loss, condensation, and water leakage. Do not use them unless you make a commitment to design and install them properly.

DESIGN: Skylight design is not something to do in a hurry. Consider the light distribution pattern, the effect on decor, the effect on cooling and heating, avoiding condensation problems, and avoiding water leakage. Provide effective controls to coordinate the electric lights with daylighting, or else the effort is wasted.

SELECTING THE EQUIPMENT: There are major differences between prefabricated units. Some have much better longevity and leakage resistance than others.

INSTALLATION: Even with the best design, avoiding water leakage requires good installation workmanship. See Measure 9.5.3 about installing the daylight-sensing lighting controls.

Index

These excerpts shows the level of detail and accuracy that you'll find in the Energy Efficiency Manual by Donald Wulfinghoff. This 1500-page manual offers the most comprehensive coverage of energy-saving measures for buildings ever assembled under one cover. For more information and to view the complete table of contents, find the Energy Efficiency Manual in the Oikos Bookstore.