Daylighting Collaborative


Reduce cooling needs for daylit buildings

The Energy Center of Wisconsin conducted an experiment at the Energy Resource Station in Ankeny, Iowa to see if cooling energy could be saved using daylighting design.

Results. The lighting and HVAC operating cost savings for the high-performance rooms are considerable, and represent a savings of more than 20 percent on operating costs of about $1.13 per square foot.

The research protocol, analysis and full findings are provided in the report Energy Savings from Daylighting: A Controlled Experiment.

what/why > why daylight?

To create beautiful spaces, save energy and operating costs and reduce our impact on our planet.

It's natural. Daylighting taps into the five-billion-year-old fusion reactor called the sun. Using natural light from the sun costs nothing to the environment but pays big dividends to building occupants. The result is a compelling, efficient lighting solution that also protects the environment. By consuming less energy, daylit buildings reduce fossil fuel use and carbon dioxide emissions associated with global warming and climate change.

It works. People thrive in naturally lit environments. Studies (as well as our own common sense) show that shoppers linger longer and buy more; students do better on tests; office workers are more productive and absent less often. And that's not all. Daylighting can also:

  • Reduce lighting costs
  • Reduce cooling costs (in almost all climates almost year round)
  • Be accomplished without increasing construction costs (in new construction)

It's just plain smart. Daylit buildings are just plain more cool—see cool daylighting—temperature wise and aesthetically. Daylit buildings make a statement about their owners and occupants: they are socially and fiscally responsible.

Whether you are seeking a signature piece of architecture or simply trying to meet a budget, daylighting is a key design strategy.

Energy savings from daylighting: a controlled experiment

It's one thing to theorize that daylighting can help reduce cooling loads and cooling energy, it's another to document it.

In an effort to see if in fact cooling energy could be saved using daylighting design, the Energy Center of Wisconsin conducted an experiment at the Energy Resource Station in Ankeny, Iowa, just north of Des Moines. Associated with the Iowa Energy Center, this highly instrumented facility is specifically designed for multiple, full-scale tests and demonstrations involving commercial building lighting and HVAC systems.

This research was conducted under a U.S. DOE grant to NASEO (National Association of State Energy Offices) in cooperation with ASERTTI (Association of State Energy Research and Technology Transfer Institutions).

The research measured lighting and HVAC energy use in two sets of rooms. Different window configurations, glazing, lighting systems and automatic lighting controls were tested against a set of control rooms. The HVAC system remained the same for all tests. Three rounds of testing to capture seasonal variation were conducted for the project:

  • Summer (July 11 to August 7)
  • Fall (September 23 to October 26)
  • Winter (December 9 to January 8)

See the sidebar at right for highlights and a link to the full report.