Text: Seth Warren Rose, Eneref Institute/USA
Photos: LichtLabor Bartenbach

23. Sep 2013

Is there more daylight in Europe compared to USA? An American viewpoint

The architectural use of natural light in Europe dates back to before the ceiling of the Roman Pantheon, to the light shafts in the palace of Knossos of Crete. With such a long history of daylighting it might seem natural for Europe to include daylighting in their architecture today. Yet Europe, like the US, still finds the abundant use of daylight harvesting in their buildings atypical.

For sure, Europe is ahead of the US in daylighting. For example, Germany has building codes that bring window-light into the workspace. Still, the obstacles to more daylight harvesting in both United States and Europe track a parallel course. And according to a study by Eneref Institute (www.eneref.org) the reasons are varied and complex.

One commonly speculated obstacle to daylighting is that daylight design in commercial buildings is controlled by engineers rather than lighting designers. “95 percent of the daylighting design is done by HVAC engineers,” says Andreas Danler, a lighting designer with Bartenbach Lichtlabor GmbH.

Nancy Clanton, founder and President of Clanton & Associates and a leading advocate for sustainable design, is one of the strongest proponents of daylight harvesting in the US. She agrees with the assessment that HVAC engineers focus too much on loading and solar gain to reduce cooling costs. “You go back to older architecture, and those architects used daylighting in and out,” Clanton asserts. “Now, our buildings aren’t working. And people aren’t happy with them.”

Good lighting design mitigates heat gain, claims Clanton, with mechanisms such as sophisticated glazing or shading which minimize direct sun penetration.

Andreas Danler explains that to combat his concern of too much control by HVAC engineers, Bartenbach is working with German manufacturer Alanod Aluminum to develop ideas that will offer lighting designers new tools. Bartenbach is designing solar tubes using 98 percent reflective material that can bring light deep into underground spaces. The improved material requires fewer solar tubes to transport the same amount of light, thus achieving less heat gain. And according to Danler, using semi-specular material from the same manufacturer as a reflector on the facade of old buildings around a courtyard can increase the light at the bottom of the courtyard by a factor of five. It is even possible to create light shafts within buildings that are only 50 meters apart.

Costs of systems

High cost is the most commonly stated deterrent to daylighting. Payback for daylighting is not simple to quantify for building owners and efficiency investments today means less money will be available to invest in other opportunities tomorrow. While there are various rebates available in the US, the complexity of the rebate rules increases the transaction costs.

Skylights on big box stores or tubular devices in a drop ceiling that offers uniform light throughout the space can have a five-year ROI or less. Artificial lights can simply be switched off. However, an office building with a light shelf or vertical blinds to reduce glare has a longer payback period and the opportunity costs stand in the way, according to architects and building owners interviewed for this report. Corporate executives generally want a return on investment of 20 percent. Individual consumers want a payback of three years or less.

Another obstacle to daylighting – as with most efficiency investments – is that the facility owner makes the investment but the occupant enjoys the benefits. However, there is plenty of evidence that human activity needs to be included in ROI calculations. Daylighting improves productivity in both schools and workplaces. Especially in learning environments, the well-known Heschong Mahone studies show that daylighting increases student performance in math and reading scores and improves attendance. In the workplace, daylight raises morale, increases productivity and decreases sick days and product defects. Retail sales can increase in day-lit stores. The BMW building near Frankfurt famously upgraded their office tower with daylighting because it meant an investment in their own employees’ health and productivity.

Competition with other technologies

Today, daylighting competes with the recently lowered price of LEDs, which now offer better lighting power densities (LPD) – watts per square meter – than even a few years ago. But, of course, lighting is not the only investment option for energy managers as more types of building systems offer better efficiencies. According to Robert McNiece, a program manager with US Postal Service, “Most of our mail processing is done at night. There are many much lower cost opportunities to reduce energy use than retrofitting skylights.”

Still, lighting accounts for roughly one-third of the electricity used by commercial or educational facilities in the United States. And when compared to the efficiency of PV cells, daylighting can offer substantially more energy for the same amount of roof space.

Lighting designer’s perception

While architects may be key to increasing more daylight harvesting in US buildings, most architects are reluctant to choose a low cost off-the-shelf daylighting solution (such as exterior shades or vertical fins) to avoid look-alike aesthetics. “We find that a lot of the architects would prefer to design something that is more integral to the architecture and more part of the design aesthetic,” explains Jake Wayne, a senior consultant and PE with Arup.

But the design-build approach to daylighting on new facilities also has the advantage of including the cost of the daylight harvesting system into the cost of the entire building, which according to Wayne is easier to sell to financial officers.

Owner’s perception

Some facility owners are concerned about the maintenance costs they will incur with daylighting systems. While a passive daylighting system requires no maintenance, active shading systems with lighting controls and sensors can seem complex and prone to maintenance problems to a facility owner. And skylights are often sited for water leaks, although properly installed skylights are unlikely to leak. Nancy Clanton retorts that when she hears concerns about leaks from building owners she reminds them that they “already make holes in the roofs for air handlers and exhaust systems”.

As with any energy saving system, the more complex the more reluctant a risk-averse facility owner is willing to specify the system. Sophisticated control systems for automated shades or external motorized louvers are difficult systems for owners to understand how to operate or repair. Daylighting can be especially complex when the system is designed to require interaction between multiple systems, all sold by different vendors. However, even the simplest system can fail if poorly implemented. Stories of occupants covering windows with cardboard boxes to block out the sun have hurt the daylighting industry. Building owners who are familiar with these stories are naturally concerned about investing in a system which may be underutilized or worse, covered with cardboard. It is therefore incumbent upon lighting professionals to explain that daylight harvesting pays substantial benefits beyond energy savings, as the Heschong Mahone studies report.

Daylighting’s future looks bright

In their contest for control with HVAC engineers who are looking to reduce heat gain, lighting designers may find an advocate that takes a more holistic approach to building design. Research by Eneref Institute is finding that sustainability officers – a growing but still undefined industry – are gaining a larger voice in the design of the building envelop. Ari Kobb, Director of Sustainability and Green Building Solutions for Siemens Building Technologies may be just the type of hero daylighting advocates need. While he does not yet have daylight in his office, he admits: “I did put skylights in my own home”.

Seth Warren Rose is Founding Director of Eneref Institute, a research and advocacy organization for sustainable development.


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