Basic Sustainable Lighting Concepts: On Daylighting

June 27, 2011 / no comments

Part 2 of an ongoing series outlining design principles for sustainable lighting design: here are a few ideas regarding daylighting, to help navigate the greenwash.

Only a little direct sun, please

Too much direct sunlight increases the indoor temperature, creating higher cooling loads. It also increases the potential for glare. If there’s too much glare, people are likely to pull the shades and leave them that way, which equals no more daylighting! Most interior shades do little to reject the heat load. Consider using exterior overhangs to keep excessive sun outside, and light-shelves to distribute the daylight indoors so it’s more useful.

Don’t add complexity and cost by creating one problem and mitigating it with another technology. The New York Times Building has been criticized for this. Its floor-to-ceiling glass has the potential to let too much light and heat inside, so the ceramic tubes outside the glass were introduced to help block some of it. If you have less glass to begin with, you can use less exterior shading… If you can afford it and don’t care, then have at it, as long as you keep your energy use down. Otherwise, try not to pile on unnecessary complexity chasing an aesthetic.

Installing shades is not daylighting

Simply installing internal glare-control shades or blinds is NOT a form of daylighting. Neither is using a lot of glass just to get more light inside. The façade of a building must engage the sunlight to utilize it in a meaningful way, coaxing the useful light in while controlling excessive light and rejecting heat. This means articulated façades, not flush glass.

If you do use shades, make them automated if you can afford it. Automated shades can adjust for different lighting conditions throughout the day, and they don’t rely on a forgetful occupant to pull them back up. If you can’t afford automated shades, try to design your envelope with external shades or a light-shelf such that you can keep the upper part of the window open all the time and still allow manual shading below it.

Dimming the lights

Daylight switching is no replacement for daylight dimming. Switching has a tendency to irritate occupants, because it flips the lights on and off throughout the day when the ambient light is near the threshold light level. More often than not, if it doesn’t work correctly, it will simply be disabled instead of fixed. You definitely can’t rely on people to make the best choices on an hourly basis either – the lights go on and stay on all day. Flipping a switch is what we’ve been trained to do all our lives.

Rely instead on dimming your perimeter spaces. There are variable levels of savings to be had here, from actual energy savings, to rebates just for putting daylight dimming systems in. Every little bit helps in terms of energy – initial cost is a different matter. There may be legislation or changes to the building codes in the near future that would require you to use daylight dimming anyway.

Digital is in!

All the ballast manufacturers, and a few lighting controls manufacturers, are finally, albeit slowly, switching over from older analog technologies, to digital or hybrid analog/digital systems that operate with greater precision and functionality. If you use one of these emerging technologies, your system is more likely to still be in style in the next decade or so (but don’t jump the gun on a brand-spanking-new product, lest it be discontinued). DALI is one of those technologies; it’s been around for about ten years now, and is slowly catching on in the US.

Don’t go crazy

Just because dimming is warranted in daylit zones and conference rooms, doesn’t mean you should use it everywhere. Some advocates claim additional energy savings by being able to dim the lights everywhere, but that would only be if you’ve over-illuminated your interior spaces to begin with. Design them correctly and you can save a lot of materials and costs. Dimming everything is another example of mitigating a problem that you may have created yourself.

A DALI Checklist: Things to Keep in Mind

January 5, 2011 / no comments

DALI checklist_lam.jpg

DALI is one of the latest buzz words in the lighting industry. Widely used in Europe, DALI is still in its infancy in the U.S., even though it was first introduced in the late ’90s. DALI stands for “digital addressable lighting interface”, a control protocol based on digital commands that are sent between ballasts and the control system. DALI has many benefits which make it a very attractive system for commercial lighting applications, however, there are a number of things to keep in mind when designing a DALI system.

How does DALI work? DALI is a standard digital communication protocol which allows DALI-compliant devices, regardless of manufacturer, to talk to one another. These devices include controllers, ballasts, switches and sensors. Since DALI is an open protocol rather than a proprietary system, there are a number of ballast manufacturers and control companies that offer DALI products.

A DALI system can include up to 64 individual DALI devices on a single loop, with each device having its own address. DALI ballasts can be individually configured, and that custom configuration resides in the electronics within the ballast itself. DALI ballasts are able to set light levels, fade time and fade rate, and individual address. These ballasts are able to be configured as part of multiple lighting scenes which can be selected by wallbox control devices or a central control system.

DALI ballasts feature two-way communication, which means that they receive digital signals from the control system telling them how to operate, while also allowing the ballast to provide feedback through the network, for instance, indicating if the ballast is on or off, how much energy it is using, and whether the lamp and ballast are functioning.

DALI systems have many attributes which make them worthy of consideration for commercial applications:

  • With DALI, wiring is easier than in a traditional system and there is less of it. The electricians don’t have to care about how they circuit the fixtures. They just run power to fixtures the easiest way they can until they load up a circuit. Fixtures are controlled solely through the digital control wire, which can also be run arbitrarily to each device.
  • The ballasts are individually addressable, allowing for control zones to be configured in the field – rather than on paper, prior to construction. Because control zones are not hard-wired, they can be easily reconfigured based on real usage. Programming zones and scenes is done through software, regardless of how the fixtures are circuited.
  • DALI ballasts can be tied into Building Management Systems, which can monitor energy usage and identify lamp failures, making DALI an ideal system for clients interested in sustainability.
  • DALI ballasts can dim to 1% for linear lamps and 3% for compact fluorescent lamps – this is of particular interest when considering daylight dimming along perimeter zones.

While there are quite a few positive features to a DALI system, there are a number of things to keep in mind when designing such a system:

  • At the moment, there are a limited number of ballast types available. While the choices are vast in Europe, as of this writing, U.S. manufacturers only offer DALI ballasts for four-foot linear fluorescent lamps (T8, T5, and T5H0), two-foot T5 lamps, 18/26/32-watt quad- and triple-tube compact fluorescent lamps, and 40-watt biax lamps. There are no manufacturers in the U.S. currently offering a three-foot linear fluorescent DALI ballast. This proves problematic if designing continuous coves or slots, which can require three-foot units to make up a continuous lighted run.
  • Something else to consider is the inability to locate a DALI-compliant ballast remotely. Lighting fixtures are becoming smaller and smaller due to the demands of both designers and architects, and in some cases the ballasts just don’t fit inside the fixture housings. For a DALI system, designers can select only fixtures with integral ballasts, because as of this writing, DALI ballasts cannot be located outside the fixture.
  • Another factor is that many people are hesitant about implementing a DALI system because they just don’t know enough about how it works. There is the notion that a DALI system will cost more than a traditional system, however, one must consider the lower cost of installation and simplified wiring configurations.

While DALI might not be right for every application, and it does indeed have some drawbacks, the time might be right for more DALI installations in the U.S., and perhaps the U.S. ballast manufacturers will soon start developing and offering more options for DALI ballast/lamp combinations – especially when it comes to three-foot lamps!

Photo Credit: © Carlene Geraci/Lam Partners

The Rise of DALI – again?

June 22, 2009 / no comments

More often than not, if you ask a lighting designer or engineer what DALI is and if they specify it, you’ll get a puzzled look or a chuckle. Some designers are dipping their toes in the pond, but most are waiting to see what the other guys are doing, not wanting to be the first for fear of getting burned on an unproven technology. The truth is, however, that while the U.S. has been plodding along with good old switching relays, 0-10V, and line-voltage dimming, the European design community has already taken lighting control into the digital age and embraced DALI as the preeminent, universal lighting control language.

While those traditional technologies are tried and true, complacency does not constitute a reason to ignore a proven system which has the potential to save time, money, and energy, while increasing beneficial functionality. Here are a few points that examine why DALI has potential and why we aren’t using it enough.

First though, we need to know what exactly DALI is. DALI (not Salvador Dalí) stands for “Digital Addressable Lighting Interface”, and is basically the computer language that devices send and respond to, kind of like Morse code for lighting. The DALI control signals are transmitted over two low-voltage wires that connect to each DALI ballast or relay, each of which has a unique address. Control commands are sent out over the wires to tell individual devices or groups of devices to turn on and off, dim up and down, etc. The devices even have the ability to report back to the controller indicating a lamp failure or how much power they are using. This kind of send-and-receive communication is analogous to a teacher (controller) and classroom full of students (ballasts and relays). The teacher gives instructions to the students (which they obediently obey), and each can answer questions when called on.

What does DALI have that your current controls systems don’t have?

DALI systems can use up to 60% less branch wiring than traditional controls

That’s a strong assertion, but if you lay out the wiring for a traditional system and measure it, for any typical room you would see that by the time those switch legs go down and back up the wall and then out to each controlled zone you have quite a bit of wire. Don’t forget to consider the conduit – lots of metal! Now, if you lay out the same space with a DALI system, you simply don’t have all those switch legs to contend with. The branch circuit flies into the room from the adjacent space, hits each light fixture or addressable relay, and continues on to the next room. All switching and dimming is done in the ceiling at each fixture, not in a wallbox or remote cabinet. While there is some control wiring that connects all the controlled fixtures into a loop, that wiring can be Class 2, run without conduit, (or Class 1 that runs in the same conduit – still cost less than switch legs) and results in much less material, labor, and cost.

DALI wiring diagram

DALI is based on an open protocol

Using an open protocol means that anyone can develop their own DALI devices, ballasts, relays, sensors, etc. The programming language is freely available to anyone that wants it.

That also means that it has the potential to be a universal language for the lighting industry (as has happened already in the EU), so Brand X DALI light fixtures will work with Brand Y DALI control systems. You don’t need to worry about compatibility and which type of dimmer to use anymore.

DALI is easy to specify

Whether the lighting designer or engineer does it, someone has to figure out which traditional dimming ballast or transformer to use with which traditional dimmer. With DALI, it’s simply DALI – DALI ballasts with DALI controllers. Most of the major ballast and gear manufacturers have DALI ballasts already available, and their product offerings continue to expand. Even better, most ballasts, DALI or otherwise, are now universal voltage – you don’t even need to coordinate that!

The proliferation of DALI will also allow for three-name ballast specifications again, unlike the forced specification of a proprietary technology caused by no two systems being alike.

DALI is easy to install

A light fixture gets power (120 or 277 volts – it doesn’t matter as far as the control is concerned) and control wires – that’s it. The rest is in the programming. The control wires are polarity-free, so it’s virtually impossible to wire a fixture incorrectly, unless you forget to. Once contractors understand how easy the installation really is, and they get past the “new technology” hesitation, they should be jumping for such an easy system. Some already have.


So why hasn’t the U.S. embraced this technology yet? Some of the reasons are more complex than others, but there are many possibilities:

Lack of specifier demand

This is simply a chicken-or-the-egg question. If specifiers don’t know about it or don’t understand it, how would they know to ask for it?

The perceived complexity of digital communication and control is something that might be hard for specifiers to wrap their heads around. It’s certainly a lot different from switching and dimming line voltage we’ve been using for the past 40 years. Since there are few manufacturers with front end systems, thus far, education has been lax.

Manufacturer hesitation

For the same reason that specifiers are hesitant to specify it before the competition weathers the “new technology” first, manufacturers are wary of investing in the development of a new system that is so different from what they already offer. They want someone else to do it first to see if it takes off or flops.

There are a few manufacturers that have come up with quasi-digitally-based systems but they’re mostly proprietary, operate in different ways (i.e. cannot be listed as equals), and usually end up converting a digital signal to analog. Unless these systems permeate throughout the industry, their fate will be to persist as a minority, or they will cease to exist.

Sometimes DALI is even discredited as “slow”, “old”, and “expensive”, rejected for specific business interests and investments in competing technologies. A lot of time and money has gone into developing all those other control systems, and to simply adopt DALI, the universal open protocol, would almost certainly cut into profit margins. This may be the single biggest hesitation factor in the U.S.

So what’s next for DALI? Will it ever fully take off in the U.S.? There certainly is vast potential for any manufacturer that wants to take up the technology. It makes sense from so many angles, and if we could just get everyone to agree to adopt it we’d really have something, but that’s a bit like herding cats – good luck!

Photos credit: Matt Latchford / Lam Partners Inc