What should distributors and contractors focus on for profitable and cost effective energy savings in interior spaces?
- Mainly lighting
- Mainly controls
- Both
It really depends.
In spaces where the lights are on for multiple hours at a time with no traffic, just occupancy sensors may be the most cost effective solution. Examples can be offices that the lights are left on all night frequently, some warehouse rack aisles that you can see dust on the floor with no footprints, library book stack aisles with books, which are not used that much, and company parking garages that there is little activity between shifts.
In most areas just lighting is often the most cost effective solution. In some areas, doing both may cost effective, but be aware of a different diminishing return than was in a previous column.
In the past it was often cost effective to do both lighting and controls, but now that LED and even high performance fluorescent being so efficient and low wattage, there is not that much wattage or KWH for controls to save cost effectively. Now, if energy codes permit, it is usually better doing one or the other, but not both.
You can do your calculations, and I bet that often lighting by itself is often more cost effective than controls by themselves or lighting with controls. If that is the case, consider lighting first, and then see if controls are sufficiently cost effective with that efficient lighting. For X amount of money, if often more cost effective doing more lighting and less or no controls.
What ever is considered second has diminishing returns, because the reference is no longer the not-that-efficient existing condition. Part 2 of this column will show this and other specific examples.
Although many energy codes are mandating efficient lighting and controls – dimming throughout North America, I hope you can see, especially for retrofits that does not seem to make ‘dollars and sense’.
You can also see and take photos of exterior windows to see how many rooms have lights on during the night. But be aware that cleaning crews may be in several rooms.
As you may already be aware, data loggers can often be very useful tools to determine the percentage of time lights are on without anybody there. Several manufacturers offer these, and contractors can purchase these from distributors. Some utilities have these in their tool lending libraries.
I learned a very important tool regarding occupancy sensors close to twenty years ago, and it is still useful. It can be called ‘owned and non-owned’. Owned spaces include private offices and elementary school classrooms where the teacher or the ‘energy police’ students feel ownership and turn off the lights most every time they leave. Occupancy sensors can cause increased annual hours of operation, because the office workers, teachers and students will allow the 10 – 15 minute delay before the occupancy sensors turn off the lights. If the private office workers, teachers and students do not currently properly turn off lights, they can often be educated and motivated to do so at low or no cost. Non-owned spaces can include open offices, conference rooms, break rooms, print rooms and restrooms. People usually do not feel ownership, so if the lights are on when they enter, they often leave them on they leave. These rooms are often cost effective for occupancy sensors.
Although there are numerous honest and knowledgeable control and dimming manufacturers, suppliers and contractors, there are others, some who play games, such as artificially specifying excessive high wattage lighting, so the dimming and controls can look attractive. For example, existing 3F32T8 18 cell parabolic troffers can often be retrofitted with fixed 20W LED troffer kits, some of these companies may specify something like dimming 40W LED troffer kits and include controls, which may bring the wattage down to 20W for each, but with the extra parts and labor costs for dimming and controls. Often with dimming and controls, the project has a worse financial return and the customer may not approve it. I have seen some people and companies combine savings from lighting and controls and try to make controls look better, while lighting is actually doing a better job. Relatively low light ambient lighting with good task lighting is better than dimming ambient lighting.
If anybody is pushing anything too much, it is often good to follow the money.
If you have any comments on this column or have an idea on an upcoming column, please let me know at stan@lightingwizards.com.
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