Appendix 5F: Optimal sequence for lighting and cooling improvements

What's the right order for improving office lighting? Most retrofitters start by improving the lighting equipment. But that starts at the wrong end of the problem. Even the most efficient lighting equipment is useless if it lights the wrong place, or at the wrong time, or at the wrong angle so it causes glare. The Illuminating Engineering Society and seasoned lighting professionals would instead recommend the following sequence for, say, retrofitting the lighting in an ordinary office where people main read papers and computer screens:
  1. Improve the quality of the visual task.1
  2. Rearrange the room to make the lighting comfortable.2
  3. Improve the quality of the light by reducing "veiling reflections"—glare that bounces from the light source off the page to your eye so you can't distinguish ink from paper. This is typically about ten times as important as adding more light. Indirect lighting, which bounces light off the room's surfaces from all directions, can let you see as well with 20 indirect footcandles as with 100 footcandles from glaring direct downlights.
  4. Rather than overlighting the whole room to a uniformly high level—which would be as inappropriate as controlling a big building with a single thermostat—get the right amount of light on each of your tasks by adjusting the ambient lighting levels to what you need for walking around and doing non-desk tasks, then filling in on your desk with an efficient swing-arm task lamp.3
  5. Try to lighten the colors of the ceiling, walls, floor, and furniture so that the light will bounce around better within the space. The smaller the areas of dark colors that soak up light, and the more you lighten those colors (without, of course, making them dazzlingly bright), the less light you'll need to add to the room in order to get a given amount bounced onto your desk.
  6. Harvest and distribute free daylight.4
  7. Improve the technical efficiency of your electric lighting equipment, for example as described in Appendix A for standard fluorescent-tube fixtures, by using better light fixtures, lamps, ballasts, and controls.
  8. Train people how to use these systems.5
  9. Improve maintenance and management of these systems so they'll stay at top performance and least cost.
Interestingly, most "lighting retrofitters" do only step 7. Doing steps 1–6 first saves more money and yields better results, because smaller, simpler and less equipment will be needed to deliver nicer light.

Or consider the proper sequence in which to help people feel comfortable in hot weather:6
  1. Expand the range of conditions in which, according to the official ASHRAE standards, people feel comfortable. There are at least ten ways to do this besides air temperature.7
  2. Keep unwanted heat out of the room.8
  3. If you still need to cool the people, first do so passively by "ground coupling" (building on an uninsulated slab that connects the space to the cool earth beneath), ventilative cooling like the Queens Building in Leicester described in Chapter 5: Building Blocks, or radiative cooling. Just a shallow roof pond, which stores up heat during the day and radiates it away to the night sky, and a ceiling fan can maintain ASHRAE comfort standards in August in Miami.
  4. If still more cooling is needed, use alternative methods: absorption, which turns heat into coolth; desiccant, which turns heat into dryness; or evaporative, which cools dry air by evaporating water, and can deliver either moist or dry cool air into the space. 9 Combining these methods into hybrids, like an absorption chiller whose waste heat regenerates a desiccant to pre-dry the air, or a desiccant to make hot dry air plus indirect evaporative to convert it to cool dry air—can be especially effective. Various combinations of these nonrefrigerative techniques can meet cooling demand anywhere in the world, and can often be operated not by electricity but by waste heat available for free from some other device.
  5. To conserve coolth once you've got it, use outgoing air to cool the incoming air through an air-to-air heat exchanger, or to dry the incoming air through a desiccant wheel or passive latent heat exchanger10, or both.11
  6. If you really want refrigerative cooling—though the previous methods can make this unnecessary, avoiding potential climatic harm by the refrigerant12—then make it extremely efficient. Techniques first proven in East Asia can make big central air-conditioning systems about three times more efficient than the norm, yet less costly to build and more effective and reliable, as described in Appendix 5G.
  7. The fancier systems (#4 or #6) may require controls, which can almost always be improved to save about 20–30% of the remaining energy. Control savings can even rise to 50% with careful training of building operators on simulators analogous to those used in flight training: big buildings are far too complicated for operators to understand intuitively without such help.
  8. Peak electric loads and some energy can finally be saved by storing coolth in big tanks in the form of chilled water, ice, etc.
Many practitioners not versed in whole-system thinking pursue these steps in exactly the reverse order—worst buys first. In fact, many air-conditioning retrofitters pursue items 8, 7, and a small part of 6 without ever getting to the cheaper ones before that. Doing this gives up all the potential to reduce the need for costly cooling capacity in the first place. Such reversed priorities maximize expenditure, minimize savings, and destroy synergies between measures. But done in the right order, the savings can be phenomenal. Referring to examples described in this and the Buildings chapters, imagine combining these steps:
  • expand the "comfort envelope" to save 20% of the cooling energy;
  • reduce the cooling requirement by 70% by improving the building and its lights, appliances, etc.—less than was achieved in two Vancouver buildings (Appendix 5C);
  • reduce energy per unit of cooling supplied by passive or alternative methods (remember the Sunset building's 93% reduction, the Davis house's 92% including or 100% excluding air-handling, the Queens Building's 100% reduction, etc.);
  • if remaining refrigerative cooling is needed, save 50% of its energy (60–70% is available, as described in Appendix C); and
  • save 20% from controls, normally near the low end of the range, and nothing from storage.
In the style illustrated earlier for successive steps in saving wood fiber, these savings multiply to 98%. As usual with chains of successive savings, you needn't save much at each step in order to get the total savings to multiply to a very large level, simply because there are so many successive steps.

1 If you're having trouble reading because the papers have been photocopied on a machine with dust on the lenses and mirrors, clean out the machine first to make the image crisper. If there's glare off the paper, consider using matte paper.

2 If there's "discomfort glare" from harsh overhead sources, so shading your eyes with your hand like a baseball-cap brim makes your face muscles relax from squinting, control the glare with louvers or lighting redesign. If bright spots are glaring in your computer screen from lights or windows behind you, shade them or change the layout of the room so they're no longer behind you. If you can't read your computer screen because it's in front of a bright window, move the screen or shade the window. If windows are too bright compared to walls, adjust the blinds properly, or use microperforated blinds or diffusing curtains.

3 You need more light when you're older, or your eyes are more tired, or when you're doing finer or more critical tasks. Task lamps make it easy to get just the amount of light you want, where and when you want it.

4 Modern techniques such as double-curved lightshelves can do this quite evenly and without glare, even as much as 50+ feet in from the nearest window. Lightshafts and atria can bounce soft daylight many stories downward. Special methods, such as lightpipes and fiber optics, can even collect concentrated sunlight on the roof or outside the building, then deliver it as intense daylight far underground. In general, direct sunlight is too strong, producing glare that makes it harder to see, so instead of being "dumped" into the space, direct sunrays should generally be bounced back up onto the ceiling. Glass-topped partitions for private offices can preserve privacy, yet spread daylight better into adjacent rooms.

5 For example, how to operate Venetian blinds: they're supposed to be not closed like opaque curtains, but tilted so they throw daylight upward onto the ceiling. Then you can still see out, but the outside isn't unpleasantly bright.

6 Cler, G., Shepard, H., Gregerson, J., Houghton, D.J., Fryer, L., Elleson, J., Pattinson, B., Hawthorne, W., Webster, L., Stein, J., Davis, D. & Parsons, S. 1997: Commercial Space Cooling and Air Handling Technology Atlas, E SOURCE, Boulder CO,

7 Herman Miller's "Aeron" chair lets you sit not on insulating upholstery but on a ventilative net or mesh, keeping your backside 4–7°F cooler. (In a nice example of design synergy, that "pellicle" also costs less than upholstery, so Herman Miller could afford to include extremely thorough and effective ergonomic adjustments to the chair without making it cost more.) Ceiling fans or other turbulent vertical air movement—not so strong that it would blow papers off your desk—can make you feel about 9°F cooler. "Superwindows" or other ways to block radiant heat from windows can greatly increase comfort. Efficient office equipment similarly radiates less heat at you than inefficient equipment. Appropriate dress codes can greatly increase comfort, and can also reduce the hard-to-accommodate differences in comfort requirements between men in suits and women in skirts and blouses. Just these kinds of measures can together save 20–30% or more of the cooling energy, and can eliminate the need for air-conditioning in many climates—even quite humid ones.

8 This means designing the building with the right shape, orientation, shading, surface properties, mass, insulation, landscaping, and ventilation design, and then not releasing unwanted heat indoors through inefficient lights and equipment. Many of these improvements can be retrofitted: for example, dark roofs can be changed to lighter colors specifically designed to bounce solar heat away without looking uncomfortably bright to your eye. Shading devices or vegetation can be added where they were originally lacking. Careful control of external and internal heat gains typically lets a "ton" (3.52 thermal kilowatts) of cooling suffice not just for 250–400 square feet of office space (a typical number in the U.S.), but for about 800–1,000 square feet in a retrofitted building and 1,200 (more in milder climates) in state-of-the-art new offices. As we'll see, that severalfold reduction in required cooling power can save a lot of capital cost.

9 An experimental office retrofit for Pacific Gas and Electric Company designed a mainly indirect-evaporative cooling system with a whole-system design power of 0.14 kilowatts per ton—25 units of cooling per unit of electricity.

10 This ingenious device, invented by Eng Lock Lee and concurrently by several U.S. heat-pipe companies for hot, humid climates, works like this. Precool the air coming into the building (you'll learn how in a moment). This will condense water out of the moist incoming air. Collect that condensate. Run it out of the building by gravity in a small pipe. Evaporate the water into the outgoing air, which, having already been dehumidified, is drier than the ambient air outside. This evaporatively cools the outgoing air nearly to the wetbulb ambient temperature. Capture that coolth with a heat exchanger and bring it back inside passively with a heat pipe. That's the source of cooling that you use to precool the incoming air.

11 This can be done either passively or with a very small and efficient fan, and can readily be added to most conventional ventilation systems.

12 Hydrocarbons, ammonia, or other relatively benign materials can be used with appropriate care, but halogenated refrigerants are a problem. Even once manufacturers complete the transition from outlawed ozone-destroying CFCs to interim HCFCs to chlorine-free HFCs, those HFCs will still be greenhouse gases thousands to tens of thousands of times more potent than CO2—partly because once released, they can stay aloft for millennia.

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