This article was originally published in the September/October 1995 issue of Home Energy Magazine. Some formatting inconsistencies may be evident in older archive content.



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Home Energy Magazine Online September/October 1995


for Lighting

by Larry Hasterok

Great potential for electricity savings lurks in the alleys, hallways, and stairwells,
and even behind the exit signs of multifamily buildings. But to realize
that potential is not always as easy as screwing in a light bulb.

Welcome to multifamily lighting. Simple in concept--but in practice, its seemingly minor technicalities tend to trip up the unwary.

Common Problems
Are Fading Fast

The replacement of incandescent lighting--particularly hallway fixtures and exit signs that consume electricity 8,760 hours a year in many multifamily buildings--with compact fluorescent lamps (CFLs) yields substantial energy savings and should be easy to promote. It is not uncommon to find 60W bulbs in the hallways and 20W incandescent bulbs (sometimes two) in the exit signs. In Wisconsin, the average price of electricity is 7¢ per kWh. I like to position the owner of the building under one of these existing fixtures and start punching keys on my calculator.

Your existing energy charge for this light alone is $37 annually, I say. By converting to a compact fluorescent lamp, your new energy bill will be $9. Although the new lamp and fixture will cost about $30, the cost for the fixture is about the same as the savings you will enjoy in just one year.

With savings potential like this, it is puzzling that owners and managers would ever forgo a lighting retrofit. One reason may be that the technology is new and the products unfamiliar. Is a tapered globe more aesthetically pleasing than a U-shaped biaxial tube, or is it just more familiar? Also, for many people fluorescent lighting means a cold light that casts a greenish hue. Often these building owners must see the better color temperature and rendition of newer fluorescent lamps to believe the difference. In common areas, we usually use CFLs with color temperatures of about 2,700K, and full-sized fluorescents in the 3,500K range, both with good color rendition.

Another consideration is length. Standard CFLs will not fit into some existing residential fixtures. A common mistake is to install shorter, lower-wattage lamps that do not produce enough light for the task. A better solution is either to replace the fixture or to leave it as is and focus on another area for the retrofit.

In the past, it was difficult to find an appropriate replacement for high-wattage incandescents in areas that need the higher illumination. Retrofitters often addressed this problem by installing multiple CFLs (for example, three 13W CFLs to replace one 150W incandescent). There is a new 38W CFL that is rated at 2,850 lumens (Lm)--about the equivalent of a 150W incandescent. The lamp carries a higher price tag than most CFL retrofits, but it is usually quite cost-effective, and the electronic ballast provides instant-on, the ability to start at 0deg.F, and good power quality.

Some compact fluorescent lamps will have trouble starting in cold weather, especially when the temperature drops below 0deg.F. When installing fluorescent fixtures outside, use enclosed fixtures, which keep the bulbs warmer by retaining more of the heat they generate. For extremely cold weather applications, lamp ballasts and fixtures are available that start reliably down to -20deg.F. In fact, we recently installed compact fluorescents in New London, Wisconsin, that had no problem starting at -24deg.F.

An additional problem in multifamily installations can be theft and vandalism. Although it is tempting to use the convenient screw-in replacements for incandescents, a $15 screw-in conversion can become a screw-out conversion when nobody is looking, turning your energy-saving project into a screw-up conversion!

Doing it right the first time can be a challenge, but it is a goal worth pursuing. It's worth it to pay a little extra up front for quality, because the savings are still so attractive. This means converting the fixture, not just the lamp--that is, doing hard-wired installations rather than screw-in conversions (with the exception of exit-light kits).

Helpful Terms

Lumen (Lm) is the quantitative measure of a lamp's brightness. A 75W incandescent bulb has 1,200 initial Lm. An 18W CFL has 1,100 Lm.

PL lamp stands for Phillips Lighting's twin-tube CFL, the first bulb of its kind to be made available in this country. Other manufacturers, of course, balk at the use of this brand-specific terminology and call compact fluorescents biaxials, twin tubes, or by their own brand name shorthand, such as Osram's EL.

Lamps with four lengths of tubing are called quad lamps, Q lamps, or double-twin tubes.

U tube, a term that describes the general shape of the bulbs, can refer to a U-shaped standard fluorescent tube 2 ft long and 11/2 inches in diameter, or to a type of compact fluorescent.

Cap light refers to encapsulated tungsten halogen lamps. The halogen capsule is encased in a heavy glass shell that looks similar to a standard light bulb.

Color rendering index (CRI) is a scale for rating the way objects look under a particular light. The color rendering index associated with incandescent light is 100. Compact fluorescent bulbs have CRIs in the low 80s, while older long-tube fluorescents usually have CRIs in the 60s.

Color temperature measures the color of the tube itself. Color temperatures are 2,700K for warm, redder applications; 3,500K for balanced color applications; and 4,100K for cool, bluer applications.

Retrofit in Haste--Repent at Leisure

Don't take the easy way out. Consider a common energy savings opportunity--basement lighting in large residential buildings. It is easy to specify a circular fluorescent for installation in a porcelain socket holding a 60W bulb. (The higher-wattage circular screw-in fixture was once popular because it does not hang down as a CFL screw-in would.) Sure, the circular fluorescent's 32 W represents a 47% reduction in electrical usage; but it also represents a lost opportunity to install a 15W compact fluorescent fixture that could save 75%. So auditors should have fixtures in their inventory.

The retrofit involves removing the porcelain fixture to reveal the junction box and wire terminals and connecting the two wires to the ballast on the new fixture. The hard-wired retrofit's advantages are its low cost, theft-resistance, and the horizontal orientation of the CFL U tube (which provides maximum light output and fits the lower ceilings found in basements).

I often recommend fixture replacement in multifamily hallways. The likelihood of unauthorized removal of the bulb is reduced and can be virtually eliminated with vandal-resistant fixtures. These tough guys of the lighting inventory are equipped with polycarbonate lenses and can be installed with tamper-resistant or set screws, such as TORX, Allen, or Roberts, all of which can be turned only with special tools. The lens can take a beating without breaking. No fixture will stand up to a determined effort by a tool- or weapon-wielding villain, but fixtures designed for high-security institutions come close, and may be appropriate in some buildings.

Replacements for Incandescent Bulbs

It is difficult to make any generalization about the light output of a given wattage of lamp because it differs among manufacturers. However, this table suggests a range of replacement wattages that reflects what we have found to be reasonable in local multifamily housing. Wall color, daylighting, lamp spacing, and orientation will also affect lamp selection. Note that the actual wattage saved by CFLs takes into account the extra few watts used by the ballast, which is not always included in the lamp's name.

5W twin tube 25W 18
7W twin tube 34W 25
9W twin tube 40W 29
13W twin tube 60W 42
15W globe or cylinder 60W 45
18W double twin tube 75W 51
22W circle 60W 35
23W triple tube 90W 67
27W triple tube 100W 73
28W quad 100W 70
30W circle 135W 105
38W double-D tube 150W 112

Exit Lights: Better Mousetraps

Exit light fixtures and conversion kits now come in a variety of technologies, ranging from an exotic tube of glowing tritium gas, for those who like their signs nuclear powered, to low-voltage light-emitting diodes. The radioactive tritium exit signs are high on first costs, are not connected to the power grid, and have no yearly energy charge associated with them, but they gradually dim and must be replaced--presenting a hazardous-waste disposal problem. However, they require no wiring or power supply, so they are considered suitable for adding signs where no electric circuit exists.

Light-emitting diode (LED) sign fixtures and screw-in retrofit kits are extremely low wattage--1.8 W and 1.1 W respectively. They are available with 25-year warranties, and manufacturers claim 30 to 100 years of expected life. If you do life cycle costing and calculate the savings from never buying a replacement bulb on top of the typical energy savings of 38 W (about $25 annually) the initial cost of this technology is insignificant. Remember, exit lights are on 8,760 hours per year. Costs are becoming more competitive also. We purchased fixtures for about $65, and the retrofit kits are in the $25-$30 range. Like other conversion kits, the LED socket adapters fit medium, intermediate, candelabra, and bayonet bases.

Electroluminescent lighting (EL) is a relatively new technology that consists of a phosphor-coated dielectric panel sandwiched between two layers of an aklar material. When the phosphors are excited, the whole panel glows evenly, and a stencil placed in front of the panel spells EXIT. These signs can run off AC power or batteries and draw only 1 W.

Table 1.Comparison of incandescent to
CFL and LED exit light conversions

40W total
PL-7 and
9W total
1.1W total
First cost $2 $17 $30
Bulb replacement $14 $19 N/A
Energy cost
for 50,000 hours
(life of PL-7 ballast)
$140 $32 $4
Life cost over 5 yrs $156 $68 $34
Cost per year $31 $14 $7

A Long Life of Savings

Some contractors' estimates include savings from labor avoided by not changing bulbs so often. I have never included this elusive value in my payback calculations. But I do inform the maintenance staff that the average life expectancy of the new bulbs is 10,000 hours and that they will be replacing bulbs less frequently. I like to get the staff who are directly involved to help me convince the owner to invest in lighting improvements. The prevalence of long-life incandescents in multifamily buildings indicates that labor is a consideration of apartment owners and managers.

One building we retrofitted had 40W long-life incandescent bulbs in hallway fixtures with white globes. They delivered only 270 lumens--less than a 34W standard incandescent. Long-life light bulbs get some of their longevity by trading off some luminous efficiency. In fact, the lumen output from a long-life bulb is about 20% less than that of a standard incandescent of the same wattage.

We retrofitted the fixtures with larger globes to accept the longer compact fluorescent lamps, and reduced wattage from the nominal 40 W to 9 W, while increasing lumens to 575 per lamp. The hallways have more light than before, and the lamps are expected to last about four times as long as the old long-life bulbs. If we had wanted even more light in the halls of these buildings, a transparent or clear prismatic globe could have been used.

Whether labor savings are considered or not, the cost of bulb replacement should be evaluated along with energy costs for a life cycle cost analysis of each retrofit measure. Life cycle costing can show that a $15 compact PL-13 costs less than a 75¢ incandescent bulb, with reduced energy costs and less frequent bulb replacement. Remember to include the energy consumption attributed to the ballast when calculating savings for new CFL installations (see Replacements for Incandescent Bulbs, p. 42).

When replacing existing incandescents with CFLs, retrofitters must choose between separate tube and ballast combinations or self-contained units that have both components. Since the ballasts last much longer than the tubes, replacement costs will be less for separate (modular) tubes and ballasts. Some one-piece units have casings that make them look more like traditional light bulbs, but their lenses reduce the light transmitted. Such loss of light output may result in specification of a higher wattage than would be appropriate if the compact tube were naked.

Reflectors can rescue some of the light lost in fixtures. CFLs used to replace incandescents in recessed-can fixtures do not direct the light output optimally. If a CFL is held end-on close to a wall, the end of the tube will cast a shadow. A reflective collar can direct some of the light downward to more closely mimic the old illumination pattern. Prepackaged compact fluorescent floods and spots are also available with built-in reflectors. The three-piece versions (separate lamp, ballast, and reflector) cost little at replacement time, because only the lamp needs to be changed. Ballasts typically last for 50,000 to 65,000 hours, while lamps need replacement at 10,000 hours.

Retrofitters can choose new fixtures that increase light quality, and can also control the direction of light output. What area needs to be illuminated: ceiling, floor, or walls? One Milwaukee building needed security lighting in a back alley at night, but apartment windows faced the fixtures. We used a fixture that illuminated the alley but was covered on top, so light did not spill into the rear-facing bedroom windows.

Selection of a fixture to meet the retrofit situation exactly can prevent problems that may occur when old fixtures meet new lamps. Fixtures light the way to lower operations and maintenance costs, better lighting quality, and persistence, as well as energy savings.

Sample Lighting Audit Form

Location Old Fixture Type Suggested Retrofit Watts per Fixture (old) Watts per Fixture (new) Number of Fixtures Total Watts Saved Daily Burn Hours Total
Annual kWh Saved
$ Saved
per Year (at 6.5 ¢/kWh)
per Fixture
Basement ceiling Porcelan socket Flour. drum 40 13 19 513 24 4,494 $292 $22 $419
1st floor hallway Incand. drum Ovel flour. fixture 40 13 14 378 24 3,311 $215 $30 $420
2nd floor hallway Incand wall sconse CFL wall sconse 40 13 5 135 24 1,183 $77 $43 $215
Exterior Incand. coachlight Brass CFL 
40 20 10 200 12 876 $57 $55 $550
Exit Incand. LED 
40 4 18 648 24 5,676 $369 $64 $1,152
Total           1874   15,540 $1,010   $2,756
The audit form above was completed for three buildings we retrofitted in New London, Wisconsin, at the end of 1994. This represents the common areas only and, although the owner was using only 40-watt incandescents for everything, the retrofit was still very cost-effective.
Figure 1.Comparison of utility bills before and after retrofit.
The actual savings from five months of billing data (January through May 1994 compared to the same months in 1995) for the three buildings are shown in the figure to the right. The bills went down by $373 total for those five months.                      

Larry Hasterok is an energy analyst with the Wisconsin Energy Conservation Corporation, a nonprofit energy consultant in Madison, Wisconsin.

Note: The original version of this article was printed in the Nov/Dec 1990 issue of Home Energy.

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