Lighting

By Kenton Shepard

Energy Use in Home Lighting

Lighting accounts for 30% to 50% of a buildings energy use or about 17 percent of total annual US electricity consumption. 90% of the energy emitted by incandescent bulbs is in the form of heat, only 10% is in the form of light. This means that not only is money wasted on inefficient lighting, but using incandescent bulbs lights increases cooling costs.

TYPES of LIGHTING

COMPACT FLOURESCENT (CFL) BULBS 

• Generate 70 percent less heat, so they’re safer to operate and can cut energy costs associated with home cooling.
• Use at least 2/3 less energy than standard incandescent bulbs to provide the same amount of light, and last up to 10 times longer.
• Save $30 or more in energy costs over each bulb’s lifetime
• Must turn on instantly, produce no sound, and fall within a warm color range or be otherwise labeled as providing cooler color tones, in addition to other quality requirements.
• Are available in different sizes and shapes to fit in almost any fixture, for indoors and outdoors.

Where to Use CFLs:

To get the most energy savings, replace bulbs where lights are on the most, such as your family and living room, kitchen, dining room, and porch, with CFL’s.

Although they are manufactured for use in recessed light fixtures, some CFLs have trouble operating in enclosed fixtures.

Compact Fluorescent Light bulbs are available for different applications

NOTE: Because they contain small amounts of mercury, CFL’s must be disposed of properly.

HALOGEN LIGHT BULBS

Although they produce significant amounts of heat and cost more than incandescent light bulbs, halogen lights last much longer than incandescents, give high-quality light and are 50% more efficient. Halogen lights are good for task lighting. Task lighting is lighting a small area where a particular task will be performed such as reading.

Halogen Light Bulbs

LIGHT-EMITTING DIODES (LED’s)

Light emitting diodes are a relatively new technology in residential lighting. They emit low levels of heat, consume little electricity and last for tens of thousands of hours.

This LED recessed light fixture had been on for about 5 hours when these photos were taken.

The 12-watt LED fixture in the photos above emitted light intensity comparable to a 60-watt incandescent, will last approximately 50,000 hours and was close to room temperature.

Full-spectrum Bulbs

Full spectrum bulbs emit light waves which cover a wide spectrum and are meant to simulate natural light. These bulbs may be either compact or tube fluorescent, incandescent or halogen bulbs. They can be recognized by markings reading “Full spectrum” or which indicate a Kelvin temperature above 5000.

RECESSED LIGHT FIXTURES

Recessed light fixtures installed in ceilings below attics should be airtight to prevent heat loss during the winter and to prevent moisture condensation problems in the attic. Attic insulation may enter the home through unsealed recessed light fixtures.

Recessed light fixtures should have reflectors installed to reflect light out of the fixture and into the room.

IC-Rated recessed light bulbs

Recessed light fixtures in contact with insulation should be IC (Insulation Contact)-rated. IC recessed light fixtures should use a bulb of 75 watts maximum. Installing bulbs with a wattage greater than 75 watts will result in a temperature-sensitive safety sensor shutting off the light periodically.

Recessed light fixtures installed in ceilings with attics or which are in contact with insulation should be IC-rated. Installing Non-IC-rated fixtures in ceilings with unheated attics will result in heat loss to the attic and the possibility of excessive moisture levels in the attic leading to problems from condensation.

Non IC-Rated recessed light bulbs

Recessed light fixtures not in contact with insulation and installed in enclosed joist bays need not be IC-rated and the can interior will be white. Non-IC-rated fixtures will work with bulbs up to 150 watts.

HOW TO TELL THE DIFFERENCE…

IC-rated fixtures will have a silver interior (left)

Non-IC-rated fixtures will have a white interior (right)

Fixture-related Moisture Problems in Attics

Under certain conditions, non-IC-rated fixtures installed in ceilings below attics can introduce up to 10 gallons of water a month into cold attics. Stack effect can move up to 10 cubic feet per minute (CFM) of moisture-laden air through fixtures, although the average is much lower.

Moisture condensing on cold attic surfaces can activate mold fungi, creating a potential health hazard. A home located in a humid climate with high stack pressure and 20 non IC-rated recessed fixtures in a ceiling below an attic could have as much as 180 gallons of moisture a month deposited in the attic. Bulb wattage makes very little difference in the rate of air leakage through recessed light fixtures.

LIGHTING CONTROLS

Lighting controls are devices used to reduce energy waste and increase home comfort levels. They do this in three ways...

1. Providing the right amount of light needed. Through dimming or through bi- or multi-level switching lighting can be adjusted to meet changing  needs in certain areas and personal preferances.

2. Providing light where it's needed.  This entails establishing control zones, which are light fixturews or groups of fixtures controlled by a single controller. Zones are typically established based on types of tasks needing lighting, lighting schedules, types of lighting, achitectural considerations and the availability of natural light.

3. Providing light when it's needed. Controls may be set to operate lighting based on time if a certain area is used on a predictable schedule. In areas in which need is not predictable, controls may operate lighting based on occupancysensors which switch lighting on and off when a person enters or leaves the sensor’s sphere of sensitivity.

DAYLIGHTING

Daylighting is the practice of using natural light to illuminate the home interior. It can be achieved using a number of different approaches...

 It’s important that they be double-pane or they may not be cost-effective. Flashing skylights correctly is key to avoiding leaks.

Light shelves are passive devices designed to bounce light deep into a building. They may be interior or exterior. Light shelves can introduce light into a space up to 2 ½ times the distance from the floor to the top of the window and advanced light shelves may introduce 4 times that amount.

Light shelves installed in window openings help bounce natural light well back into the building. Reflective countertops of windows cabinets also serve as lightshelves.

Reflective Awnings

Source

Permanently-installed sails reflect light into the lobby atrium of the EPA Region 8 Headquarters in Denver, CO.

Left: Five metal halide lights help provide light on overcast days and at night.

Clerestory Windows

Clerestory windows are low, wide windows set high on the wall. Protected from the summer sun by the roof overhang, they allow winter sun to shine through for natural lighting and warmth.

Clerestory windows at the upper left also have a light shelf, which bounces light off the ceiling and reduces glare.

Light Tubes

Light Tubes use a special lense designed to amplify low-level light and reduce light intensity from midday sun. Sunlight is channeled through a tube coated with a highly-reflective material, then enters the living space through a diffuser designed to distribute light evenly.

Source

One example of a light tube

Exterior lighting

Limiting Light Pollution

Light pollution causes the following problems...

• Wasted energy- electricity must be generated to power lights. Unnecessary exterior lighting wastes this energy and the money it costs to produce it.
• Air Pollution- generating plants using fossil fuels to produce electricity to power lighting also produce air pollutants such as particulates, acid rain, heavy metals and greenhouse gases.
• Wildlife Habitat Degradation- Light pollution can effect wildlife habitat by by attracting animals and repelling them.

Lastly, light pollution prevents us from seeing the night sky. 90% of the poplulation of the U.S. lives in areas of reduced view of the night sky due to light pollution.

Here are basic guidelines to follow to reduce light pollution

• Light Only What Needs to be Lit
• Light Only When You need it Lit
• Use Only As Much Light as is Required
• Use Only Full Cutoff Fixtures
  

  All photos with no source given are by Kenton Shepard

Sources for More Information

Illuminating Engineering Society of North America (IESNA)- Techinical authority on illumination, offering a forum for the exchange of ideas and information, educational oportunities and technical papers.