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Field Test Best Practices: A Resource for Practical Residential Building Science

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Lighting

Lighting accounts for about 10-12% of residential energy use, and with the advancement of compact fluorescent lamp (CFL) and light-emitting diode (LED) light bulbs, lighting is often a easy place for homeowners to make energy efficient upgrades. Most types of light bulbs can be found in a more energy efficient configuration and the prices and quality of both CFL and LED bulbs continues to improve. In addition to replacing incandescent bulbs with a more efficient version, adding dimmer switches and lowering lighting levels can also reduce lighting energy use. Daylighting can also reduce electric lighting loads during the day.

However, none of these measures for reducing lighting loads are particularly novel and so a field test would not likely be testing the energy consumption of a house full of CFL bulbs. A lighting control system, on the other hand, could be the focus of a residential field test. Lighting control system using photo sensors and dimmable lighting is a more common feature in advanced commercial buildings but can also be found in residential buildings.

Electric Lighting Types

Traditional light bulbs are incandescent and are slowly being phased out in favor of more efficient options. A new crop of energy-saving incandescent bulbs are coming on the market, making it easier for consumers to keep their incandescent bulbs and still save about 25% on their lighting energy. Compact fluorescent lamp (CFL) bulbs use less energy than energy-saving incandescent and their features have improved dramatically since they first came on the market. The newest addition to this line of energy efficient lighting products is the light-emitting diode (LED) bulb. These bulbs use a completely different type of lighting, which is extremely long-lasting and efficient. They are still expensive relative to CFL bulbs, but the price has already begun to come down.

Daylighting

Daylighting in a residential building has the potential to cut lighting energy during the day and bring natural light into the home. Daylighting can be as simple as drawing blinds or curtains to allow light to come into the house through the windows. The use of skylights allows natural light to illuminate interior spaces in the house in areas without windows or far from windows. One drawback of standard skylights is that they can be a large source of heat loss and do not distribute light evenly. A more efficient alternative to the large rectangular standard skylight is a tubular skylight, shown in the figure below. Tubular skylights have a domed collector on top, which can collect more light with a smaller cross-sectional area. The light goes through a diffuser before entering the house so the light is diffuse, which is better for reducing ultraviolet (UV) damage inside the house. The smaller penetration in the roof also reduces heat losses.

Other ways to introduce daylighting into a residential building include daylighting shelves and clerestory windows, both of which are more commonly found in commercial buildings. Daylighting shelves bring light into the building, while reducing the direct sunlight. This works well in office spaces and in multi-story buildings. Clerestory windows also bring light into the house near the ceiling, which helps to illuminate the space without the glare of direct sunlight. Clerestory windows are sometimes seen in residential buildings but are common in new, energy efficient commercial buildings.

Lighting Controls

Simple forms of lighting control are commonly found in homes and commercial buildings, consisting of dimmer switches, timers, and motion sensor-controlled lighting. Traditionally, motion sensors, using ultrasonic sensor technology, are notoriously bad when controlling lights in an office where people are not very active. However, occupancy sensors are becoming more sophisticated in that they combine motion sensors with infrared sensors to detect the heat of people. Occupancy sensors can be used to control a variety of lights through out a house, but they are most often located in rooms like hallways and bathrooms where use is intermittent.

Dimmer switches are a more manual form of lighting control, but using dimmer switches to reduce the lighting output of a fixture can extend the life of the bulbs and save the occupant money on their electricity bill. Timers are also an easy way to control lighting, and are great for special occasion lighting such as Christmas lights. Currently, most of these pieces of lighting control are disjointed and not used to their full potential in the residential building space.

Commercial buildings have made more progress in lighting control as lighting makes up a larger part of the building's energy use and there are often building managers in charge of building operations. While most homes don't have a building manager to oversee energy use, more advanced residential lighting control systems are starting to come onto the market that manage lights based on input from occupancy sensors, light sensors, and schedules. These respond to the programmed control logic to turn lights on or off, dim them, and even open and close shades. There are also control systems that can be used to create a whole house "green switch" that could be programmed to turn all lights off in the house with the press of a single button by the front door. Combining more sophisticated lighting control systems with more efficient lighting should eliminate a large chunk of electricity spent on residential lighting.

Window Coverings

Window coverings include shades, blinds and curtains. Shades can be internal (probably the most common) or external. External shades are more effective if the shades are being used in a cooling-dominated climate to keep solar heat gain out the house. Internal shades will help, but external shades keep any radiation from entering the house. Window coverings can be very effective at cutting the cooling loads on a house during the summer, which generally will outweigh the additional lighting load that will likely be needed to compensate for the lack of natural light.