The building envelope is the outer shell of the building that separates the interior space of a building with the outside elements. It is essential to maintaining a dry, heated or cooled indoor environment. The building envelope consists of the roof, wall and foundation of the building as well as the window assemblies.

Roof and Wall Insulation

Roof and wall insulation can help reduce the amount of energy required to condition space inside buildings (cooling or heating) by decreasing the rate of heat transfer with the outdoor environment. Insulation is typically rated with an “R-value” (higher numbers correlate with greater insulating properties).

Air Infiltration Reduction

Sealing gaps or other leakage sites in the building envelope, including heating and cooling ducts, can reduce energy losses, improve overall building and system efficiency and reduce energy bills.

Windows and Glazing

The energy efficiency of windows is enhanced by quality frame materials, multiple layers of glass, low-emissivity (infrared-insulating and ultraviolet light-reflecting) glass and insulating gas fill.

Lighting is often considered the low hanging fruit of energy efficiency improvement due to its short investment payback period. Light Emitting Diodes (LED) bulbs are considered top tier in terms of energy efficiency and have recently become more price competitive with less expensive technologies like Compact Fluorescent Lightbulbs (CFLs). For example, if a commercial building replaced all of its traditional 60-watt light bulbs with 19-watt LED lamps, and electricity costs USD $0.13 per kWh, the estimated payback period is just under two years. Additionally, daylight and occupancy sensors can be paired with lighting systems to reduce energy use when natural light is adequate and when buildings and rooms are unoccupied.

LEDs

Light Emitting Diodes, or LEDs, are small light sources that are illuminated by the movement of electrons through a semiconductor material. LEDs are exceptionally energy efficient when producing individual colors, many use up to 90 percent less energy than an incandescent bulb to produce the same amount of light and last 25 times longer before needing to be replaced. They can be used in almost any application: street lighting is one particularly effective application for LEDs. The upfront cost of LEDs is typically higher than CFLs or incandescent lamps but has been steadily dropping in many markets.

CFLs

Compact Fluorescent Lightbulbs (CFLs) use one-fifth to one-third the electric power of incandescent light bulbs and last eight to fifteen times longer. CFLs have replaced incandescent light bulbs in many markets, although LEDs are rapidly becoming the preferred choice due to their efficiency and length of operation. Additionally, CFLs contain small quantities of mercury, which can complicate disposal.

High Performance T8s

High performance T8 (HPT8) systems are comprised of two components: a high-lumen, long-life T8 lamp and low-power electronic ballast. This combination results in energy savings over older systems that use T12 lamps with magnetic ballasts and improves light output by reducing flickering and noise. HPT8s are typically used for commercial lighting applications.

HID Lamps

High-intensity discharge (HID) lamps use electricity arcs between two electrodes to create an intensely bright light with mercury, sodium or metal halide gas acting as the conductor. HID lighting provides the second highest efficiency and longest service life of any lighting type. HID lamps are up to 90 percent more efficient than incandescent lighting and are used to light large indoor areas such as gymnasiums and sports arenas as well as outdoor areas such as car lots.

T5HOs

High Output T5 lamps (T5HOs) are four-foot fluorescent lamps that are narrower in diameter than the comparable T8 fluorescent but produce roughly twice the light output. The light output of T5HOs makes them well-suited to high ceiling applications both in commercial and industrial contexts.

Most major appliance manufacturers offer energy-efficient versions of their products, which are sometimes marked with a label to designate them as such. See the Standards, Rating and Labeling Technical Guide for more information on appliance labeling.

Clothes Dryers

Energy-efficient dryers use less energy than conventional models without sacrificing features or performance. They do this using innovative energy saving technologies, such as moisture sensors that detect when clothes are dry and automatically shut the dryer off or incorporate low heat settings, which perform longer drying cycles using less energy.

Clothes Washers

Energy-efficient washers have greater tub capacities which means fewer loads can be used to clean the same amount of laundry. They can include technologies such as sensors to monitor incoming water levels and temperature as well as repeated high-pressure spraying, used instead of soaking clothes in a full tub of water. Front-loading clothes washers also use substantially less water than top-loading models. According to the U.S. Environmental Protection Agency (EPA), highly efficient clothes washers can use 25 percent less energy and 40 percent less water than regular washers.

Dehumidifiers

Energy-efficient dehumidifiers have more efficient refrigeration coils, compressors and fans than conventional models, which means they remove the same amount of moisture but use 15 percent less energy.

Dishwashers

Efficient dishwater technology includes a number of different features. Soil sensors, for instance, adjust the cycle to achieve minimum water and energy use by testing for dish dirtiness while improved water filtration removes food soils from the wash water to allow efficient use of detergent and water. Finally, efficient jets use less energy to spray detergent and water over dishes when cleaning, and innovative dish rack designs maximize cleaning by strategically positioning dishes.

Refrigerators and Freezers

Efficient refrigerators and freezers used in residential, commercial and industrial applications employ more effective insulation and higher efficiency compressors to save energy.

Vending Machines

Efficient vending machines incorporate more efficient compressors for refrigeration, fan motors and lighting systems and sometimes include motion sensors which automatically switch to low-energy lighting and/or low-energy refrigeration mode during times of extended inactivity.

Electric and Electronic Equipment (Computers, Phones, TVs)

The efficiency of electric and electronic appliances can be improved through features such as switch-mode power supplies (that convert electrical power efficiently), “smart” chargers (that communicate with batteries to ensure optimal charge), efficient backlighting and low-power mode.

Heating and cooling (i.e. conditioning) the indoor environment is critical to ensuring occupant comfort and can improve productivity. Ventilation systems can help improve indoor air quality and, when implemented correctly, can have positive health benefits for occupants. HVAC systems include a variety of technologies and can be used in residential, commercial or industrial settings.

Air Conditioning

Air conditioning is the process of altering air temperature and humidity to distribute air and improve occupant comfort and indoor air quality. Air conditioners function in much the same way refrigerators do by using energy to transfer heat from the interior of a building to the outside environment.

Boilers (gas or oil-fueled)

Boilers heat water or produce steam, which is circulated through the building to radiators or other terminal units in order to heat the building. A boiler’s efficiency is measured by annual fuel utilization efficiency (AFUE), which is the ratio of useful energy output to energy input expressed in percentage terms. Higher AFUE percentages indicate higher efficiency.

Furnaces (gas or oil-fueled)

Furnaces heat air which is delivered directly to interior spaces. The efficiency of a furnace in converting gas into heating energy is reflected in its annual fuel-utilization-efficiency (AFUE) rating, which is expressed as a percentage. The higher the number, the more heat the furnace can take from each unit of gas.

Heat Pumps: Air Source and Ground Source

Heat pumps transport heat from outside to inside (in heating mode) or transport heat from inside to outside (in cooling mode). There are two major types of heat pumps—air source and ground source. Air source heat pumps usually use a separate outdoor compressor unit to move heat in and out of a residence or building. Ground source heat pumps (or geothermal heat pumps) provide heating, cooling and water heating by taking advantage of the Earth’s natural heat and stable temperatures. Ground source heat pumps use an underground piping system called a “loop” to move heat between the ground to the inside of the building (in heating mode) or vice versa (in cooling mode).

Air Compression Systems

Energy efficiency opportunities for air compressors include comprehensive system evaluations, new compressors, refrigerated dryers, additional storage, enhanced controls, piping improvements and leak repairs.

Chillers

There are two types of high-efficiency chillers—air-cooled chillers and water-cooled chillers. A chiller’s efficiency is measured by the Coefficient of Performance (COP), which is the ratio of heating or cooling provided to electrical energy consumed. Higher COPs indicate greater efficiency.

Chiller efficiency may be improved through enhanced controls, enlarged and improved condenser sections, and high-efficiency compressors with VSD motor drives. The use of evaporative or swamp coolers, which are packaged units that cool the air by humidifying it and then evaporating the moisture, can significantly reduce peak electric demand when compared to electric chillers.

Heat Recovery

During inefficient manufacturing processes, as much as 20 to 50 percent of energy consumed is ultimately lost via waste heat contained in streams of hot exhaust gases and liquids, as well as through heat conduction, convection and radiation from hot equipment surfaces and from heated product streams. Waste heat recovery technologies capture these heat losses for re-use in different processes. An example of one of these technologies is an economizer. There are different types of economizers (condensing, air source) that can be paired with different equipment to improve the efficiency of that equipment. For example, a condensing economizer can be paired with a boiler to improve its efficiency by recovering useful heat from fluid that is hot but not hot enough to be used in the boiler itself.

Ventilation Fans

Ventilation fans, typically integrated into central HVAC systems, may have increased efficiency through measures such as humidity sensors and motion sensors.

Ceiling Fans

Efficient ceiling fans use improved motors and blade designs to deliver greater efficiency when compared to conventional models.

Water heaters are often categorized by the type of fuel they are powered by (electric, natural gas or solar) and whether or not they heat a storage tank or provide heated water on demand (also known as “tankless” systems).

Electric Storage Water Heaters

Also known as heat pump water heaters (HPWH), electric storage water heaters use a highly efficient heat pump to transfer heat from the surrounding air to an enclosed tank. During periods of high hot water demand, HPWHs switch to standard electric resistance heat automatically. These heaters also come with selectable operating modes, such as efficiency/economy to maximize energy efficiency and vacation/timer to place the unit in “sleep” mode.

Natural Gas Water Heater, Gas Storage

In high-efficiency gas storage water heaters, a glass-lined steel tank is heated by a burner located at the bottom of the tank. Efficient models simply have better insulation, heat traps and more efficient burners, and very high efficiency models use a secondary heat exchanger that extracts more heat from the combustion gas, cooling it to the point where there is condensation—hence these types of heaters are called “gas condensing.”

Natural Gas Water Heater, Whole Home Gas Tankless

Whole-home gas tankless water heaters save energy by heating water only when needed and thereby eliminating energy lost during standby operation. When a hot water tap is turned on, cold water is drawn into the water heater. A flow sensor activates the gas burner, which warms the heat exchanger. Incoming cold water encircles the heat exchanger and leaves the heater at its set-point temperature. Combustion gases safely exit through a dedicated, sealed vent system. More efficient gas tankless water heaters use a secondary heat exchangers to extract more heat from the combustion gas, cooling it to the point where there is condensation—hence these types of heaters are called “gas condensing.”

Solar Water Heater

Solar water heaters come in a wide variety of designs which all include a collector and storage tank. They use the sun’s thermal energy to heat water and are typically described according to the type of collector and the circulation system.

Motors and pumps represent a substantial opportunity for energy efficiency improvements. The International Energy Agency estimates that electric motors (including those that drive pumps) account for 69 percent of electricity use in the industrial sector, 38 percent in the commercial sector, 22 percent in the residential sector, and 39 percent in the transportation and agriculture sectors combined.

Variable Speed and High Efficiency Motors

A variable speed drive (VSD) is a type of adjustable-speed drive used in electro-mechanical drive systems to control AC motor speed and torque by varying motor input frequency and voltage. VSDs are a relatively new technology that has not yet been widely implemented. The installation of VSDs closely correlates motor demand to the effort expended by the motor and, therefore, results in significant energy savings.

Automated control technology enables building managers and owners to reduce the need for lighting, heating or cooling during low-occupancy hours of operation.

Lighting: Occupancy Sensors and Timers

An occupancy sensor is a lighting control device that detects occupancy and turns the lights on or off automatically, using infrared, ultrasonic or microwave technology. Timers are set to turn lights or other equipment such as fans off after a specified period of time.

Lighting: Dimming controls

Dimmers are devices used to lower the brightness of a light. Modern dimmers are built from semiconductors and are highly efficient since they dissipate very little power compared with older, variable resistor-type dimmers.

HVAC: Programmable Thermostats

A programmable thermostat is a thermostat which is designed to adjust the temperature according to a series of programmed settings that take effect at different times of the day. Heating and cooling losses from a building become greater as the difference in temperature between the interior and exterior increases. A programmable thermostat allows reduction of these losses by allowing the temperature difference to be reduced at times when the reduced amount of heating or cooling would not be objectionable to occupants or detrimental to processes.

HVAC: Building Automation Systems

A building automation system improves occupant comfort and achieves efficient operation of building systems. Such systems can reduce energy consumption and operating costs through the automatic centralized control of a building’s heating, ventilation, air conditioning, lighting and other systems.

Process Equipment: Automatic Scheduling

Process controls schedule the amount of time that equipment is required to operate by continuously turning the equipment on and off as needed.

Smart Meters

A smart meter is an electronic device that records the consumption of electric energy in intervals of an hour or less and communicates that information to the utility for monitoring and billing. Smart meters enable communication between the meter and the central system. These types of meters may also communicate with ‘smart’ equipment, depending on device design as well as intermediary communication between the meter and other equipment, such as a Wi-Fi network or a power line carrier network. Smart meters provide greater control over the quantity of energy consumed and time-of-use.

Since smart meters allow consumers to monitor household electricity consumption rates in real time, they can be paired with other behavioral incentives (i.e. price signals during peak consumption hours) to positively reinforce energy conservation. The American Council for an Energy-Efficient Economy (ACEEE) reported in 2012 that across nine pilot studies involving real-time energy consumption feedback using smart meters, the average savings was 3.8 percent.

Transportation: Vehicles

Several jurisdictions around the world have put regulations into place to improve the average fuel economy of vehicles, such as the Corporate Average Fuel Economy (CAFÉ) standards in the United States. Improvements in fuel economy are measured using miles per gallon (mpg) for this particular standard. Technological improvements include higher efficiency drivetrains and improved aerodynamics.

Transportation: Low-rolling Tires

Fuel-efficient low-rolling tires use tread design and new materials to minimize the amount of gasoline required to move the car.

Agricultural: Water Distribution Systems (Drip Irrigation)

Drip irrigation, also known as trickle irrigation, is a method that saves water and fertilizer by allowing water to drip slowly to the roots of plants, either onto the soil surface or directly onto the root zone, through a network of valves, pipes, tubing and emitters. Drip irrigation is more efficient than sprinklers or flood irrigation because a much higher proportion of the water delivered to the plants is absorbed by the soil. Drip irrigation saves energy by reducing the quantity of water that needs to be supplied and pumped.