Reducing Air Leakage: Your Home's Envelope - To reduce your heating costs, your home's exterior walls-also known as the "envelope"-need to be as airtight as possible yet still provide healthy indoor air. Methods to achieve an airtight home are now practiced by many building contractors. Air-sealing measures include wrapping the shell of the new house with an air infiltration barrier and installing gaskets and sealants to thoroughly seal joints and penetrations in the building shell. However, these steps are not foolproof. Complicated floor plans, irregular roof lines, protruding windows, cathedral ceilings, fireplaces, or recessed light fixtures can make air sealing during construction difficult, if not impossible. As a result, homes with some or all of these features often have high heating costs due to excessive air leakage. See section Sources Of Air Leaks In Your Home.
Your Home's Duct Work: A forced-air furnace's air ducts also influence residential air leakage. Homes with furnaces and ducts sometimes have greater air leakage than homes without ducts, such as radiant-heated or baseboard-heated homes. Heat is frequently lost through leaky or uninsulated ducts. Joints between sections of ducts, between ducts and registers, and between ducts and the furnace can lose as much as 30% of the air being moved by the blower.
Leaking ductwork can create positive and negative room pressures that often increase air leakage through floors, exterior walls, and ceilings. Reducing or eliminating air leaks will make your home more energy efficient and comfortable.
The importance of airtight ducts has only recently been recognized by the building industry. New ducts need to be sealed with commercial duct mastic as they are assembled. Existing duct systems can be leak-tested and sealed by an experienced professional. See section Ductwork.
Zone Heating: Zone heating cuts costs by heating the rooms occupied by you or your family while allowing unoccupied sections to remain cooler. Zone heating can produce energy savings of more than 20% compared to heating both occupied and unoccupied areas of your house. Of course, the amount of savings you will achieve depends on how the portable or built-in zone heaters are combined with your centralized heating system.
One recommended zone heating strategy involves controlling the centralized heating system with an automatic setback thermostat. During the times when everyone is at home and active, the automatic setback thermostat provides a comfortable temperature throughout the house. For the remainder of the day or night, it lowers house temperatures to between 50°F and 60°F (between 10°C and 15.6°C). During these setback times, zone heaters provide additional room heat only as needed.
Furnace Filters: Furnace filters are designed to keep the blower, heat exchanger, and ductwork clean. Your furnace cannot run as efficiently if the filters, blowers, and heating coils are dirty. Plus, it is much easier to change or clean filters than to clean blowers, heating coils, and ductwork.
Filters are composed of either fiberglass wool framed in cardboard, air-permeable foam rubber, or fibrous plastic. They are usually positioned near the blower. Depending on the type of filter used in your system, it is a good idea to replace or clean them monthly during the heating season. Read your furnace's instruction manual for more information.
Indoor Air Quality and Ventilation: Many homes that use zonal electric heating systems (baseboard or radiant heat) have very low air leakage rates. Chimneys and leaky ducts promote air leakage, because they can create pressure differentials within the home. This unintentional ventilation keeps the air indoors moving. However, uncontrolled air leakage is a poor way to keep air fresh in any home-and especially in an electrically heated home. A controlled mechanical heat recovery ventilation (HRV) system is the preferred way to provide good indoor air quality.
Zone-heated homes with fairly airtight building shells can have moisture and air pollution problems because of very low air leakage along with the lack of a ventilation system. Mechanical ventilation can remove air pollution and moisture. A relatively airtight, electrically heated home should be supplied with fresh air from a controlled mechanical ventilation system. This ventilation system can consist of exhaust fans, a central exhaust air system, an air-to-air heat exchanger with its own ducts, or an outdoor-air inlet into an electric furnace or heat pump.
Thermostats for Electric Heating: Choosing the right thermostat for your electric heating system is crucial to maintaining a comfortable indoor environment and enhancing your home's energy efficiency. Thermostats are classified as line-voltage or low-voltage thermostats, depending on whether the heater's electric current flows through them. Thermostats are called built-in if they are attached to the heater and remote if they are mounted on a wall.
Line-Voltage Thermostats: The most simple thermostat is the line-voltage thermostat, which is used for baseboard and radiant electric heat. The electricity it controls flows through it-much like a light switch. Line-voltage thermostats can be either built-in or remote. Built-in, line-voltage thermostats are attached directly to the heater and are subjected to temperature extremes. Therefore, they often do not sense room temperatures accurately. While portable electric heaters must have built-in thermostats, baseboard or radiant heaters provide better room comfort when controlled by remote thermostats. Line-voltage thermostats, installed on interior walls, are more accurate because they measure the temperature of the air of the occupied space rather than the temperature at the heater itself.
Low-Voltage Thermostats: Low-voltage thermostats are used on electric furnaces, heat pumps, and on baseboard and radiant heaters in large rooms for better temperature control. Low-voltage thermostats require a transformer to reduce voltage and a relay (remote-controlled switch) to turn the heater on and off.
Low-voltage thermostats are always installed in remote locations, rather than being integrated into the heater. They control temperature more precisely than line-voltage thermostats. Low-voltage thermostats are preferred for larger rooms, heated by radiant panels or electric baseboard heaters, because they produce better comfort.
Automatic Setback Thermostats: Automatic setback thermostats combine a clock and a thermostat to control the heater automatically. They are convenient and very effective at saving energy. If your family has a regular schedule of being at home and away, a setback thermostat could save you 5% to 20% of your heating and cooling costs depending on the duration of setback periods and the degrees of temperature setback.
Automatic setback thermostats can be used to control all types of electric heat. For baseboard and radiant heat, line voltage setback thermostats are available. These are either programmed with a clock or they require the user to push a button at regular intervals to avoid the setback temperature (usually 10 or 15 degrees). See section Automatic And Programmable Thermostats.
Further Information: Many utilities offer grants, loans, or rebates to encourage energy efficiency. Contact your local electric utility for information about residential energy conservation, insulation and weatherization programs, electric thermal storage, or heat pumps.