AFUE - Annual Fuel Utilization Efficiency. A measure of gas furnace’s efficiency in converting fuel to energy. The higher the rating, the more efficient the unit. For example: A rating of 90 means that approximately 90 percent of the fuel is used to provide warmth to your home, while the remaining 10 percent escapes the exhaust.

Air Cleaner - Also an air purifier; device that removes indoor air toxins and particulates from the air in the home.

Air Handler - Part of your HVAC system that is connected to your home's ductwork and moves heated or cooled air throughout your home via the ductwork.

BTU - British Thermal Unit. This is the amount of heat it takes to raise one pound of water one degree Fahrenheit. For your home, it represents the measure of heat given off when fuel is burned for heating or the measure of heat extracted from your home for cooling.

Bypass Humidifier - A humidifier that uses the pressure difference of the supply duct and the return duct of the HVAC equipment to move air over the evaporative pad.

Capacity - The output or producing ability of a piece of cooling or heating equipment. Cooling and heating capacities are referred to in BTUs.

CFM - Cubic Feet Per Minute. A standard measurement of airflow. A typical system requires 400 CFM per ton of air conditioning.

Comfort-R Airflow System - An exclusive feature of a high efficiency home comfort system from Trane. The method of ramping airflow gives you greater humidity control in cooling and provides warmer air during heat start up.

Compressor - The heart of the air conditioning and heat pump system. It is part of the outdoor unit and pumps refrigerant in order to meet the cooling requirements of the system.

Condenser Coil - In an air conditioner, the coil dissipates heat from the refrigerant, changing the refrigerant from vapor to liquid. In a heat pump system, it absorbs heat from the outdoors.

Damper - A type of "valve" used in ductwork that opens or closes to control airflow. Used in zoning to control the amount of warm or cold air entering certain areas of your home.

Ductwork - Pipes or channels that carry air throughout your home. In a home comfort system, ductwork is critical to performance.

Downflow - A type of furnace that takes cool air from the top and blows warm air to the bottom - common when your furnace must be located in a second-floor closet or utility area.

Electronic Air Cleaner (EAC) - An electronic device that filters out small particles and contaminants in indoor air. It then electronically pulls out tiny particles that have been magnetized, such as viruses and bacteria, drawing them to a collector plate.

Energy Recovery Ventilator (ERV) - A ventilator captures heating or cooling energy from stale indoor air and transfers it to fresh incoming air.

Load Estimate - A series of studies performed to determine the heating or cooling requirements of your home. An energy load analysis uses information such as the square footage of your home, window and door areas, insulation quality and local climate to determine the heating and cooling capacity needed by your furnace, heat pump or air conditioner.

Evaporator Coil - Part of a split system air conditioner or heat pump located indoors. The evaporator coil cools and dehumidifies the air by converting liquid refrigerant into a gas, which absorbs the heat from the air. The warmest refrigerant is then carried through a tube to the outdoor unit (condenser coil).

Gas Furnace Heat Exchanger - Located in the furnace, the heat exchanger transfers heat to the surrounding air, which is then pumped throughout your home.

HSPF - The Heating Seasonal Performance Factor is a measure of the heating efficiency of a heat pump. The higher the HSPF number, the more efficiently the heat pump heats your home.

Horizontal Flow - A type of furnace, installed on its "side," that draws in air from one side, heats it and sends the warm air out the other side. Most often used for installations in attics or crawl spaces.

Humidifier - A piece of equipment that adds water vapor to heated air as it moves out of the furnace. This adds necessary moisture to protect your furnishings and reduce static electricity.

Matched System - A heating and cooling system comprised of products that have been certified to perform at promised comfort and efficiency levels when used together, and used according to design and engineering specifications.

MERV Rating - The Minimum Efficiency Reporting Value is the standard comparison of the efficiency of an air filter. The MERV scale ranges from 1 (least efficient) to 16 (most efficient), and measures a filter's ability remove particles from 3 to 10 microns in size.

Operating Cost - The day-to-day cost of running your home comfort equipment, based on energy use.

Package Unit - A heating and cooling system contained in one outdoor unit. A package unit is typically installed outdoor at ground level or on the roof

Programmable Thermostat - A state-of-the-art electronic thermostat with a built-in memory that can be programmed for different temperature settings at different times of the day.

Refrigerant - A chemical that produces a refrigerating effect while expanding and vaporizing. Most residential air conditioning systems contain R410A or R22 refrigerant.

Payback Analysis - Overall measure of the efficiency and value of your home comfort system. By combining your purchase price and ongoing operating costs, a payback analysis determines the number of years required before monthly energy savings offset the purchase price.

SEER - The Seasonal Energy Efficiency Ratio is a measure of the cooling efficiency of your air conditioner or heat pump. The higher the SEER number, the more efficient the system is at converting electricity into cooling power.

Split System - The combination of an outdoor unit (air conditioner or heat pump) with an indoor unit (furnace or air handler). Split systems must be matched for optimum efficiency.

Thermostat - Unit that monitors and controls your HVAC system products.

Ton - A unit of measure for cooling capacity. One ton=12,000 BTUs per hour.

Total Home Comfort System - The ultimate solution to providing you with consistent, customized home comfort, despite the ever-changing weather.

Upflow - A type of furnace that draws cool air from the bottom and blows the warmed air out the top into the duct work. This type of furnace is usually installed in a basement or an out-of-the-way closet.

Zoning - A method of dividing a home into different comfort zones, so each zone can be independently controlled, depending on use and need.