Heating, ventilation, and air conditioning, which are the three core components of home comfort, form the acronym of HVAC. The HVAC world includes a group of technologies that many of us take for granted until we purchase our own homes. At that point, we’re not only responsible for the monthly utility bill but regular maintenance, potential repairs, and the inevitably of one day replacing that equipment. With that in mind, let us explore the core HVAC concepts that every new homeowner should understand.


Furnaces are the most prevalent residential heating equipment in the United States. The four primary types of furnaces run on gas, electric, oil, and propane. Boilers and radiators are alternatives that involve the use of water to heat a home. Although these technologies are generally not installed in new homes, they are still fairly common in older homes. Another option is the heat pump, and while this technology has long been limited to moderate climates, geothermal heat pumps can be used in hot and cold climates as well.

AFUE Rating

AFUE—annual fuel utilization efficiency—is a rating of thermal efficiency. If a furnace is rated 80%, 80% of the fuel consumed is used to heat the home while 20% is lost. You can use this rating to compare heating equipment and estimate the total cost of ownership.

Air Conditioning

There is a wide range of air conditioner styles, including portable, window, and mini-split. However, the AC system most used in the U.S. is central air. It features an outdoor unit, which includes a condenser and compressor. The indoor unit includes a blower and evaporator, and it is often shared with the furnace or other heating equipment if applicable. Warm air is cooled through the use of a refrigerant. Refrigerant is not consumed as a fuel and, if no leaks happen, should last about 15 years.

SEER Rating

SEER—seasonal energy efficiency ratio—is a rating of air conditioner energy-efficiency. As with AFUE, you can use it to compare air conditioners and to estimate the total cost of ownership of a given unit.

Heat Pump vs Separate Cooling and Heating

The average home in the U.S. has an air conditioning unit and a furnace. An alternative is a heat pump, which can provide both heated and cooled air. Heat pumps transfer heat differently than air conditioners and furnaces. They work by transferring it in both directions—inside and outside the home. As mentioned in the heating section, conventional heat pumps are only practically in climates that neither gets too hot in summer nor too cold in winter. More recent geothermal technology, however, works in almost any climate by tapping deep into ground temperature rather than ambient temperature.


As far as residential HVAC is concerned, there are two types of ventilation: natural and mechanical. Opening a window to enjoy some fresh air is an example of natural ventilation, but even with all access points closed, most homes have some degree of natural ventilation. Central heating and cooling systems distribute fresh, heated, and cooled air through a network of ducts using a blower. This is an example of mechanical ventilation. In recent years, a great emphasis as been placed on the effectiveness of mechanical ventilation. The reason for this is that modern construction has resulted in tightly sealed homes, which can lead to high indoor air pollution if mechanical ventilation does not function well.


A thermostat is your interface to your HVAC system. The most basic of thermostats will detect the current temperature and let you set a target temperature. It will then activate the air handler, heater, and air conditioner as needed in order to maintain it. The proper placement is a core thermostat concept. You should position your thermostat on an interior wall, toward the center of your home and away from sunlight, air vents, appliances, and so on. Failure to do so can result in bad readings and thus poor performance—both in terms of efficiency and comfort. Thermostats are available in a wide range of manual and digital styles. Programmable thermostats let you save by not cooling and heating the air unnecessarily, such as when you are at work. Smart thermostats can learn, be accessed remotely through smartphones, and be customized with apps.

Single vs Multiple Zones

A traditional central heating and air system distributes air through ductwork to the entire home. The entire home is a single zone. Modern HVAC technology allows for multiple zones. You could, for instance, keep the first floor at a different temperature than the second or maintain cooled bedrooms at night but keep the rest of the home at a more cost-efficient temperature. Such systems often involve multiple thermostats, variable-speed air handlers, and even multi-stage heating and cooling. While this may seem complicated, it’s a great way of keeping everyone comfortable in your home.

Single vs Multiple Stages

Conventional heating and cooling equipment are what is known as single-stage HVAC. Essentially, the equipment is either operating or it is not, and when it is running, it has just one temperature setting. Multi-stage heating and cooling equipment have multiple stages. Two and three stages are most common, and you can think of these stages as low, medium, and high. Such systems are generally more efficient because how much energy is used can be modulated based on what is actually needed. Note that zoned central air systems are not necessarily multi-staged, but many of them are.

Humidification and Dehumidification

Humidity in your home affects your comfort because it dictates how you perceive hot and cold. Moist air feels warmer, and dry air feels cooler. Your air conditioner removes moisture from the air in the process of cooling it. But if the temperature and humidity are very high, the air in the home may remain humid because the unit cannot do better than that. In humid environments, an option is to install a whole-home dehumidifier, which will make the home more comfortable and the AC not work as hard. In the winter, running the heat will dry out your air. Whole-home humidifiers are an option, but many homeowners get by with portable humidifiers that they can move from room to room.

Our Family Serving Yours

Our family-owned and -operated company serves homeowners in Los Angeles and throughout the neighboring communities. Jeff Williams—the JW in JW Plumbing, Heating and Air — has more than 30 years of industry experience, and all of our technicians are certified, insured, and highly experienced. We offer a full range of heating and cooling services, including installation, maintenance, and repair. Our team cleans air ducts and specializes in indoor air quality, and you can count on us for all of your plumbing needs. This includes plumbing repair, drain cleaning, and storage and tankless water heaters.

Call us at JW Plumbing, Heating and Air to learn more about these services and schedule an appointment. With our help, you don’t have to be an expert in HVAC technology.

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