All Year - What is HVAC (Heating, Ventilation, and Air Conditioning) All About 06

What is HVAC (Heating, Ventilation, and Air Conditioning) All About?

The purpose of an HVAC system is more than just heating or cooling a space. Instead, it serves to improve indoor air quality and provide comfort for everyone within a building.

HVAC stands for heating, ventilation, and air conditioning. An HVAC system provides heating and cooling for all sorts of buildings– both residential and commercial. The HVAC system includes not just the equipment for heating, cooling, and ventilation. It also the technology and processes behind their operation.

A good HVAC system aims to provide thermal control and comfort indoors and is designed thoughtfully using the principles of thermodynamics, fluid mechanics, and heat transfer.

Equipment commonly associated with HVAC systems includes air conditioners, heat pumps, furnaces, air handlers, ductwork, ventilation lines, filters, and products that ensure air quality within an establishment or home.

Parts of an HVAC System

Now that we know that HVAC stands for heating, ventilation, and air conditioning, it stands to reason that these are the three main components of the entire system.


The H, or heating element in HVAC, generally refers to a furnace or boiler. Furnaces come in different types and can use different fuel sources, including the following:

  • Natural gas furnaces
  • Electric furnaces
  • Propane furnaces
  • Oil furnaces
  • Geothermal furnaces

The most common heating systems in Sacramento homes these days are natural gas furnaces and electric furnaces. Winters in Northern California are generally milder (compared to the rest of the United States) but some owners might consider the cost of gas to be prohibitive nevertheless.

Heating also includes the piping system for the fluid that carries the heat or ducts if you are working with a forced-air system. Other components of the home’s heating system include a blower motor as well, which moves air throughout the property.

Another way to heat your home is via a radiant floor, also known as a hydronic heating system. This system uses piping under a floor and is made up of flexible tubes that are filled with water or a glycol solution. Radiant flooring can heat any kind of floor, including concrete, making it an effective method of providing warmth in a home. They can even be retrofitted into wooden flooring, though they need to be carefully installed in sheathing for wooden floors.

A hot water heater, gas furnace, and air conditioning unit.

A hot water heater, gas furnace, and air conditioning unit.


The V in HVAC, or ventilation, is the process of replacing or exchanging air within a space. By doing so, ventilation provides an improvement in indoor air quality. Proper ventilation involves the removal of moisture, smoke, odor, heat, dust, airborne bacteria, carbon dioxide, and other gases, as well as temperature control and oxygen replacement.

Your home’s ventilation system may include any mechanisms that help to process and move air throughout your home and HVAC system. This typically includes:

    • Ductwork, which houses the air that is conditioned by the AC or heated by the furnace.
    • Floor, wall, and ceiling vents, which are located at various exit points of your ducts throughout the home to distribute air.
    • Ventilation shafts, including chimney flues or PVC ventilation for indoor HVAC equipment, help vent excess heat from a system’s furnace.

Some homes may have ductless HVAC systems. There will still be an indoor and outdoor unit (for heating and cooling), but these are usually installed for a smaller, individual room or section of a home, such as a finished basement or attic.

Utilizing a home’s natural ventilation falls into this component as well. The ability to create a decent cross-flow from windows and doors can be an important factor in keeping your home comfortable.

Air Conditioning

Air conditioning is often used interchangeably for any type of home heating or cooling device. But really, the main objective of the air conditioning component is to remove the existing heat from inside the house.

A home will typically have an air conditioning unit installed, while larger properties or establishments might have several of these units in operation. Heat pumps also work similarly to air conditioners, but these can also heat a home (rather than just be limited to a cooling function).

In practice, heat pumps are traditionally paired with electric furnaces, which supplement a heat pump’s ability to provide efficient heat. Meanwhile, air conditioners work in tandem with gas furnaces.

A trained HVAC professional performs preventative maintenance on an air conditioning unit.

A trained HVAC professional performs preventative maintenance on an air conditioning unit.

HVAC Basics

While there are many different types of HVAC systems, they all start with the same basic elements.

How Does an HVAC System Work?

The three main functions of an HVAC system are interrelated, in particular, providing acceptable indoor air quality and thermal comfort. Your heating and air conditioning system is often one of the most complex and extensive systems in your home, but when it stops working, you’ll find out soon enough.

Your HVAC system has eight sections that you should be familiar with including:

1. The Air Return

First, there is a fresh air intake source from outside or from the home. This process is called ventilation and it occurs in two different ways.

  • Natural ventilation is present in most homes and refers to the way air generally enters and leaves through windows, doors, vents, and other openings. This air exchange is necessary to replenish oxygen and remove odor, carbon dioxide, and excess moisture.
  • Mechanical ventilation uses a mechanical system, the V in HVAC, to move air in and out. In the past, most houses had a lot of natural ventilation due to gaps and cracks in the construction, as well as doors that were opening and closing. However, modern construction is creating much tighter sealed homes, which is why ventilation is becoming increasingly important in home HVAC systems.

2. The Filter

Once the air is introduced, it is introduced into an air handling unit where work begins. Here, the air passes through filters to remove dirt, dust, allergens, and other particles.

Furnaces generally come standard with a 1-4 inch filter that traps these particles that enter and pass through your system. These filters need to be cleaned or changed periodically.

3. Exhaust Outlets

These include any areas where heat is vented from the home.

4. Humidity Control

Dehumidifiers and humidifiers are an important part of a whole-home HVAC system. They can lessen the burden on your heating and cooling equipment, not just making you more comfortable but also increasing your system’s overall efficiency.

A licensed HVAC contractor installing a blower motor into a water-based heat pump.

A licensed HVAC contractor installing a blower motor into a water-based heat pump.

5. Electrical Components

Each major piece of HVAC equipment needs to be able to relay information to other relevant areas of the system. This is particularly true when you have multi-speed equipment that adjusts automatically to the temperature. Proper electrical circuitry and controls manage all of this.

6. Thermostats

Thermostats are the endpoint for user control over the system and relays instructions throughout the system. Depending on how complex your system is, and how much it needs to communicate with various devices, several electrical inputs may be needed in a thermostat.

7. Compressor

The compressor is a major part of an air conditioner or heat pump. It is what regulates the pressure of the refrigerant. Because it works a lot when your system is in use, the compressor requires routine maintenance to avoid breakdowns.

8. Coils

Coils absorb and transfer moisture and heat, and help to regulate the temperature of the refrigerant. The size of the coils can vary significantly depending on the efficiency of your unit.

Examples of HVAC Systems

You can find HVAC systems anywhere, from single-family homes to malls to large multinational offices, where they provide a more comfortable, more pleasant environment for those within.

Heating and air conditioning units in a Sacramento home.

Heating and air conditioning units in a Sacramento home.

Some examples are the large air conditioning boxes that you can see on top of apartment or office blocks of (the visible part of) HVAC systems. They are typically used in large industrial buildings, skyscrapers, apartment blocks, and large indoor environments. They are also an essential part of environments where there are sanitary regulations that require maintaining temperature and humidity at certain levels, using air extracted from outside.

The heating and cooling systems you use in your home are also similar to these larger, more elaborate HVAC systems. They may take a different form, but many of the basic principles that determine their operation, as well as their effectiveness, remains the same.

What is the difference between HVAC and air conditioning?

Is there actually a difference between HVAC and air conditioning? Well, air conditioning is the last part of the term “HVAC” so think of HVAC as the all-encompassing term and air conditioning as a piece of the puzzle.

Who Can Service HVAC Equipment?

Unless you’ve received training in HVAC repair and maintenance, you’re better off leaving the service of your HVAC equipment to the professionals.

Installing or servicing HVAC equipment requires years of training as well as state, local, and national certifications as required by your area. 

Small tasks such as replacing filters might be done by any homeowner. But when we’re talking about unit repairs, part replacements, or full installations, let’s call in a properly licensed HVAC contractor. Contact the All Year team today!

An HVAC technician pulls a breaker from a condensing unit.

An HVAC technician pulls a breaker from a condensing unit.