HVAC: Heating, Ventilation, and Air Conditioning

HVAC which stands for “Heating, Ventilation, Air Conditioning”, refers to the different control systems in a building used for moving air between indoor and outdoor areas, along with heating and cooling a residential or commercial environment. An HVAC system is a control system designed to maintain thermal comfort, safety requirements, sustainability and efficiency. It helps to ensure the comfort and health of occupants of a building. 

HVAC system types come in many forms, some are split system heat pumps, which provide both heating and cooling. The HVAC system could also be a furnace and air conditioning unit, and any ducts or vent-work designed to release moisture. However, not all units within HVAC are air conditioning units; HVAC components often fall under many of the same umbrella. The HVAC process works by keeping the air inside comfortable, absorbing heat from the indoor air and releasing it outside the building. HVAC systems can also include heating elements, these heating elements can be powered by various sources, including natural gas, electricity, or even solar panels, helping to keep the air inside comfortable in any weather using an HVAC system.

HVAC systems also help to improve the air quality within a building. They do this by using air filters to remove dust, allergens, and other contaminants from the air, and by using ventilation systems to bring in fresh, clean air from outside. Overall, system efficiency, effectiveness, and suitability are vital in maintaining temperature control and comfort of the occupants; not to be taken lightly when choosing a control system for a building in HVAC.

What is HVAC?

HVAC controls the climate for a building, ensuring the comfort of it’s occupants; HVAC system control includes regulating the temperature and humidity, as well as improving the air quality by filtering and circulating the air. HVAC systems can also help to conserve energy by using energy-efficient technologies and techniques, such as insulation and programmable thermostats. In addition to maintaining the comfort of the occupants, HVAC systems can also help to protect the building itself. For example, an HVAC system can help to prevent damage caused by excess moisture or extreme temperatures. It can also help to extend the lifespan of the building and its components, such as the roof, windows, and other technology.

Technology used for climate control in HVAC is essential for maintaining the comfort, health, and well-being of the occupants of a building, as well as the integrity of the building and it’s heating, ventilation, and air conditioning.

Heating

The HVAC system is responsible for regulating the temperature inside a building, and the heating component is an essential part of this process. It works by generating heat and distributing it throughout the building, helping to keep the air warm and comfortable for the occupants.

There are a variety of ways in which the heating component of an HVAC system can be powered. Natural gas and electricity are two common sources of energy for heating systems, but other options such as wood-burning stoves or solar panels can also be used.

The heating component of an HVAC system is typically paired with the ventilation system, which helps to circulate the warm air throughout the building. This is especially important in larger buildings, where it can be difficult to evenly distribute the heat.

The HVAC system can also be designed to take advantage of the outdoor air temperature to help heat the building. This is often done by using a heat pump, which is a type of air-conditioning system that can be reversed to also function as a heating system. Heat pumps work by transferring heat from the outdoor air into the building, making them an efficient and environmentally-friendly way to heat a building.

Heating plays a crucial role in maintaining the comfort of the occupants of a building, especially in cold weather. It works in conjunction with the ventilation system to circulate and distribute the warm air throughout the building, helping to keep the occupants warm and comfortable with heating, ventilation, and air conditioning.

Furnaces Within an HVAC System

Home furnaces heat air which is moved into the living areas through ducts. Some furnace designs, like wall units, can directly discharge warm air. The furnace uses various fuels such as gas, oil, solid fuel, and more. Gas furnaces, the most common type of furnace, heat buildings by drawing air in and forcing it into the heat exchanger, which heats to the desired temperature and blows the heated air back through the home. Oil furnaces work similarly.

Boilers Within an HVAC System

In HVAC, high-temperature boilers, commonly found in commercial and industrial applications, supply steam to the piping zone circuits. Low-temperature boilers, commonly found in residential areas, produce hot liquid, supplying heat to the piping zone circuits. Both boiler types are commonly gas-fired. A boiler heating system is preferred by many because of its extremely even heat zoning capabilities. Hot water to the tap is also possible, with a type of hot water tank installed using a zone of its own.

Ventilation

Ventilation is an important component of the HVAC system that is responsible for providing fresh, clean air to the occupants of a building. It works by bringing in outdoor air and circulating it throughout the building, helping to improve the air quality and maintain a healthy environment.

The ventilation component of an HVAC system is typically paired with the air conditioning and heating components, which help to regulate the temperature and humidity of the indoor air. This is especially important in buildings where the occupants are present for long periods of time, such as offices or schools, as it helps to ensure that the air is comfortable and healthy to breathe.

In addition to improving the air quality and comfort of the occupants, ventilation can also help to protect the building itself. By bringing in fresh, dry air from the outside, ventilation can help to prevent damage caused by excess moisture or mold growth.

The ventilation component of an HVAC system plays a vital role in maintaining the air quality and comfort of the occupants of a building, as well as protecting the building.

What Is Ventilation Ductwork?

Home ducting
Home ducting

Ductwork is the system of flex and solid tubes that circulate air throughout your home using a fan or furnace blower.

Ventilation systems use air ducts and vents to transport air in and out of a building. The filters in these systems need to be regularly checked, replaced, or cleaned (if washable) to work correctly. Ductwork is the most common way that HVAC systems transport air. Ductwork is directly connected to the HVAC system. Homes with ductwork have a network of ridged and flex tubing to carry air-conditioned or heated air throughout the home. Ductwork systems require testing and balancing for effective operation. Ventilation equipment is used for exchanging indoor and outdoor air. The ventilation mechanism in an HVAC system is responsible for moving air into and out of your home.

There are many types of ventilation equipment used in HVAC systems. Some components of this equipment include blowers, fans, ductwork, and filters. Replacing or maintaining this equipment is important to keep your system running efficiently. Ducts are necessary for forced air systems and transporting both hot and cold air. Ducting grilles should be best positioned to eliminate stale air pockets. Ventilation and air dispensing points from the duct system come in different forms, such as wall, floor, or ceiling vents. Chimneys or flues ventilate hot combustion or exhaust gasses out and away from the home. High-efficiency furnaces operate with a cooler exhaust gas temperature, commonly disperse to the outside, on the sides of buildings away from windows, doors, and vents.

Air Conditioning

The air-conditioning system is a key component of the HVAC system. It is responsible for cooling and dehumidifying the air inside a building. The system works by using refrigerants to absorb heat from the air, and then releasing that heat outside the building. This helps to regulate the temperature and humidity inside the building, keeping it comfortable for the occupants.

In addition to cooling the air, the air-conditioning system also helps to improve the air quality within a building by circulating and filtering the air. It can also work in conjunction with the ventilation system to bring in fresh, clean air from outside.

While the main function of the air-conditioning system is to cool the air, it can also be used to heat the air in certain situations. This is often done by reversing the flow of the refrigerant through the system. This can be useful in buildings that are located in climates where the temperature can vary widely throughout the year.

The air-conditioning system plays a vital role in maintaining the comfort of the occupants of a building. It helps to regulate the temperature and humidity, and also helps to improve the air quality within the building.

Air Conditioners within an HVAC System

Air conditioning is a subset of HVAC and involves cooling and humidity control for buildings, whereas HVAC encompasses all aspects of thermal comfort control within an enclosed space. In the construction industry, the term HVAC is often used instead of AC.

Air conditioning units operate under a shared concept, from window units to package units to rooftop units and onto the standard split system heat pumps; they all use refrigerant and coil heat exchangers. Heat is absorbed from the inside air evaporator coil by the cold refrigerant and carried out to the condenser coil, finally dispersing into the outside environment via refrigerant in the outside condenser coil. Some exceptions include recreational vehicle ammonia units, swamp coolers, commercial chiller systems, and geothermal.

An air conditioner unit generates cool air by removing heat, which creates cool air. The cooling system uses a liquid/gas chemical called the refrigerant, or Freon. The evaporator coil (AC heat exchanger) is very cold when running and extracts heat from the passing air. The heat is absorbed by the circulating refrigerant in the evaporator and dispensed to the outside environment. A cold evaporator turns the warm air humidity into beads of liquid, which fall into a collector tray below, for dispensing to the outside through the condensate drain line.

Central air conditioning systems, like central air conditioning and heating systems, condition air from a centrally located unit called the air handler. The conditioned air is moved through ducts to the targeted rooms. Central air systems are generally more expensive to install and maintain than individual air conditioning units. Additionally, central air systems cool the entire home at once, while individual air conditioning units can only cool one room or area at a time.

Heat Pumps Within an HVAC System

A heat pump moves heat from one place to another with refrigerant. Heat pumps have two parts: air handler and a condenser unit. Together, these are also referred to as split systems. Some split systems are cool-only and do not provide heat. A heat pump cools inside air or heats inside air depending on the refrigerant flow direction request. The condenser unit, upon command, controls the refrigerant flow direction, depending on the refrigerant flow direction request: heat or cool mode.

HVAC Measurements and Calculations

HVAC systems are measured based on energy efficiency, capability, power, size, and more. Below is a list of terminology and how they are used to measure HVAC systems:

  • BTU stands for British Thermal Unit. BTUs are a way of measuring how much energy is needed to heat or cool a space. The higher the BTU rating, the more power your system will need to heat or cool a room.
  • SEER2 Rating measures the cooling efficiency of an HVAC system.
  • HSPF2 Rating measures how efficient an HVAC unit is at heating.
  • AFUE means “Annual Fuel Utilization Efficiency”. AFUE for a home furnace or boiler, analogous to miles-per-gallon for automobiles, gauges the efficiency of a system to convert energy into warm air from fuel.
  • CFM means “Cubic Feet per Minute”, which is a way to measure how much air an HVAC unit can move. A higher CFM rating means that the system can move more air in a shorter amount of time.
  • CADR means for “Clean Air Delivery Rate”. To calculate Clean Air Delivery Rate (CADR), the volume of air in a room must be taken into account. In addition to CADR, the effectiveness of filtration is important when considering the air we breathe indoors.
  • Watts are a unit of measurement that tells you how much power an HVAC unit uses. The higher the wattage, the more electricity your system will need.

Common HVAC Components

Below is a list of HVAC parts and their functions:

  • Compressors can be considered the heart of the system. The compressor circulates the refrigerant.
  • Refrigerant is a chemical mixture that absorbs heat and collects and transfers heat within HVAC systems.
  • Condensers disposes of the inside air collected heat in cooling mode and collects heat from the outside air in heat mode.
  • Coils are heat exchangers, transferring heat from the air to the inside refrigerant. These heat exchangers can also transfer heat from the inside refrigerant to the outside air to cool buildings.
  • Fans are blower motors that help move air through coils.
  • Thermostats detect temperature and control the HVAC system.
  • Combustion chambers consists of flame burners and a heat exchanger, creating usable heat.
  • Carbon dioxide detectors, which alarm the occupants when carbon dioxide is detected, are required when any flame-producing appliances are used or when a garage is attached to a home.
  • Radiators heat the air with convection by transferring it from heated water.
  • Pipes transport water to radiators and act as a heat source for radiant heating systems.
  • Blower motors deliver warm air via ductwork in forced air systems and also play a role in cooling some HVAC systems.
  • Air Filters ensure that air remains as clean as possible and protects the system from dust and other contaminants.
  • Ducts help transfer air to the intended locations.

What Does an HVAC System Do?

The primary purpose of an HVAC system, and within it, the HVAC unit, is to regulate the temperature and air quality inside a home or building. As part of an HVAC system, HVAC units can include a furnace with an air conditioning unit or heat pump, as well as ductwork and other equipment to improve indoor air quality. HVAC units can also include air purifiers, filtration, and humidity control systems. HVAC also includes a mechanical ventilation system and/or natural ventilation, which has the role of keeping your home at the ideal clean air level. These combined systems, by controlling humidity, ensuring proper ventilation, and removing excess moisture, ensure a comfortable indoor environment. HVAC can also filter out airborne particles like dust and pollen, helping to create a healthier living environment.  Depending on the type of home, there may be additional HVAC components such as air purifiers, infrared and UV lights, dehumidifiers, humidifiers, and zoning systems.

  • The furnace heat exchanger and evaporator unit (air handler).
  • Condensing system (compressor and line set).
  • Control system (thermostat)

The thermostat is the HVAC unit’s command center and human interface, allowing for temperature, humidity, and scheduling adjustments. In today’s HVAC systems, a smart thermostat is preferred. There are also many electrical components needed to keep this mechanical system operational.

How Does an HVAC System Work?

HVAC Equipment Diagram

The HVAC system perfects indoor air quality and comforts everyone inside a building. Fresh air is either heated or cooled while removing excess humidity via the air handler before being sent into the home (through a network of ducts and registers for central systems).  There are different types of HVAC systems, but they all share a basic HVAC concept: The importance of fresh air. A new home building requirement is a fresh air intake method. If natural ventilation is insufficient to the required percentage, self-standing mechanical ventilation must be applied like whole-home ventilation systems, or special-design restroom ventilation fan units. HVAC systems with fresh air ducting draw outside air into the air handling unit, moving through filters which remove dirt, dust, allergens, and other particles.

An HVAC system’s equipment might work separately, like a radiant heating system combined with window air conditioning units. More commonly, HVAC equipment works together as one system, like a central heating and AC system using a single blower to move warm or cool air through ducts inside of a home. Another type of system is a ductless system that can heat or cool separate rooms or areas in the home independently.

HVAC systems circulate air using the air handler’s blower, sending the air through a series of ducts in the home; or with a ductless system, the controlled air services separate rooms or zones in the home independently.

HVAC System Types

The four most popular HVAC systems include: Split systems, ductless systems, hybrid systems, and package heating and air systems. Each HVAC system type has its own design use; the future of the HVAC industry, including the latest SEER2 requirements, continues to strive toward higher energy efficiency. The type of HVAC system you have will determine how the different parts work together to heat or cool the air in your home.

What Is an HVAC Split System?

Air handler in a split system
Air handler in a split system

A split system is a mechanical configuration of a forced air system and is the most popular type of HVAC unit in residential buildings. Split HVAC systems consist of two separate machines working together: one outside, the condenser unit, and one inside, the air handler. The HVAC unit that’s inside called the furnace or air handler. Typically, these are located in a basement, garage, attic, or a specially designed closet. The indoor unit contains an evaporator coil that removes heat and moisture from the air, while the outdoor unit contains a condenser coil that releases the heat outside your home. The HVAC unit that’s outside called a condenser. The outdoor unit is usually located in an area where noise is less of a concern; it has been known that putting the condenser unit in a shaded area helps with efficiency.

Average cost: $3,800 to $7,500

A split system is a good choice for serving a home. It can work in almost any climate, which is especially useful in areas with both hot summers and cooler winters.

Pros:

  • A split system provides comfortable temperatures in both summer and winter.
  • Customizable to fit your needs.
  • Split systems are the best bang for your dollar in whole-home applications with reasonable operating costs.

Cons:

  • Space outside has to be provided with an airflow area.
  • A fairly specific maintenance program must be followed.

Ductless AC – Mini Split System

Head of a wall-mounted indoor ductless mini-split
Head of a wall-mounted indoor ductless mini-split

Ductless or duct-free systems such as window units and stand-alone emergency units dispense cool air directly without any ducting.

Mini-split units are all mostly ductless, except for a few manufacturer designs that have been engineered to receive ducting. Mini-splits have small wall-mount evaporator units or can be seen as air handlers on the wall. Mini-split systems are evolving quickly into a very versatile concept. The wall mount “air handler units” are actually referred to as heads or cassettes, and newer designs have the ability to run multiple heads off a single or double condenser unit outside. Some of these systems have been installing heads in attics and look like standard duct venting from inside the room.

All ductless systems offer independent room control. Offering silent operation, another major advantage to using a mini-split is extreme energy efficiency.

Average cost: $5,000 to $28,000

Since ductless HVAC systems have no ducting, engineered assistance may be required to introduce natural ventilation capabilities.

Hybrid Split System

A hybrid HVAC system uses both gas and electricity, which makes it more energy efficient. A heat pump system pulls air through a heat exchanger, which uses the electricity in your home to heat the air in emergency heat mode. At this point, the gas furnace takes the place of the electric heat strips reducing high electric costs.

Average cost: $2,500 to $10,000

This is best for people who live in climates that don’t experience extreme temperature swings. They can use a hybrid system, utilizing the most efficient fuel source for each season.

HVAC Systems can be both gas or electric. Hybrid systems, formerly known as dual fuel, use both propane and electricity. Forced air systems can be gas or electric. Both will do the job of keeping your home warm. Gas heaters and electric heating systems work in similar ways.

HVAC Packaged Systems

HVAC package unit
HVAC package unit

A package heating and air system is a type of HVAC system that is, as the name states, an all-in-one unit similar to a very large window unit. Package units are very useful for modular or mobile home use; they sit on pads next to the home and attach to the ducting below the home. They produce both warm air and cool air.

Average cost: $10,000 to $14,000

This is better for people who live in warmer climates and who do not have to deal with extremely cold weather.

Pros:

  • Relatively energy efficient.
  • Compact as in all-in-one installation.
  • Quiet.

Cons:

  • The heating system may need to be larger for some climates.
  • FEMA has an elevation requirement that complies with known or expected 100-year flood elevations; the home has the ability to be set near some 100-year flood areas because they are elevated; however, the package units always end up installed lower than the floor for ducting attachments. This has caused problems at final home inspections.

What Is an HVAC Zoning System?

An HVAC zoning system (also known as “zoned HVAC”) is a zoning system that directs and redirects air through ductwork in order to provide the ideal temperature in a particular area of the home. Zoned HVAC systems allow for the creation of temperature zones throughout the home for more comfort and efficiency. This is done with either hydraulic zone valves or electric dampers in ducts.

Are HVAC Systems Changing in 2023?

Yes. The U.S. Department of Energy (DOE) will begin enforcing new efficiency standards for HVAC on January 1, 2023. The new regulations and codes vary by region.

How Much Does an HVAC Cost?

Not including labor, the average cost of a new HVAC system nationally runs about $7,500 according to Angi. The cost of an HVAC system ranges anywhere from $2,500 (low-end) to $10,000 (high-end), depending on the HVAC system’s size, type, efficiency rating, features, and brand, along with your home’s size and layout.

Additional factors to consider are the cost of labor, which varies based on the HVAC contractor, as well as ductwork and insulation.

How Much Does HVAC Labor Cost?

Most HVAC technicians charge around $40 to $150 per hour, with most homeowners spending $150 to $450 for HVAC service. HVAC labor costs cover wages of the technician (according to the U.S. Bureau of Labor Statistics, the median pay for an HVAC tech is $23.38/hour), traveling expenses, as well as the overhead costs.

What Is the Life Expectancy of an HVAC system?

The average longevity of different HVAC systems: Air conditioning systems and heat pumps, 10 to 15 years; furnaces and boilers, 15 to 20 years; geothermal, 30 years.

It is recommended that all systems be upgraded to the new SEER2 system whenever possible for parts, maintenance, and DOE and Environmental Protection Agency (EPA) requirement reasons.

Which HVAC System Is the Quietest?

Ductless mini-split systems are the quietest air conditioning units on the market today. With an average noise level of 32 decibels, ductless systems are not only whisper-quiet but also offer some of the highest SEER ratings and most efficient performance on the market.

Which HVAC System is Most Efficient?

Mini-splits are a split system containing both a heat pump and an air conditioning unit. The mini-splits in today’s residential HVAC systems are incredibly efficient. Newer systems are often most efficient, with higher energy efficiency ratings – especially SEER2 systems, being required after January 2023.

How to Size HVAC systems?

When determining what size HVAC you need, BTU rating should be taken into account. The HVAC rule of thumb: Your HVAC system should should not exceed 15% of the BTUs needed for heating and 40% of the BTUs for cooling. Heat pumps should never exceed 25% of the BTUs needed for warming and cooling air.

Is Upgrading HVAC Worth it?

The cost of a new HVAC system may be high, but the long-term benefits are worth it. You not only increase property value but significantly reduce utility bills. Just as importantly, many common repair parts along with the technician’s tooling list will be more fit for later model units.

What Is HVAC Maintenance?

HVAC maintenance is one of many HVAC services offered by HVAC companies. HVAC services often include expert HVAC installation, repair, and maintenance.

During regular HVAC maintenance, an HVAC tech should inspect electrical and mechanical connections, motor operations, and thermostat functionality as well as cleaning coils, drains, and elements. The refrigerant pressure should be tested and moving parts should be lubricated. Safety controls should be tested.

It is recommended that HVAC systems have a yearly service from an HVAC technician for preventative maintenance. Periodic inspections can help it run more efficiently and last longer. Bi-yearly inspections are recommended for many HVAC systems for preventing damage, extending the lifespan of your system, and ensuring efficiency. There are some things that you can do yourself to fix common HVAC problems, but it is usually better to have a professional do any maintenance that is recommended by the manufacturer.

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