HVAC Systems and Ductwork

HVAC Systems and Ductwork

Whether you’re looking to improve your home’s comfort or boost its resale value, an HVAC system is a smart investment. With a long life expectancy and a new manufacturer’s warranty, you can enjoy years of efficient heating and cooling.


From allergens and germs to chemical vapors, indoor air carries all sorts of unwanted contaminants. High-efficiency HVAC Lexington KY systems can remove the majority of these unwanted particles from your living space.

When you think about your HVAC system, there’s more than just a compressor in the yard or a furnace in the basement. There’s also a system of ductwork running through the house, and that’s where air vents come into play. There are two types of vents: supply and return, and understanding the difference between the two can make a big difference in how well your home HVAC system works.

The main function of supply vents is to push conditioned air into the house. The air is heated or cooled by the heat exchanger inside the HVAC unit, and it’s then circulated through the ductwork to be distributed throughout the house. There are several different kinds of air duct systems, but the most common are a plenum system with the HVAC unit at the center of the house and the ducts reducing into the walls like the legs of a spider, or a perimeter loop system with the HVAC unit on the outside of the home and the ducts encircling it.

In contrast, return vents pull stale air back into the system so that it can be reconditioned and recirculated to the rest of the house. It’s important to keep return vents open in every room and make sure that there are no furniture pieces, draperies, or rugs blocking them.

Many people close the return air vents in rooms they don’t use, thinking that this will save energy and make the rest of the house more comfortable. However, closing air vents actually decreases efficiency and can cost you money. It forces your system to overwork to heat a smaller space than it is designed for, and it also decreases the lifespan of the heat exchanger.


Ductwork is an essential part of HVAC systems. It funnels conditioned air to rooms with vents and returns the air back to the furnace after it’s passed through a filter system. The ductwork is typically made from sheet metal, often galvanized steel with an aluminum or zinc coating. This type of ductwork is durable, rustproof, and less likely to harbor mold than other types of ductwork.

Depending on your needs and budget, you can get a whole-home system of ducts or a smaller duct system that runs in a single room or zone. Regardless of the size of the system, it’s vital to have good insulation and seals to keep hot or cold air from seeping through the ducts into unconditioned spaces.

A basic duct system begins with a plenum, an air distribution box that sends or retrieves air to rooms with air vents from a central air unit. The ducts attached to the plenum connect to branch ducts with reducers that change duct size. The reducers can be round or rectangular, and they’re usually fitted with turnouts, which help minimize air turbulence and resistance to flow.

The main branch ducts may also have dampers, which control the volume of airflow automatically or manually. Vibration isolators, also inserted into the ducts before and after the air handler, cut down on vibrations that could be transmitted through the ducts to the home’s inhabitants. These are rubberized canvas sections that absorb the blowers’ vibrations before they can spread throughout the house. They’re also useful in reducing noise from the blowers. Other duct system components include take-offs, which have openings that allow small portions of air to enter the ducts; turning vanes, which reduce air turbulence and resistance to flow; and acoustic insulation.

Evaporator Coil

The evaporator coil is a key part of your central air conditioning system. These copper tubes house a super-cold chemical refrigerant that absorbs the heat in your home to lower indoor temperatures. Once the AC system reaches your set temperature on the thermostat, the refrigerant moves through lines that connect your indoor and outdoor units to dump the heat outdoors. The blower fan then pushes cool air back into your home.

Evaporator coils come in various types but share the same core design. The coils feature radiator-style fins that help them transfer heat efficiently. A piece of tubing welds into the coil fin assembly to carry refrigerant. More advanced systems use expansion valves to control the flow and increase energy efficiency.

An HVAC technician can replace the evaporator coil in your ductless AC unit, mini-split, packaged HVAC system, or geothermal heat pump. The cost of the replacement depends on the type of HVAC unit and its SEER rating. Choosing an energy-efficient replacement will save money over time.

It’s important to keep the evaporator coil clean because dust and dirt can make it less efficient at transferring heat. These contaminants can also clog the air filter and cause the system to work harder than it should.

The evaporator coil can be found in two variations: an A-coil and an N- or Z-coil. The only difference is that N or Z coils have a third leg of radiator-style fins, which increases the surface area for heat transfer. This extra space allows them to collect (in AC mode) or disperse (in heat mode) more indoor heat, and they are also more compact.

Blower Fan

A blower fan is one of the most critical components of your HVAC system. It’s what moves the air through your ductwork, whether you have a centralized system or a ductless mini-split. Without the blower fan, your system wouldn’t be able to circulate cold or hot air into your home.

When your thermostat signals the blower fan to start, the motor will turn on and begin pushing the air through your ductwork. The ductwork then delivers the air to each room in your house. Ultimately, the goal of your HVAC system is to create ideal living conditions for your household.

The blower fan is also referred to as an impeller fan or positive displacement fan. It’s similar to a centrifugal fan, but it has a higher pressure rise ratio (discharge pressure over inlet pressure). It can be used for a variety of applications, including ventilating, cooling, exhausting, aspirating, and conveying.

Blower motors are available in a wide range of sizes and speeds, making it easy to find the right model for your needs. Many blower fans are designed with variable speed options, which can help prevent hot or cold spots in your home. The right blower motor can also make your system more efficient.

If you notice that your system isn’t operating as efficiently as it once did, it may be time to replace the blower fan. A professional can evaluate your system to determine the root of the problem and recommend the best solution.


Filters protect the mechanisms in your HVAC system from dust and dirt by keeping harmful particulates out of the air. When the blower fan pulls air into your HVAC system, it goes through a filter before being warmed or cooled and pushed throughout your home via ducts. The filter’s material, typically pleated cloth or paper, traps contaminants that would otherwise be recirculated around your home. It’s important to change or clean your filter regularly to keep your HVAC system running smoothly and your family healthy.

There are a variety of different types of filters available, each with its own unique characteristics. Some are designed to be more efficient than others. You can also find filters with varying MERV ratings (minimum efficiency reporting value) that are rated by how many particles they can trap. The higher the MERV rating, the more efficient your filter will be, but it can cause your HVAC system to work harder to push air through the filter.

Spun glass filters, made of strands of fiberglass in either a disposable or reusable format, can stop larger debris like pet dander and mold spores from getting into the blower fan. The strands are also arranged into pleats, which increase the surface area of the filter and make it more resistant to clogging. These are good options for those with allergies or who want a more cost-effective filter, but they don’t offer the same level of filtration as hospital-grade filters.

Pleated filters, often made of polyester fabrics or cotton folds, are more effective than spun glass filters but less efficient than HEPA filters. They have a greater surface area and can trap more particles, including bacteria, viruses, smoke, smog, and droplet nuclei. However, these are a more expensive option and require regular cleaning or replacement to prevent them from clogging.