How to Install HVAC Zone Control Dampers (Existing Ductwork)

In the past, houses were built to accommodate only a single duct system. Now, bigger and newer homes usually have multiple systems associated with ductwork.

In dual-story homes, the lack of zoning can result in colder rooms on the lower story during winter and hot upstairs rooms in the summer. Due to this, achieving consistent comfort can be challenging.

The great news is that you can increase zones by installing dampers in existing ductwork, even when you have a furnace attached to a single compressor, single air handler, or a heat pump.

If you want to know more on the subject and how to install HVAC zone control dampers, keep reading.

What Are HVAC Zone Control Dampers?

Air Duct Dampers, typically known as duct dampers or HVAC dampers, are movable plates placed in your ductwork. An air duct damper will typically perform two critical jobs:

  • Spreading the central air conditioning to other rooms
  • Regulating the temperature in each room

Due to the amount of energy consumed by air conditioning and heating, any changes you make here will count. That is why you need to understand the importance of location when installing dampers in existing ductwork.

Air Duct Cleaning Service

5 Types of HVAC Zone Dampers

HVAC application dampers come in numerous variations and can be operated in automatic, mechanical, and manual ways. Here are five different types of dampers employed in the HVAC system:

Butterfly Dish Dampers

Specifically designed for increased efficiency and lower maintenance, butterfly dish dampers use a blade on a hinge built for filling the duct.

It restricts airflow when lined up accurately and is very efficient at doing so. These dampers also come with multiple blades if required.

Blade Dampers

Blade dampers are made using thin metal plates. They are excellent for regulating airflow inside air handling equipment such as ducts, chimneys, and HVAC systems.

This kind of damper has blades that move in opposite directions and are designed for their exceptional control and metering.

Guillotine Dampers

Taking its name from the famous 18th-century execution device, Guillotine dampers are most commonly known because they provide the best possible seal.

These dampers maintain a single place to block airflow completely. Furthermore, they can be employed anywhere suitable isolation is required for maintenance.

Louver Dampers

Louver dampers are used for their quick response times and strong air blocking properties. They use flat blades on hinges filling any sized duct and are among the most commonly used HVAC dampers.

Inlet Vane Dampers

Inlet vane dampers are frequently used in fan inlet applications providing better pressure control and flow of materials.

Their use can be most commonly seen in the HVAC settings in facilities requiring complete regulation over their ventilation.

What Do I Need to Install Zoning to My Existing System?

Before you get to install HVAC zone control dampers, you need to arrange for the following things:

Zone Control Panel

This central control panel is responsible for communicating between the dampers, thermostats, and HVAC system. You can think of it as the brains of the general zoning application.

The zone control panel collects information on the preferred zone. It then directs the dampers towards producing enough airflow to satisfy the cooling and heating in every area.

Nest Learning Thermostat – 2nd Generation T200577

They read air temperature in each zone of the house.

If the temperature gets too hot or too cold for your liking, the thermostat sends a signal to the Zone control panel to bring warm or cool air to that zone.

You should install a thermostat in all of your zones/rooms to monitor temperature effectively.

Zone Dampers

Zone dampers are located in the ducts for controlling airflow to specific zones/rooms of your house.

They are wired to a particular zone on a control panel headed by a specified thermostat in your house. The zone dampers open and close automatically, depending on the thermostat.

According to the United States Environment Protection Agency, it is better to label all the ventilation zone components for effective maintenance.

How to Install Dampers In Existing Ductwork: Step by Step Instructions

Now that you have everything you need, let’s get down to installing a damper!

Step 1 – Understanding the Terminology

We all know that cold air descends and hot air rises. You will notice a discernable temperature change in your house in the summer with the air conditioning on or in winter with the heater on.

This can be balanced using a manual or electric damper. The basic installation will be addressed going forward. However, it is better to consult the manufacturer when installing the electric damper.

Step 2 – Cleaning The Ductwork

It is better to clean your ducts before you install HVAC zone control dampers because there might be dust, dander, or allergens trapped within your ductwork.

Step 3 – Installation Location Determination

Observe your ductwork or furnace. If you’re thinking of putting a damper in the line upstairs, you might need to also place one at the other end of the duct.

Step 4 – Measuring

After determining the duct where you want to install the damper, you have to measure its diameter. After measuring, you will require a damper of the same size.

Step 5 – Installing the Damper
  1. Open the duct
  2. Drill two holes on the opposite ends of the duct (the holes must line up with predrilled damper holes)
  3. Remove fasteners from the damper, connect via the new holes and tighten
  4. Seal both sides by using duct tape

If you are installing an electric damper, make sure that it is not in line with any spray or water source.

Step 6 – Seasonal Adjustments

You can adjust the damper according to the season, diverting air to various parts of your home where it may be required.

Automatic Dampers VS Manual Dampers

Some HVAC systems come equipped with manual dampers to regulate the air. A manual damper’s zone control system uses a lever located outside air vents to regulate the flow. Furthermore, manual dampers are easy to maintain and operate.

However, suppose you want a precision control system and prefer auto-regulation of the air. In that case, you should go for automatic dampers. These are controlled via thermostats and are positioned inside air ducts.

Comparing Single-Stage vs. Two-Stage Zone Systems

The two-stage zone system reduces the output of your HVAC system. It runs at 65% capacity on low and 100% capacity on high.

When you have low heating or cooling demand in various zones, the system will also run on a low setting, reducing energy use and cost.

The single-stage system must not be zoned because they always run at 100% capacity. You cannot reduce energy even though you are only using a single zone.

Additionally, because they function at full capacity, it is common to see excessive heating or cooling, leading to mechanical failures and temperature swings.

Problems That Can Develop with Zone Control Systems

However simple it may be to install HVAC zone control dampers, your system can still develop problems with it.

These include:

  • Faulty Thermostat
    It is the most common problem; however, it can most commonly be resolved by restarting it. Replacing batteries or cleaning contact points also makes sure that the thermostat is operating continuously.
  • Stuck Dampers
    Accumulation of dust or lack of lubrication can result in the moving parts getting stuck. Cleaning the dampers is complex and more often requires professional help due to their location.
  • Bad Control Panel
    If the control panel malfunctions, the whole house will be affected. If you find it to be unresponsive, immediately call a professional.

People Also Ask (FAQ)

What Does Zone Damper Fault Mean?

If a damper is closed or open but provides limited airflow, there is a fault in the damper zone. Immediately seek professional help.

How Do You Install A Bypass Damper?

Here is a step by step guide on how to install bypass dampers in existing ductwork:

  1. .Use a duct cutter and drill to make holes in each duct
  2. .Attach a start collar to both the return and supply ducts
  3. .Ensure that you connect each end of the bypass damper to an elbow
  4. .Put the bypass damper between the two collars, and connect the supply duct to the return duct
How Do I Know If My Ventilation Damper Is Open Or Closed?

The damper’s horizontal position means it is open and the angled down position means it is closed. You should never close your dampers completely as it creates excess static pressure inside the HVAC system.

What Is The Purpose Of A Fresh Air Damper?

A fresh air damper controls the inflow of fresh air into the home.

How Much Does It Cost To Add A Zone To HVAC?

Depending on the number of zones, you will get an idea of the cost to install dampers in HVAC. It can range from $2000 to $3300 as a rough estimate. Get a free quote below by using the form we have provided.


Dampers are an efficient way to control the airflow into your house. An effective two-stage zone system can ultimately result in reducing the energy cost.

Therefore, installing dampers in existing ductwork is a process to consider. It is also very easy; all you have to know are your ducts’ dimensions and follow the steps.

Josh Mitchell

Josh Mitchell

My name is Josh and I am obsessed with DIY and improving my family home. HVAC topics can be tricky for homeowners so I decided to share my knowledge on the subject. When I am not working on DIY projects, you can find me at the beach or my local coffee shop.