Everything You Need To Know To Find The Best Ventilation Dampers

Author: CC

Jul. 28, 2025

HVAC Dampers Guide | How to Find & Adjust for HVAC Systems

What exactly is an HVAC damper, and how can it contribute to the comfort of your home all year? If you're asking this question, you are not alone.

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To be honest, this is one of the less well-known components of a heating and cooling system. The compressor, air filter, vents, and other HVAC system parts are far more well-known. However, most homeowners are unaware that dampers play an important part in maintaining temperature throughout your home.

Our heating and air conditioning Comfort Advisors Team gets a lot of questions about HVAC dampers, their benefits, and how to properly use them throughout the year along with their heating and cooling system. In this guide, we'll cover multiple common questions, including:

  • What are HVAC dampers?
  • Why are dampers used in HVAC systems?
  • What are the different types of dampers used in HVAC systems?
  • Where are HVAC dampers located?
  • Do all HVAC systems have dampers installed?
  • When should I open and closed my HVAC dampers?

Now let's get started with the most frequently asked question on the subject...

What Is an HVAC Damper? What Does a Damper Do in an HVAC System?

Dampers are an important part of HVAC systems. Consider a dam, for example. When closed, a damper prevents the air from going across it like a dam does with water.

HVAC dampers are an important part of your zoning system. They function as valves in the ducts. Their use determines which portion of your property gets heated/cooled air until desired settings are reached. Since cold air sinks and hot air rises, HVAC dampers control the amount of air that is supplied to different parts of your property.

Different Types of HVAC Dampers

There are various dampers that can be found within an HVAC system, and each particular damper serves a purpose. Let's go ahead and break down what each type of dampener does so you know which one is right for your home.

Butterfly Flat Dish Dampers

These dampeners look like little butterflies sitting up on top of the duct work so they get their name from what they look like. They're super easy to install and they don't take up any space. Their purpose is to keep the airflow going in one direction so if you want dampers that can be used for both heating and cooling, butterfly dampers are a great option because dampers of this type only care about pressure, not which way the air is flowing.

Blade Dampers

Blade dampers come with two blades that look like big fans that close slowly together. The effect these have on your airflow happens at the point where the blades meet each other. This creates more of an abrupt stop of airflow than butterfly dampers do but these also work equally well for heating or cooling purposes.

Inlet Vane Dampers

If dampeners are like tiny little doors that close off the airflow, inlet vanes dampers are like small vents that open up and allow air to flow. They don't dampen or direct your airflow but they do help control the pressure of the air moving throughout your entire HVAC system.

Louver Dampers

Louvers dampen down on their own when there is higher pressure in an area. If you need dampers that can only be used for heating season, louvers dampers might be a good choice for you.

Where Are HVAC Dampers Located?

HVAC dampers are most commonly located in the main trunk line right before and after any major junctions. They can also be located at certain points on multiple system ducts, with two dampers found on every main line 90 degrees apart. Although dampers may vary from manufacturer to manufacturer and even from unit to unit, most dampers share a few common characteristics:

  1. They are round discs made of thick fiberglass or dense cardboard (similar to egg crate bedding)
  2. They have a handle that can be turned either direction to allow or stop airflow through the damper
  3. Some dampers have a pointed metal pin attached for easy grip when turning

Every house is different. Some homes have no dampers at all. A supply duct may travel to the right or left off of your furnace depending on where your home is situated. A damper will generally be inserted in the supply duct that leads to your upper level. Examine all of the runs and see if any have dampers if you have exposed ductwork. Some houses include dampers in every run, which is excellent for air balancing.

When Should I Open and Close My HVAC Dampers?

In most houses, dampers on the upper level are opened in the summer and shut in the winter. In the winter, closing the dampers on your HVAC system to the upstairs allows for heat to rise naturally as it is distributed throughout the home. In the summer, the lower level is naturally cooler, and most people report having hot rooms. In the summer, it's critical to open the dampers on the upper level and block as much air from entering the basement as possible.

If you have someone to assist you, one simple method to see whether the dampers are open or closed is to have someone go up and cover each vent with their hand. By covering a bedroom's vent with your hand, you may check each damper to ensure it is open or shut. It takes some cooperation, but it's a fantastic and easy technique to get maximum comfort for hot and cold spots in your house.

When the weather changes, you must know how to adjust your HVAC dampers. It's a good idea to create an alert on your calendar so you're not caught off guard when the house gets too hot or cold. If you label your dampers correctly, you won't be perplexed as to how to alter them.

Suffering From Hot Spots or Cold Spots in Your Home?

Dampers are fantastic, but they may not be enough to fully eliminate hot or cold air spots in your house. There might be a variety of reasons why you're still having air balance difficulties.

At ARS/Rescue Rooter, our team of HVAC system professionals can diagnose weak air flow or air leaks in your ductwork. We can also help replace or repair any existing control dampers in your home. If your heating or air conditioning is experiencing some air duct damper issue, find your nearest ARS/Rescue Rooter location or call us at 866-399- to book an appointment with us today!

Additional Damper Questions & Answers

What distinguishes automatic dampers from manual dampers?

Automatic dampers are controlled by your thermostat or central control system. Manual dampers, on the other hand, must be adjusted by hand. This makes them a more cost-effective solution but also means you will have less control over the airflow in your system.

What is the primary function of guillotine dampers?

These are designed to provide positive isolation and are used most during maintenance on HVAC systems. They serve as a temporary means of regulating airflow, ensuring the integrity of the system as well as efficiency during repairs. This makes them crucial for HVAC maintenance.

How do inlet vane dampers contribute to HVAC system performance?

Inlet vane dampers are critical for modulating airflow and pressure on the inlet side of your system’s blowers, offering precise control over them. They are perfect for anyone looking to fine-tune airflow management within their systems to optimize their overall performance.

What makes louver dampers popular in HVAC systems, and how are they unique in terms of construction and function?

These are used in many HVAC systems because of their versatility and compatibility with various duct sizes. Many choose them because they also feature high-quality construction and reliability for regulating airflow.

How do HVAC dampers benefit homeowners in terms of comfort and energy efficiency?

They control airflow to different zones, reducing hot or cold spots in the home. They also enhance energy cost savings because they optimize the distribution of conditioned air.

Why may dampers not be enough to fix hot or cold spots at home, and what should you do in such situations?

Dampers may not be enough to resolve all your comfort issues because there may be airflow or ductwork problems. This is why you should have professional HVAC technicians servicing your systems to ensure long-term comfort and efficiency.

If you want to learn more, please visit our website E3 Green Technology.

Five Things to Know When Selecting Dampers - MCDLG Newsstand

Damper selection requires more than a keen eye. You need to understand what you're looking for. Here are five things to know when selecting dampers.

Starting a new project and need HVAC equipment? Chances are you’re going to need dampers to control airflow and balance air pressure. Finding the right dampers isn’t a simple task. There are several types of air control dampers out there, and each type will serve a particular function.

Some dampers may perform a similar role, but in specific ways. Other damper types will be specific to the type of duct. Each damper type will work best with the right application. The wrong damper will drag down your HVAC system and even put unnecessary strain on components, like system fans. You will need to know a few things about dampers to make the right choice. Start by understanding what each damper will do in your system.

1 - Know the Application

The application refers to the damper’s purpose in your HVAC system. It will also involve several other factors, such as the damper’s location in the system and the typical operating conditions of the system.

Start by asking the most important question: what do you need the damper to do? Will it direct airflow to other parts of the system? Will it regulate airflow through a particular section of duct? You would use a control damper for these applications. It’s important to know what each damper type does. Check out our article “Five Types of Dampers” for a quick guide to various damper types and their applications.

Know where each damper will be in your system. This will help narrow down your choice. For instance, you may have a section that uses spiral ductwork. You would like to use a round damper for this application. You will also want to review any special considerations for the application. Certain dampers may work better for the same task.

Let’s say you need a damper for moving exhaust air out of the building. You know that the exhaust will only flow out and that air shouldn't be able to pass back through. For this application, you can use a backdraft damper instead of a standard control damper. Backdraft dampers don’t require an actuator to rotate the blades, which saves you money, but they won’t work in situations where air flows in both directions.

You will also need to know a few things about the duct work or opening receiving the damper, such as maximum air velocity. Consult an engineer to determine these data points. It’s important to understand the damper’s application when making your decision.

2 - Know the Size

The next step will be to determine the size of each damper. You will need to know the size of the ductwork or opening to receive the damper.  First, determine the damper's mounting location: over or inside the duct opening. This will involve the type of frame used by the damper, among other considerations.  Our article on damper dimensioning can help.

The final size of the damper will either match the duct or be slightly smaller. When building dampers, manufacturers will often undercut the damper to accommodate both installation types and to account for thermal expansion. If the damper needs to be exact dimensions provided, then you will need to specify exact sizing with the manufacturer. Your dampers will need to fit wherever they go. Make sure each damper is the right size.

3 - Know the Damper

Will the damper perform the task? Learn more about the damper before finalizing your decision. To know the damper, check its submittal for performance data. For most dampers, you will look for air leakage and pressure drop. These two traits will affect the damper’s air performance, or its ability to pass air through its open blades.

Be sure to check for the AMCA rating seals printed on the submittal. Each rating seal verifies that an AMCA-approved laboratory conducted the tests under AMCA standards. An AMCA ratings seal means you can trust the data. A lower pressure drop means air will move more freely through the open damper.

Pressure drop will change based on the damper’s size and on the velocity of air flowing through the damper. A smaller damper will have more pressure drop, because there will be less free area for the air to pass. Increasing air velocity will also increase pressure drop. Determine the maximum air velocity for the duct receiving the damper, then consult the pressure drop graph for the closest size.

Air leakage is also a crucial factor to consider. AMCA shows air leakage as a separate rating, but both ratings may appear on the same rating seal. A Leakage Class will accompany the air leakage rating. Class 1 and 1A allow the least amount of air leakage. The damper may have different class ratings at assorted sizes. Read this article for more information on air leakage.

Review the data and make sure the damper works for your application. By knowing your dampers, you will choose the best one for the task.

4 - Know the Options

Every damper will have optional accessories that help the damper perform its task. Certain accessories, like actuators, are a simple decision for control dampers, but there may be aspects of the applications that you need to consider first.

There are three types of actuators, and which type you choose will depend on a few factors. Engineers commonly choose electric actuators to tie them to a central control system. However, electric actuators need power to operate and will require an electrician to help with the installation process. Pneumatic actuators have a cheaper initial cost than electric actuators, but they need a central air compressor to work.

If your damper is in an easily accessible location, then you can use the cheapest option, a manual actuator, to open and close it. Manual actuators need someone present to pull the handle. Each actuator type has its advantages. Determine which actuators will work best with your application.

Other accessories, like jackshafts, will apply to specific damper types and specific builds. Jackshafts synchronize blade rotation between damper panels, so that they all open and close on the same action. Transition collars allow square and rectangular dampers to be installed in spiral ductwork, but they place the full damper inside the airstream. Counterweights can assist or resist the opening action of backdraft dampers. For a full explanation of the available options, check out our full article on accessories for control dampers.

Not all options will work with your damper. That’s why it’s important to understand your options and what they do.

5 - Know When They Arrive

The last thing you need to know is when to expect your dampers. Manufacturers provide lead time schedules for all their products. Be sure to review the lead times of the dampers when you order them. The exact lead times will differ between damper types. There may also be other factors involved that extend lead times, such as extra-large damper assemblies and dampers made from special materials.

Lead times will not include shipping time. Manufacturers will often provide rush programs to reduce lead times on certain products for an additional fee. Consult the manufacturer if you have questions.

There is more to choosing the right damper than shopping through a catalog. You need to know what dampers you need, and what they can do for your project, for every application. Knowing your dampers is a crucial step in building an efficient HVAC system.

For more information on control dampers, check out these Newsstand articles:

The company is the world’s best Ventilation Dampers supplier. We are your one-stop shop for all needs. Our staff are highly-specialized and will help you find the product you need.

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