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Range Hood Letting in Cold Air? (Easy solution)


In general, range hoods need backdraft dampers to prevent exhausted air and cold outside air from entering the kitchen through the hood’s ductwork. Low quality, broken, or wrongly installed dampers will let cold air in through the hood. Replacing, repairing, or reinstalling the damper will solve this problem.

Cold air coming through your range hood is one thing: inconvenient. It’s not easy to cook food when the temperature is affected by unconditioned air, and gas stoves have a higher risk of blowing out, not to mention what it does to your heating bill!

While small amounts of leakage might occur with some dampers, this should be such a small amount that it’s unnoticeable. So, if the leaking is a problem, the question is why. There are a couple of options to consider, and I will help break down the different ways that your damper can be compromised and how you can deal with it.

Do You Have a Backdraft Damper?

Range hoods are not required by the International Residential Code (IRC). However, there are some areas where the local codes do require range hoods to be installed, such as California, and others that require some kind of mechanical ventilation, such as Ontario.

However, if you do decide to install a range hood, then the IRC governs the installation, capacity, ducting, clearance, etc., of the range hood, which you can read about in Section M1503 of the IRC.

Included in these regulations from Section M1503.3 of the IRC is the following:

“The duct shall have a smooth interior surface, shall be airtight, and shall be equipped with a backdraft damper and shall be independent of all other exhaust systems.”

So, if you have a range hood or are looking to install one, it needs to be airtight and it needs to have a backdraft damper.

Kitchen duct and exhaust exiting the house, fitted with a backdraft damper

The only reason that your range hood should not have a backdraft damper will be if the manufacturer’s instructions say so (and even then I would consult a reliable professional on the matter).

What Does a Backdraft Damper Do?

A damper controls airflow, air temperature, air humidity, and air pressure in some way or another. Different types of dampers specialize in various forms of controlling air. A backdraft damper is one of these and serves a specific purpose.

There is a lot to know about them and you might find it helpful to have an ultimate guide to backdraft dampers, but the basic function of a backdraft damper is this: they are designed to allow the air in a duct to exit, but prevent air from flowing back into the system from the outside or from the connecting duct.

4 Inch Backdraft Damper Galvanized Steel Inline Fan Vent with Spring-Loaded Folding Blades and 6 Pieces Duct Clamps for Ducting in Range Hoods and Bathrooms Fans

There are different styles of backdraft dampers that come in several shapes, with or without blades, and various mechanisms for opening and closing. Spring, gravity, and electric mechanisms are used in backdraft dampers.

Importantly, when a backdraft damper closes, it is designed to seal against any air that may try to enter the vent or duct in which it is installed, This it does through the use of a set of blades or flaps.

Checking if Range Hood Has Damper

Your first point of call is to determine if there is a damper on your range hood. If not, your solution is as easy as fitting one into the duct of your range hood.

To locate a damper, you will need to look in one of two places, depending on your residence.

An apartment building will have a backdraft damper nearer to your range hood connection (not right behind it, but nearer than the exterior of the building). In shared residences, backdraft dampers are installed where the private vent or duct enters the central duct for the building.

In a house, you will need to look at the vent where it exits the house. This is often on the roof or wall nearby.

The most common backdraft damper used is a butterfly damper. This valve is made up of two semi-circle plates and is most commonly a round shape. Other dampers might have a set of blades that can lie flat.

Solution: Install a Quality Damper

A quality backdraft damper has high performance without aging or wearing quickly. A good damper is also one that suits your needs. This means that it must be listed and labeled for the function you require and have the correct specifications.

parts of a backdraft damper

Looking for a good quality backdraft damper can be easier than you think. You can look for a backdraft damper that is listed according to the IRC. If you are selecting a damper that can be installed for a range hood as per manufacturer instructions, picking one with the proper IRC qualifications can assure you that it meets all the functionality and quality requirements.

If you are looking for the best backdraft damper for your range hood, you should go for a spring mechanism damper. The spring dampers have a better air-seal than a gravity damper as something physically keeps the flappers from opening a certain direction.

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iPower 6 inch Backdraft Shutter Damper Back Draft Blocker, One-Way Airflow Ducting Insert Backflow Preventer with 2 Inline Springs Loaded Folding Blades, 6", for HVAC Extractor Fan Vent, Range Hoods
  • Lightweight valve wings: The valve wings open under the pressure created by the airflow and then automatically close with the spring work. The backflow flap closes automatically at low air volumes....
  • Keep away from rattling: It has an internal foam strip and a smooth-running spring to keep the valve wings from rattling. The position of the spring should be horizontal for horizontal installations...
  • One-way airflow ducting insert: Back-flow valve with 2 spring-loaded wings prevents the reverse airflow movement through the ventilation duct when the ventilation system is turned off
  • Material: The 6 inch Backdraft damper is made out of a Galvanized steel, the flap leaves are made of aluminum, while the Axis and spring are made of stainless steel and can withstand temperatures from...
AC Infinity 6" Backdraft Damper, One-Way Airflow Ducting Insert with Spring-Loaded Folding Blades for 6” Ducting in Range Hoods and Bathrooms Fans
  • An antidraft duct insert designed for use with range hoods, bathroom fans and other home HVAC applications.
  • Features outer rubber gaskets that create an airtight seal and grip between the damper and ducts.
  • Mounts horizontally or vertically to prevent backflow and debris from entering ducting.
  • Galvanized steel body with spring-loaded aluminum damper blades that open with minimal airflow.
neverest RK 5" Professional Backdraft Shutter Damper Connector Duct
  • The backflow damper prevents the ingress of cold or warm air and wind from entering through the ventilation duct. The 8 inch Backdraft damper is made out of a Galvanized steel, the flap leaves are...
  • Designed for use in air conditioners (AC), dryers, exhaust, extractor or range hoods, heating ducts, vents and other HVAC applications
  • The backflow flap opens and closes automatically at low air volumes. It has a smooth-running spring and an internal foam strip to keep the blades from rattling and can be installed horizontally or...
  • INSTALLATION: The backflow flap is installed by inserting it into the ventilation pipe until it stops. The position of the spring should be horizontal for horizontal installations so that it can open...

Last update on 2022-06-26 / Affiliate links / Images from Amazon Product Advertising API

Installation Tips

  • Ensure that you thoroughly clean the area for the seal.
  • Check that there are no screws or ridges of metal on the ducting that might interfere with the fit of the damper.
  • Wear latex gloves to avoid a big mess on your hands.
  • You can tape around the area you will be caulking to prevent mess.

HVAC OV 4" Inch Backdraft Damper, One-Way Airflow Ducting Insert with Spring-Loaded Folding Blades

Is Your Damper Working Correctly?

The only damper that will isolate outside air will be a backdraft damper with their specialization for letting air out and keeping it out.

If you examine the damper installed for your range hood, it will not be working the way you need it to if it is, say, a balancing damper. These are meant to balance air pressure between the room and the vent or duct.

If you have a backdraft damper, then there are some common issues to look out for if you find your damper is leaking.

Common Causes of Damper Leaks

Stuck Flappers

Your flappers might be stuck due to damaged or malfunctioning mechanisms, because they are bent, because there may be a screw from the duct getting in the way, or it can be due to a build-up of kitchen grease that is gumming up the works.

Cracked Flappers

If the flappers or blades are cracked, this results in a compromised air seal, whether due to the air flowing back through the damper because of the actual chips or cracks or because they prevent everything from sitting flush.

Worn/Pitted Seal

The seal is vital to the purpose of a backdraft damper. Air from the kitchen carries moisture and cooking fumes and by-products, which means mold can easily grow on the seal and compromise it.

If the seal around the damper is damaged in any way or old and worn, the connection between the damper and the ducting will not be airtight.

Improper installation

Backdraft dampers function according to orientation, meaning improper installation can compromise the item. If your damper is installed back-to-front, it will be letting unconditioned air from outside into your kitchen and not allowing the air that your range hood is trying to exhaust out.

Solutions: Fix or Replace

Stuck Flappers

If the damper mechanism is malfunctioning due to corrosion, you can use a rust remover and then grease the mechanism to allow the valve to operate smoothly.

Should the mechanism be damaged, you will need to replace it, which includes situations when the blades have become bent.

Backdraft Exhaust Damper Seal 4 Inch by Calimaero One Size Fits All 4 Duct Backdraft Damper Gravity Powered Made in Germany 4 Inch HVAC Damper Dryer Vent Valve Keep Cold Air Out

Dealing with a screw that is blocking the damper is a little trickier. You are not allowed to have screws or fastenings in place that interfere with the opening and closing of the damper. But you cannot compromise the ducting either. It’s probably best to get a professional consult for this particular problem.

Using a degreasing product, such as Oil Eater Cleaner Degreaser (amazon link), will be effective if your problem is built-up kitchen grime. Kitchen grease is stubborn, but there are products designed to remove it and these are safe to use on your damper flaps. With the gunk gone, the damper should be back to working at full functionality.

Cracked Flappers

You will need to replace your backdraft damper if there is extensive damage to the object. If there is minimal cracking, you might be able to seal it using caulk, but this will likely be a temporary solution only until you can replace the damper.

Seal

Should the seal of your damper be the issue, you should fix this and you can easily do so.

Cut out the seal and remove the damper to clean around it and the ducting properly. Then you can put the damper back and redo the seal. Grab yourself some caulk and reseal the edges.

Installation

If you have a gravity backdraft damper installed and there is no obvious damage, you may want to consider replacing it with a spring version. This is because the spring dampers have better airtightness, and the gravity damper may be allowing cold air to leak in.

You should follow the manufacturer’s instructions for installing the damper. If the damper was installed by a previous owner or resident, you need to make sure that the damper is installed so that the flaps flip up towards you if it is at the exit point, or away from you if it is going into a main ducting line. The air must be able to flow away from the range hood and towards the open air, without being able to push the flaps down and enter back into the house.

Sources

https://www.prolinerangehoods.com/blog/how-to-seal-range-hood-vent/

https://www.prolinerangehoods.com/blog/cold-air-range-hood-vent/

https://www.famcomfg.com/product-info/backdraft-damper/

https://www.ncamfg.com/doc/backdraft-dampers-installation-15930.pdf

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