Proper ventilation is a key feature that all buildings need. However, it involves deliberately cutting holes into your house that can cause unwelcome drafts if the extractor fan ventilation system is not properly installed and equipped.
In this article, we will review backdraft damper installation as well as how to fix an existing backdraft damper. I have also included helpful videos that show step-by-step processes of installing dampers and fixing common issues.
Backdraft dampers are supposed to stop wind from blowing through an extractor fan. If there is no backdraft damper, install one. Dampers can also be ineffective if the seal is broken or the blades are damaged or blocked. Seals can be replaced and blockages cleared, but if the blades are damaged, the damper need to be replaced.
How Do Backdraft Dampers Work?
Backdraft dampers are used to allow air to flow out of a building and prevent outside air from coming into a building.
By regulating airflow, backdraft dampers prevent backdrafts (obviously!) and promote efficient use of cooling and heating systems by preventing the loss of conditioned air and the entrance of unconditioned air.
Backdraft dampers are made of hinged blades that move to block or allow air to pass. This creates a one-way tunnel that will allow air to circulate out of the building, but prevent unwanted air from coming in.
Benefits of a properly working backdraft damper include consistency in temperature, reduced odors, and removal of harmful particles (like germs and bacteria) from the air.
Check for a Backdraft Damper
If you don’t have a backdraft damper, that is the reason why wind is blowing through your extractor fan. Here’s how to check for one in a few simple steps:
- Locate the exhaust duct in your home – it should lead outside and may be accessible by the attic or basement.
- Look inside the duct opening for a round, tunnel-like device with one or more moveable blades or flappers that span the diameter of the duct.
If you are unable to find a backdraft damper, installing one is a simple solution that will keep the wind out of your extractor fan.
How To Install a Backdraft Damper
Before installing a backdraft damper, it is a good idea to clean the area where you’ll be placing the device. This ensures that no dust or particles are accumulating in the duct.
Measure the exhaust duct where the damper will go, and purchase a damper with the same measurements. For a high-quality, well-priced option, check out the AC infinity damper (amazon link).
Next, insert the damper into the duct. The device may be smaller or have ridges on the side that should enter the duct. Most backdraft dampers will work whether the blades are orientated horizontally or vertically, but the blades need to open towards the outside.
You will need to drill three evenly-spaced screws into the damper. Place them where the duct overlaps with the edge of the damper.
To ensure the best seal possible, you can caulk along the damper’s edge.
Check the Condition of the Existing Damper
If you already have a damper, you will need to examine it to figure out what’s causing the problem. Here is a helpful table about different issues it may have.
| Problem | How to fix it | Helpful video | Helpful Amazon products |
| The caulk is lifting or breaking | First, remove the old caulk with a putty knife. Next, clean the area where the old caulk was. Finally, apply the new layer of caulk. | How to caulk | Caulk Putty knife |
| The seal (or clamp) is broken, or the damper is loose in the duct | Replace or install a duct clamp to close the space between the damper and the duct. To install the clamp, just place it around the damper and tighten using a flathead screwdriver. If your ducts are aluminum, you will need to use HVAC tape instead of a clamp to avoid crushing the duct. | Installing a duct clamp How to use HVAC tape | AC Infinity duct clamps Flathead screwdriver HVAC tape |
| Duct blockage | Hold the blades of the backdraft damper open. If there is an object blocking the damper or duct, remove it. If not, cleaning the duct may help. You can hire someone to do this for $467 on average (USA). Refer to the linked video demonstrating a detailed process for cleaning ducts yourself. | How to clean air ducts | Duct cleaning kit |
| The damper needs to be replaced (blades are bent, pitted, or cracked) | If none of these strategies resolve the problem, you will need to replace the damper. Remove the screws, tape, seal, or anything else keeping it in place. To install the new damper, refer to the ‘How to install a Backdraft Damper’ section of this article. | Back Draft Damper | AC Infinity backdraft damper |
Sources
https://www.doityourself.com/stry/how-to-install-a-damper-in-ductwork
https://homeguides.sfgate.com/replace-hvac-dampers-102446.html