2019-11-15
Backflap - ventilation in a house with a cooker hood
Backdraft Damper – Ventilation in a Home with a Kitchen Hood
Kitchen hoods connected by ducting to ventilation channels expel humid and contaminated air out of the kitchen. To prevent this air from re-entering the room, a backdraft damper is essential. This makes ventilation effective and safe. Here’s what to remember when installing a kitchen hood in your home.
Hood Connection: Recirculation Mode
There are two ways to connect a kitchen hood. The first is recirculation mode. This involves installing the hood in a designated location (wall, ceiling, countertop, or specially prepared structure) and fitting it with a carbon filter.
The purpose of the carbon filter, which contains activated carbon particles, is to neutralise unpleasant odours created during cooking. Air is drawn in by the hood’s motor, grease and dirt particles settle on the metal filter, and then the air passes through the carbon filter before being released back into the kitchen. The carbon filter should be replaced every 3–6 months.
Recirculation is ideal for those who prefer hoods without a ventilation option (e.g., for aesthetic reasons) or in buildings without a designated ventilation duct.
Connecting the hood is usually quicker and easier and eliminates the need for additional accessories required for ventilation duct connections. A backdraft damper is unnecessary in this case.
Hood Connection: Extraction Mode
An extraction hood, on the other hand, is connected by ducting to a ventilation duct. It operates solely with a metal filter, which should be cleaned monthly.
Air, contaminants, grease particles, steam, and unpleasant odours, such as burning smells, are drawn through the hood’s fan and expelled outside the kitchen and building. This is considered the optimal solution as the hood is more efficient and quieter in operation. We recommend connecting the hood to ventilation whenever possible.
In open mode, a backdraft damper is essential for ventilation, fulfilling several important functions:
- prevents expelled unpleasant odours and humid air from re-entering the kitchen
- protects the interior from cold or contaminated outside air (e.g., exhaust fumes, smog)
- prevents contaminated air from entering other apartments in shared ventilation shafts
Remember: when connecting a hood to an external ventilation duct, be sure to include a backdraft damper in the system.
Home Ventilation with a Kitchen Hood – Types of Ducts
When connecting a kitchen hood in open (extraction) mode, two types of ducts are used:
- round ducts (usually 12 cm or 15 cm in diameter)
- flat ducts (usually 22 cm/9 cm or 20 cm/6 cm)
The duct system should be as short as possible, matching the outlet diameter of the hood’s motor and free of unnecessary bends. The entire length should not exceed 3 metres, but shorter distances are preferable (e.g., 1.5 m). Recommended ducts are PCV ducts – durable, easy to install, lightweight, and economical. Avoid aluminium ducts, as they can increase noise. If your hood’s location requires bends, opt for two gentle bends at 45 degrees instead of one at 90 degrees. The elbow should be installed after about 30 cm of straight duct – avoid placing it directly at the hood’s motor outlet.
When to Install a Backdraft Damper?
A backdraft damper should be installed whenever:
- the duct exits directly to the outside of a residential building
- the duct connects to a shared ventilation shaft (e.g., in multi-residential buildings)
Types of Backdraft Dampers:
- backdraft damper mounted at the hood outlet – typically included with the hood; one of the most common solutions
- Collar with Damper – mounted on the wall where the duct connects to the ventilation shaft
Backdraft dampers can also be used along connected round or flat ducts and come in the following types:
- round duct connector with backdraft damper
The round duct connector with a backdraft damper enables the connection of round ducts while preventing air backflow (using a valve). This model has a diameter of 10 cm (fi 10), made of PCV, and allows duct connections without additional sealant.
- flat duct connector with backdraft damper
Flat ducts are often used when installing downdraft hoods (e.g., in the floor) or ceiling hoods. Using a flat duct connector with a backdraft damper protects your kitchen from air backflow from outside or air entering from shared ventilation channels (e.g., in an apartment block).
Healthy and Effective Ventilation
Ventilating living spaces is one of the fundamental principles of healthy and hygienic living. Ventilating a home by opening doors and windows is insufficient. In the kitchen, where there’s an abundance of steam, grease, moisture, and microbes daily, ventilation is even more crucial. Therefore, whenever possible, connect your hood to a ventilation duct, so impurities are directed outside. If the duct exits directly outdoors or in a single-family home – always use a backdraft damper to enhance ventilation efficiency.