VENTILATION TYPES Extraction is when the stale air is extracted to the outside of your house through ducting. With recirculation, the air that enters the cooker hood is cleaned using a carbon filter and extracted back into the room. Most hoods are interchangeable and can be used for either external extraction or recirculation, depending on how it is installed. For recirculation, the hood only requires a carbon filter to very easily be placed inside the hood, whereas the installation for external extraction requires ducting to run from the hood to the outside of the house. Extraction: Extraction (or duct out), is without a doubt the better option. Extraction completely removes any odour, moisture, and harmful air out of the home and allow much better control over air quality. Pros: • Most efficient and economical way to maintain a fresh and healthy environment for inhabitants and reduces moisture that could cause damp / mould to the property. Quieter than recirculation if ducted correctly. Cons: • Requires ducting through an outside wall, which limits its location in the kitchen. • Having a professional fit the ducting is essential. A badly fitted duct would greatly decrease level of extraction (and result in higher electricity bills), cause the ventilation to be noisy and could trap moisture/leak/organic material. • For every meter of ducting or 90 degree bend, the hood loses approximately 25 m³/h extraction, therefore could require a higher extraction rate to compensate. • Generally greater heat loss during winter times, due to blowing out warm air. Recirculation: Top-end cooker hoods with good quality filters works well at eliminating odours, but still require more maintenance in comparison to extraction and the filters are often costly and needs to be replaced frequently in order to stay efficient. The cheaper recirculation filters are often very ineffective when it comes to reducing odour (as low as 30%) and with shorter life-span (as low as monthly). It’s therefore important to study the effectiveness of the filter before making a choice of hood. Pros: • The Hob and Hood can be placed anywhere in the kitchen with little design limitation. • Easy installation with no additional structural work needed (not needed to modify walls) • No heat loss during winter time due to the discharge of warm air. Cons: • Costly filters that require more maintenance. • Depending on the quality filter and use, it needs replacement between once a month to once every 5 years. • Cheaper recirculation hoods generally have poor filters, which means it is of little benefit or function. • Poor control over air-quality and little control over humidity. • Building regulations require new builds to have external ventilation in the kitchen, which means that if recirculation is used, additional external ventilation would be required. • Recirculation requires intensive airing to ventilate the room after cooking to remove moisture (leading to a loss of heat during winter). • Louder than extraction hoods. • Airflow rate is reduced by a carbon filter. WHAT IS THE DIFFERENCE BETWEEN EXTRACTION (DUCT-OUT) OR RECIRCULATION? WHICH IS BETTER EXTRACTION OR RECIRCULATION? Design tip for recirculating hoods: It is advisable to take the exit point into account from where the recirculated air would blow back air into the room. It would be wise to leave an adequate open distance from exit-grid. The more powerful the ventilation the greater the distance would be required. This will reduce the amount of turbulence caused by blowing air back into the room. Allows the installer the option of ducting out from the top (vertically) or straight out the back (horizontally). 01 – VENTILATION TYPES 18
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