How to choose the right extraction capacity for your new hood
We recommend you go for a hood vented to the outside with:
- a maximum air extraction capacity as close to 650 m3/h as possible,
- a boost function close to 1,000 m3/h,
- several and/or flexible speed levels starting at 250 m3/h.
Note: Not all the different hood types are equally effective, far from it. Wall-mounted models are likely to do a better job of extracting the hot air and cooking smells from your kitchen than, e.g. free-hanging hoods.
Please also note that your hood’s air extraction capacity might be reduced by over 100 m3 if the tubing is less than optimal.
We recommend extraction hoods vented to the outside rather than recirculation models with a charcoal filter.
In 2016, the EU set a limit on how much air a cooker hood can extract. Prior to this, the rule of thumb for calculating the airflow that was theoretically necessary for efficient removal of steam, smell and grease from your kitchen, made good sense (please see note in the footer). Having said this, the recommendations varied from 10 to 40 times kitchen air volume extraction per hour. Furthermore, the current preference for open-plan or fairly large kitchens means that no hood can extract sufficiently well. Even less so now, with this new legal limit.
Use the EU data sheet
The EU data sheet contains useful airflow information (see info-box below). Since 2016, 650 m3/h has been a key figure for both consumers and manufacturers. It represents the maximum air extraction volume when the hood is on its max speed setting (not boost).
In addition, hoods with a more powerful boost function are able to extract up to 100 m3 before automatically returning to the maximum setting. This means manufacturers can still focus on developing hoods that allow the user to actively increase the airflow when necessary.
Attention should be paid to the difference between max. and boost levels: data available on this at the point of sale is not always clear. This goes for noise data as well.
We note that the 20-20-20 European energy targets seem to be putting constructive pressure on hood manufacturers. It is no longer a race to offer the most powerful (and energy-consuming) cooker hoods. The goal is rather to offer the best possible hood while minimising energy consumption!
The EU data sheet states both the maximum, minimum and the boost capacity. This is extremely relevant legal information, so do use it! To do so, click on the NeutraTEST Score.
The EU Energy Label however, does not indicate the extraction capacity, but only the energy efficiency class for energy consumption at optimal suction (called ’hydraulic efficiency’ or ’Fluid Dynamic Efficiency’, FDE).
The noise indication on the Energy Label concerns max. air suction. This is useful but only directly comparable if the maximum airflow for two hoods is identical. First, you need to check the max. airflow in terms of m3/h for each hood, and then you can compare the noise levels in decibels.
The standard EU66/2014 on environmental performance requirements for energy efficiency, airflow and lighting states the legal extraction capacity for household cooker hoods.
Grease filtering efficiency vs. extraction capacity
One positive result of the generally lower extraction capacities we see today is that the cooking grease has more time to settle in the grease filters (which can be cleaned in the dishwasher) rather than settling in the hood tubing.
We recommend you start by looking at the maximum extraction capacity of the hood, and then evaluate its grease filtering efficiency (GFE). GFE, as indicated on the EU data sheet and the Energy Label, is exclusively measured at max. speed. Typically – and unfortunately – a low max. capacity produces a good GFE result. We prefer a good GFE and a powerful airflow on max level. And some hoods do offer this desirable combination.
Note: A hood with several (adjustable) airflow levels might be very GFE efficient (on the lower speed levels); even if its GFE performance level (at the highest setting) may not appear to be particularly good.
Noise level (dB) vs. extraction capacity
Remember, to obtain a valid noise rating you should compare it against extraction capacity at each speed setting. Sound emission values are to be found on both the Energy Label (max. speed) and the EU data sheet (min., max. and boost). We recommend you take a look: they are useful as well as fair, especially for wall-mounted hoods for which test procedures are now well established. As of October 2016, the acoustic test procedure for noise levels (e.g. IEC 60704-2-13, Edition 3.0) for most other types of cooker hoods has been significantly improved. However, the noise rating on the Energy Label needs to be compared against airflow in order for it to really make sense.
Unfortunately, EU data sheets are often absent or inadequate at the point of sale. When inadequate they often lead to confusion, and the lack of clear information prevents meaningful comparisons being made between different hood models. For an easy overview we recommend our hood comparison chart: our NeutraTEST Score will guide you to the right cooker hood for your kitchen.
Here are some outdated ways of calculating the airflow. Just for your information: information you may find useful:
As stated above, the calculated capacity levels are difficult to achieve with the new energy-saving cooker hoods that remove up to 650 m3/h at maximum level. A powerful boost function is therefore a very useful feature.
- For a closed kitchen, the traditional method requires multiplying kitchen volume (that is height x width x length) by at least 10. The result is the necessary airflow capacity expressed in m3/h. The kitchen should be closed off, with an airshift of 10 times its volume per hour being appropriate when cooking, rarely the case:
Small kitchen 3m x 4m x 2.4m = 28.8 m3 x 10 when cooking = 288 m3/h.
Small kitchen 3m x 4m x 2.4m = 28.8 m3 x 40 when grilling = 1152 m3/h.
- The professional traditional method takes into account the type of cooking being done. Again, based on the size of the kitchen, the premise is that the air should be replaced 40 times per hour when grilling or frying, 25 times when cooking ordinary hot meals and 8 times per hour when preparing cold meals or serving food.
Larger kitchen 4m x 4m x 3m = 48 m3 x 40 = 1920 m3/h.
- The alternative professional method requires that the width of the hood exceed the hob by 25 cm on all sides that have no wall to help guide the air. It is assumed that 0.3 m/s (1080 m/h) is an appropriate airflow regardless of the type of cooking being done. For grilling and frying the value could be defined as 0.5 e.g. (1800 m/h). Hood size is multiplied by stipulated speed, to give the minimum airflow capacity.
Thus with a stove 60 x 60cm placed next to a wall and a cooker hood size of 1.1m x 0.85m = 0.935 m2, you get an average air extraction capacity for all types of cooking of: 0.935 x 1080 = 1010 m3/h. And for grilling and frying of 0.935 x 1800 = 1683 m3/h.
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