Home Improvement Blog

It’s all very well having an ideal kitchen layout with every labour-saving appliance imaginable, but if the ventilation isn’t right the kitchen of your dreams could soon become one of your nightmares. So choose carefully to make sure you get the best system for your particular needs.

In its most basic from ventilation can be provided by opening a window, unless you have permanently fixed double-glazing, of course. Open-window ventilation is seldom if ever very effective and in bad weather just not practical; in winter you could also pay a fortune in lost heat. What you need is a mechanical method of ventilation.

The simplest mechanical ventilator is called a ’self-actuating’ fan. This is designed for mounting in a window pane and literally runs on air, the fan blades turning in either direction according to the difference in pressure between the inside and outside air. For the kitchen use, however, this type of fan is rarely suitable because you cannot always extract fumes and steam when you want to; if the pressure is higher outside than inside the fan will draw in fresh air and may, in fact, push the fumes, smells and steam further round the house.

A good kitchen ventilation system must provide you with positive control over fume, steam, and smell extraction, which means installing a system that incorporates an electrically-powered fan. There are two basic types: extractor fans and fan-operated cooker hoods. No kitchen, whatever its size, should be without one or the other.

Extractor fan
The majority of extractor fans are available for window or external wall mounting, although there are ceiling-mounted fans which can be used, for example, in single-storey kitchen extensions. Most leading fan manufacturer have a comprehensive range of leaflets on their products and you would be advised to obtain a selection to help you make your choice.

Window-mounted extractor fans are generally the cheapest to buy and to install. They do, however, tend to be rather noticeable, especially if you have only a small window area in your kitchen. They also restrict your choice of position, which will affect the ventilation efficiency. Most are circular shape, but rectangular models are available if you want one in keeping with the rectangular shape of your window. Mounting in the wall, although involving more work, does make the fan less obtrusive and also gives you greater flexibility in siting.

The correct size of fan is of vital important for effective ventilation. The size is related to the number of air changes per hour recommended and the amount of air to be moved. In kitchens, approximately 15 air changes per hour are required to cope adequately with fumes, steam and smells.  To work out the size of fan required first calculate the volume of your kitchen (length x width x height) in cubic metres (or cubic feets). Multiply by 15 to obtain the total air movement required per hour. Then look through manufacturers’ leaflets to find a fan capable of handling that amount of air.

Siting the fan is also important. It should be as high as possible in the wall or window, in hot air which rises to the top of the kitchen. It should also be sited close to the cooker, if possible, for it is there that most of fumes originate. Don’t place the fan too near an air intake point such as a door or an airbrick, since this will affect the extractor’s efficiency by diverting the flow of fumes away from the fan. Bear in mind you may have to reach a compromise between these various siting considerations to arrive a suitable position.

In certain situation, such as a basement kitchen or a long, narrow kitchen in a terraced house where the cooker is well away from the window, a window extractor or a fan mounted on an external wall may not be practical. Here you will either have to install a combination of extractor fan and ducting to take fumes and steam away from the cooker or fit a suitable cooker hood. If you decide on a ducted extract system contact the fan manufacturer or a heating and ventilating engineer for advice on suitable ductwork/fan combinations as the length and diameter of the ducting must be related to the power of the fan.

There are two further points that are important when designing a kicthen ventilation layout. If you have a gas or a oil-fired boiler in the kicthen there must be provision for air to enter the kitchen when extractor fan is working and the kitchen door is closed or the boiler wull not operate efficiently. Also remember when you extract fumes, smells and steam you also extract heat. This is obviously worthwhile in summer, but can be expensive in winter as you will be paying to put the heat there in the first place. You can, of course, cut this loss by using the fan sparingly but this may mean having to sacrifice some of your ventilation system’s effectiveness. There is, however, a special ventilator available for wall or window mounting which is designed to recover some of the warmth from stale extracted air and return it, mixed with fresh air, into the room space.

Cooker hoods
In most kitchen a cooker hood is an alternative and generally a more expensive one to an extractor fan, although in very large kitchens both can be used to good effect. The cooker hood has the advantage that it picks up most of the fumes, smells and steam at source, which is more effective. It will not, however, deal with the steam from your kitchen sink unless it is close by.

There are basically two types of cooker hood: recirculating hoods simply clean the air and return it to the room, while ducted types extract the air to the outside (in fact, most ducted types can be adjusted either to recirculate or extract). Included in the ducted types are models specially designed for use with island hobs.

The majority of hoods available are of the recirculating type. Though not as effective as the ducted ones they are simple to fit and as no extraction is involved they save heat too. They usually contain two filters: a metal one to catch grease from fumes and a charcoal one to adsorb smells.

If you wish you can have the canopy to surround the basic hood mechanism made to order. This may be circular, three-sided or rectangular and in brass, copper, stainless steel or other metal. A local firm of panel beaters will probably make up the canopy for you, but consult manufacturers on the size of fan needed for the size of canopy.

Siting a cooker hood at the correct height is important. Check with the instruction leaflet for the manufacturer’s recommendations, but as a general rule a cooker hood should be between 560 and 770mm (22 and 30in) above the cooker hob. On cookers with an eye-level grill there should be not less than 300mm (12in) and not more than 450mm (18in) between the hood and the grill. For eye-level grills most manufacturers provide a bracket to extend the canopy an extra 125mm (5in) or so from the wall for maximum efficiency. If a bracket is not supplied you can mount the hood on a suitable wood block screwed and plugged to the wall.
Warning Some types of hood are not suitable for use with eye-level grills, so check with the manufacturer to ensure you buy
the right type.

Operating hints and running cost
Provided you have sited your ventilation system correctly, it should work efficiently from the moment you switch on. Remember it is important to avoid ’short circuiting’ an extract fan system, so if the fan is near or in a window, keep the windows closed when you want to remove fumes in a hurry. It probably will not make a great deal of difference to the ventilation efficiency whether you have the door from the kitchen to the rest of the house open or closed, try it and see. And don’t wait until you kitchen fils with steam and cooking smells to swith on the fan or cooker hood. Switch it on the moment you start cooking to make sure the air stays clean and fresh.

Running costs of electric ventilation systems are very low. Many extractor fans and ductless cooker hoods are rated at less than 100 watts and so will give more than ten hours continuous operation for only one unit of electricity.

Comments are closed.