In apartment blocks, terraced houses and holiday homes, the removal of cooking smells is often arranged via a ventilation unit.
It is recommended to implement the cooking smell removal with a system that is independent of other ventilation – with a cooker hood or a combination of a cooker hood and roof fan. When an independent system is used, the extract air flow from the cooker is usually significantly higher than an extract air flow generated by the ventilation unit. Cooking smell removal through a ventilation unit is, however, common in apartment blocks, terraced houses and small holiday homes, and there is no obstacle to it in terms of technology or building regulations.
There is no need to bypass the heat recovery of cooking smell removal
A frequent question is whether cooking smells should bypass the heat recovery cell inside the ventilation unit. If a Vallox ventilation unit is used, there is no need for a bypass. This is because the plate heat exchanger never brings the smells and humidity from the extract air back into the supply air.
Vallox has also studied the issue with regard to the reliability of the ventilation system and has found that if a heat recovery bypass is used for cooking smell removal, it may cause problems to the ventilation unit in winter. This is because bypassing the heat recovery reduces the volume of warm extract air passing through the cell, while the flow of cold outdoor air remains unchanged. In such circumstances, the freeze protection of the unit responds too early to the outdoor air temperature; at worst, the cell may freeze completely.
It is also possible that the cooker hood damper may remain open despite the timer. If heat recovery is not working properly, the need for more efficient post-heating of the ventilation unit increases, and the temperature of air blown into the home may decrease. If post-heating is arranged with a water-circulating radiator, a bypass situation also increases its freezing risk.
If, for instance, 8 l/s of air is extracted through the cooker hood, more than 1,500 kWh of energy per year is lost from heat recovery in one apartment. The loss equals almost a third of the heat energy recovered from extract air in a small apartment. This can – and must – be avoided with an independent extraction for the kitchen and with a tight cooker hood damper. Even a minor leak in the cooker hood damper or incorrect use can, however, increase your electric bill by tens of euros.
With respect to the maintenance of the ventilation unit, a bypass has no practical significance. Relatively heavy grease particles that have passed the grease filter of the cooker hood usually do not travel very far in the duct but stick to the duct wall along the first metres of the duct. The smallest particles may travel to the extract air filter of the unit, which needs regular maintenance in any event.
The impact of the heat recovery cell on the extract air flow of the cooker hood is quite small. For instance, at an airflow of 80 l/s, the pressure loss of the heat recovery cell of Vallox 096 is 92 pa. With a bypass, the air flow could theoretically increase by about 15 l/s if there was no pressure loss in the bypass duct. At an air flow of 30 l/s, the pressure loss of the cell is only 23 pa. The dimensioning of the duct system and careful installation have a greater impact on the air flow of the cooker hood.
Vallox hoods have a good trapping capacity
The factors affecting the cooker hood’s efficiency in removing cooking smells include the size and design of the vapour collection part, the distance from the cooker top and the extraction air flow of the cooker hood or fan. With respect to cooking smell removal, the air flow is a less important factor than the hood’s capacity to capture cooking smells.
Already at an air flow of 50 l/s, the Vallox X-Line cooker hoods have the capacity to capture 72% of cooking smells. If the air flow of the cooker hood rises to 60 l/s, the cooking smell capturing capacity increases by 8 percentage points. The cooking smell capturing capacity of the Vallox Delico cooker hoods is approximately 74% at an air flow of 50 l/s, and it increases to nearly 85 per cent at an airflow of 75 l/s.
Tips for more efficient cooking smell removal
For better cooking smell removal, choose a cooker hood with a good capacity to capture cooking smells. Install the cooker hood at an adequately low height and use spacious dimensioning for the cooker hood duct. The grease filter must be washed regularly. Automatic boosting of the ventilation when the cooker damper opens is also helpful. Automatic boosting can be arranged with the help of the timer of the Vallox PTXPA MC cooker hood damper, the Vallox ProControl control panel and the Vallox KTXA cooker hood or, in Vallox MV models, with the KTXA cooker hood.