Forced ventilation: save by making better use of your air conditioning

The air conditioning unit has gone from being a luxury item to something very common in almost every home, especially newly built ones. While it was very difficult to find it in a household three or four decades ago, its low installation cost has made it very popular today. But, what is the initial problem of air conditioning? Undoubtedly its consumption, which will likely account for the highest electricity expenditure in the hot months. The solution may involve combining it with an ecological alternative of very low consumption, forced or mechanical ventilation.

First of all, what will the air conditioning bill depend on? We could give approximate prices -although there are too many factors influencing this-, but first of all, we must consider the type of use, the dwelling in question, and factors like our routine. However, it will not be difficult for traditional air conditioning to account for the highest electricity expenditure in the home.

What will influence the electricity consumption of air conditioning are:

• The most recent units can consume up to 25% less thanks to energy savings. However, just because they are efficient does not mean they stop having significant consumption.
• The size of the appliance will be very important. Very large units may generate a high level of cold, which will not find sufficient comfort.
• The type of construction of the home is almost as important as having or not having air conditioning. If insulation is minimal, cooling needs will be much higher.
• The temperature at which we set the air conditioning unit will be decisive at all times, just like the speed at which the fan is set.
• The hours the cooling function is on will be critical to the appliance's consumption.

This estimated expense, however, does not have to be exactly this way. We have also mentioned that refrigeration units and their consumption depend largely on external temperature conditions and also on thermal insulation, but on average, they would function correctly. While it is possible to cut this, for example, by using a timer to turn off the air conditioning at night. In this case, it would be easy to reduce consumption to about 40 euros per month.

These consumption figures are completely different from those of conventional fans. For example: let’s imagine we use a 55W fan for 30 days in a month. Without stopping. The consumption that the device will reach will be, at most, about five euros.

This is where the option of combining the use of air conditioning -or just limiting it- with forced ventilation comes into play. Mechanical ventilation systems, which renew the air indoors, can not only clean impurities from the environment we breathe and ensure health but can significantly improve temperatures without traditional refrigeration systems.

Energy efficiency and its relation to air conditioning

As we previously mentioned, air conditioning systems do not automatically regulate temperature. Many people assume that by choosing a specific temperature, the unit will automatically adjust the emitted air temperature. Unfortunately, this is not the case.

Air conditioning units have a refrigeration capacity of between 9° C and 12° C. They will emit cold air at that temperature at all times. From there, they have a thermostat that will regulate the internal temperature to determine when it needs to adjust the temperature. How will they adapt to the temperature chosen by the user? They will simply stop emitting cold air and will ventilate only.

This can be easily verified by observing the compressor. When we see that it stops functioning, it is because it does not need to emit cold air and will not do so again until it is truly necessary.

Unfortunately, thermostats are not as efficient as they should be. Therefore, when choosing an air conditioning unit, it is important to choose one that has the necessary dimensions and does not exceed, as in that case, we would feel cold inside the house. Additionally, the electricity bill will skyrocket.

In any case, based on what we have discussed here, we can say that air conditioning systems are not of high energy efficiency. Although we may find models that communicate this, they basically alert us that they consume less than competing products or those common in the past. But that does not mean they are energy-saving or low consumption.

Next year, the obligation of Nearly Zero Energy Buildings will come into force, and this will restrict the use of traditional air conditioning systems, such as air conditioning units and HVAC systems. This new regulation is committed to high energy efficiency HVAC systems. In this case, the best solution is mechanical double flow ventilation with heat recovery.

Nevertheless, mechanical ventilation and air renewal can be great allies in reducing the electricity bill by making much more rational use of air conditioning systems.

Air renewal in combination with air conditioning

Air conditioning systems basically blow cold air into spaces, but their operation is somewhat more complex. The compressor -which is located outside- extracts hot air and, by compressing it along with refrigerant gas, creates the sub-cooling process through what is known as a refrigeration circuit. The resulting gas is cold, and it enters the rooms at a temperature of around 9° C and 12° C.

However, it does not provide air renewal - at no point does it consider the temporary values of the air indoors - and does not take into account health or the presence of contaminants. And to extract hot air, the price to pay is very high, as the compressor needs a lot of energy to operate normally.

In contrast, forced ventilation -also known as mechanical ventilation- is responsible for renewing the air in spaces through extraction fans. In this way, it removes hot air from the rooms at a minimal energy cost.

It can also extract humidity, which, if excessive, is one of the main causes of increased heat sensation and sweating. However, the possibilities of mechanical ventilation to reduce air conditioning consumption go much further.

Forced ventilation as an alternative to air conditioning

In modern construction, we can dispense with the air conditioning system in most situations thanks to double flow ventilation. In this forced ventilation system, air is renewed according to the breathing conditions in each room. Furthermore, it is capable of introducing cooled air in warm months. And with no greater consumption than that of fans.

The system works as follows:

• The double flow ventilation has sensors and gauges for temperature, humidity, and pollution. It can analyze the state of the air at various points in each room.
• If the air quality decreases -due to high humidity or especially due to pollution from cleaning or cooking- air extraction will begin automatically.
• At the same time, the double flow ventilation system can filter air from outside and push it inside.
• By introducing outside air through a heat recovery unit, it is able to temper it. Thus, in summer, it can cool outside air as it passes beside the air exiting outside.

Double flow forced ventilation can temper rooms to an appropriate temperature without needing to use air conditioning. Even so, its efficiency will also depend on the thermal insulation of the dwelling and other factors. In that case, if one has an air conditioning unit, it could be used to lower the temperature at specific moments, utilized at very opportune times and for very short durations.

In the same way, double flow ventilation focuses on extracting poor quality air or that which has higher humidity. This way, it avoids using air conditioning units, whose functionality is to extract hot air to compress and cool it. Forced ventilation, likewise, is much more efficient and, above all, generates energy savings, which makes it an ideal and future option, as it is indeed a true solution for energy efficiency.