What to consider when buying a ventilation unit?

We often end up buying a product simply due to its nice packaging, perhaps we were attracted by the ad, or the salesperson persuaded us into buying the product by telling us what we wanted to hear. This is also often the case when people buy ventilation units. Due to a relatively fierce competition in the market your need to properly prepare for the purchase, and consider the facts; especially, you need to compare the technical specifications in detail – so you do not end up with apple-to-orange comparisons. You do not buy a ventilation unit for a short term – it is an investment in your health, and a long-term investment.

The main task of ventilation units is to supply healthy air to the room, while contributing to lower costs. What matters, are the properties of air when it enters the room after travelling along ducts and through filters.

The ventilation unit must supply fresh, purified air, rich in negative ions to the room. This can only be achieved by using high quality F7 filters, which can retain harmful fine air particles, such as accumulated black carbon and dust particles.

Unidirectional ventilation units apply the regenerative principle of heat recovery. In such units, the air travels along one duct and the energy is stored in a ceramic plate while the unit operates with interruptions.

In bidirectional recuperative ventilation units, the air travels along two separate ducts, thereby preventing transfer of bacteria and dust particles from the duct to the inlet air. The energy from the outlet air is continuously transferred to the inlet air without interruptions. As a result, bidirectional recuperative ventilation systems provide for a healthier ventilation of your premises.

At a lower air flow rate, the unit achieves a higher heat recovery rate – the air travels slower, it transfers energy to the inlet air for a longer time, thus providing a smaller difference in the temperature of inlet and outlet air.

Manufacturers of ventilation units often claim that their unit can achieve up to a 95% heat recovery rate. This is mostly true, but they often fail to mention at what air flow rate. For example, if the unit normally operates in the 20-80m³/h air flow rate range and achieves a 78% heat recovery rate at a 30 m³/h airflow rate, it will definitely not reach a similar recovery rate at the maximum air flow rate (e.g. 80m³/h). In such cases, try to find a structured heat recovery rate table for different air flow rates – e.g. 20, 40, 60, and 80m³/h. You can usually find it in the technical catalogue and it will allow you to make a more detailed comparison of products. You can also find this information (heat recovery rate of the unit at a specific reference air flow rate) in the technical product datasheet.

Another important aspect when comparing ventilation units is the power of the unit. Technical specifications of numerous manufacturers include information about the power of the fan, which is not so relevant.

More relevant is the information about the actual power of the ventilation unit, which is indeed powered by the fan, however, if the fan is not at least as powerful as the unit itself, the unit will fail to achieve the same air flow rate. Therefore, do not be misled by the information, e.g. the fan supports air flow rates up to 150m3/h.

If, due to its technical characteristics (i.e. flaps, outlet nozzles, electronics calibration, etc.), the unit itself does not support such air flow rates, the information about the capacity of fan to support supply and discharge air flow rates up to 150m3/h is completely irrelevant. We advise you to focus on the actual power of the unit and the air flow rates it supports.

It turns out that offers which may seem less expensive at first sight, are often misleading. Just because the product itself is actually cheaper, this does not mean that the final investment will also be lower. When purchasing a ventilation unit, do not focus only on the product and its price, but make sure the offer includes all accessories for smooth operation as well as installation services, which can significantly increase total costs, if not included.

It may happen that the price of the ventilation unit stated by the unit manufacturer leaves out additional costs, related to the purchase of control units (needed to control the unit) or more efficient filters. The manufacturer may also forget to mention you need to purchase ducts for in-wall installation without which the air cannot flow and without which the unit cannot be installed. We thus advise you to pay attention to the scope of delivery, so you do not buy a pig in a poke.

Ventilation units that are capable of recovering heat and energy (not ordinary fans) are fitted with specific sensors to detect and maintain the desired air properties during their operation. If the ventilation unit is fitted only with a temperature sensor, it will adjust its operation according to the set temperature regulation protocol. The same also applies to other sensors and detectors – e.g. humidity, CO2, VOC, radon, and others.

There are also several modes to control your ventilation unit. You can control it with a wall-mounted control unit (for which you need to install cables and wiring from the unit to the location of the control interface in the absence of Bluetooth connectivity, ultimately incurring additional costs), with a remote control or remotely via a WiFi connection.

Both the sensor types as well as control modes are important factors when comparing products in terms of functionality and additional costs.