To reduce carbon emissions and energy consumption in the construction industry, the current approach to building energy efficient buildings is to increase the airtightness of the building envelope. This inevitably reduces uncontrollable building ventilation through the gaps, cracks and other unintentional openings in the building fabric. To meet building regulations and maintain good indoor air quality, ventilation is often required in these newly constructed, sustainable buildings.
In addition, during the course of the current pandemic, evidence has shown that adequate ventilation, a process of bringing a sufficient supply of outdoor air into a building, can effectively reduce the transmission rate of airborne infections within confined indoor spaces. The general public has also become more aware of the link between indoor air quality and building ventilation. This rising awareness and growing consciousness of the importance of good indoor air quality has brought the building ventilation issue to the forefront of people’s minds. Building facility managers are required to take steps to address poorly ventilated buildings, especially those with densely occupied indoor spaces, such as meeting rooms, classrooms, assembly halls and lecture theatres and the like.
Furthermore, the recently updated Building Regulations, which came into effect in England on 15th June 2022, have also highlighted the importance of indoor air quality and its impact on the health and wellbeing of the building occupants.
ERV work Principle
Energy Recovery Ventilation (ERV) is a ventilation device, where the exhaust indoor air passing through a heat exchanger is used to pre-heat or pre-cool the incoming outdoor air. The heat exchanger also helps to maintain the indoor humidity by transferring moisture between the exhaust air and incoming air without mixing them. The primary aim of installing an ERV unit in buildings is for energy recovery while ventilating. This can significantly reduce the cooling or heating load of the air-conditioning system in the building, and therefore save energy costs for the building owner.
LG has recently launched two small capacity ERVs that are mainly used for residential buildings. These products are equipped with an air cleaning system consisting of a UV-C germicidal radiation technology (i.e. UVnano), two pre-filters and a high efficiency fine filter (ISO ePM1 95%), constant monitoring sensors for indoor CO2 and particle concentration to ensure good air quality for the building occupants. More details are given in the next section.
The work principle, sensors and the multi-process air cleaning system are schematically shown in the drawing above.
The central part of the ERV is the high efficiency cross-flow heat exchanger. The supply air path and the exhaust air path are arranged at right angles to each other. There are no moving parts within the heat exchanger and therefore it has high durability and reliability.
What LG offers
As shown in the schematics, LG’s Resi-ERVs have the following features built within the unit.
- Air Cleaning System
The air cleaning system consists of UVnano, two pre-filters and a high efficiency fine filter.
- UVnano: the UV lights generated by LEDs are used to damage the DNA of the micro-organisms, such as bacteria and viruses in the form of an aerosol floating in the air, to stop them from spreading. The LED lights are located in front of the pre-filter and the emitted rays are directed towards the pre-filter. The aim of this process is to kill the airborne germs captured by the pre-filter.
- Pre-filter: the aim of the two basic air filters (G3 classification according to EN779) is to capture coarse particles and protect the heat exchanger from clogging. They are made from fibrous fleeces and washable.
- High efficiency filter (ISO ePM1 95%): it captures the fine particles carried by the incoming supply air stream. In accordance with filter classification standard ISO EN BS 16890:2016, this high efficiency air filter is rated as ISO ePM1 95%. This type of filter is highly efficient and can capture 95% of PM1 fine particles with sizes ranging from 0.3-1 micron (i.e. 10-6m). PM1 are tiny particles and therefore the most dangerous to health, as they are more likely to reach deep into the respiratory system and can cause serious diseases to humans.
To ensure good quality of the supplied air, the Resi-ERVs also have the following preventative measures to suppress possible bacteria and mould-growth inside the unit:
- Heat exchanger is made of special thin paper membranes which are not only fungi-resistant to prevent harmful bacteria growth, but also flame-retardant treated for fire safety
- Air pathways, where air flows through the unit, are also lined with grade zero anti-bacterial and anti-mould foam material (EPS). This is to suppress the growth of bacteria and mould on the internal surface of the air passageway.
Both materials are independently certified as zero grade with no bacteria growth according to the ASTM G21-15 test specification.
- Embedded CO2 Sensor
The CO2 sensor is located within the inlet of the return air (i.e. exhaust air). Its function is to monitor the indoor CO2 level which acts as a surrogate indicator for indoor air quality and can be used as part of the building ventilation management system. This provides a monitor and control system to improve indoor air quality.
To maintain indoor air quality, the output signal from the CO2 sensor can be used to control the fan speeds automatically to change building ventilation rates (i.e. fan speed Auto mode). Depending on the specific CO2 ppm in the room, the fan can be controlled to run at different speeds. If the CO2 concentration is too high, it can automatically regulate the fans speed to increase air change rate of the building. The fan has 3 speed options: Super-High, High and Low, plus an Auto setting where the fan speed will change automatically between the 3 speed settings according to the indoor CO2 level.
To use this function, the installer/user needs to set it up in advance via the wired remote controller. The measured instantaneous CO2 concentration can also be displayed in the wired remote controller.
- Dust Sensors
Two laser dust sensors are included in the unit to monitor the particle concentrations of the incoming outside air and the supplied air to the room respectively. When the measured dust level in the supplied air (by the sensor located after the heat exchanger) is higher than the pre-set value, a notification or text message for filter replacement will be sent out to the user.
- Special Application-Interlocking AC and Ventilation
Fast improving indoor air quality (i.e. reducing fine particle concentration) can be achieved, when the Resi-ERV is interfaced with the air purification kit of a suitable air conditioning indoor unit. This IDU should be one of the models with the air purification kit such as 1-Way Cassette, Dual Vane 4-Way Cassette and Round Cassette, where the indoor air quality is shown in a different colour in the smart indicator.
- Operation Modes
There are three operation modes available for these products. Details are given in the table below.
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Mode
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Description
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ERV mode
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This is the mode of ventilation in which the incoming outdoor air and out-going exhaust air pass through the heat exchanger and transfer energy between them to pre-condition the supply of air to the building.
This mode is often used in summer or winter where the indoor/outdoor temperature difference is large.
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Bypass
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This is the mode of ventilation where the out-going exhaust room air is taken out of the building without passing through the heat exchanger.
This mode is often used in spring or autumn when energy recovery is not productive or required (i.e. temperature difference between indoor and outdoor is small), and free cooling or heating of the space can be provided by the outdoor air conditions.
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Auto
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In this mode, the unit automatically operates in the optimum mode, by switching between the above two modes, according to the indoor/outdoor air temperatures.
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- Overall features
This section summaries the many features that these new products have.
- Low noise in operation, high efficiency, small size, lightweight and easy filter maintenance
- “A” rated Energy label (in A+ to G scale).
- To improve the indoor air quality, the product has an air cleaning system, heat exchanger and air pathways are made from bacteria-resistant materials.
- Embedded CO2 sensor is used to monitor indoor air quality and control building ventilation automatically.
- Two laser dust sensors are used to monitor dust concentration in outdoor air and supplied indoor air, sending out notification for fine filter replacement.
- The measured CO2 level, particle concentrations from the dust sensors can be displayed on the wired remote controller. With optional accessory Wi-Fi, smartphones can also access this information.
- The product is designed for automatic operation and can interface with other central control systems such as BMS via an LG gateway device.
- When interfaced with some of LG’s Multi V air conditioning indoor units, rapid cleaning indoor air (i.e. particle removal) can be achieved.
- Group control is available (connecting one wired remote controller to multiple IDUs, or connecting two wired remote controllers to one ERV).
- Other energy saving features: night time free cooling (this mode is controlled by the user via the remote controller) and delay the start of ERV operation after air conditioning IDU in the same room.
Most importantly, these units can help clients to meet the new requirements for good indoor air quality in the recently revised Building Regulations in England.