Products & Services

The “air-borne” risk of infection by the coronavirus has caused design engineers and building operators to re-evaluate primary air exchange rates and the effectiveness of increased ventilation. Based on the most relevant facts and information to date, here are the recommendations for the use of LTG air-water solutions and products.

COVID-19 is an infection transmitted between humans by airborne droplets.

• Therefore, redistribution of the virus throughout the building via the return air ductwork, recirculating AHU and supply ductwork should be prevented.
• Furthermore, the viral load within the room must be lowered. This means that any potentially contaminated air must be effectively diluted with increased primary (fresh) air. The reasonable recommendation of all professional associations in this context is to increase the outdoor fresh air volume and ideally work these systems as a 100 % DOAS.

Decentralized facade ventilation units

When using the decentralized facade ventilation units (i.e. LTG PulseVentilation or Eco₂School), these are effectively a DOAS system where 100 % outside air is supplied directly into the space and the return air is exhausted directly to atmosphere eliminating room to room cross-contamination.  In contrast to a central AHU, this condition is close to ideal since there is no ductwork distribution system in the building that would facilitate redistribution and spread of the virus.

One special benefit of the LTG Decentralized PulseVentilation unit is the design and operation of its heat recovery recuperator to prevent freezing during the winter. This ensures an uninterrupted fresh air supply to the room all year rount.

An additional option that doubles the fresh air volume supplied to the space is to run the unit in ‘hybrid’ mode. Only possible when the FVPpulse units is installed   in a building with openable windows, the unit doubles the filtered fresh air supplied to the room and allows the return air to be exhausted through the open windows. This is achieved without increasing the units fan speed, power consumption or noise level.

UNITS WITH OUTDOOR fresh AIR SUPPLY

All units operated with an outdoor air supply (decentralized facade ventilation units, induction units, chilled beams, and fan coils with a primary fresh air supply) should not be turned off. We recommend the following:

• Increase outdoor fresh air volume (as far as this is acoustically acceptable)
• Extend runtimes (i.e. by starting ventilation in the early morning hours and continuing it for a few hours after the end of occupation)
• Constant ventilation of meeting rooms, even when they are not occupied
• For CO₂ control, we recommend lowering the target value, i.e. to 500 ppm, to increase the outdoor fresh air volume and/or runtime of the ventilation units. Alternatively, CO₂ control can be replaced by a timed program.
• Change the throw of induction units from vertical mixed flow discharge to mixed flow displacement.
• Change the throw of wall mounted and in-floor mounted fan coils from vertical mixed flow discharge to mixed flow displacement.
• Prioritize the use of displacement over to mixed flow in HVAC designs.

RECIRCULATION UNITS WITHOUT OUTDOOR fresh AIR SHARE

Although the distribution of COVID-19 via air conditioning units has not been proven, it is generally recommended to turn off any systems that uses only recirculated air especially in rooms that are occupied by more than one person.

Natural convection currents will cause some of the virus laden aerosols to spread throughout the room even without any air recirculation.

Therefore, if the recirculation units cannot be turned off (i.e. due to high or low outdoor temperatures and internal loads), sufficient fresh air supply (i.e. via window ventilation) is essential. One good indicator for sufficient ventilation of the rooms would be by monitoring CO₂ concentration and to install CO₂ level indicators in each room since a concentration of <1000 ppm also has a correspondingly lower aerosol concentration.

Most recirculating fan coils are fitted with low grade dust filters that are not effective at filtering out virus laden room air. An upgrade of filter type and reduced maintenance swap out period must be adopted. Additional care must be taken, and protection used, when swapping out potentially virus laden filters.

AHU OUTDOOR AIR FILTERS

Filtration of 100 % outdoor air is less important since it is not an infection path.

Dependent on the type and location of any filters in the return section of the AHU (if fitted at all) and prior to return air being mixed with incoming fresh air, these filters can have varying effects (dependent on grade and swap out period) on capturing the virus. Therefore, it would be better to adopt a 100% DOAS approach and avoid altogether mixing return air and fresh air. Heat recovery could still be achieved with solutions such as run-around coils if the supply & return AHU’s were positioned locally to each other.

In all cases regular planned filter exchange is especial to ensure the target volume flow is maintained and any extra energy needed to overcome the increased pressure drop from dirty contaminated filters is avoided.

Please note – Units with wind pressure control (i.e. LTG FVPpulse) maintain a constant volume flow even if the filters are contaminated.