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Returning to the workplace after lockdown

Advice for effectively managing your HVAC system

30th June 2020
Working safely during coronavirus (COVID-19)

As organisations start to open back up after lockdown, certain considerations need to be made to ensure the safety of staff, and potentially customers, who enter the workplace. The UK government has published guidance which outlines measures that should be taken before anyone returns to work. With more people within a building, one of the greatest challenges will be keeping clean air circulating so that the risk of transmitting the virus through aerosols that can be coughed, sneezed or simply inhaled from an infected person is reduced.

The Chartered Institution of Building Services Engineers (CIBSE) has provided useful guidance for building owners/managers and operators who are planning on opening buildings following a period of inactivity and considering the requirements for the ventilation system.

The main advice is to provide as much dilution with clean air as possible, which is why the rate of transmission is far lower outdoors. For indoor areas, the key to reducing risks is to review a buildings heating, ventilation and air conditioning (HVAC) systems.

HVAC strategy

The building owner must develop strategies that are proportionate to the risk and it is likely that the ventilation and HVAC strategy will need to evolve as other parameters change. These would include;

  • Changes to government alert levels – The government has set 5 levels of alert with levels 4 and 5 probably resulting in offices being closed to most staff. However, whilst level 3 (virus in general circulation) may lead to high demands for ventilation in buildings, it is reasonable to consider reducing these when the Government reduces the alert level to 1 or 2.
  • Building occupancy – Many building owners are likely to restrict the number of staff and visitors that return to the site. However, if occupancy levels increase then the HVAC strategy would need to determine whether additional measures are needed.
  • Weather – If higher ventilation rates are needed during colder weather and heating systems are unable to cope, then the HVAC strategy may need to consider measures such as additional temporary heating, or reductions in building occupancy so that ventilation can be reduced.
  • Timers – CIBSE provides recommendations on when the HVAC should be started and stopped for sites that are only occupied at certain times of the day. The strategy will, therefore, need to include the review of timers for both weekdays and weekends.

Measure and verify

All actions need to be measured and verified to ensure that they are achieving their aim. For example, for CO2 controls it is important that the sensor is operating correctly and the use of a portable sensor would not only check this operation but could be used to ensure that there are no parts of the buildings where levels are elevated, indication local stagnation of air and increased risk of Covid transmission.

Such testing provides confidence for both the building owner and its occupants that measures are effective.

Measurement and verification can also track the impact of the HVAC strategy on energy use. This may be required by energy managers for budgeting purposes but may also provide an early indication of whether the heating systems would be able to cope with the coming winter.

Making your strategy sustainable

Making a building Covid secure requires a robust strategy, which may involve manual interventions and control upgrades. This needs to be documented to demonstrate to building users that appropriate measures have been taken and the effectiveness needs to be regularly measured and verified.

However, the HVAC strategy along with other parts of the Covid secure plan should not be seen as a one-off cost, they could also be integrated into wider sustainability strategies. We have already realised that the pandemic will lead to permanent changes in behaviour regarding working from home, video conferencing and commuting, but there will also be lessons learned over HVAC controls.

Most years, the UK sees increased employee sickness in the winter caused by seasonal flu outbreaks, it is reasonable that many people catch this flu whilst at work. However, if the Covid secure measures are introduced at such times, it seems likely that rates of infection will reduce resulting in lower employee absenteeism, which improves business sustainability and staff morale.

Importantly, an increased understanding of your HVAC systems, the use of sensors and the measurement and verification of operations are fundamental to reducing energy use in buildings so the HVAC strategy should eventually be integrated into your environmental sustainability programme.

So, when you are finalising your Covid-19 secure strategy, don’t forget to keep your energy and sustainability consultant involved in the process.

Natural ventilation

The simplest way to increase ventilation of a building may involve the opening of windows and doors (not including fire doors). However, such actions must consider whether this may introduce additional security or health and safety risks.

Some buildings may have ‘wind catchers’ on the roof, which allow a more controlled ingress of natural ventilation and these could be set to run at maximum openings.

The main concerns with the use of natural ventilation will be seen during windy weather and, as we approach winter, the increasingly cold air temperatures outdoors. Building occupants may find the draughts uncomfortable and the building heating system may not be able to maintain suitable temperatures.  Even if the heating system can cope, the impact on heating costs would be severe.

HVAC Review

For most offices and other workplaces, the solution will need to involve a combination of natural ventilation and adjustments to the existing HVAC system.

The first step is to understand what HVAC equipment is already installed and how it is controlled.  Some equipment may need to be disabled to prevent the recirculation of potentially contaminated air, other equipment may be adjusted using existing controls, whilst some may require new controls to be installed or a manual over-ride process to be implemented.

For HVAC systems that recirculate air through filters, it may be possible to upgrade these to MERV-13 or better performance. However, you should first ensure that the equipment is designed to work with such filters.

For building areas where ventilation is inadequate and cannot be easily upgraded, this could lead to other ways of managing risks such as restricting access, increased social distancing and enhanced cleaning processes.

HVAC controls

Whilst most HVAC systems control temperature and relative humidity. More advanced controls use CO2 detection which adjusts the rate of ventilation depending on the number of people who are in that environment. If the setpoint is adjusted to 400pm then this matches the levels found in the air outside, so the control system will increase the amount of ventilation to the maximum.

If no such control is available, then it is likely that there will be a way to manually over-ride the equipment. However, the installation of better controls will offer energy savings potentials in a post-Covid world.

If your organisation is in the process of welcoming people back into the workplace and you would like more information on how to develop an effective HVAC strategy that reduces risk and manages any changes in a cost-effective way, please give us a call on 08451 46 36 26.