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As we enter Year 3 of the pandemic, it’s obvious that COVID-19 is going to be with us for a while. In response to living with the virus, some buildings have implemented revised ventilation strategies in an attempt to reduce likelihood of transmission in buildings and to demonstrate to occupants that value is being placed on their health. This post won’t go into the details and efficacies of various strategies (although we will provide helpful links). What we will investigate is the short term energy impacts of some of these strategies and demonstrate how Buildings Alive’s “Rapid Efficiency Feedback” service allows building owners and operators to quickly assess these energy impacts.

Some Examples

All buildings involved were based in Sydney, Australia and are commercial offices. While specific details of strategies implemented were not captured, general details are summarised below.

Property

Outside Air increased

Recycled Air reduced

Ventilated Air increased

Overnight Purge Cycle introduced

Building A

Y

Y

Y

Y

Building B

Y

Y

Y

Y

Building C

Y

Y

Y

Table 1: HVAC Strategy Summary

For each of the sites a 15 day baseline period was selected immediately prior to introducing the strategies and a 15-day period after implementation was used as a comparison. The table below shows the increase in the weather normalized energy consumption and the percentage increase in energy use.

Results

Building

Baseline period

Increase in energy (kWh)

% Increase

Building A

December (Summer)

1759

11.7%

Building B

September (Spring)

1406

8.3%

Building C

October (Spring)

1583

16.4%

Table 2: Summarised Results

Some result diagrams are shown below, with the first image for each building showing the effect of total energy consumption under similar weather conditions. Red dots show the energy consumption after the strategies were introduced and the blue dots before the introduction of the ventilation strategies.

The second image shows the average profile before and after the introduction of the ventilation strategies to show the time series effect of it.

Building A

Building B

Note that the night purge is hardly noticeable suggesting it was not implemented building-wide. Also note the earlier stop time after changes were made – this is likely unrelated to the COVID ventilation changes.

 

Building C

Conclusions

While the analysis periods are quite short in this study, it is obvious that strategy changes have had a significant impact on energy consumption at all sites. These impacts will change as seasons / occupancy of buildings change. It is recommended that prior to any strategy changes being made, available literature should be reviewed to ascertain the efficacy of the strategies. While SARS-CoV-2 is still relatively new, viruses have been around as long as humans. HVAC standards were developed with the knowledge of viruses and a well-maintained HVAC system operating according to local standards should be the immediate focus for any building owner / operator as workers return to the office. An additional note is that there is significant scope different interpretations for implementation of all of these strategies. For example – how long should night purges run for at what speed or how many air changes are required or exactly how much extra outside air is introduced. So if any strategies are being implemented, specifics should be decided on for exactly how the strategies should be implemented.

Some useful links for advice on COVID ventilation measures:

  • ASHRAE – The American Society of Heating, Refrigerating and Air-Conditioning Engineers
  • CIBSE – Chartered Institution of Building Services Engineers
  • REHVA – Federation of European Heating, Ventilation and Air Conditioning Associations
  • AIRAH – Australian Institute of Refrigeration, Air conditioning and Heating (
  • CDC – Centers for Disease Control and Prevention
  • World Health Organisation
  • Breath Freely UK – Ventilation Tool

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