The initial opinion of the public may over-look or refuse to accept these three alterations. This would be environmental devastation regarding GHG emissions if we produce unnecessary GHG emissions. I believe a path must be found to scientifically quantify the virus content in the supply air of mixed air systems in 100% recirculation, with virus present in the occupied space. (Worst case scenario) The two case studies in the Alberta Health Report and the social distancing rule of two metres suggest the virus cannot travel through the fan system and back to the occupied space, but real data in virus content of the supply air is required to confirm this. Demand Ventilation Control (DVC) based on temperatures only, allows the code requirement of minimum fresh air (example 20% fresh air) until the warmest zone has closed its heating device and requires cooling. The remaining 80% of the mixed air volume is increased in fresh air beyond the minimum just enough to satisfy the cooling requirement of the warmest zone. The variable cooling demand is limited to a minimum temperature of 55˚F (13˚C). DVC may also vary the minimum fresh air quantity based on CO2 levels in the occupied space. The requirement to alter back to (DVC) is urgent now in that: 1) Many systems with DVC have been altered from variable mixed air temperatures to provide constant mixed air temperature at 55˚F (13˚C). 2) The day time outdoor air temperatures during spring and fall will cause the fans to be on about 100% outdoor air most of the time. 3) This causes a 15F˚ (8.3C˚) ∆T heating demand to warm the room to 70˚F (21˚C). 4) If the DVC is re-instated the mixed air temperature would vary automatically adjusting to 67˚F (19.4˚C) with outdoor air temperature at 55˚F (13˚C) and 20% minimum fresh air if the warmest zone required no cooling. 5) DVC control on minimum ventilation would require a 3F˚ (1.7C˚) ∆T to rise to the 70˚F (21˚C) room temperature rather than the altered circuit’s 15F˚ (8.3C˚) ∆T. This is a 500% increase in heating required with the altered circuit. 6) During many spring and fall days the school’s boiler with DVC can be run for a couple of hours in the morning to take the chill off the building and then shut down for the remaining day. The altered circuit with a 55˚F (13˚C) mixed would require the boiler to run all day compensating for the unnecessary cooling. A study identifying virus concentrations at various locations in the HVAC system is required immediately. If that study contradicts existing studies identifying maximum virus travel and the social distancing rule of two metres, then both positions have to be thoroughly analyzed. If new studies indicate that the virus can travel from the occupied space, through the HVAC fan system and back to the occupied space, the provable fact of escalating Climate Change by increasing HVAC fresh air intake should be considered in the final plans. ASHRAE’s support to convey the information in their October 5, 2020 announcement to the public is imperative now as the maximum benefit of DVC occurs in the spring and fall of the year. 11.199
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