FOCUS HVAC
OPTIMISING BUILDING
VENTILATION Don Foy, a Director and HVAC specialist at the multi-discipline
engineering solutions business BGEN, provides practical tips on
how businesses can improve building ventilation and reduce the
SossiEiOit\ oI &29,' anG otKer Zinter YirXses circXOatinJ inGoors
With Omicron variant contributing towards
record cases of COVID-19 across the country,
building ventilation is under the spotlight like
never before. Professor Cath Noakes told the
Building Engineering Services Association
(BESA) national conference that the pandemic
had increased understanding of how disease is
transmitted around indoor spaces and raised
public awareness of the importance of mechanical
ventilation.
“I never thought I would see the day when the
Prime Minister and the Chief Scientific O icer were
talking about ventilation,” said Noakes, who is one
of two engineer members of the government’s
Scientific Advisory Group for Emergencies (SAGE).
Measures continue to be introduced to improve
building ventilation. In January for example, the
Government announced an additional 7,000 air
cleaning units to be provided to early years, schools
and colleges to improve ventilation in teaching
spaces.
But with COVID-19 here to stay, alongside winter
viruses such as influenza, organisations throughout
the UK need to consider how they can improve the
ventilation of their premises – whether that be an
o ice, factory or school.
MITIGATING THE SPREAD
Eliminating the spread of COVID-19 and other
winter viruses is virtually impossible, but there are a
number of ways building ventilation can be improved
36 FEBRUARY 2022
and transmission of the virus can be reduced.
Conduct a risk assessment
Undertake a risk assessment to identify ventilation
challenges specific to a building and develop a plan
to improve ventilation. Given the focus in recent
decades has been on minimising fresh air entering a
building to aid employee comfort and optimise the
energy consumption of HVAC systems, this may be a
challenge, but a HVAC specialist will be able to o er
support.
Balancing fresh air and employee comfort
‘Displacement ventilation’, where air is introduced
in a room at a low level and extracted at a high level,
using the theory ‘warm air rises’, is one of the most
e ective methods of removing air contaminants.
However, while maintaining good levels of
ventilation is important, employee discomfort should
be minimised. While there is no legal requirement
on temperatures in the workplace, the Government
suggests a minimum of 16C or 13C if employees are
doing physical work.
Currently most mechanical building ventilation
systems for occupants have fresh air supply mixed
with recirculated air at a high level in ceiling voids
before they are supplied to the room to help avoid
dra s and lower temperatures. This method however
makes it di icult to remove the COVID virus from the
air e ectively. Therefore, additional fresh air through
lower inlets should be considered.
Encourage cross room air flow
You might think opening some natural room vents
fully will help to improve ventilation. However, to get
the best results, open room vents on opposite sides
of a room to encourage cross room air flow.
Minimise air recirculation
Unless your HVAC system is designed to mitigate the
risk of COVID-19 and other viruses, keep their use to
a minimum.
Air purifiers
Air cleaning and filtration units can help to reduce
the airborne transmission of COVID-19 and other
viruses. These should be considered in areas where it
is not possible to maintain good levels of ventilation.
Check/install sensors
Think about installing sensors which can detect
CO© levels, especially in highly populated areas
such as open plan o ices and meeting rooms. This
can provide a guide as to when additional fresh air
is required. Levels should be agreed on a case-bycase
basis, but it is generally accepted that the limit
should be a maximum of 800ppm.
In addition to CO© monitors, consider disabling
sensors designed to optimise fresh air per employee.
The standard 10 litres of fresh air per person
(minimum) should be re-evaluated while we work
through the pandemic.
Consider UVC light and upgrade filters
Ultraviolet (UV) light can kill the COVID-19 virus.
Consider the use of UVC lights in HVAC systems (UVC
lights can also be installed directly in rooms if there is
no mechanical ventilation). F7 grade filters or better
in HVAC systems will also help to capture SARS-CoV-2
and other virus particles.
Put pressure in the spotlight
Slightly higher or lower air pressure can help reduce
virus contaminated air from stagnating. There should
be a pressure di erential of approximately 25 pascal
units between rooms to achieve this.
Think about the environment
Many measures to improve ventilation will involve an
increase in energy consumption. Heat recovery units
and other technologies can help to negate this. Heat
recovery units, which utilise the heat from extracted
air to heat the fresh air being introduced from the
outside, will help to maintain a comfortable room
temperature and significantly reduce energy bills.
Finally… use common sense
If needed, open doors (where possible) and windows
as required. Also, consider providing extra space
between workstations in open plan o ices.
THE FUTURE
While Government advice continues to change in
accordance with variants, the reality is that we need
to find a way to live with COVID. Optimising building
ventilation can play a key role in helping society to
return to some kind of normality, and in the process
also help to reduce the spread of other winter viruses.