1) The document discusses enabling resilient indoor environments in light of the COVID-19 pandemic by learning from past outbreaks and focusing on improving indoor air quality and ventilation. 2) It recommends immediate actions like improved guidance for building owners on balancing infection control with other priorities like energy efficiency. It also recommends long-term strategies around standards, regulations, and research to embed infection resilience in building design, operation, and retrofits. 3) Real-world evidence shows ventilation is a key factor in reducing disease transmission indoors, but the relationship is complex depending on activities, space usage, and other environmental factors. More health-focused metrics and monitoring are needed.

1. @BreathingCity breathingcity.org
contact@breathingcity.org
Enabling resilient indoor environments – learning from a
pandemic
Professor Cath Noakes OBE, FREng, CEng, FIMechE, FIHEEM
School of Civil Engineering, University of Leeds
Honorary Fellow, IAQM

2. The environment has always mattered
“…..the very first requirement in a hospital is
that it should do the sick no harm”
Florence Nightingale, 1859, Notes on Hospitals
John Shaw Billings, John Hopkins
Medical Advisor, 1895

3. Clean air for respiratory health

4. Growing IAQ focus pre-pandemic

5. SPF Clean Air Networks
Back in January 2020…

6. Factors
Constraints
Theme 1: Coupled indoor-
outdoor flows
How do we connect flow &
transport models across scales?
Theme 2: Health-centred
ventilation design
How do we innovate technology
for design and retrofit?
Theme 3: Breathing City into
practice
How do regulation, practice and
guidance need to change?
Breathing City: Integrated
health evidenced framework
Research
Programme
Sustainable
Network
Building envelope, ventilation, urban layout, weather & climate, feasibility, usability,
control, cost, building regulation & planning, behaviour, demographics
Pollutants, health conditions, thermal comfort, noise, energy, climate impact
Region ↔ City ↔ Neighbourhood ↔ Building ↔ Indoor ↔ Human
Scales
Demonstration projects Impact & dissemination
FUVN Scope

7. Disruptive effects of a pandemic
• Human biological source
• Risks across different settings
• Importance of ventilation, air
cleaning and building design
• Behavioural interfaces
• Application of sensors
• Real world complexity
• Exposed strategic weaknesses

8. Respiratory transmission
Source Transport and deposition Exposure
Microbe characteristics
Human characteristics
CDC, USA
• Respiratory source
• Activity
• Size distribution
• Location & duration
• Inhaled Aerosol
• Short & long range
• Larger droplet
• direct deposition
• Via surfaces/fomites
Tang J et al. J Hosp Infect 2006; 64: 100-11
Fluid Dynamics

9. Risk factors
Buildings set baseline conditions and enable interactions
Buildings can’t manage all the behavioural factors
Environmental Factors
High occupant density
Poor ventilation
Highly shared spaces
Temperature and humidity
Human factors
Activity and breathing rate
Duration of exposure
Contact network/frequency
Hygiene behaviours
Socio-economic factors

10. • Commission from Sir Patrick Vallance
– how can buildings be more resilient
to infection?
• Phase 1 - Immediate action – what
should be done before winter
2021/22?
• Phase 2 – longer term strategic
challenges
How can buildings be infection resilient?

11. 2021 challenges

12. Impacts of lack of resilience

13. Competing priorities
Balancing
ventilation and
energy
Outdoor air
pollution
Infection control
not part of
design
Build tight
Noise and
security
Comfort
and drafts
Cost of space
Environment vs
other
investments
Delivering net-
zero

14. Phase 1 Recommendations
Immediate Actions
• Communications to building
owners and occupiers on WHY
infection control matters
• Guidance on balancing
risks/priorities and technology
selection
• Incentives to improve the
poorest spaces

15. Phase 2 recommendations
Strategy and
design
1. Standards for design, operation and products
Construction and
handover
2. Health and wellbeing in building regulations including linking to
sustainability
3. Improve commissioning & testing + enforcement
In-use and retrofit 4. In-use regulations established with local authorities
5. BSI standards for technology certification
6. Infection resilience in major retrofit programmes
7. Communications for public and building owners/managers
Leadership 8. Strategic leadership from government
9. Interdisciplinary research and collaboration

16. Practicalities of Infection Resilience
• No one size fits all – who, what,
where?
• Align and balance to other priorities –
air quality, comfort, energy/carbon
• New build or retrofit?
• Passive or active strategies?
• Resources and timescales
Risk
Vulnerability
hospital
school
offices
construction

17. Ventilation and exposure?
Jones et al (2021) Building
and Environment

18. Real world complexity of emissions

19. Real-world ventilation complexity
Very few spaces are fully mixed
Connected zones
Air distribution between zones
Ventilation rates are variable, especially
in naturally ventilated spaces
Driven by combined temperature & wind
Further influence from movement of people and heat sources
Measurement is challenging
CO2 as a proxy guide - but depends on number of
people, activity, variation between people, size of space
,flow rates

20. Passive vs Active approaches
Natural
ventilation
Thermal
conditions
Materials
Spatial
layout
Water
systems
Daylight

21. What are good environments?
What metrics do we need
for health based
performance?
How is performance linked
to behaviour and
understanding?
What are the current
conditions in our buildings?
How do we measure and
monitor?

22. Ventilation for health?
Treadgold 1836,
2 l/s/p
Metabolic needs
Billings 1895,
14 l/s/p
Disease
ASHVE 1925,
4.7 l/s/p
Odour, comfort
ASA standard
1946, 7.5 l/s/p
Comfort
1970s 5 l/s/p
Energy crisis
ASHRAE 1980s,
7.5 l/s/p
Smoking
ASHRAE/CIBSE, 1989-
8-10 l/s/p
Comfort &
contaminants
?
Sundell et al
2011, 25 l/s/p
Health

23. How much does ventilation impact?
Epidemiology evidence
• Low ventilation rates cited
in nearly all big outbreaks
• Georgia schools: 35%
reduction with ventilation,
48% reduction with
ventilation + air cleaning
• Addenbrookes air cleaning:
removed virus RNA from air
• Other diseases suggest 30-
50% reductions
Modelling evidence
• Most important in places
where people spend a long
time
• Double ventilation rate,
halve the aerosol risk
• Higher risks for
louder/more active
activities
• Potential to stop outbreaks?

24. Evidencing interventions
Upper-room UVGI
Riley & Wells, TB
Baltimore 1958-62
Wells et al, Measles,
1942
35% 14% 9.5%
0
5
10
15
20
25
30
35
40
45
Control Ionizers UV
TB
infection
(%
of
animals)
p<0.0001
p<0.0001
p=0.07
35% 14% 9.5%
0
5
10
15
20
25
30
35
40
45
Control Ionizers UV
TB
infection
(%
of
animals)
p<0.0001
p<0.0001
p=0.07
Escombe et al, TB, 2009

25. Real world impact in schools
Class-ACT study
• 30 primary schools in Bradford – 540
classrooms
• Control group, filter unit group, active air
UVC group
• Measuring IAQ parameters (T, RH, CO2,
PM) in every room
• Measuring infection rates and absence
including COVID
• Evaluating practicalities of implementing
and using air cleaners – behaviour matters

26. Cost effectiveness
Yellow – Cost Benefit Ratio > 1.5

27. Enabling impact
• Policy dreams – simple
messages and magic bullets
• Evidence – Complex, emerging
and uncertain
• Overturning embedded beliefs
• Impacts of decisions
• Translating science
• Communications
#HandsFaceSpaceFreshAir

28. A paradigm shift
• Focus on human centred design
• Holistic approach to indoors & outdoors
• Recognise the complexity – this is not easy
• Recognise the behaviour-technology link
• Driving the economic and societal case for better
buildings
• Embed in policy, design, training and education to build
capability and capacity

29. Acknowledgements
• Leeds academic colleagues, postdocs, PhD students,
technicians
• SAGE and SAGE EMG
• Research project teams: TRACK, PROTECT, HECOIRA, Far
UV, Class ACT, FUVN
• Royal Academy of Engineering, CIBSE, IMechE
• Group of 36, ISIAQ
• Funders: EPSRC, DHSC, HM government, NHS Scotland

30. There are no magic bullets…..
Thank you
C.J.Noakes@leeds.ac.uk
@CathNoakes