FM Nectar
Presented by Ian Mawditt
Can we rely on good ventilation?
IAQ and ventilation effectiveness
February 2017
London
Healthy Buildings Conference slide 2
Slide from Tom Woolley presentation, October 2016
Healthy Buildings Conference slide 3
Slide from Tom Woolley presentation, October 2016
Healthy Buildings Conference slide 4
Contents
Ventilation performance summary – how are we doing?
Ventilation effectiveness overview – results from field
monitoring:
House Dust Mites
Carbon Dioxide
TVOCs
Nitrogen Dioxide
Radon
Summary – can we rely on good ventilation?
Healthy Buildings Conference slide 5
0
1
2
3
4
5
6
7
8
9
10
40-60% 60-80% 80-100% 100-120% 120-140% 140-160% 160-180%
Nu
mb
er o
f H
om
es
% of Required EQA
Installed ventilator area vs. AD F minimum specification
Data from DCLG 2009: Ventilation and IAQ in Part F 2006 homes study
Healthy Buildings Conference slide 6
Ventilation extract rates in new homes: continuous MEV
Site 1 Site 3 Site 4 Site 5 Site 6
Design 43.00 37.00 45.00 31.00 15.00
ZCH Measured 20.80 19.10 21.00 12.30 5.50
% of Required Duty 48 52 47 40 37
0.00
10.00
20.00
30.00
40.00
50.00
litre
s p
er s
eco
nd
Chart for Zero Carbon Hub: Ventilation in New Homes study
Healthy Buildings Conference slide 7
Measured flow rates – MVHR
Minimum boost rate met in:
44% kitchens
71% bathrooms
30% en-suites
38% utility rooms
Minimum supply air flow rates
met in 33% of dwellings
0.00
5.00
10.00
15.00
20.00
25.00
Kitchen Bathroom En Suite Utility W.C.
Litr
es p
er s
eco
nd
(l.s
-1)
Minimum AD F
Chart from Characteristics and performance of MVHR systems (meta study): MEARU/OISD/Fourwalls
Healthy Buildings Conference slide 8
Successful ventilation installation
requires a full house of happy
faces!
One unhappy face in the chain
(row) will likely result in failure.
None of the sites visited in this
study had a complete row of
happy faces.
None of the ventilation systems
met the minimum requirements
specified in AD F
Chart by Zero Carbon Hub: Ventilation in New Homes study
Healthy Buildings Conference slide 9
30.00
35.00
40.00
45.00
50.00
55.00
60.00
65.00
70.00
75.00
80.00
16.00 17.00 18.00 19.00 20.00 21.00 22.00 23.00 24.00
Rel
ativ
e H
um
idit
y (%
)
Temperature (oC)
No PP Ventilation PEH 7g.kg CEH min (DP2)
Hygrothermal conditions without purpose-provided ventilation
Healthy Buildings Conference slide 10
Hygrothermal conditions with purpose-provided ventilation
30.00
35.00
40.00
45.00
50.00
55.00
60.00
65.00
70.00
75.00
80.00
16.00 17.00 18.00 19.00 20.00 21.00 22.00 23.00 24.00
Rel
ativ
e H
um
idit
y (%
)
Temperature (oC)
No PP Ventilation With PP Ventilation PEH 7g.kg CEH min (DP2)
Healthy Buildings Conference slide 11
Seasonal performance – MVHR and non-MVHR
CO2 data from 43
monitored homes
CO2 levels higher in non-
MVHR dwellings through
spring and summer
Increasing CO2 levels in
MVHR dwellings in
summer may indicate shift
toward natural vent during
warmer periods 0%
20%
40%
60%
80%
100%
MVHR Non-MVHR MVHR Non-MVHR MVHR Non-MVHR
February April August
Perc
enta
ge o
f m
on
ito
red
bed
roo
ms
Percentage ≤1000 ppm Percentage >1000, <1500 ppm Percentage ≥1500 ppm
Chart from Characteristics and performance of MVHR systems (meta study): MEARU/OISD/Four Walls
Healthy Buildings Conference slide 12
CO2 – is not harmful
below 5000ppm, but it
can keep bad company.
CO2 is a useful indicator
for ventilation
effectiveness
Correlations can be found
with CO2 and chemical
pollutants
Formaldehyde is a
human carcinogen
CO2 concentration – a useful metric?
Chart with permission: MEARU
Healthy Buildings Conference slide 13
0.00
0.10
0.20
0.30
0.40
0.50
0.60
0.70
0.80
0.90
1.00
0 200 400 600 800 1000 1200 1400 1600 1800
mea
sure
d a
ir e
xch
ange
rat
e (a
ch)
measured TVOC (µg/m3)
Air exchange rates and TVOC concentrations in 30 bedrooms
Higher ach,
higher TVOC
=3Higher ach,
lower TVOC
=7
Lower ach,
higher TVOC
=14
Lower ach,
lower TVOC
=6
Healthy Buildings Conference slide 14
0
1
2
3
4
5
6
7
8
9
10
0-10 10-20 20-30 30-40 40-50 50-60
NO2 (micrograms.m-3)
Dilution of combustion by-products
Data from DCLG 2009: Ventilation and IAQ in Part F 2006 homes study
Healthy Buildings Conference slide 15
0
100
200
300
400
500
600
Bq
.m-3
Week
Radon (weekly mean)
Managing Radon – can we rely on ventilation?
≈ 0.5 ach
≈ <0.1 ach
≈ 0.5 ach
??
Healthy Buildings Conference slide 16
Summary – Can we rely on good ventilation?
We know there are significant performance issues with domestic ventilation
installations.
But, moving some air is still better than allowing it to stagnate and become
polluted – particularly the more airtight the building.
Source control is important: building occupants have little or no control over
background levels related to construction materials.
Design for low emission is a priority
At <8 l/s/p source control becomes more important: AD F is based on ≈3.5 l/s/p
Moisture and bio-effluents are key pollutants in domestic environments
Can we rely on ventilation?…
Well, not entirely (at domestic rates). But we do need to ventilate, so it had better
be good!
Healthy Buildings Conference slide 17
And finally…
Context is everything. E.g.:
What are you ventilating for – activities?
What is the building’s geometry/exposure/airtightness?
Is it in a Radon risk area?
How do (or will) occupants use the ventilation (including window use)?
What are the occupancy patterns and how does this relate to pollutants?
Risk relates to period of exposure and concentration of pollutant(s)
Etc., etc., etc.…
We don’t need to answer these to demonstrate Part F compliance. But we should
be asking when we determine appropriate ventilation strategies.
Ventilation should not be seen as an add-on – it is essential for safety.
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