Control of the indoor humidity in a marine climate is a challenge, especially under operating conditions where high indoor humidity is a norm. Outdated mechanical equipment, inefficient ventilation design, and occupants’ life styles are some of the contributing factors to high indoor humidity. In this field experimental study, the moisture buffering potential of unfinished drywall in reducing daily indoor humidity peaks, coupled with various ventilation strategies are investigated. Two identical test buildings exposed to real climatic conditions in Burnaby, BC are monitored under varying ventilation rates and schemes. The interior of the test building is clad with unfinished drywall, while the control building is covered with polyethylene, which has negligible moisture buffering. In this way, the moisture buffering potential of drywall under four test cases is isolated. Under the test cases, the indoor air quality in terms of CO2 concentration, and ventilation heat loss of the two buildings are also evaluated. The results show that the moisture buffering potential of drywall effectively regulates indoor humidity peaks, and maintains relative humidity levels within acceptable thresholds, when coupled with adequate ventilation as recommended by ASHRAE. When coupled with time-controlled and demand-controlled ventilation schemes, the moisture buffering effect of drywall shows competing benefits. Presented at the 15th Canadian Conference on Building Science and Technology

1. Moisture Buffering And
Ventilation Strategies To
Control Indoor Humidity
in a Marine Environment
A Field Experimental Study
Shahrzad Pedram, MASc, P.Eng. – RDH Building Science Inc.
Fitsum Tariku, PhD – BCIT Building Science Centre of Excellence

2. Outline
Introduction
What is moisture buffering?
Methodology
Experimental Set-up
Indoor moisture and CO2 load
Ventilation strategies
Results
Indoor humidity, CO2 levels, and ventilation heat loss
Conclusions and future works

3. indoor humidity
materials
condensation
/ evaporation
sinks &
sources
HVAC
outdoor
environment

4. High Indoor Humidity

5. Building air leakage rate
Ventilation systems
Occupants’ lifestyle
High Indoor Humidity

6. Building Airtightness
Source: http://en.wikipedia.org/wiki/Blower_door

7. Building Airtightness
Source: http://www.nanaimo-info-blog.com/2010/05/nanaimo-leaky-condo-townsite-raod.html

8. Ventilation Systems
Source: Ricketts & Straube (2014)

9. Occupants’ Behaviour

10. indoor humidity
materials
Moisture buffering
Hygric inertia
Humidity buffering

11. What is moisture buffering?

12. High Humidity
Source: American Clay

13. Low Humidity
Source: American Clay

14. Svennberg, et al. (2007)
Low Moisture
Buffering Potential
High Moisture
Buffering Potential

15. Previous research has shown that moisture buffering
can greatly affect indoor relative humidity.
Tariku (2011)

16. Previous research has shown that moisture buffering
can greatly affect indoor relative humidity.
Tariku (2011)
Up to 1/3 of indoor moisture affected

17. Can moisture buffering help manage indoor
humidity in a marine climate under varying
ventilation schemes?

18. Field Testing
Control building
no moisture buffering with moisture buffering
Test building

19. Why field testing?
Exposure to real climatic conditions
Can control interior operating
conditions
Data can be used for verification of
building simulation models

20. Field studies of moisture buffering have been
undertaken in predominantly cold climates
Sweden (Hameury, 2004)
Denmark (Woloszyn et al, 2005)
Germany (Kuenzel et al, 2004)
No field studies in a marine climate to date
Why Vancouver’s marine climate?

21. Whole-Building Performance
Research Lab

22. Whole-Building Performance
Research Lab

23. Q Q Q
T °C
&
RH%
Varying ventilation strategies
Q

24. Occupancy
CO2
CO2 CO2
H2O
H2O CO2
CO2 CO2
H2O
H2O
Simulated occupant loading

25. Actual indoor humidity data from a real suite

26. Occupancy simulators

27. Test # Test Period Ventilation Scheme Ventilation Strategy
1 April 2014 Constant 15 CFM
2 April 2014 Time Controlled 30 CFM at 8am - 12pm and 7pm - 11pm,
7.5 CFM all other times
3 June 2014 RH Controlled 7.5 CFM at 50% RH or less, 30 CFM at
60% RH or more, between 50-60% RH
linearly increasing CFM between 7.5 and
30 CFM
4 July 2014 CO2 Controlled 7.5 CFM at 800ppm or less, 30 CFM at
1000ppm or more, between 800-
1000ppm linearly increasing CFM
between 7.5 and 30 CFM
Constant Ventilation Time-Controlled Ventilation
RH-Controlled Ventilation CO2-Controlled Ventilation
0
5
10
15
20
25
30
35
40
CFM
-10
10
30
50
70
90
110
130
150
0
5
10
15
20
25
30
35
40
45
50
1 5 9 13 17 21
MoistureProduction(g/hr)
CFM
Time of day (hour)
CFM Moisture Profile
OFFSET
0
5
10
15
20
25
30
35
40
0 10 20 30 40 50 60 70 80 90 100
CFM
Relative Humidity (%)
0
5
10
15
20
25
30
35
40
0 200 400 600 800 1000 1200 1400
CFM
CO2 Concentration (PPM)
Constant Ventilation
RH-Controlled Ventilation
Figure 1: Ventilation rates (in ft3
/min.) and schemes for constant, time
0
5
10
15
20
25
30
35
40
CFM
CFM
0
5
10
15
20
25
30
35
40
0 10 20 30 40 50 60 70 80 90 100
CFM
Relative Humidity (%)
CFM
Constant Ventilation Time-Controlled Ventilation
RH-Controlled Ventilation CO2-Controlled Ventilation
Figure 1: Ventilation rates (in ft3
/min.) and schemes for constant, time-controlled, RH-controlled, and CO2-controlled ventilation.
0
5
10
15
20
25
30
35
40
CFM
-10
10
30
50
70
90
110
130
150
0
5
10
15
20
25
30
35
40
45
50
1 5 9 13 17 21
MoistureProduction(g/hr)
CFM
Time of day (hour)
CFM Moisture Profile
OFFSET
0
5
10
15
20
25
30
35
40
0 10 20 30 40 50 60 70 80 90 100
CFM
Relative Humidity (%)
0
5
10
15
20
25
30
35
40
0 200 400 600 800 1000 1200 1400
CFM
CO2 Concentration (PPM)
Constant Ventilation
RH-Controlled Ventilation
Figure 1: Ventilation rates (in ft3
/min.) and schemes for constant, time-
0
5
10
15
20
25
30
35
40
CFM
CFM
0
5
10
15
20
25
30
35
40
0 10 20 30 40 50 60 70 80 90 100
CFM
Relative Humidity (%)
CFM

28. Constant Ventilation Time-Controlled Ventilation
0
5
10
15
20
25
30
35
CFM
-10
10
30
50
70
90
110
130
0
5
10
15
20
25
30
35
40
45
1 5 9 13 17 21
MoistureProduction(g/hr)
CFM
Time of day (hour)
CFM Moisture Profile
OFFSET
0
5
10
15
20
25
30
35
40
0 10 20 30 40 50 60 70 80 90 100
CFM
Relative Humidity (%)
0
5
10
15
20
25
30
35
40
0 200 400 600 800 1000 1200 1400
CFM CO2 Concentration (PPM)
Constant Ventilation Time-Controlled Ventilation
0
5
10
15
20
25
30
35
CFM
-10
10
30
50
70
90
110
130
0
5
10
15
20
25
30
35
40
45
1 5 9 13 17 21
MoistureProduction(g/hr)
CFM
Time of day (hour)
CFM Moisture Profile
OFFSET
0
5
10
15
20
25
30
35
40
0 10 20 30 40 50 60 70 80 90 100
CFM
Relative Humidity (%)
0
5
10
15
20
25
30
35
40
0 200 400 600 800 1000 1200 1400
CFM CO2 Concentration (PPM)
Constant Ventilation Time-Controlled Ventilation
0
5
10
15
20
25
30
35
40
CFM
-10
10
30
50
70
90
110
130
150
0
5
10
15
20
25
30
35
40
45
50
1 5 9 13 17 21
MoistureProduction(g/hr)
CFM
Time of day (hour)
CFM Moisture Profile
OFFSET
0
5
10
15
20
25
30
35
40
0 10 20 30 40 50 60 70 80 90 100
CFM
0
5
10
15
20
25
30
35
40
0 200 400 600 800 1000 1200 1400
CFM
Constant Ventilation Time-Controlled Ventilation
0
5
10
15
20
25
30
35
40
CFM
-10
10
30
50
70
90
110
130
150
0
5
10
15
20
25
30
35
40
45
50
1 5 9 13 17 21
MoistureProduction(g/hr)
CFM
Time of day (hour)
CFM Moisture Profile
OFFSET
0
5
10
15
20
25
30
35
40
0 10 20 30 40 50 60 70 80 90 100
CFM
0
5
10
15
20
25
30
35
40
0 200 400 600 800 1000 1200 1400CFM

29. Results

30. Control
Building
Test
Building

33. Relative Humidity Amplitudes

34.  in Relative Humidity Amplitudes

35. CO2 Levels
Ventilation
Scheme
Control
Building
Test
Building
Constant 40% 48%
Time-controlled 51% 55%
RH-controlled 0% 0%
CO2-controlled 0% 0%

36. Ventilation Heat Loss

37. Ventilation Heat Loss
Total ventilation heat energy loss in kJ and kW-hr

38. Findings of Research
Moisture buffering works!
• Effective in regulating humidity levels as
a passive measure when coupled with
adequate ventilation
• Not a substitute for ventilation
• Effective under high moisture loading
• Different ventilation schemes provide
competing interests between moisture
management and IAQ
• Moisture buffering can increase
ventilation demand

39. Findings of Research
Moisture buffering works!
• Time-controlled ventilation + moisture
buffering achieved 20% energy savings
versus constant ventilation + moisture
buffering without compromising indoor RH
levels (CO2 levels were comparable)
• Moisture buffering of unpainted gypsum
board generally helped regulate indoor
humidity in our climate

40. Future Research
• Optimization of ventilation strategy and moisture
buffering properties
• Alternative finishing materials
• Design criteria for moisture buffering performance
• Seasonal changes in occupants’ loading
• Optimized ventilation algorithms

41. Thank you for your attention!
Questions?