Investigation of the Moisture Buffering Potential of Investigation of the Moisture Buffering Potential of Magnesium Oxide Board

Introduction

• Excess humidity is one of the main factors affecting building envelope failures.

• Additionally, it creates a favorable environment for mold growth on the interior finish of the building envelope which pose respiratory health risks to occupants.

• Controlling indoor humidity within an acceptable range is therefore important.

• Indoor humidity control is typically achieved by ventilation, however, excess ventilation negatively impacts the building energy performance.

• By employing interior finishes with moisture buffering potential; the ability of materials to absorb excess moisture when the indoor humidity is high and vice versa, indoor humidity control can be achieved passively thereby reducing the ventilation energy requirements.

• More benefits attributed to this moisture buffering phenomenon are: reduction of building latent heat load, cooling load and equipment size.

• Knowing that the moisture buffering potential varies for different materials, that of Magnesia board; a relatively new product, is not known and is investigated in this research project.

Research Scope

• The objective of this project was to investigate the moisture buffering potential of Magnesia board under different operation scenarios.

• This involved monitoring two identical side-by-side buildings while measuring the indoor air temperature and relative humidity to evaluate the moisture buffering potential.

• These two test buildings are called the Whole-Building Performance Research Laboratory (WBPRL). Laboratory (WBPRL).

• One of the buildings is set as a reference building and the second one as a test building.

• The interior of the reference building is finished with gypsum panels; the most common interior finish, and the test building will be finished with the magnesia board.

• Both buildings are exposed to the identical indoor hygrothermal loads generated by an in-house developed Indoor simulation system.

• The different operation scenarios are designed to access the effect of finishing, occupancy density, ventilation rate and control strategy and a combination.

Whole-Building Performance Research Laboratory (WBPRL)

Overview of Test Facilities

Occupancy Simulation System

TRIAD MAGNETICS F-401U

TRANSFORMER

OMRON G3NA-205B SOLID

STATE RELAY

AALBORG PSV-D SOLENOID

VALVE DRIVER

TRIAD MAGNETICS WSU240-1000 DC POWER SUPPLY

FTDI-USB-RS485-PCBA CONVERTER

ADAM-4024 CONTROLLER

Occupant simulation system control box

Humidification system components of the occupant simulator system

MethodologyMethodology

TEST #1:Normal Moisture

Production and 15cfm

TEST #2:Normal Moisture

Production and 7.5cfm

TEST #3: High Moisture

Production and 15cfm

TEST #4:Normal Moisture

Production and RH control

Field Verification of Moisture Production

Laboratory Calibration of Occupant Simulator Units

NORTH BUILDING (Painted Gypsum)

SOUTH BUILDING (Painted MAGO Board)

PARAMETERS: Indoor Temp, Relative Humidity

COMPARE

ANALYZE MOISTURE BUFFERING POTENTIAL

PARAMETERS: Indoor Temp, Relative Humidity

Phase I: Laboratory Calibration of the Phase I: Laboratory Calibration of the Occupant Simulator Units

Calibration Procedure

Determination of pump refill water level trigger

Laboratory setup for calibration of the indoor simulation units

Run #1: Linear fit of cumulative weight loss over time for occupancy simulator unit 1

y = 100.97x - 0.386

y = 89.837x + 1.6631R² = 0.9989

y = 88.664x + 1.9943R² = 0.9986

y = 85.26x + 4.8729R² = 0.997

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40

50

60

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90

100

Cum

mul

ativ

e W

eigh

t L

oss

(g)

y = 100.97x - 0.386R² = 0.9991

0

10

20

30

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1

Cum

mul

ativ

e W

eigh

t L

oss

(g)

Time (hr)

Trial #1-1st quarter Trial #1-2nd quarter Trial #1-3rd quarter

Trial #1-4th quarter Linear (Trial #1-1st quarter) Linear (Trial #1-2nd quarter)

Linear (Trial #1-3rd quarter) Linear (Trial #1-4th quarter)

Phase II: Field Verification of the Moisture Production Rate of the Moisture Production Rate of the

Occupant Simulator Units

Experimental Setup of WBPRL

RH-T’s

RH-T’s

POLY LINING OF THE CEILING,

OCCUPANT SIMULATOR

UNITS

RADIANT HEATER

RH-T’s

THE CEILING, FLOOR AND

WALLS

Field verification of the moisture production rate in the north and south building: Indoor temperature comparison

21

22

23

24

Tem

pera

ture

(oC

)

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19

20

2/3 17:00 2/3 23:00 2/4 5:00 2/4 11:00

Tem

pera

ture

(oC

)

SB Indoor Temp NB Indoor Temp

Field verification of the moisture production rate in the north and south building: Relative humidity comparison

70

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90

100

Rel

ativ

e H

umid

ity

(%)

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50

60

2/3 17:00 2/3 23:00 2/4 5:00 2/4 11:00

Rel

ativ

e H

umid

ity

(%)

SB Indoor RH NB Indoor RH

Comparison of the Laboratory derived and field derived calibration rates of the occupant simulator units

SouthBuilding Occupant

Simulator 1

SouthBuilding Occupant

Simulator 2

NorthBuilding Occupant

Simulator 1

NorthBuilding Occupant

Simulator 2

Calibrated Rate [g/hr] 90 141 70 126

Actual Rate [g/hr] 120 189 102 185

Phase III: Field testing of the moisture buffering potential of painted Magnesia buffering potential of painted Magnesia

board

Experimental Setup of WBPRL

Ceiling Fan

Poly Lining

Ceiling Fan

RH-T’s

Occupant Simulator

Unit

Radiant Heater

Poly Lining Of Ceiling And Floor

RH-T’sRH-T’s

Radiant Heater

Occupant Simulator

Unit

Poly Lining Of

Ceiling And Floor

South Building: MAGO BoardNorth Building: Gypsum Board

Test case #1: Relative humidity comparison of both buildings exposed to normal moisture production and normal ventilation rate

60

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80

90

100

Rel

ativ

e H

umid

ity

(%)

0

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50

4/11 4:00 4/11 10:00 4/11 16:00 4/11 22:00 4/12 4:00

Rel

ativ

e H

umid

ity

(%)

MAGO_RH Gypsum_RH

Test case #2: Relative humidity comparison of both buildings exposed to normal moisture production and low ventilation rate

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60

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100

Rel

ativ

e H

umid

ity

(%)

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50

4/25 15:00 4/25 21:00 4/26 3:00 4/26 9:00 4/26 15:00

Rel

ativ

e H

umid

ity

(%)

MAGO_RH Gypsum_RH

Test case #3: Relative humidity comparison of both buildings exposed to high moisture production and normal ventilation rate

50

60

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100

Rel

ativ

e H

umid

ity

(%)

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4/16 4:00 4/16 10:00 4/16 16:00 4/16 22:00 4/17 4:00

Rel

ativ

e H

umid

ity

(%)

MAGO_RH Gypsum_RH

Test case #4: Relative humidity comparison of both buildings exposed to normal moisture production and RH controlled ventilation rate

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Rel

ativ

e H

umid

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(%)

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5/3 4:00 5/3 10:00 5/3 16:00 5/3 22:00

Rel

ativ

e H

umid

ity

(%)

MAGO_RH Gypsum_RH

Test case #4: Ventilation Rate comparison of both buildings exposed to normal moisture production and RH controlled ventilation rate

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25

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45V

enti

lati

on R

ate

(CF

M)

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5/4 14:00 5/4 20:00 5/5 2:00 5/5 8:00 5/5 14:00

Ven

tila

tion

Rat

e (C

FM

)

MAGO_CFM_Rate Gypsum_CFM_Rate

Conclusion

• No measureable difference in moisture buffering performance between the gypsum and magnesia board.

• This is attributed to the interior surface coating of both interior finishes.

• To put in perspective, the permeability of ½” gypsum wall board is 51 perms, according to ASHRAE HOF, priming and coating gypsum has the potential to drop the permeability to about 10 perms.

• Falls under the category of Class II vapor retarders.• Falls under the category of Class II vapor retarders.

• The same could be said about the magnesia board, hence the similarity in moisture buffering performance of both interior finishes.

• In Phase IV of this research project both interior finishes will be tested without the interior primer or paint coating for maximum moisture buffering potential

Phase IV: Investigation of the moisture buffering potential of unpainted Investigation of the moisture buffering potential of unpainted

Magnesia board

Experimental Setup of WBPRL

Ceiling Fan

Poly Lining

Ceiling Fan

RH-T’s

Occupant Simulator

Unit

Radiant Heater

Poly Lining Of Ceiling And Floor

RH-T’sRH-T’s

Radiant Heater

Occupant Simulator

Unit

Poly Lining Of

Ceiling And Floor

South Building: MAGO BoardNorth Building: Gypsum Board

Test case #1: Relative humidity comparison of both buildings exposed to normal moisture production and normal ventilation rate

60

70

80

90

100

Rel

ativ

e H

um

idit

y (%

)

MAGO_RH

Gypsum_RH

0

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20

30

40

50

60

8/14 4:00 8/14 10:00 8/14 16:00 8/14 22:00 8/15 4:00

Rel

ativ

e H

um

idit

y (%

)

Test case #2: Relative humidity comparison of both buildings exposed to normal moisture production and low ventilation rate

60

70

80

90

100

Rel

ativ

e H

umid

ity

(%)

MAGO_RH

Gypsum_RH

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30

40

50

7/14 4:00 7/14 10:00 7/14 16:00 7/14 22:00 7/15 4:00

Rel

ativ

e H

umid

ity

(%)

Test case #3: Relative humidity comparison of both buildings exposed to high moisture production and normal ventilation rate

60

70

80

90

100

Rel

ativ

e H

umid

ity

(%)

MAGO_RH

Gypsum_RH

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40

50

60

8/26 0:00 8/26 6:00 8/26 12:00 8/26 18:00 8/27 0:00

Rel

ativ

e H

umid

ity

(%)

Test case #4: Relative humidity comparison of both buildings exposed to normal moisture production and RH controlled ventilation rate

60

70

80

90

100

Rel

ativ

e H

umid

ity

(%)

MAGO_RH

Gypsum_RH

0

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20

30

40

50

9/3 3:00 9/3 9:00 9/3 15:00 9/3 21:00 9/4 3:00

Rel

ativ

e H

umid

ity

(%)

Test case #4: Ventilation Rate comparison of both buildings exposed to normal moisture production and RH controlled ventilation rate

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30

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40

45

Ven

tila

tio

n R

ate

(CF

M)

MAGO_CFM_Rate

Gypsum_CFM_Rate

0

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20

25

9/3 3:00 9/3 9:00 9/3 15:00 9/3 21:00 9/4 3:00

Ven

tila

tio

n R

ate

(CF

M)

Conclusion/Further Work

• Magnesia board showed similar moisture buffering capability to gypsum in that the discrepancies in the relative humidity comparisons

• Considering the similar moisture buffering behavior different surface characteristics of both boards, gypsum is more receptive to mold growth as a substrate

• Reason: Gypsum is paper faced compared to the hard and smooth magnesia board surfaceboard surface

• That being said, the experimental setup was designed to investigate the maximum buffering potential and it was found to be significant when compared with the previous phase

• Following, both boards will be coated with high permeable paint to investigate its impact on the moisture buffering.