Influence of material properties on the moisture response of an ideal stucco wall : results from hygrothermal simulation

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Influence of material properties on the moisture response of an ideal

stucco wall : results from hygrothermal simulation

Mukhopadhyaya, P.; Goudreau, P.; Kumaran, M. K.; van Reenen, D.

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Influence of material properties on the moisture

response of an ideal stucco wall: resuls from

hygrothermal simulation

Mukhopadhyaya, P.; Goudreau, P.; Kumaran,

M.K.; van Reenen, D.

A version of this document is published in / Une version de ce document se trouve dans : 6th Nordic Building Physics Symp., Trondheim, Norway, June 17-19, 2002, pp. 611-618

www.nrc.ca/irc/ircpubs

Influence of Material Properties on the Moisture Response of

an Ideal Stucco Wall: Results from Hygrothermal Simulation

Phalguni Mukhopadhyaya, PhD*

Patrick Goudreau

, BS Student

Kumar Kumaran, PhD*

David van Reenen, BS*

1. INTRODUCTION

In a composite wall, each constituent component plays a specific role in effective moisture

management. The moisture movement to and from the wall assembly, subjected to climatic

forces, such as relative humidity (RH), temperature, rainfall and solar radiation, is influenced

by the basic hygrothermal properties of the component materials. Studies conducted at the

National Research Council (NRC) Canada, over the years, show that the hygrothermal

properties of materials vary over a wide range. Quite naturally, such variation may influence

the overall moisture response of the wall. This paper investigates the extent to which each

component of the wall can influence the overall drying and wetting characteristics of an ideal

(i.e., without any deficiency) wood-frame stucco wall when it is exposed to weather

conditions typical of coastal Western Canada.

The component materials selected include stucco, sheathing board, a sheathing membrane

and a vapour barrier. Hygrothermal material properties compiled in the laboratory at the NRC

and the hygrothermal modelling tool, hygIRC, developed by the NRC, are used for this

purpose. The findings of this study indicate that, with further work and analysis, practical

guidance could be developed to assist designers and engineers to identify the critical

components and properties of the stucco wall assembly to achieve a desirable moisture

management strategy for the building envelope.

2. BACKGROUND

The moisture management effectiveness of the building envelope depends on the construction

technique and component materials used to fabricate it. Each component has a role to play.

Specific hygrothermal properties of each material greatly affect that material's ability to fulfil

its intended role in the moisture management strategy. However, very little is known about

the extent to which the hygrothermal properties of the individual materials control the overall

moisture response of the wall assembly. Limited research has been conducted at the Institute

for Research in Construction (IRC) of the National Research Council, in the recent past on

cement board. These results indicate that moisture diffusivity, water vapour permeability and

sorption characteristics influence the drying characteristics of the material (Kumaran and

Wang 1999).

This paper attempts to move beyond the studies already conducted at the IRC/NRC

(Kumaran and Wang 1999) to find out what effect of the hygrothermal properties of

individual materials have on the overall moisture response of a composite wall assembly. The

assembly that is considered in this study is a traditional wood-frame stucco wall. The

response of the wall is simulated using an advanced hygrothermal model (Karagiozis 1997;

Mukhopadhyaya and Kumaran 2001), developed by the NRC known as hygIRC. The

component materials studied here are stucco, sheathing board, sheathing membrane and

vapour barrier.

*

Institute for Research in Construction, National Research Council, Ottawa, Canada,

K1A OR6, (Email: phalguni.mukhopadhyaya@nrc.ca)

3. HYGROTHERMAL MODELLING

AND hygIRC

Hygrothermal models are powerful tools for building envelope designers (Hens 1996). The hygrothermal modelling tool hygIRC is a research tool continuously evolving at the IRC/NRC (Karagiozis 1997; Mukhopadhyaya and Kumaran 2001). The utility and reliability of hygIRC outputs have been established through laboratory measurements and benchmarking exercises (Maref et al. 2002). Well-defined basic material properties and environmental boundary conditions are the necessary input parameters for hygrothermal modelling.

3.1 Material Properties for

hygIRC

Eight sets of material properties are required for hygIRC simulation: air permeability, thermal conductivity, dry density, heat capacity, sorption characteristics, suction pressure, liquid diffusivity and water vapour permeability. These properties, for all the materials, are obtained from IRC/NRC's database.

3.2 Boundary Conditions

Two major environmental conditions that govern the moisture response of the building envelope are the outdoor climate and the indoor climate. The outdoor climatic condition required for hygIRC simulations has seven major weather components (i.e., temperature, relative humidity, wind velocity, wind direction, rain fall, solar radiation and cloud index) recorded on an hourly basis. The hourly indoor climatic condition (i.e., temperature, relative humidity) is derived from outdoor climatic data using the latest weather analysis tool Weathersmart (Djebbar et al. 2001a,b) developed at the IRC/NRC. Weathersmart takes into account the hourly outdoor climatic data and derives the indoor temperature and relative humidity based on the established relationship between outdoor and indoor climatic conditions (Figure 1).

Figure 1

Indoor climate

3.3 Location and Exposure Period

Researchers at the IRC/NRC have collected the complete weather data required for hygIRC simulation for all the major locations in North America for the last 30 years. In this study, a typical weather year representing weather conditions of coastal Western Canada (i.e., temperate oceanic cool) with a total exposure or simulation duration of two years (same weather year repeated) is used for the parametric studies.

3.4 Initial Moisture Content

In any hygrothermal simulation, the user defines the initial moisture content of each wall component at the beginning of the first year. It is assumed that the initial moisture content of each wall component is equivalent to the corresponding relative humidity of 50 percent, derived from the sorption isotherm of the respective materials. This is not a realistic choice, but a useful starting point. Hence, a two-year (repeat of a weather year) exposure period is considered to obtain realistic moisture distributions inside the wall, irrespective of the assumed initial moisture content, for the second year. The first year of the simulation is considered to be an initial conditioning period, and all the observations are made on the basis of the hygrothermal response of the wall assembly during the second year.

4. WALL CONSTRUCTION DETAILS

The basic construction details of the wood-frame stucco wall are shown in Figure 2. Note that the construction details (i.e., component thickness and wall height) of the wall remain the same for

20 21 22 23 24 25 0 2000 4000 6000 8000 10000 Time (hours) Temperature (deg. C) 0 10 20 30 40 50 60 70 80 90 100 Realtive Humidity (%) Temperature Relative Humidity 1 st January 31 st December

all the simulations done in this study, and only the material properties are changed for the parametric studies as described in the following sections.

Table 1

Parametric variation

Material

Modified

Parameter

Simulation ID

ST

Mean material

ST

Water vapour

permeability

VASTVAP***

ST

Air permeability

ST

Sorption

isotherm

ST

Liquid

diffusivity

SM

Mean material

SM

Water vapour

permeability

VASMVAP***

SM

Air permeability

SB

Mean material

SB

Water vapour

permeability

SB

Sorption

isotherm

VB

Mean material

VB

Water vapour

permeability

VAVBVAP***

VB

Air permeability

ST: Stucco

SM: Sheathing Membrane SB: Sheathing Board VB: Vapour Barrier

***: MIN and MAX were added to all but the mean materials since every property was tested for a maximum (upper) and a minimum (lower) value.

Figure 2

Basic wall construction details

5. PARAMETRIC STUDIES

Four major wall components considered for the parametric analysis are stucco, sheathing membrane, sheathing board and vapour barrier (Table 1).

The eight basic material properties for each component are taken from the IRC's material property database compiled during last 10 years. Each material has a number of characteristic properties available in the database; close observation showed that they vary over a range. To reflect this phenomenon in the parametric studies, each material property is represented by three different sets of values: upper, mean, and lower. Upper and lower values are real material properties but mean values are derived from numerical averaging of all the values available in the database for any particular material. In each simulation, the material properties for the wall components that are not under parametric evaluation the representative average materials (i.e., neither the best nor the worst of the available materials) are chosen

.

5.1 Stucco

External stucco cladding is the first line of defence against moisture penetration inside the wall (Figure 2). As a material it has got notable moisture absorption, retention and transmission capacity. Hence, basic material properties that vary considerably and would influence its moisture response are air permeability, liquid diffusivity, sorption isotherm, and water vapour permeability. The upper (STI), mean and lower (STII) values of all these four properties are shown in Figure 3. They are derived from a total of six stucco materials available in the database. For the sorption isotherm (Figure 3c), the upper (STI), mean and lower (STII) values are not

Top Plate ht. [76 mm] Gypsum [12mm] Vapour Barrier [0.152mm] Insul. Space [89 mm] Sheathing Board [11 mm] Sheath. Memb. [0.23mm] Stucco Cladding [19 mm] Bott. Plate ht. [76 mm] Area [225x1.5 mm2] of the sheathing board selected for RHT index calculation

consistent over the entire relative humidity range as they are selected on the basis of their behaviour close to full saturation (98% to 100% relative humidity).

Figure 3

Material properties (stucco)

5.2 Sheathing Membrane

The sheathing membrane is placed behind the stucco cladding on the sheathing board (Figure 2). Primarily, it controls moisture transportation, but has very little or an insignificant moisture retention capacity. Therefore, the properties of the sheathing membrane that would most likely influence the overall moisture response of the wall are the water vapour permeability and air permeability. The upper (SMI), mean and lower (SMII) values of these two properties from a total of nine materials available in the database are shown in Figure 4.

Figure 4

Material properties (sheathing membrane)

The upper and lower limit values for water vapour permeability are determined based on the

observation between 80% to 100% relative humidity.

5.3 Sheathing Board

Theeight sheathing boards considered in this study are all engineered wood-based materials (e.g., oriented- strand-board or OSB, plywood, fibreboard etc.). Sheathing board with a thickness of 11 mm (Figure 2) has notable capacity to absorb and retain moisture, and transmit moisture through it. However, as it is positioned behind the stucco and sheathing membrane, it is reasonably well protected from direct contact with liquid (rainwater). Hence, the material properties selected for

P e rm e a b ili ty 1E-17 1E-16 1E-15 1E-14 1E-13 1E-12 0 0.2 0.4 0.6 0.8 Moisture Content (kgw/kgd) Air Permiability (m 2) SMI SMII Mean 0.E+00 1.E-12 2.E-12 3.E-12 0% 20% 40% 60% 80% 100% Relative Humidity

W. Vap. Permiability (kg/msPa)

SMI SMII Mean

(a) Water vapour permeability

(b) Air permeability

P e rm e a b il it y P e rm e a b il it y 1E-17 1E-16 1E-15 1E-14 1E-13 0 0.05 0.1 0.15 0.2 0.25 0.3 Moisture Content (kgw/kgd) Air Permeability (m 2) STI STII Mean 1.0E-16 1.0E-14 1.0E-12 1.0E-10 1.0E-08 1.0E-06 0 0.05 0.1 0.15 0.2 0.25 Moisture Content (kgw/kgd) Liquide Difusivity (m 2 /s) STI STII Mean 0.00 0.04 0.08 0.12 0.16 0.20 0% 20% 40% 60% 80% 100% Relative Humidity Moisture Content (kg w/kg d) STI STII Mean 0.0E+00 5.0E-12 1.0E-11 1.5E-11 2.0E-11 2.5E-11 3.0E-11 0% 20% 40% 60% 80% 100% Relative Humidity

Vapour Permiability (kg/msPa)

STI STII Mean

(a) Air permeability

(b) Liquid diffusivity

(c) Sorption isotherm

(d) Water vapour permeability

W . V a p . P e rm e a b il it y L iq u id D if fu s iv it y

the parametric studies are the sorption isotherm and water vapour permeability. The upper (SBI), mean and lower (SBII) values of these two properties are shown in Figure 5

.

Figure 5

Material properties (sheathing board)

5.4 Vapour Barrier

The vapour barrier (Figure 2), like the sheathing membrane, has very little moisture absorption or retention capacity, but can influence the air and water vapour movement across the wall. Hence, the properties of the vapour barrier selected for parametric studies are air permeability and water vapour permeability. The upper (VBI), mean and lower (VBII) values of these two selected material properties are shown in Figure 6.

Figure 6

Material properties (vapour barrier)

6. ANALYSIS OF RESULTS

The simulations done with hygIRC generated a huge amount of data. These include moisture and temperature distributions across the wall cross-section at different time intervals (a 10-day time interval was used), and the moisture content variation in the wall and its components with time. These outputs provide a comprehensive picture of the hygrothermal response of the wall. However, it is important to identify suitable indicators or yardsticks for the evaluation of drying and wetting characteristics of the wall assemblies that can be easily interpreted. The two indicators used in this study are moisture content and the RHT index (Kumaran et al. 2002).

6.1 Moisture Content

Moisture content (kg/m) is defined as the mass of moisture (k g) per unit length (metre) of the wall. The total moisture content in the composite wall and in the selected major wall components (stucco, sheathing board and insulation), available as hygIRC output at different stages of exposure, are compared to evaluate of wall performance.

0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 0% 20% 40% 60% 80% 100% Relative Humidity Moisture Content (kg w /kg d ) _SBI SBII Mean 0.E+00 2.E-11 4.E-11 6.E-11 8.E-11 1.E-10 0% 20% 40% 60% 80% 100% Relative Humidity

W. Vap. Permiability (kg/msPa)

SBII SBI Mean

(a) Sorption isotherm

(b) Water vapour permeability

P e rm e a b il it y 1.0E-21 1.0E-20 1.0E-19 1.0E-18 1.0E-17 1.0E-16 1.0E-15 0 0.2 0.4 0.6 0.8 1 1.2 Moisture Content (kgw/kgd) Air Permeability (m 2 ) VBI VBII Mean 1.0E-16 1.0E-15 1.0E-14 1.0E-13 0% 20% 40% 60% 80% 100% Relative Humidity

W. Vap. Perrmeability (kg/msPa)

VBI VBII Mean

(a) Air permeability

(b) Water vapour permeability

P e rm e a b il it y

6.2 RHT Index

A novel concept called the RHT Index has recently been developed at the IRC/NRC (Kumaran et al. 2002) that can be used to quantify and compare the localised hygrothermal response of any part of the wall component. The part of the wall component selected here for the RHT calculation is a thin layer (height 225mm; width 1.5mm) of sheathing board facing the exterior stucco cladding above the bottom plate (Figure 2). Relative humidity (RH) and temperature (T) at different output time steps (every 10 days over the entire second year of the study) are the output values required to obtain the RHT index in any selected area. Hence, the RHT index as defined in this study:

Cumulative 1 year (2nd year) RHT =∑ (RH-RHX) × (T-TX), for RH>RHX% and T>TX°C [1]

where user-defined threshold values for RHX = 80% and TX = 5°C. (During any time step when

either or both RH ≤ RHX% and T ≤ TX°C, the RHT value for that time step is zero.)

As can be seen from these definitions of the two chosen indicators, moisture content gives an idea of the overall moisture response of the complete wall or its components, but the RHT index brings out the localised combined moisture and temperature response of the selected area of the material.

7. RESULTS AND DISCUSSION

The values for moisture content and the RHT indices calculated as described in the previous section, are presented in Tables 2 to 5. The influence of various material properties on the overall moisture response of the wall is to be discussed in the following paragraphs with the help of these tabulated results.

7.1 Influence of Stucco Properties

As Table 2 indicates, the air permeability of stucco has the least influence, and liquid diffusivity has the greatest influence on the overall moisture response of the wall in terms of both moisture content and the RHT index. The water vapour permeability of stucco affects the moisture response of the wall more significantly than the sorption characteristic variation.

On closer observation the results (Table 2) reveal that the combination of maximum water vapour permeability and minimum liquid diffusivity would be very desirable characteristics for exterior stucco cladding.

Table 2

Simulation results – stucco

Moisture Content at

the Beginning of 1

Year [kg/m]

Moisture Content at

the Beginning of 2nd

Year [kg/m]

Moisture Content at

the End of 2

Year

[kg/m]

RHT

Index

Simulation ID

Stucco SB Insu. Total Stucco SB Insu. Total Stucco SB Insu. Total

VASTME 2.26 0.98 0.59 5.89 8.61 4.78 0.90 16.67 8.94 4.81 0.87 17.01 2093 VASTAIRMIN 2.26 0.98 0.59 5.89 8.61 4.78 0.90 16.67 8.94 4.81 0.87 17.02 2093 VASTAIRMAX 2.26 0.98 0.59 5.89 8.61 4.78 0.90 16.67 8.94 4.81 0.87 17.01 2092 VASTVAPMIN 2.26 0.98 0.59 5.89 8.61 4.78 0.90 16.69 8.95 4.81 0.87 17.04 2187 VASTVAPMAX 2.26 0.98 0.59 5.90 8.58 4.73 0.90 16.55 8.91 4.76 0.87 16.91 1443 VASTSORPMIN 2.84 0.98 0.59 6.48 7.31 5.22 0.92 15.90 7.61 5.24 0.88 16.21 2458 VASTSORPMAX 0.55 0.98 0.59 4.19 9.21 4.35 0.88 16.78 9.61 4.39 0.85 17.21 2033 VASTDIFMIN 2.21 0.98 0.59 5.85 4.96 1.78 0.62 9.55 5.06 1.84 0.62 9.72 34 VASTDIFMAX 2.26 0.98 0.59 5.90 8.89 4.92 0.90 17.11 9.18 4.95 0.87 17.42 2065

7.2 Influence of Sheathing Membrane Properties

The effect of the air permeability of the sheathing membrane on the overall moisture response of the wall is negligible as found in this study (Table 3). The variation of the water vapour permeability of the sheathing membrane has a small effect but is still insignificant (Table 3). An increase in the water vapour permeability slightly increases the moisture content and RHT index. This effect is most prevalent in the sheathing board moisture content but is still relatively small.

7.3 Influence of Sheathing Board Properties

The variation in the water vapour permeability of the sheathing board shows a small effect on the moisture content and RHT index of the wall (Table 4). The sorption characteristic variation of the

sheathing board has slightly more influence on the overall moisture response of the wall (Table 4), but is mostly limited to the moisture content of the sheathing board itself. In general, the effect of sheathing board properties on the overall RHT index is very small.

Table 3

Simulation results – sheathing membrane

Moisture Content at

the Beginning of 1

Year [kg/m]

Moisture Content at

the Beginning of 2nd

Year [kg/m]

Moisture Content at

the End of 2

Year

[kg/m]

RHT

Index

Simulation ID

Stucco SB Insu. Total Stucco SB Insu. Total Stucco SB Insu. Total

VASMME 0.53 0.98 0.59 4.16 9.22 3.79 0.82 16.11 9.30 4.02 0.83 16.48 2128 VASMAIRMIN 0.53 0.98 0.59 4.16 9.22 3.79 0.82 16.12 9.30 4.02 0.83 16.48 2128 VASMAIRMAX 0.53 0.98 0.59 4.16 9.22 3.79 0.82 16.12 9.30 4.02 0.83 16.48 2128 VASMVAPMIN 0.53 0.98 0.59 4.16 9.27 3.59 0.80 15.94 9.32 3.95 0.83 16.42 2113 VASMVAPMAX 0.53 0.98 0.59 4.16 9.22 3.92 0.83 16.11 9.27 4.07 0.83 16.48 2134

Table 4

Simulation results – sheathing board

Moisture Content at

the Beginning of 1

Year [kg/m]

Moisture Content at

the Beginning of 2nd

Year [kg/m]

Moisture Content at

the End of 2

Year

[kg/m]

RHT

Index

Simulation ID

Stucco SB Insu. Total Stucco SB Insu. Total Stucco SB Insu. Total

VASBME 0.53 0.47 0.59 3.65 9.22 2.68 0.77 14.98 9.23 3.02 0.80 15.38 2112 VASBSORPMIN 0.53 0.14 0.59 3.33 9.29 1.85 0.76 14.22 9.29 2.15 0.77 14.55 2093 VASBSOPRMAX 0.53 0.79 0.59 3.97 9.19 4.15 0.82 16.48 9.24 4.34 0.83 16.77 2132 VASBVAPMIN 0.53 0.47 0.59 3.65 9.22 2.57 0.78 14.54 9.23 3.06 0.81 15.44 2112 VASBVAPMAX 0.53 0.47 0.58 3.65 9.22 2.66 0.80 14.67 9.22 2.92 0.79 15.27 2117

7.4 Influence of Vapour Barrier Properties

As shown in Table 5, the effect of the variation in the air permeability properties of the vapour barrier on the overall moisture response of the wall is not visible in terms of both moisture content change and the RHT index. The influence of the change in the water vapour permeability properties is also very small but more noticeable than air permeability effects (Table 5).

Table 5

Simulation results – vapour barrier

Moisture Content at

the Beginning of 1

Year [kg/m]

Moisture Content at

the Beginning of 2nd

Year [kg/m]

Moisture Content at the

End of 2

Year

[kg/m]

RHT

Index

Simulation

ID

Stucco SB Insu. Total Stucco SB Insu. Total Stucco SB Insu. Total

VAVBME 0.53 0.98 0.59 4.16 9.24 4.08 0.84 16.49 9.29 4.16 0.84 16.65 2102 VAVBAIRMIN 0.53 0.98 0.59 4.16 9.23 4.08 0.84 16.48 9.27 4.16 0.85 16.64 2102 VAVBAIRMAX 0.53 0.98 0.59 4.16 9.23 4.08 0.84 16.48 9.28 4.16 0.84 16.65 2102 VAVBVAPMIN 0.53 0.98 0.59 4.16 9.22 4.03 0.83 16.40 9.26 4.12 0.84 16.58 2135 VAVBVAPMAX 0.53 0.98 0.59 4.16 9.24 4.10 0.84 16.51 9.29 4.18 0.85 16.67 2080

8. SUMMARY OF OBSERVATIONS

The observations presented in this paper are derived using a number of specific conditions or criteria:

- The material property database of the IRC/NRC, has been developed over the last 10 years. - The material property variations are as normally available in the market. No designed or intentional variation in the material properties is considered.

- Ideal stucco wall construction (i.e., without any deficiency or unintentional moisture entry) is used.

- Simulations done with IRC's hygrothermal model hygIRC.

- Walls are exposed to coastal Western Canada (i.e., temperate oceanic cool) weather conditions for two years.

- Indoor climate (temperature and relative humidity) is a function of exterior climate as defined by the IRC's latest weather analysis tool Weathersmart.

The observations made in this study are useful, practical and applicable only for the conditions stated above. Specific observations from this study include the followings.

(1) Detailed analysis of the IRC's material property database shows the hygrothermal properties of the building materials used in North America vary and can be represented by the upper limit, mean and lower limit values.

(2) In general, material property variation affects the hygrothermal response of the wall.

(3) Not all materials or every material property affects the overall moisture response of the wall to the same extent.

(4) Among the four materials (stucco, sheathing membrane, sheathing board and vapour barrier) considered for the parametric analysis, stucco has the most significant variation in the material properties that influence the overall moisture response of the ideal stucco wall exposed to coastal Western Canada climate. More specifically, water vapour permeability (maximum) and liquid diffusivity (minimum) are the two most important properties for the stucco that need to be chosen carefully to obtain optimum moisture management in the wall assembly.

(5) Within the material property range available, variations in sheathing membrane, sheathing board or vapour barrier properties have little or no effect on the moisture response of the ideal stucco wall exposed to coastal Western Canada climate.

(6) Apart from the aforementioned specific observations, the effectiveness and utility of the novel concept of the RHT index to quantify and compare the localised hygrothermal response of a wall assembly is encouraging. Further development and research on the RHT index will be reported in due course.

9. ACKNOWLEDGEMENT

The authors would like to acknowledge the contribution of Mr. Steve Cornick of the IRC/NRC for providing hygIRC-compatible outdoor weather files for this study.

10. REFERENCES

Djebbar, R.; van Reenen, D. and Kumaran M. K. 2001a. Environmental boundary conditions for long-term hygrothermal calculations, 8th International Conference on Building Envelopes, Clearwater Beach, Florida, USA, p. 13.

Djebbar, R.; van Reenen, D. and Kumaran, M. K. 2001b. Indoor and outdoor weather analysis tool for hygrothermal modelling. 8th Conference on Building Science and Technology, Toronto, Ontario, Canada, pp. 140-157.

Hens, H., 1996, Heat, Air and Moisture Transport, Final Report, Vol. 1, Task 1: Modelling, International Energy Agency Annex 24, Laboratorium Bouwfysica, K. U.-Leuven, Belgium. Karagiozis, A. 1997. Analysis of the hygrothermal behaviour of residential high-rise building components. Client Report A-3052.4, IRC/NRC, National Research Council Canada, Ottawa. Kumaran, M. K.; Mukhopadhyaya, P.; Cornick, S. M.; Lacasse, M. A.; Maref, W.; Rousseau, M.; Nofal, M.; Quirt, J. D. and Dalgliesh, W. A. 2002. A methodology to develop moisture management strategies for wood-frame walls in North America: Application to stucco-clad walls. 6th Symposium on Building Physics in the Nordic Countries.

Kumaran, M.K.; and Wang, J. 1999. How well should one know the hygrotheraml properties of building materials?. Proceeding of CIB W40 Meeting (Prague, Czech Republic), pp.47-52.

Maref, W.; Kumaran, M. K.; Lacasse, M. A.; Swinton, M. C. and van Reenen, D. 2002. Laboratory measurements and bench marking of an advanced hygrothermal model. 12th International Heat Transfer Conference, Grenoble, France (in press).

Mukhopadhyaya, P. and Kumaran, M. K. 2001. Prediction of moisture response of wood frame walls using IRC’s advanced hygrothermal model (hygIRC). 2nd Annual Conference on Durability and Disaster Mitigation in Wood-Frame Housing. pp. 221-226.