Mid-rise wood: characterization of hygrothermal properties: report to Research Consortium for Wood and Wood-Hybrid Mid-Rise Buildings

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Mid-rise wood: characterization of hygrothermal properties: report to

Research Consortium for Wood and Wood-Hybrid Mid-Rise Buildings

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NATIONAL RESEARCH COUNCIL CANADA

REPORT TO RESEARCH CONSORTIUM

FOR WOOD AND WOOD-HYBRID

MID-RISE BUILDINGS

Mid-Rise Wood – Characterization of

Hygrothermal Properties

CLIENT REPORT: A1-100035-03.4

December 31, 2014

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REPORT TO RESEARCH CONSORTIUM FOR WOOD AND

WOOD-HYBRID MID-RISE BUILDINGS

Mid-Rise Wood – Characterization of Hygrothermal

Properties

P. Mukhopadhyaya, S. Bundalo-Perc and D. van Reenen (NRC)

J. Wang (FPInnovations)

Report No.

A1-100035-03.4

Report date:

December 31, 2014

Contract No.

B-7000 (A1-100035)

Prepared for

Canadian Wood Council

FPInnovations

Régie du bâtiment du Québec

HER MAJESTY THE QUEEN IN RIGHT OF ONTARIO as represented

by the Minister of Municipal Affairs and Housing

18 pages

This report may not be reproduced in whole or in part without the written consent of both the client and the National Research Council of Canada.

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Table of Contents Part I – Hygrothermal Properties of Four Materials

1 Introduction 1

2 Hygrothermal Properties Determination 1

2.1 D-Blaze Treated Plywood 1

2.2 Dricon Treated Plywood 4

2.3 Gypsum Sheathing 6

2.4 Closed Cell Spray Polyurethane Foam Insulation (Purple in Colour) 8

3 References 10

Part II – A Package of Property Data for Hygrothermal Simulation of CLT Assemblies

1 Hygrothermal Properties 12

2 Appendix: 15

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MID-RISE WOOD – CHARACTERIZAT IO N OF HYGROTHERMAL PROPERTIES P. Mukhopadhyaya, S. Bundalo-Perc and D. van Reenen (NRC)

J. Wang (FPInnovations)

To evaluate the building envelope performance of the generic exterior wall assemblies

developed for use in mid-rise wood buildings, hygrothermal properties of materials used in the assemblies are needed as input data for hygrothermal modelling. Hygrothermal properties were developed for fire retardant treated plywood, regular gypsum sheathing, spray polyurethane foam and cross-laminated timber. This report documents results of the hygrothermal property determinations.

Part I – Hygrothermal Properties of Four Materials 1 Introduction

The objective of this part of the research project was to generate a set of reliable and

representative data on hygrothermal properties of a number of selected building materials as mentioned below.

1. D-Blaze Treated Plywood 2. Dricon Treated Plywood 3. Gypsum Sheathing

4. Closed Cell Spray Polyurethane Foam Insulation (Purple in Colour) 2 Hygrothermal Properties of Materials

The results of the testing, along with the methods used, are provided in this section. 2.1 D-Blaze Treated Plywood

The test specimens used for the various measurements presented in this report were taken from a board of 12.0 mm thickness.

Density: 525.4 kg m-3

Heat Capacity: 1880 J K-1_kg-1_{(Kumaran, et al. 2002)}

Thermal Conductivity:

Measurements were conducted in accordance with ASTM standard C518 (ASTM International 2010). One specimen was tested in an apparatus with a 30.5 cm x 30.5 cm cross section. Heat flow was perpendicular to this primary surface.

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Specimen Thickness mm Hot Surface Temperature °C Cold surface Temperature °C Conductivity W m-1_K-1 12.0 34.8 12.9 0.103

The average thermal conductivity was 0.103 W m-1_K-1_{tested with a mean temperature of}

23.9 °C.

Sorption Measurements

Five specimens with a size of 50 mm X 50 mm were used in these measurements. The

measurements were done following the procedure described in ASTM Standard C1498 (ASTM International 2004). The results of the testing are shown below.

RH, % Moisture content_{kg kg}-1

50.4 0.0737

69.1 0.0898

89.8 0.2036

95.2 0.2609

Derived Water Vapour Permeability

Water vapour permeability testing was conducted following the procedure described in ASTM Standard E96/96M (ASTM International 2010). The procedure specified in this standard for calculating the dependence of water vapour transmission rate on relative humidity was used. For each test condition, 3 circular specimens, having a diameter of about 15 cm were tested. The derived curve for water vapour permeability was based on values shown below.

RH, % Permeability kg m-1_s-1_Pa-1 RH, % _{kg m}Permeability-1_s-1_Pa-1 10 3.05×10-13 ₆₀ _3.13×10-12 20 5.21×10-13 ₇₀ _5.10×10-12 30 8.16×10-13 ₈₀ _8.57×10-12 40 1.26×10-12 ₉₀ _1.51×10-11 50 1.97×10-12 ₁₀₀ _2.84×10-11

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Water Absorption Coefficient

Water absorption coefficient was determined according to procedure described in ISO

15148:2002. Six test specimens, each having dimensions of 5 cm X 5 cm were used in these measurements. One major surface of each test specimen was placed in contact with liquid water and four edges were sealed with layers of wax. Water was maintained at (22 ± 1) °C. The numbers in parentheses give the standard deviations.

Square Root of time,

s½ Water Absorption_{kg m}-2 0.0 0.00 (0.00) 24.5 0.19 (0.02) 34.6 0.23 (0.03) 42.4 0.26 (0.03) 60.0 0.34 (0.04) 73.5 0.39 (0.05) 84.9 0.43 (0.06) 103.9 0.49 (0.07) 120.0 0.54 (0.08) 134.2 0.59 (0.09) 169.7 0.72 (0.11) 275.0 1.12 (0.14)

Linear regression using all the data from the first linear part of the absorption process for the five specimens was done to derive the water absorption coefficient as: 0.0034 kg m-2_s-½_.

Air Permeability

The measurements and calculations were executed according to the procedure reported by Bomberg and Kumaran (1986). Three circular test specimens, having the same dimensions as specimens used to derive water vapour permeability properties, were used for the

measurements. Measurements were executed at a temperature of 22 ± 1 ° C. The resulting air permeability was:

(2.39 ± 2.65)×10-3_{L(75 Pa)}-1_·m-1_·s-1

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2.2 Dricon Treated Plywood

The test specimens used for the various measurements presented in this report were taken from a plywood board of 15.8 mm thickness.

Measurements were conducted in accordance with ASTM standard C518 (ASTM International 2010). One specimen was tested in an apparatus with a 61 cm x 61 cm cross section. Heat flow was perpendicular to this primary surface.

The average thermal conductivity was 0.0936 W m-1_K-1_{tested with a mean temperature of}

24.2 °C

Sorption Isotherm

Up to nine specimens with a size of 40 mm X 40 mm were used in these measurements. The measurements were done following the procedure described in ASTM Standard C1498 (ASTM International 2004). RH % Moisture content kg kg-1 50.4 0.074 69.1 0.090 89.8 0.186 95.2 0.267

Water Vapour Permeability

Water vapour permeability testing was conducted following the procedure described in ASTM Standard E96/96M (ASTM International 2010). The procedure specified in this standard for calculating the dependence of water vapour transmission rate on relative humidity was used. For each test condition, 3 circular specimens, having a diameter of 15 cm were tested.

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RH, % _{kg m}Permeability-1_s-1_Pa-1 RH, % _{kg m}Permeability-1_s-1_Pa-1 10 3.39×10-13 ₆₀ _3.55×10-12 20 5.82×10-13 ₇₀ _5.81×10-12 30 9.14×10-13 ₈₀ _9.81×10-12 40 1.42×10-12 ₉₀ _1.73×10-11 50 2.23×10-12 ₁₀₀ _3.23×10-11

Water absorption coefficient was determined according to procedure described in ISO 15148:2002. One major surface of each test specimen was placed in contact with liquid water and four edges were sealed with layers of wax. Five test specimens, each having dimensions of 5 cm X 5 cm, were used in these measurements. Water was maintained at 22 ± 1 °C. The numbers in parentheses give the standard deviations.

Square Root of

time, s½ Water Absorption_{kg m}-2

0.0 0.00 (0.00) 24.5 0.16 (0.04) 34.6 0.22 (0.05) 42.4 0.25 (0.06) 60.0 0.33 (0.06) 73.5 0.39 (0.06) 84.9 0.43 (0.07) 103.9 0.50 (0.07) 120.0 0.57 (0.07) 180.0 0.82 (0.09) 268.3 1.35 (0.47) 297.0 1.56 (0.55) 311.8 1.67 (0.60)

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The measurements and calculations were executed according to the procedure reported by Bomberg and Kumaran (1986). Three circular test specimens, with the same dimensions as the specimens used to determine water vapour permeability properties, were used for the measurements. Measurements were executed at a temperature of 22 ± 1 ° C.

The resulting air permeability was:

(3.24 ± 4.16)×10-4_{L(75 Pa)}-1_·m-1_·s-1

(5.12 ± 6.57)×10-12_kg·Pa-1_·m-1_·s-1

2.3 Gypsum Sheathing

The test specimens used for the various measurements presented in this report were taken from Gypsum sheathing board that had a thickness of 12.8 mm.

Derived Water Vapour Permeability

Water vapour permeability testing was conducted following the procedure described in ASTM Standard E96/96M (ASTM International 2010). The procedure specified in this standard for calculating the dependence of water vapour transmission rate on relative humidity was used. For each test condition, a minimum of 3 circular specimens, having a diameter of about 15 cm were tested.

The derived curve for water vapour permeability is shown below.

RH, % Permeability kg m-1_s-1_Pa-1 RH, % _{kg m}Permeability-1_s-1_Pa-1 10 1.35×10-11 ₆₀ _4.54×10-11 20 1.88×10-11 ₇₀ _5.39×10-11 30 2.45×10-11 ₈₀ _6.33×10-11 40 3.08×10-11 ₉₀ _7.39×10-11 50 3.78×10-11 ₁₀₀ _8.59×10-11

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Six test specimens, each having dimensions of 5 cm X 5 cm X 5 cm, were used in these measurements. Water is maintained at 22 ± 1 °C. The numbers in parentheses give the standard deviations.

Square Root of time,

s½ Water Absorption_{kg m}-2 0.0 0.000 (0.000) 24.5 0.070 (0.003) 34.6 0.090 (0.003) 42.4 0.103 (0.003) 60.0 0.130 (0.005) 73.5 0.146 (0.006) 84.9 0.159 (0.007) 103.9 0.172 (0.009) 120.0 0.175 (0.010) 147.0 0.171 (0.012) 169.7 0.168 (0.014) 180.0 0.168 (0.016) 297.0 0.168 (0.018) 317.5 0.169 (0.017) 339.4 0.171 (0.017) 424.3 0.177 (0.017)

Linear regression using all the data from the first linear part of the absorption process for the five specimens was done to derive the water absorption coefficient as: ± 0.0015 kg m-2_s-½_.

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The measurements and calculations were executed according to the procedure reported by Bomberg and Kumaran (1986). Three circular test specimens, with the same dimensions as the specimens used to determine water vapour permeability properties, were used for the measurements. Measurements were executed at a temperature of 22 ± 1 ° C.

The resulting air permeability was:

(2.82 ± 0.91)×10-4_{L(75 Pa)}-1_·m-1_·s-1

(4.44 ± 1.43)×10-12_kg·Pa-1_·m-1_·s-1

2.4 Closed Cell Spray Polyurethane Foam Insulation (Purple in Colour)

The test specimens used for the various measurements presented in this report were taken from insulation that had a nominal thickness of 50 mm.

Measurements were conducted in accordance with ASTM standard C518 (ASTM International 2010). The specimen was tested in an apparatus with a cross section of 61 cm x 61 cm. Heat flow was perpendicular to this primary surface.

The thermal conductivity was 0.0212 W m-1_K-1_{tested with a mean temperature of}

24.0 °C.

Sorption Measurements

Specimens of size 40 mm X 40 mm were used in these measurements. The measurements were conducted following the procedure described in ASTM Standard C1498 (ASTM

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RH

% Moisture Contentkg kg-1

50.2 0.00905

69.4 0.00804

Water Vapour Permeability:

Water vapour permeability testing was conducted following the procedure described in ASTM Standard E96/96M (ASTM International 2010). The procedure specified in this standard for calculating the dependence of water vapour transmission rate on relative humidity was used. For each test condition, a minimum of 3 circular specimens, having a diameter 1of 5 cm were tested.

The derived curve for water vapour permeability is shown below.

RH, % _{kg m}Permeability-1_s-1_Pa-1 RH, % _{kg m}Permeability-1_s-1_Pa-1 10 9.14×10-13 ₆₀ _2.23×10-12 20 1.09×10-12 ₇₀ _2.68×10-12 30 1.31×10-12 ₈₀ _3.21×10-12 40 1.56×10-12 ₉₀ _3.85×10-12 50 1.87×10-12 ₁₀₀ _4.62×10-12

Water absorption coefficient was determined according to procedure described in ISO

15148:2002. Eight test specimens, each having dimensions of 5 cm X 5 cm X 5 cm, were used in these measurements. One major surface of each test specimen was placed in contact with liquid water and four edges were sealed with layers of wax. Water is maintained at 22 ± 1 °C. The numbers in parentheses give the standard deviations.

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Square Root of

time, s½ Water Absorption_{kg m}-2

24.5 0.027 (0.006) 34.6 0.029 (0.005) 42.4 0.031 (0.005) 60.0 0.034 (0.006) 73.5 0.039 (0.005) 84.9 0.036 (0.006) 103.9 0.041 (0.006) 120.0 0.043 (0.006) 147.0 0.044 (0.006) 169.7 0.046 (0.006) 210.0 0.047 (0.006) 293.9 0.071 (0.008) 305.9 0.076 (0.007)

The measurements and calculations were executed according to the procedure reported by Bomberg and Kumaran (1986). Three circular test specimens, with the same dimensions as the specimens used to determine water vapour permeability properties, were used for the measurements. Measurements were executed at a temperature of 22 ± 1 ° C. The resulting air permeability was:

(1.69±2.42)×10-4_{L(75 Pa)}-1_·m-1_·s-1

(2.64±3.77)×10-14_kg·Pa-1_·m-1_·s-1

3 References

ASTM International. ASTM Standard C1498-04a "Standard Test Method for Hygroscopic

Sorption Isotherms of Buidling Materialas". West Chonshocken, PA: ASTM International,

2004.

ASTM Standard C518-10 "Standard Test Method for Steady-State Thermal Transmission Properties by Means of the Heat Flow Meter Apparatus". West Conshohocken, PA,

2010.

ASTM Standard E96/E96M - 10 "Standard Test Method for Water Vapor Transmission of Materials". West Conshohocken, PA: ASTM International, 2010.

Kumaran, M. K., and M. T. Bomberg. "A Test Method to determine ari flow resistane of exterior membranes and sheathings", Journal of Thermal Insulation, 1986: 9: 224-235.

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Kumaran, Mavinkal K, John K Lackey, Nicole Normandin, Fitsum Tariku, and David van Reenen. "A Thermal and Moisture Transport Property Database for Common Building and Insulating Materials: Final Report from ASHRAE Research Project 1018-RP." 2002.

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Part 2: A Package of Property Data for Hygrothermal Simulation of CLT Assemblies 1 Hygrothermal Properties

This package of hygrothermal property data for CLT (cross-laminated timber) panels is assembled to help facilitate hygrothermal simulation and durability by design of CLT building enclosure assemblies. The data are mostly based on the collaborative research between the National Research Council (NRC) of Canada and FPInnovations on CLT hygrothermal property testing, as well as characterization of wood sorption under critical moisture conditions. For the hygrothermal property testing three types of 5-layer CLT panels (about 130 mm thick) were made with three groups of species for Canadian softwood. These were: SPF (Spruce-Pine-Fir) dimension lumber from Eastern Canada (predominantly black spruce, Picea mariana), SPF lumber from British Columbia (predominantly lodgepole pine, Pinus contorta), and Hem-Fir lumber from British Columbia (predominantly western hemlock, Tsuga heterophylla). The CLT panels were manufactured at the FPInnovations Laboratory in Vancouver using Emulsion Polymer Isocyanate (EPI) as the adhesive. In addition to these locally made CLT panels, specimens cut from a commercial 3-layer CLT product (about 90 mm thick) manufactured in Austria were also included in the testing. They were made with European spruce (also known as Norway spruce, Picea abies) lumber and polyurethane adhesive. Variations in properties were found among these different CLT specimens during the testing; however, it was generally concluded that the differences caused by wood species and manufacturing methods would not be large enough to cause significant differences in the hygrothermal properties or impact on the outcomes of hygrothermal simulation. Among the three Canadian species groups tested, Hem-Fir appeared to show slightly higher water absorption than the two SPF groups. Most of the following data are based on the hygrothermal property testing results of the CLT specimens made with SPF lumber from British Columbia. The production of SPF in Western Canada is greater than any other lumber commodities in the country.

The hygrothermal properties listed here include density, thermal conductivity, liquid water

absorption, water vapour permeability, sorption (moisture storage function), and air permeability. The density (or specific gravity) of CLT should be close to the published density of the wood species (or species groups) used to manufacture the CLT panels. The density can be further assessed based on methods developed for solid wood specimens such as ASTM D2395 – 07a (2007). During the collaborative research project on determining CLT hygrothermal properties undertaken by NRC and FPInnovations, thermal conductivity was assessed using 600 mm square full-thickness CLT specimens (with a moisture content of about 5%), with a heat-flow-meter apparatus following ASTM Standard C518-10 (2010). Water absorption tests were conducted based on ISO Standard 15148 (2002), using 100 mm × 50 mm specimens having a 25 mm thickness. The specimens were cut from the CLT panels, including two layers of wood, approximately 18 mm and 6 mm thick, respectively, with a layer of adhesive between them to account for the lamination effect. The water vapour transmission tests were conducted using dry cup and wet cup methods, under three nominal relative humidity (RH) levels of 50%, 70%, and 90% by following ASTM Standard E96/E96M – 10 (2010). The specimens had a diameter of 150 mm and a thickness of 18 mm. They also included two layers of wood, approximately 12 mm and 6 mm thick, respectively, and a layer of adhesive between them. The sorption tests used adsorption mostly based on ASTM Standard C1498-04a (2004), using small solid specimens having a thickness of about 5 mm. The air permeability of the CLT specimens was tested based on the principles used for determining air permeability of acoustical materials, as described in ASTM Standard C 522 -03(2009)e1 (2009).

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Table 1 Recommended hygrothermal properties for CLT simulation

Property index

Recommended values

Remarks

Density

(kg/m

3

₎

420 Based on CSA O86-01 (2005), on an

_{oven-dry basis}

Thermal

conductivity

(W/(m·K))

0.1114

Based on testing at NRC for air-dry

CLT specimens (with a moisture

content about 5%) made with SPF

produced in BC. The temperature of

the hot surface of the

heat-flow-meter apparatus was 35.1 °C, and

that of the cold surface was 12.7 °C

Water

Absorption

Coefficient

(kg/(m

2

_·s½))

1.95 x 10

-3

Based on testing at NRC for CLT

specimens made with SPF produced

in BC. See the water absorption

curve in the Appendix

Water vapour

permeability

(kg m

-1

_s

-1·

_Pa

-1

₎

RH (%)

Permeability

Based on both dry cup and wet cup

tests at NRC for CLT specimens

made with SPF produced in BC (see

Appendix X3 of ASTM E96/E96M –

10)

10 1.2639E-13

20 3.4096E-13

30 6.5425E-13

40 1.1189E-12

50 1.8008E-12

60 2.7737E-12

70 4.1182E-12

80 5.9197E-12

90 8.2683E-12

100 1.1258E-11

Sorption

(Moisture

storage

function)

RH (%)

Equilibrium

moisture

content (%)

0

0 Based on adsorption tests at NRC

for solid wood cut from CLT

specimens made with SPF produced

in BC

50

8

70

11

90

19

94

21

98

28 Based on a literature review,

communication with Dr. Sam Glass

of the Forest Products Laboratory

and sorption tests of red pine at high

RH levels ( Wang et al. 2012)

99

32

99.9

40 Air

permeability

The air permeance of the

CLT specimens without

visible gaps and checking

was negligible.

The airtightness of CLT

Based on testing at NRC for CLT

specimens made with SPF produced

in BC.

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assemblies highly depends

on the sealing of joints

between CLT panels

(Skogstad et al. 2012).

In addition, recommended thicknesses of CLT panels to be used for general hygrothermal or thermal simulation for different types of buildings is provide in Table 2. This was a table is also provided below to summarize the recommended thicknesses of CLT panels to be used for general hygrothermal/thermal simulation of different building types, in discussion with Marjan Popovski and Conroy Lum of FPInnovations.

Table 2 Recommended thicknesses of CLT panels to be used for general hygrothermal/thermal simulation of different types of buildings

Building types

Exterior/interior walls (mm)

Floors

Roofs

Single family houses

100

120

100 Multi-unit residential

buildings

Supporting up to 10

stories

200 Supporting up to 6 stories

150 Supporting up to 4 stories

120

Notes: The CLT thicknesses used in buildings are mostly governed by structural requirements as well as available products, panel lay-up, and other factors. CLT floor and roof thickness will also depend on spans and loading requirements.

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Appendix

Figure A1 A water absorption curve from the partial immersion test using specimens cut from CLT panels made with SPF produced in BC

Figure A2 Water vapor permeability of specimens cut from the CLT panels made with SPF produced in BC 0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0 0 50 100 150 200 250 300 350 M as s G ai n kg /m ² Time, sec½ 1.00E-13 1.00E-12 1.00E-11 0 20 40 60 80 100 W at er V ap ou r P er m ea bi lit y, k g m ¯¹ s¯ ¹ P a¯ ¹

Mean Relative Humidity, %

Dry Cup

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Figure A3 Sorption isotherms based on adsorption tests under RH 95% using two sets of solid wood specimens cut from CLT panels made with SPF produced in BC

5

10

15

20

25

30

45

55

65

75

85

95

Eq ui lib riu m M oi st ur e Co nt en t ( % ) Relative Humidity (%)

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Table A1 - Air permeability and permeance of specimens cut from CLT panels

Test specimens

Thickness (mm)

_{l/((75 Pa)m·s)}

Permeance

_{l/((75 Pa)m²·s)}

Permeability

SPF No.1, East

18.85

0.356 0.00672

SPF No.2, East

18.29 0.0320

0.000585

SPF No.3, East

18.48 Impermeable

Impermeable

SPF No.1, West

18.84 Impermeable

Impermeable

SPF No.2, West

18.87 Impermeable

Impermeable

SPF No.3, West

18.97 0.0134

0.000254

Hem-Fir No. 1

18.39

0.452 0.00831

Hem-Fir No. 2

18.45 0.0136

0.000251

Hem-Fir No. 3

18.48 0.0780

0.00148

Europe No.1

18.39 Impermeable

Impermeable

Europe No. 2

18.69 Impermeable

Impermeable

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2 References

ANSI/APA. 2011. Standard for Performance-rated Cross-laminated Timber. ANSI/APA PRG 320-2011. Approved December 20, 20111, American National Standards Institute.

ASTM C1498-04a. 2004. Standard Test Method for Hygroscopic Sorption Isotherms of Building Materials. ASTM International, West Conshohocken, PA, the USA, www.astm.org.

ASTM D2395-07ae1. 2007. Standard Test Methods for Specific Gravity of Wood and Wood-Based Materials. ASTM International, West Conshohocken, PA, the USA, www.astm.org.

ASTM C1699-09. 2009. Standard Test Method for Moisture Retention Curves of Porous Building Materials Using Pressure Plates. ASTM International, West Conshohocken, PA, the USA, www.astm.org.

ASTM C522-03(2009)e1. 2009. Standard Test Method for Airflow Resistance of Acoustical Materials. ASTM International, West Conshohocken, PA, the USA, www.astm.org.

ASTM C518-10 (2010) Standard Test Method for Steady-State Thermal Transmission Properties by Means of the Heat Flow Meter Apparatus. ASTM International, West Conshohocken, PA, the USA, www.astm.org.

ASTM E96 / E96M – 10. 2010. Standard Test Methods for Water Vapor Transmission of Materials. ASTM International, West Conshohocken, PA, the USA, www.astm.org.

CSA O86-01. 2005. Engineering Design in Wood. Canadian Standards Association, Toronto, Ontario, Canada.

ISO 15148. 2002. Hygrothermal performance of building materials and products-determination of water absorption coefficient by partial immersion. International Standard ISO 15148:2002. Geneva, Switzerland: International Organization for Standardization.

Skogstad, H.B., L. Gullbrekken, and K. Nore. 2012. Air leakages through cross laminated timber (CLT) constructions. Downloaded from: www.treteknisk.no (June 30 2012). Norwegian Institute of Wood Technology (Treteknisk), Norway.

National Reserach Council. 2012. Characterization of hygrothermal properties of CLT. Report to FPInnovations. Ottawa, On, Canada.

Wang, J., M. Phalguni, M., and P.I. Morris. 2012. Sorption and capillary condensation in wood and the moisture content of red pine at high relative humidity. Journal of Builidng Physics. In press.