Benchmarking of the advanced hygrothermal model hygIRC

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Benchmarking of the advanced hygrothermal model hygIRC – large scale drying experiment of the mid-rise wood frame assembly: 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

Benchmarking of the Advanced

Hygrothermal Model

hyg

IRC – Large

Scale Drying Experiment of the

Mid-Rise Wood Frame Assembly

CLIENT REPORT: A1-100035-03.5

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REPORT TO RESEARCH CONSORTIUM FOR WOOD AND

WOOD-HYBRID MID-RISE BUILDINGS

– Large Scale Drying Experiment of the Mid-Rise Wood

Frame Assembly

W. Maref, H.H. Saber, G. Ganapathy, K. Abdulghani, M. Nicholls,

Report No. A1-100035-03.5

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

36 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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ACKNOWLEDGMENTS

The research consortium has been supported by Natural Resources Canada and the Ontario and Quebec building authorities, with research being conducted by the National Research Council (NRC), Canadian Wood Council (CWC) and FPInnovations (FPI). Two working groups were established, with participants from NRC, CWC, FPI and Municipal Affairs and Housing (Ontario) – one on fire and building envelope and the other on structure and acoustics. Working group meetings have been held on a biweekly basis to develop and design test methods, design test assemblies and select materials for the test arrangements. The results of tests are discussed on an ongoing basis.

The following staff members of project partner/collaborator organizations have contributed to the working groups and this progress report:

CWC: Rodney McPhee, Ineke Van Zeeland, Peggy Lepper;

FPI: Richard Desjardins, Mohammad Mohammad, Christian Dagenais, Chun Ni, Lin Hu, Lindsay Osborne, Ling Lu, Ciprian Pirvu; Julie Frapper (Nordic);

MAH: Nancy Smith;

NRC: Khaled Abdulghani, Steve Cornick, Bruno Di Lenardo, Gnanamurugan Ganapathy, Michael Lacasse, Wahid Maref, Travis Moore, Phalguni Mukhopadhyaya, Mike Nicholls, Hamed Saber, Mike Swinton

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TABLE OF FIGURES

FIGURE 1: GENERAL CONFIGURATION OF WALL ASSEMBLY SPECIMENS... 5

FIGURE 2 : ENVELOPE ENVIRONMENTAL EXPOSURE FACILITY (EEEF)... 7

FIGURE 3: SCHEMATIC OF THE FULL-SCALE WEIGHING SYSTEM... 8

FIGURE 4: WOOD STUD FRAME CONSTRUCTION SHOWING PERIMETER SEAL (RED TAPE)AND INSTALLATION OF THE BOTTOM AND TOP OSB SHEATHING PANELS... 10

FIGURE 5: SPRAY FOAM PREPARATORY WORK AND INSTALLATION OF FOAM IN STUD CAVITIES... 10

FIGURE 6: SHAVED FOAM (FOAMING COMPLETED) ... 11

FIGURE 7: GAP IN BETWEEN THE FOAM AND THE STUD... 11

FIGURE 8: DRYWALL INSTALLATION WORK TO TEST SPECIMEN AND SUBSEQUENT INSTALLATION IN THE EEEF 12 FIGURE 9: WALL AIRTIGHTNESS SECURING SYSTEM INSTALLATION IN EEEF ... 13

FIGURE 10: PREPARATION OF SPECIMEN FOR MATERIAL CHARACTERIZATION. ... 14

FIGURE 11: PREPARATION OF SPECIMEN FOR MATERIAL CHARACTERIZATION:FIRST PASS... 14

FIGURE 12: PREPARATION OF SPECIMEN FOR MATERIAL CHARACTERIZATION: SECOND PASS... 14

FIGURE 13: SPECIMEN FOR MATERIAL CHARACTERIZATION COMPLETED WITH THREE PASSES... 14

FIGURE 14: INSTALLATION OF SURFACE THERMOCOUPLES (TCS)ON SHEATHING BOARD (OSB) ... 15

FIGURE 15: INSTALLATION OF SURFACE THERMOCOUPLES (TCS)ON EXTERIOR STUD FRAME... 15

FIGURE 16: INSTALLATION OF SURFACE THERMOCOUPLES (TCS)ON GYPSUM BOARD... 16

FIGURE 17: INSTALLATION OF SURFACE THERMOCOUPLES (TCS)ON EXTERIOR STUD FRAME BOUNDARY (B.C. FOR SIMULATION)AT THE MID-SECTION AND IN THE MID OF CENTRAL CAVITY... 16

FIGURE 18: INSTALLATION OF SURFACE THERMOCOUPLES (TCS)ON INTERIOR STUD FRAME... 16

FIGURE 19 - INTERIOR RH & TSENSORS ON VERTICAL STAND AT 6”FROM THE WALL. ... 17

FIGURE 20 - ZOOM ON THE INTERIOR RH & TSENSORS AT THE TOP SECTION OF THE STAND. ... 17

FIGURE 21 - EXTERIOR RH & TSENSORS ON VERTICAL STAND AT 6”FROM THE WALL. ... 17

FIGURE 22 - ZOOM ON THE EXTERIOR RH & TSENSORS AT THE MID-SECTION OF THE STAND... 17

FIGURE 23: PRE-CONDITIONING BATH... 18

FIGURE 24: SEALED BASIN... 18

FIGURE 25: MOISTURE CONTENT MEASUREMENTS USING DELMHORST MOISTURE METRE... 19

FIGURE 26: MOISTURE CONTENT DATA ON EXTERIOR AND INTERIOR SIDE OF THE FRAME... 20

FIGURE 27: ENVIRONMENTAL CONDITIONS OF THE CLIMATIC CHAMBER EEEF ... 21

FIGURE 28: ENVIRONMENTAL CONDITIONS AT THE MID-SECTION – TEMPERATURE (T)... 21

FIGURE 29– ENVIRONMENTAL CONDITIONS – RELATIVE HUMIDITY (RH%)... 22

FIGURE 30: RELATIVE HUMIDITY (RH %)AT MID-SECTION OF WALL ASSEMBLY... 22

FIGURE 31: DRYING OF THE WALL ASSEMBLY DURING 108DAYS... 24

FIGURE 32: MOISTURE CONTENT OF THE WALL ASSEMBLY... 24

FIGURE 33: BOTTOM SECTION TEMPERATURES AND TOTAL WEIGHT OF THE WALL ASSEMBLY... 26

FIGURE 34: MID-SECTION TEMPERATURES AND TOTAL WEIGHT OF THE WALL ASSEMBLY... 26

FIGURE 35– TOP SECTION TEMPERATURES AND TOTAL WEIGHT OF THE WALL ASSEMBLY... 28

FIGURE 36 TEMPERATURE DIFFERENCE ACROSS THE STUD-FRAME... A-1 FIGURE 37 TEMPERATURE DIFFERENCE ACROSS THE WALL... A-1 FIGURE 38 TEMPERATURE DIFFERENCE ACROSS THE FOAM INSULATION... A-2 FIGURE 39 TEMPERATURE PROFILE AT THE HALF-DEPTH OF THE FOAM INSULATION... A-2 FIGURE 40 AVERAGE TEMPERATURE DIFFERENCE ACROSS THE STUD... A-3 FIGURE 41 AVERAGE TEMPERATURE DIFFERENCE ACROSS THEWALL... A-3 FIGURE 42 AVERAGE TEMPERATURE DIFFERENCE ACROSS THE FOAM INSULATION... A-4

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REPORT TO RESEARCH CONSORTIUM FOR WOOD AND WOOD-HYBRID MID-RISE BUILDINGS

Benchmarking of the Advanced Hygrothermal Model hygIRC – Large Scale Drying Experiment of the Mid-Rise Wood Frame Assembly

EXECUTIVE SUMMARY

Constructing mid-rise wood-frame buildings will extend the exposure of the structural wood components to moisture and its effects during the construction phase, unless additional measures are implemented to prevent this from occurring. This means that the wood-based components of the walls will be more exposed to wind-driven rain.

Designers should consider these effects when designing and specifying components and systems. A good understanding of material behaviour will significantly minimize the effects of moisture on the building when constructed. However, during construction phase, it is important to prevent the wood studs and wood panels from exposure to moisture for

prolonged periods. For example, moisture can be stored in the building envelope components during the construction process. The wood studs can be wet during the construction, and not dry sufficiently before the interior finish is installed and painted. The building materials can get wet during construction due to rain, or by lying on the damp ground. The question to be answered in this report is “how long does the high moisture content of the wood-based

elements would take in order to be less than the acceptable limit to enclose and finish the wall (19% moisture content) so as to minimize the risk of biological damage to the wood structure? Furthermore, this report will focus on an experiment of drying potential of an insulated wood-frame wall with spray-in place foam and with initially wet wood studs.

Recent research in the field of assessment of hygrothermal response has focused on either laboratory experimentation or modelling, but less work has been reported in which both aspects are combined. Such type of studies can potentially offer useful information regarding the benchmarking of models and related methods to assess hygrothermal performance of wall assemblies. This report documents the experimental results of a benchmark experiment that was designed to allow benchmarking of stud drying predicted by NRC’s an advanced hygrothermal computer model called hygIRC, when subjected to nominally steady-state environmental conditions. hygIRC uses hygrothermal properties of materials derived from tests on small-scale specimens undertaken in the laboratory. The drying rates of wall

assembly featuring wet studs that result from moisture accumulated during the framing stage of a 5 or 6 storey building. The drying rate of those studs was assessed in an experiment undertaken in a controlled laboratory setting. The results were subsequently used to help benchmark hygIRC reported under separate cover.

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1. INTRODUCTION

In this research task the experimental approach to the drying response of an insulated wood frame- wall assembly incorporating spray-in place polyurethane foam (SPF) is

documented and test results derived from the experiment are also provided. The wood frame wall assembly was subjected to high initial moisture content. The drying rates of the wall assembly were assessed and in particular that of the studs of the wood frame wall. The experimental results were subsequently used to help benchmark results derived from numerical simulation of the representative wood frame assembly using the hygIRC model.

Recent research in the field of assessment of hygrothermal response has focused on either laboratory experimentation or modelling, but less work has been reported in which both aspects are combined. Such type of studies can potentially offer useful information regarding the benchmarking of models and related methods to assess hygrothermal performance of wall assemblies. This report documents the experimental results of a benchmark experiment that was designed to allow benchmarking of stud drying predicted by NRC’s advanced

hygrothermal computer model called hygIRC, when subjected to nominally steady-state environmental conditions. hygIRC uses hygrothermal properties of materials derived from tests on small-scale specimens undertaken in the laboratory. The drying rates of wall

assembly featuring wet studs that result from moisture accumulated during the framing stage of a 5 or 6 storey building. The drying rate of those studs was assessed in an experiment undertaken in a controlled laboratory setting. The results were subsequently used to help benchmark hygIRC reported under separate cover.

2. PREVIOUS WORK ON BENCHMARKING SIMULATION MODELS

There are some known attempts at providing validation of simulation models, notably from the combined efforts of those who contributed to the IEA Annex 24 (Hens 1996) and more recently, from work carried out in Norway at the Norwegian University of Science and Technology (Geving and Uvsløkk 2000).

The work carried out by those working within the IEA Annex 24 focused on using inter-model comparison as one of three possible means identified to provide validation of

simulation models, the other two being analytical and empirical verification respectively. Analytical verification, recognised as being useful for testing algorithms, was not attempted and empirical verification was only tried in certain instances. Verifications were restricted to summing up mass quantities such as total moisture content and amounts of condensed

moisture, and thermal values such as temperature, fluxes and total energy flow. Although these comparisons provided some insight into the applicability of the different models, no straightforward validation through experimentation was completed. It was, however,

suggested that more rigorous validation through well-controlled experimentation should form the basis for future work in this area.

Geving and Thue (1996) undertook measurements and computer simulations of the hygrothermal performance of lightweight roofs from which a comparison was made between

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experimental results and simulations undertaken on a number of different models.

Comparison was made between the moisture content at a specific location in a given wood component derived from the experiment and that obtained from the simulation. In none of the cases was there complete agreement between results for moisture content of the components obtained from either method and no explanations were provided as to why the discrepancies occurred.

Geving and Karagiosis (1996) reported on field measurements and computer simulations of the hygrothermal performance of wood frame walls in which temperature and moisture content were measured at various locations in the wall assembly. In was conjectured that the ‘overall trend’ was in good agreement between measurements and model predictions of moisture contents in wooden components although the most significant lack of agreement was the higher values obtained from simulation in the early winter period. No specific reasons were afforded for the discrepancies although it was noted that there existed many difficulties related to simulating field experiments in particular, modeling an adequate representation of the imperfections inherent in the real structure as well as uncertainties in the input data.

Studies that incorporate both laboratory experimentation and simulation thus offer possibilities to compare results and hence ‘benchmark’ the response of the model to know conditions such as hygIRC (Maref et al. 2002a, 2002b, 2002c, 2002d and 2003a), Maref et al, 2002e, 2002f, 2003b, 2004 and 2008. The results presented in those studies offered an overview of the work carried out on mid-scale and full-scale drying experiments. The experimental results presented in these papers gave not only the bulk moisture content of the OSB sheathing with different assembly, but also the local moisture content.

The overall agreement between experimental and simulated results is good in terms of the shape of the drying curve and the time taken to reach equilibrium moisture content.

Conclusions from these studies are definite for both full-scale tests - simulation results compare favourably with those obtained from the experiments. This suggests that the model adequately emulates the hygrothermal response of specific wood-frame assembly

components, such as wood sheathing, over a range of environmental conditions to which it was subjected in the experiments. These results further enhanced confidence towards the implementation of hygIRC in broader based parametric studies.

The task of validating simulation models is apparently both difficult and time-consuming task without appropriate tools from which, at least, an overall assessment of the degree to which the model reproduces the experimental results can rapidly be ascertained. It was to this end that a weighing system was conceived that would help assist in determining the total weigh change in a specimen over a test period (Maref et al. 2001). It was reasoned that this would provide quantitative data from which average moisture contents in key components could readily and rapidly be obtained and reconciled with simulations results and as well, that the measurable hygrothermal effects, evident over the course of the test period, could likewise be continuously monitored.

This report describes the design of, and experimental results derived from, a precision weighing system for full-scale wall assemblies. The system is capable of weighing 2.5-m x 2.5-m walls having nominal weights of up to 250 kg roughly to the nearest gram continuously over a test period. The weight data has been used to determine weight loss over time in wood sheathing affixed to a wood-frame wall assembly when exposed to steady state laboratory

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conditions. The data was used as a basis for helping benchmark hygIRC, a hygrothermal computer simulation model. Details regarding the design and operation of the device are provided, as well as result derived from a specific drying experiment. The usefulness of the experimental results is highlighted from a comparison to computer simulations using

hygIRC1_.

3. FULL-SCALE EXPERIMENTAL DESIGN

The experiment has been conducted to gather data on the hygrothermal behaviour of full-scale wood-frame wall assembly and wall components when subjected to steady and transient state climatic conditions such that the results were used to evaluate the expected performance and predictive capabilities of the advanced hygrothermal model hygIRC. The model has been used in this project as the main analytical tool to conduct a parametric study to assess the hygrothermal performance of various wall assembly types subjected to different climatic conditions.

The results of this experimental work, described in detail below, were compared to those derived from the use of the hygrothermal model hygIRC.

This report provides a rationale for carrying out the experimental work, the pertinent objectives, scope, proposed approach and related technical details that together comprise the experimental procedures to obtain results useful in helping assess the performance of hygIRC.

3.1 Objectives

 To determine the hygrothermal behaviour of full-scale (2.43-m x 2.43-m) wood-frame assemblies when subjected to steady and transient state hygrothermal conditions in a controlled laboratory environment.

 To assess the drying effect of the wood-stud frame with high initial moisture content. To assess the degree to which hygIRC predicts key hygrothermal effects.

3.2 Approach

To achieve the objectives, the experimental work consisted of undertaking a full-scale experiment on panel assemblies having nominal dimensions of 2.43 by 2.43-m. An Experiment was carried out in controlled laboratory conditions over a period of time

sufficiently long as to permit quantifying gravimetrically, the change, and rate of change, in moisture content of critical wall assembly components, more specifically the wood studs of which the assembly was comprised. Measurable hygrothermal effects were recorded.

1_{NRC report A1-100035-03.6 Mid-Rise Wood Constructions – Hygrothermal Modelling Benchmark:} Comparison of hygIRC Simulation Results with Full Scale Experiment Results, 2014.

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 The wall components that were specified for the benchmark experiment were

consistent with the LWF mid-rise wall specifications2_{, but did not include a cladding}

assembly. The list of components and their respective hygrothermal properties are those taken from the results of testing of materials performed in this study3_{, and from}

the NRC hygIRC material database.

 Steady state or transient laboratory conditions to which the components and

assemblies were subjected in NRC’s Envelope Environmental Exposure Facility were selected to emulate moderately cold cloudy winter conditions; e.g., outdoor

temperatures between -12°C and -18°C.

 Measurable hygrothermal effects included changes in moisture content of materials and changes in weight of wall components or assemblies over time.

 Experimental results were submitted to the hygrothermal modelling team for

comparison to simulated results for the same assembly and environmental conditions. The proposed combinations of materials used in the full-scale experiments include the following: Wet wood stud + OSB + Spray foam Insulation + Dry wall

The nominal environmental conditions to which they were subjected were the conditions established for the EEEF which were:

 Interior temperature ( 23C),  Interior relative humidity ( 18 %),

 Exterior (weather side) temperature (-12C and -18C),  Exterior relative humidity ( 65 %)

2_{NRC report A1-100035-03.1 Mid-Rise Wood Constructions – Specifications of Mid-Rise Envelopes} for Hygrothermal Assessment, 2014.

3_{NRC report A1-100035-03.4 Mid-Rise Wood Constructions – Characterization of Hygrothermal} Properties, 2014

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4. DRYING EXPERIMENT TO HELP BENCHMARKING hygIRC

A view of a general configuration of the specimens is provided in Figure 1 showing only the heat, air and moisture control components of the wall. The nominal size of the specimen is 2.43 x 2.43-m with the structural components comprised of 11.5-mm (7/16 ") OSB sheathing placed on 50 x 138-mm (2" x 6") wood studs at 406-mm (1'-4") centres with spray-in place polyurethane foam in the stud cavity of the wall assembly.

Figure 1: General configuration of wall assembly specimens

4.1 Equipment

4.1.1 Climatic Chamber (EEEF)

NRC-Construction's Envelope Environmental Exposure Facility (EEEF) was used in this experiment as a means to create both an indoor and outdoor environment that reflects winter conditions on the outside of the wall and indoor conditions on the inside. It incorporates a computer automated environmental chamber with a weighing system for full-scale wall assemblies and includes climate sensors, data acquisition systems and post-processing tools. The EEEF gathers key information regarding the rate of drying of specific wood-frame wall components when subjected to simulated rain events.

2X6 wood stud frame Exterior sheathing (OSB)

Sprayed Insulation

Average air gap

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Effective moisture control implies both minimizing moisture entry into the system, and maximising the exit of moisture which does enter, so that no component in the system stays 'too wet' for 'too long'. But what is "too wet" and "too long"? This facility has proven to be an essential component in determining the limits to which the results from simulation of moisture transport through wall assemblies can be used to help address these issues. It was the primary benchmarking tool of the MEWS4_{project and the comprehensive series of results}

derived from full-scale real-time and controlled laboratory experiments have helped substantiate those obtained through simulation.

The climatic chamber is capable of simulating environmental conditions over extended periods of time. Conditions within the chamber can be varied from temperatures of -47 to 48 C, with humidity levels ranging from 10 to 100% RH. Given the range of climatic conditions and the level of automation, the chamber can, for example, readily mimic the temperature and relative humidity profiles for a given location in real time. As well, steady-state climates within the chamber can be achieved or be maintained according to

predetermined set points. The flexibility of the climate control system permits establishing the response of a wall to the effects of many different climate variations from which elements critical to the performance of the assembly can be identified.

The issues of "too wet" and "too long and the ability of the wall to “dry out” are tackled in part through the use of the weighing system and related sensors. The system can determine the weight of a full-scale wall assembly (2.43 m x 2.43 m) to the nearest gram over the test period. This permits observing, for example, the “drying out” of a wall component and thereafter focusing on the times at which levels of moisture within the component fall below levels critical to the long-term performance of the component. The weighing system also features several other innovations, including:

 Gasket and wall pushing system to insure an airtight seal between the wall specimens and to system frame without interfering with the weighing process;

 State-of-the-art moisture sensor system;

 Complete control and data acquisition package to monitor experiments;  Post-processing and data analysis techniques for interpreting results. .

4_{Beaulieu, P., Cornick, S.M., Dalgleish, W.A., Djebbar, R., Kumaran, M.K., Lacasse, M.A., Lackey,} J.C., Maref, W., Mukhopadhyaya, P., Nofal, M., Normandin, N., Nicholls, M., O'Connor, T., Quirt, J.D., Rousseau, M.Z., Said, M.N., Swinton, M.C., Tariku, F., van Reenen, D., MEWS methodology for developing moisture management strategies : application to stucco-clad wood-frame walls in North America, pp. 21, September 01, 2001. (NRCC-45213)

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Figure 2: Envelope Environmental Exposure Facility (EEEF) 4.1.2 Weighing System

The weighing system shown in the schematic diagram in Figure 3 is capable of determining the rate of evaporation of water from a wall assembly specimen that has been pre-conditioned to adsorb significant quantities of water in certain key wall components. Specimen weights may vary up to approximately 250 kg whereas the initial weight of water in wood-stud of the test panel would be in the order of approximately 26 kg. The required resolution to conduct the test is 5 grams or better. The panel must be weighed repeatedly every 10 to 15 minutes for over 3 months (108 days) . From a technological point of view there are two main difficulties: (i) compensating for the zero drift which will undoubtedly occur in the load cells over an extended period of time, and; (ii) the extremely high resolution analogue-to-digital converters required.

4.1.2.1 SYSTEM DESCRIPTION

In order to overcome the problem of zero drift, the load cells are zeroed prior to each measurement cycle. This is accomplished by unloading the load cells between acquisition cycles. During the weighing cycle, the panel is suspended from two tension load cells, both having been custom built for the application. Between acquisition cycles, an air over oil pneumatic system is used to gently lift the panel approximately 1 inch to unload the load cells.

To achieve the required resolution (5 grams or 1 part in 80,000), a 24 bit integrating analogue-to-digital converter is used to digitise the analogue signals from the load cells. This type of converter is typically used for weighing applications. While the resolution is high, the bandwidth is poor; approximately 2 acquisitions per second.

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4.1.2.2 MEASUREMENT PROCEDURE

(1) The load cells are initially unloaded. The pneumatic cylinders are extended so as to

carry the weight of the test panel. At the beginning of the measurement cycle, the load cells are automatically zeroed by the micro-controller.

(2) The load is gradually applied to the load cells by slowly retracting the pneumatic cylinders. An air over oil system is used to provide smooth operation. In an air over oil system, the medium is oil; however, the pressure is supplied by a conventional 100-psi shop air supply. The valves and cylinders are all pneumatic.

(3) Once the load has been applied to the load cells, a series of measurements is taken from both load cells. Digital filtering is then applied (i.e. averaging over a number of samples).

(4) Once the measurement cycle is complete, the cylinders are extended to remove the load

from the load cells. Since the time between acquisition cycles is relatively long, on the order of 10 to 15 minutes, the load cells could be removed and re-calibrated from time to time between acquisition cycles.

4.1.2.3 SOFTWARE

A relatively simple user Windows-based interface is envisioned to allow the operator to modify the system parameters (acquisition rate, length of test, etc.) and visualise the data.

Figure 3: Schematic of the full-scale weighing system TENSION LOAD CELLS PNEUMATIC CYLINDERS TEST PANEL TO BE WEIGHED SERIAL LINK RS232 HIGH RESOLUTION ACQUISITION MODULE HIGH SPEED SERIAL LINK DOCO MICROCONTROLLER HOST COMPU INPUT LC #  INPUT LC #  SUPPORTING FRAME  

CONTROL & D/A SYSTEM

100 PSI - SHOP AIR

PNEUMATICS CONTROL MODULE

SIGNAL FILTERING

24 BIT A/D CONVERTER

AIR ACTUATED DIGITAL CONTROLLED SOLENOID VALVE

AIR OVER

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5. WALL ASSEMBLY

The experiment consisted of evaluating the hygrothermal properties of a wood-stud frame that is sealed at the perimeter with lacquer in order to allow the drying from the main surfaces (see Figure 1 and Figure 4).

5.1 Construction Steps

Mid-Rise wood wall construction was started in November 2012. The nominal size of the wall is 8’ X 8’ with 2X6 Pine studs. The Figure 4 shows the stud frame. The perimeter of the frame was masked with construction tape to avoid moisture escape through the perimeter of the wood frame when the experiment is carried out. This simulates a wall section within an overall wall, where we would expect moisture and heat loss to be predominantly outward and inward, not sideways, since all adjacent wall sections are assumed to be performing at similar conditions, minimizing lateral temperature and moisture gradients. The modelling team makes the same assumption for consistency.

After the two OSB sheets were installed with 1/8” gap between panels, the wall was shipped to the shed located just outside the lab for foaming work. Figure 5 shows the preparation for foaming work and the foam installation. The wall stud cavities were filled with spray foam, the different stages of which are shown in the accompanying figures.

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Figure 4: 2”X6” stud frame construction showing perimeter seal (red tape) and installation of the bottom and top OSB Sheathing panels

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Foaming work took approximately 8 hours. The foamed wall was shipped back to the lab right after foaming work was completed. Figure 6 shows the completed foaming and where the exterior of the foam has been shaved.

It was noticed in some locations of the studs there were some gaps in between foam and the stud; a photo of one spot is shown in Figure 7. Of note is that spray foam applicators would not in practice undertake the application of the foam on wet studs. An exception was made here, since measuring the drying rate of wet studs was the objective of the experiment. It was surmised that foaming under these ‘forced’ conditions would be the most likely cause of subsequent delamination of the foam from the stud. The delamination was later accounted for in the modelling comparisons.

Figure 6: Shaved foam (foaming completed)

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Drywall (gypsum panels) was then installed on the interior side of the wall and thereafter mounted in the Environmental Exposure of Envelopes Facility (EEEF) for testing.

Figure 8: Drywall installation work to the test specimen and subsequent installation in the EEEF

5.2 Wall airtightness securing system

A special pneumatic wall push system was built to secure the wall specimen against the seals to avoid cold air leakage from the outdoor to the indoor chamber. The system was built in such a way that the wall specimen could hang freely on load cells during each brief

weighing period and thereafter was secured tight against the seals the rest of the time, thereby maintaining the separation between of the indoor and outdoor environments on either side of the wall. A set of photos provided in Figure 9 attempt to show how this it system worked.

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6. FOAM MATERIAL CHARACTERIZATION

For the purposes of simulation, there was a need to establish the hygrothermal material properties of the foam. As such, two 3-ft. X 3-ft. foam specimens were made onto 2 X 4-ft. stud frame backed with Teflon sheet. The photos of the process are provided in Figure 10 to Figure 13. The spray foam properties were characterized5_and

reported under separate cover, along with other materials and properties.

Figure 10:Preparation of specimen for material characterization.

Figure 11: Preparation of specimen for material characterization: first pass

Figure 12: Preparation of specimen for material characterization: Second pass

Figure 13: Specimen for material characterization completed with three passes

5_{NRC report A1-100035-03.4 Mid-Rise Wood Constructions – Characterization of Hygrothermal} Properties, 2014.

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7. WALL INSTRUMENTATION

The wall was instrumented with 39 thermocouples to measure temperature at different layers as required, details of which are provided in Figure 14 to Figure 18.

Figure 14: Installation of surface thermocouples (TCs) on Sheathing Board (OSB)

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Figure 16: Installation of surface thermocouples (TCs) on Gypsum Board

Figure 17: Installation of surface thermocouples (TCs) on exterior stud frame boundary (B.C. for Simulation) at the mid-section and in the mid of central cavity

Figure 18: Installation of surface thermocouples (TCs) on interior stud frame

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In addition, to measure the indoor and outdoor conditions, three relative humidity and temperature sensors and pressure sensor were installed 6-in. away from and either side of the wall, as shown in Figure 19, Figure 20, Figure 21, and Figure 22.

Figure 19 - Interior RH & T sensors

on vertical stand at 6” from the wall. Figure 20 - Zoom on the Interior RH & T sensors at the top section of the stand.

Figure 21 - Exterior RH & T sensors on vertical stand at 6” from the wall.

Figure 22 - Zoom on the Exterior RH & T sensors at the mid-section of the stand. Top Mid Bot Top Mid Bot Top Mid

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8. INITIAL AND BOUNDARY CONDITIONS

8.1 Specimen Pre-conditioning Initial conditions

The wood-stud frame was be pre-conditioned by soaking in a water immersion basin to insure that the studs are brought to elevated moisture contents. The pre-conditioning consisted of two phases: immersion and stabilisation. The immersion phase permitted the components to reach an elevated level of moisture content. The stabilisation phase was included to promote equilibrium of the moisture content throughout the component. The immersion phase took place in an immersion basin, essentially a water tank of sufficient size as to permit the complete immersion of all faces of studs in the frame (Figure 23). Since it is intended that the studs of the assembly be brought to elevated moisture contents, it was envisaged that the wood-stud frame needed to be totally immersed in water and for sufficient amount of time to insure that these components reached the desired degree of moisture content (well over 20%).

The stabilisation phase took place over three days. The water in the bath was drained and the specimen then remained in the dry basin for another two days to allow moisture to re-distribute itself evenly within the wood-stud. Care was taken to prevent the stud from drying out by sealing the basin lid with adhesive tape (Figure 24).

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8.2 Initial conditions

8.2.1 Initial condition - weight of the wall

In the following table the measured moisture content of the studs are provided and the derived value of the average moisture content of the wall when all other dry

components were added to the assembly. Weight at Dry condition (g) Weight at wet condition (g) Moisture Content (%) Stud frame 51119 74717 46.2 Complete wall 163379 191425 14.1

8.2.2 Initial condition – moisture of the wall

The wall frame was taken out of the basin on the day that was scheduled for foam spraying and the moisture content was measured at different locations of all studs. In Figure 25-A & 24-B are shown the moisture content measurement work and in Figure 26 the moisture content measurement data on either side of the wall frame is provided. The average moisture content on the exterior side was 32.17% and on interior side 31.64%. These measurements do not reflect the moisture content by weight of the wood stud as these readings were taken close to the surface of the stud.

Figure 25: Moisture content measurements using Delmhorst moisture metre

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1 2 3 4 5 6 33.2 30.4 33.0 32.8 39.6 30.9 30.0 29.2 30.6 35.5 31.2 29.6 27.9 26.7 35.5 35.5 35.2 34.3 35.2 36.2 33.5 33.9 29.3 30.9 31.6 30.1 30.6 29.5 28.1 35.1 40.1 31.8 36.8 32.6 27.6 31.8 30.7 30.4 30.8 29.2 27.9 34.1 30.1 31.5 30.6 29.4 31.4 34.1 39.0 24.5 28.9 29.2 31.3 31.8 31.4 30.4 30.9 28.0 32.8 30.4 36.1 32.5 30.5 31.9 35.9 35.1 33 6 5 4 3 2 1

Mid- stud cavity Stud frame/Drywall - Interface

Figure 26: Moisture content data on exterior and interior side of the frame

8.3 Boundary conditions

In theory, the wood studs would, upon removal from the bath, immediately start to lose moisture to the surrounding air. Hence in order to maintain specimens at close to saturated conditions and minimise the loss in moisture prior to the start of the experiment, the wall assembly was assembled as quickly as possible and covered with a tarp and remained in this condition until the following day when the foam was applied.

For inputs to the simulation, the interior and exterior conditions of the Envelope Environmental Exposure Facility chamber (EEEF) were recorded, i.e. Temperature (T) and Relative Humidity (RH) as a weather file during the full-scale experiment.

In Figure 27, Figure 28, Figure 29, and Figure 30 are provided the temperature and relative humidity profiles recorded for interior and exterior conditions across the

assembly and at three levels, i.e. Top, Mid and Bottom of the wall assembly, completed over a period of 108 days.

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The initial conditions are the interior temperature ( 23C), the interior relative humidity ( 18 %), the exterior temperature (-12C and -18C), the exterior relative humidity ( 65 %) and the total moisture content (given by the experiment) for the full-scale set.

Figure 27: Environmental conditions of the climatic chamber EEEF

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Figure 29: Environmental conditions – Relative Humidity (RH%)

Figure 30: Relative Humidity (RH %) at mid-section of wall assembly; 51-in. from bottom of wall and 6-in. from surface.

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9. EXPERIMENTAL RESULTS

The Mid-Rise Wood benchmark experimental results are provided in the subsequent sections in which the results obtained from the change in weight of the wall are first provided followed by the temperature profiles of the different components of the wall assembly when subjected to hygrothermal loads and as obtained over the course of the experimental program.

9.1 Results from drying experiment

Figure 31 shows the change in mass in kg in the wall assembly derived from the drying test. All results are presented as the total weight change distribution over a 2.43-m width of wall as a function of ti2.43-me.

The drying results of the whole wall assembly in terms of moisture content (MC %) are given in Figure 32. For the first two days of the drying the wall lost more than 2% of its moisture content (MC%) starting at 14% MC by weight for the whole system. After 108 days the total moisture content of the wall reached 7.8% by weight. This result does not mean that the stud-frame or the OSB sheathing are completely dry. To obtain this information, simulation using hygIRC was needed to quantify the moisture content of the stud frame alone and the OSB sheathing alone.

It can also be observed from Figure 32 that although an Equilibrium Moisture Content (EMC) was reached after 108 days, the studs in the wall assembly nonetheless retained a high level of moisture content (above 50% MC).

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Figure 31: Drying of the wall assembly during 108 days

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9.2 Temperature data

Figure 33, Figure 34 and Figure 35 provide information on the temperature profiles over the course of the drying experiment for the different portions of the wall as well as information on the total weight of the wall and from this latter information, the drying process can be readily visualised. More specifically, in Figure 33 is given the temperature profiles of the bottom section of the wall in relation to the time, in days, of the drying process and the corresponding weight of the wall assembly. In Figure 34 and Figure 35 the corresponding temperature and weight profiles, respectively, for the mid-portion and top portion of the wall.

In Figure 33, two events are identified and labelled Section 1 and 2. For the event labelled Section 1 the temperature of the weather side chamber was seen to dramatically increase over the course of the experimental program (see, e.g., Figure 27 and Figure 28). This was due to the malfunctioning of the compressor valves and as a consequence, the control system was shut down and restarted once the problem was fixed. This event occurred over a 7 day period, from 12-Mar-2013 to 19-Mar-2013. Subsequent to this event the weather side chamber temperature was maintained at 18˚C as compared to -12˚C prior to the occurrence of the event. This accounts for the lower temperatures on the surface of the OSB and inboard from this plane following the Section 1 event.

For the event labelled Section 2, this occurred over a 2-day period between 19-Apr-2013 to and 21-Apr-19-Apr-2013. In this instance, the data acquisition system for the collection of temperature data malfunctioned; hence the lack of such data over that time period; weight data was unaffected as this data had a separate acquisition system.

The following thermocouples can be found for the different layers at the bottom of the wall and are identified in Figure 33:

 Exterior sheathing panel (OSB): TC 3  Exterior Stud-frame: TC9, TC10, TC 11  Exterior Foam at the mid width cavity: TC 16  Middle of the foam: TC 17

 Interior Foam: TC 20  Perimeter stud: C24, C27

 Interior Stud frame: TC 34, TC 35

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Figure 33: Bottom Section Temperatures and Total Weight of the Wall Assembly

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In Figure 34 the surface temperatures for the middle portion of the wall assembly are provided and the following thermocouples can be found for the different layers of the wall:

 Exterior sheathing panel (OSB): TC 2  Exterior Stud-frame: TC 7, TC 8

 Exterior Foam at the mid width cavity: TC 14  Middle of the foam: TC 15

 Interior Gypsum panel (room side): TC38

In Figure 35 the surface temperatures for the top portion of the wall assembly are provided and the following thermocouples can be found for the different layers of the wall:

 Exterior sheathing panel (OSB): TC 1  Exterior Stud-frame: TC 5, TC 6

 Exterior Foam at the mid width cavity: TC 12  Middle of the foam: TC 13

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Figure 35: Top Section Temperatures and Total Weight of the Wall Assembly

In Appendix-A are given additional results such as the temperature differences across the wall assembly within the stud-frame and within the foam at each level (i.e. Top, middle and bottom of wall assembly) and other items such as the average temperature difference across the wall assembly, the spray foam insulation, or at the studs.

The entire data set of the mid-rise wood benchmark experiment was transferred to the modelling team to enable their comparisons of simulated to experimental results6_.

10. CONCLUDING REMARKS

Constructing mid-rise wood-frame buildings will extend the exposure of the structural wood components to moisture and its effects during the construction phase. This means that the walls are more exposed to wind-driven rain.

The building materials can get wet during construction due to rain, or by lying on the wet floors of the building during construction.

6_{NRC Report A1-100035-03.6 Mid-Rise Wood Constructions – Hygrothermal Modelling Benchmark:} Comparison of hygIRC Simulation Results with Full Scale Experiment Results

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This study focuses on the benchmark experiment for the Mid-Rise wood project, showing the drying rate of moisture in the wood framing, after the studs get wet during construction. This was done to benchmark NRC’s hygrothermal model before

undertaking a parametric analysis on the performance of mid-rise wood wall assemblies. In addition to satisfying the needs for benchmarking NRC’s hygrothermal model for mid-rise wood parametric studies, the results obtained from this experiment showed the importance of keeping the wood-based material dry and also the importance of foaming on a dry substrate, as per industry guidelines and standards for foam installers. We have seen that the foam did not completely adhere to the stud faces and the gap between stud and foam can be up to ¼-in. Such gaps can create paths for air movement in the stud cavity, which may affect the thermal resistance of the wall assembly.

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11. REFERENCES

Moisture Control in Buildings, Philadelphia, PA. American Society for Testing and Materials, 1994. pp. 18-34 (ASTM Manual Series MNL-18)

Kohonen, R. 1984. A Method to Analyse the Transient Hygrothermal Behaviour of Building Materials and Components. Technical Research Centre of Finland Publication 21, pp. 33-35

Ojanen, T. and M.K. Kumaran 1992. Air exfiltration and moisture accumulation in residential wall cavities. Thermal Performance of the Exterior Envelopes of Buildings V, Proceedings of the ASHRAE/DOE/BTECC Conference (Clearwater Beach, FL., USA, 1992) pp. 491-500, 1992. (NRCC-33974) (IRC-P-1758)

Ojanen, T. and M.K. Kumaran 1996. Effect of exfiltration on the hygrothermal behaviour of a residential wall assembly" Journal of Thermal Insulation and Building Envelopes Vol. 19, pp. 215-227. (NRCC-39860)

Ojanen, T., R. Kohonen and M.K. Kumaran 1994. Modeling heat, air, and moisture transport through building materials and components. In: Moisture Control in Buildings, Philadelphia, PA. American Society for Testing and Materials, 1994. pp. 18-34 (ASTM Manual Series MNL-18) (NRCC-37831) (IRC-P-3677).

Ojanen, T. and M.K. Kumaran 1995. Effect of exfiltration on the hygrothermal behaviour of a residential wall assembly: Results from calculations and computer simulations. International Symposium on Moisture Problems in Building Walls (Porto, Portugal, 1995) pp. 157-167, 1995. (NRCC-38783)

Salonvaara, H.M. 1994. TRATMO II. VTT Finland.

Salonvaara, M. and A.N. Karagiozis 1994. Moisture Transport in Building Envelopes using an Approximate Factorization Solution Method. CFD Society of Canada, Toronto, June 1-3, 1994.

Karagiozis, A., M.H. Salonvaara and M.K. Kumaran 1995. The Effect of Waterproof Coating on Hygrothermal Performance of High-Rise Wall Structure. Thermal Performance of the Exterior Envelopes of Buildings VI, Clearwater, FL- USA, 1995.

Karagiozis, A. and M.K. Kumaran 1997. Applications of Hygrothermal Models to Building Envelope Design Guidelines. 4th_{Canada/Japan Housing R&D workshop. Pp. III-25-III-36,}

1998. Sapporo, Japan, Nov. 16-21, 1997.

Salonvaara, M.H. and A.N. Karagiozis Influence of waterproof coating on the hygrothermal performance of a brick facade wall system. ASTM Symposium on Water Leakage Through Building Facades (Orlando, Florida, U.S.A., 1996) pp. 295-311, 1998 (ASTM Special Technical Publication vol. 1314) ASTM-STP-1314.

Kumaran, M.K. 1996. Heat, Air and Moisture Transfer in Insulated Envelope Parts, International Energy Agency, IEA Annex 24, Final Report, Vol 3, Task 3: Material Properties.

Kumaran, M.K. and J. Wang 1999. How well should one know the hygrothermal properties of building materials? Proceeding of CIB W40 meeting (Prague, Czech Republic, 8/30/99), pp. 47-52, August 30, 1999.

Hens, H. 1996. Final report Task 1. Modeling Common Exercises. Summary reports.

International Energy Agency, Energy Conservation in Buildings and Community Systems, Annex 24 Heat, Air and Moisture Transport in New and Retrofitted Building Envelope Parts (HAMTIE).

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Geving, S. 1997. Moisture Design of Building Constructions, Hygrothermal Analysis Using Simulation Models, Part II: Collection of papers and reports, NTNU Trondheim, Norway, Ph.D. Thesis, June 1997. Faculty of Civil and Environmental Engineering, Department of Building and Construction Engineering, NTNU, Norway.

Geving, S. and A. Karagiosis 1996. Field Measurements and Computer Simulations of the Hygrothermal Performance of Wood Frame Walls. In: Geving, S. 1997. Moisture Design of Building Constructions, Hygrothermal Analysis Using Simulation Models, Part II: Collection of papers and reports, NTNU Trondheim, Norway, Ph.D. Thesis, June 1997. Faculty of Civil and Environmental Engineering, Department of Building and Construction Engineering, NTNU, Norway.

Geving, S. and J.V. Thue 1996. Measurements and Computer Simulations of Hygrothermal Performance of Lightweight Roofs, in: Proceedings of the 4th _{Symposium of Building}

Physics in Nordic Countries, September 9-10, Espoo, Finland, pp. 541-548.

Geving, S. and S. Uvsløkk 2000. Moisture Conditions in Timber Frame Roof and Wall Structures, Test house measurements for verification of heat-, air and moisture transfer models. Project Report 273-2000, BYGGFORSK, and Norwegian Building Research Institute, Oslo, Norway, 50p.

Hens, H. 1996. Final Report, Volume 1, Task 1: Modeling. International Energy Agency, Energy Conservation in Buildings and Community Systems, IEA Annex 24 Heat, Air and Moisture Transport Through New and Retrofitted Insulated Envelope Parts (HAMTIE), 90p.

Kumaran, M.K. and J. Wang 1999. How Well Should One Know the Hygrothermal Properties of Building Materials? Proceedings of the CIB W40 meeting (Prague, Czech Republic, August 30, 1999), pp. 47-52.

Maref, W., M. A. Lacasse and N. Krouglicof. "A Precision weighing system for helping assess the hygrothermal response of full-scale wall assemblies", Proceedings of Performance of Exterior Envelopes of whole Building VIII- Integration of Building Envelopes, December 2-6, 2001, Clearwater Beach, FL (USA), and pp.1-7 (NRCC-45202).

Maref, W. (2002a), Kumaran, M.K., Lacasse, M.A., Swinton, M.C., van Reenen, D., "Laboratory measurements and benchmarking of an advanced hygrothermal model," Proceedings of the 12th International Heat Transfer Conference (Grenoble, France, August 18, 2002), pp. 117-122, October 1, 2002 (NRCC-43054)

Maref, W. (2002b), M. A. Lacasse, M. Kumar Kumaran, Michael C. Swinton, (2002), “Advanced Hygrothermal Model–hygIRC: Laboratory Measurements and Benchmarking”, 12th International Heat Transfer Conference (18-23 August 2002, Grenoble, France) Maref, W. (2002c), Lacasse, M.A., Kumaran, M.K., Swinton, M.C., "Benchmarking of the

advanced hygrothermal model-hygIRC with mid-scale experiments," eSim 2002 Proceedings (University of Concordia, Montreal, September 12, 2002), pp. 171-176, October 1, 2002 (NRCC-43970)

Maref, W. (2002d), Lacasse, M.A., Booth, D.G., Nicholls, M., O'Connor, T., "Automated weighing and moisture sensor system to assess the hygrothermal response of wood sheathing and combined membrane-sheathing wall components," 2, 11th Symposium for Building Physics (Dresden, Germany, September 26, 2002), pp. 595-604, October 1, 2002 (NRCC-45696)

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Maref, W. (2002e), Lacasse, M.A., Booth, D.G., Benchmarking of IRC's Advanced Hygrothermal Model - hygIRC Using Mid- and Large-Scale Experiments, Research Report, Institute for Research in Construction, National Research Council Canada, 126, pp. 38, Dec, 2002 (RR-126) Conference, Montreal (Canada) Sept 12-13, 2002.

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Experiments, and Benchmarking, Research Report, Institute for Research in Construction, National Research Council Canada, 127, pp. 15, Dec, 2002 (RR-127)

Maref, W. (2003a), Lacasse, M.A., Booth, D.G., "Assessing the hygrothermal response of wood sheathing and combined membrane-sheathing assemblies to steady-state environmental conditions," Proceedings of the 2nd International Conference on Research in Building Physics (Leuven, Belgium, September 14, 2003), pp. 1-10, September 1, 2003 (NRCC-46103)

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International Conference on Computational Heat and Mass Transfer (Banff, Alberta, May 26, 2003), pp. 243-251, May 1, 2003 (NRCC-45215)

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APPENDIX - A

Figure 36: Temperature Difference across the stud-frame at the three section levels: Top, Mid and Bottom

Figure 37: Temperature Difference across the wall at the three section levels: Top, Mid and Bottom

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Figure 38: Temperature Difference across the foam insulation at the three section levels: Top, Mid and Bottom

Figure 39: Temperature profile at the half-depth of the foam insulation at the three section levels: Top, Mid and Bottom

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Figure 40: Average Temperature Difference across the stud at the three section levels: Top, Mid and Bottom

Figure 41: Average Temperature Difference across the Wall at the three section levels: Top, Mid and Bottom

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Figure 42: Average Temperature Difference across the foam insulation at the three section levels: Top, Mid and Bottom

Benchmarking of the advanced hygrothermal model hygIRC – large scale drying experiment of the mid-rise wood frame assembly: report to Research Consortium for Wood and Wood-Hybrid Mid-Rise Buildings