In-situ Evaluation of Long-Term Performance of CLT Panels in Below-Grade Applications: Mould Risk, Dimensional Stability, and Hygrothermal Responses
Bibliographic record
Abstract
Reinforced concrete basements are the most popular solution in North American low-rise construction. However, cement and concrete production account for 5 to 8% of the global CO2 emission, corresponding to 3 to 6% of greenhouse gas emissions. Resilient and mechanically stable cross-laminated timber (CLT), a construction material for mid-rise buildings, is promising in basement construction. CLT panels have the potential to be more thermally efficient and offer better interior comfort than concrete wall basements. In addition, mass timber produces lower carbon emissions than concrete in the life cycle. However, research and applications of CLT panels in basement construction remain limited, leading to a knowledge gap in the in-situ performance of this innovative construction. The present study was developed as part of an extensive program to create the design concepts and methodology for constructing house basements using mass timber panels, focusing on CLT usage. A large-scale experiment was developed to assess the durability, deformation and thermal performance of using CLT panels in basement building construction. This research program investigated the mould growth risk, moisture content uptake, swelling and shrinkage coefficient and deformation modes, and the thermal performance CLT used as basement walls by monitoring a 6 m × 3 m basement in the field experiment constructed at the University of Alberta campus in Edmonton, Canada. An in-situ monitoring instrumentation program was established to measure the lateral earth pressure, CLT deflection, timber strain, soil temperature, soil moisture content, panel relative humidity and CLT panel temperature, and the program lasted for 24 months. In addition, a laboratory experiment was conducted to test the efficiency of a liquid waterproofing barrier in protecting the panels from moisture. A second laboratory experiment was conducted to calibrate the strain gauges in conditions similar to the filed construction and to derive shrinkage and swelling coefficients of a Spruce-Pine-Fir solid wood specimen to guide field testing determinations of these parameters. A mould growth risk assessment was conducted to evaluate the behaviour of the CLT panel under the below-grade environment throughout the year. The results indicated that the acceptable mould index of three was surpassed during periods of abundant water below the basement floor due to flood events, showing that the CLT panels were at risk of mould growth development. The average swelling and shrinkage coefficients calculated for CLT were around 2 times larger than the longitudinal and 20 times smaller than the transverse coefficients obtained from the laboratory experiment on solid wood specimens, indicating the effect of the cross-lamination on these coefficients. Cracks were the most visible in areas of the panel surface that presented knots and in the end-to-end joints of the panel lumber. Four deformation modes were observed according to the strain measurements and verified with the displacement measurements.The average heat loss per square meter calculated for the CLT basement wall was 0.793 W/m2, and the average cumulative heat loss for 720 days was 112.07 MJ/h/m2. The calculated thermal conductivity varied from 0.022 W/(m°C) to 0.363 W/(m°C). The average confirmed the value from the literature, 0.11 W/(m°C). This study explores a sustainable solution for concrete basements by proposing CLT as an alternative to enhance thermal efficiency and comfort in below-grade living spaces in cold climates. While research on CLT basement walls remains undeveloped, this is the first CLT basement to be reported, and this research may lead to a more sustainable approach to basement construction. This research aims to foster growth in the forestry industry and open new opportunities for CLT adoption in the Canadian housing market.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.001 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".