Moisture storing insulation such as cellulose has gained a large segment of the residential market, both in new and retrofit construction. Moisture deposited by exfiltration and adsorbed within the envelope reduces the thermal performance of the envelope and favors fungus growth leading to deterioration of the materials and contamination of the indoor air. Roof assemblies thus insulated are particularly vulnerable to the mechanism of moisture accumulation. The objective of this study is to investigate the pattern of moisture accumulation in single cavity flat roofs fully insulated with cellulose insulation. Through an extensive experimental program using two test huts in an environmental chamber, patterns of moisture movement and accumulation for a full wetting-drying cycle have been developed for the first time. Using these results for validation, a model using the water potential concept as the driving force for moisture movement was developed to simulate the complete wetting and drying of wood components within the envelope. Within an Environmental Chamber, which allows for testing full scale specimens, a 190-day test with daily cyclic conditions was designed and performed during which moisture transfer was monitored with electronic sensors and gravimetry. The test consisted of eight flat roof assemblies fully insulated with cellulose subjected to one complete, quasi real-time wetting-drying cycle. The research presents a methodology to evaluate the performance of retrofitting energy efficiency measures using moisture storing insulation in residential buildings. An hygrothermal model using the concept of water potential gradient as the driving force for moisture movement in wood has been developed for flat roofs insulated with cellulose and integrated into an existing finite element computer model. The model includes the geometrical representation of the wood component, moisture content-water potential relationships, effective water conductivity and mass and heat transfer coefficients. The results from the computer model compare favorably with the experimental results and validate the use of the water potential approach in predicting moisture movement through building envelope assemblies. The experimental and modeling data document the moisture condition of the assemblies. This moisture condition is an indicator of durability in terms of fungus growth. Design guidelines have been derived from this study for flat roof assemblies incorporating moisture storing materials. This information can be used by the designer to evaluate the hygrothermal performance and the durability of his/her design.

• durability: building envelope
• experiment: hygrothermal performance
• Fazio's student: thesis
• roof

1. Approach for the simulation of wetting due to rain infiltration for building envelope testing
2. Behavior of wall assemblies with different wood sheathings wetted by simulated rain penetration
3. Comparaison de m¨¦thodes de mesure de flux de chaleur pour sp¨¦cimens de grandes et moyennes dimensions
4. Essai sur les toits plats isol¨¦s ¨¤ la fibre de cellulose
5. Experimental setup for the study of air leakage patterns
6. Hygroscopic behavior of paper and books
7. Impact of added insulation on air leakage patterns
8. Impact of air leakage pattern on reinsulated walls
9. Large scale testing of two flat roof assemblies insulated with cellulose
10. Mapping of air leakage in exterior wall assemblies
11. Methodology and Application of Simulated Wind-Driven Rain Infiltration in Building Envelope Experimental Testing
12. Methods for the assessment of moisture content of envelope assemblies
13. Modeling of moisture behavior of wood planks in nonvented flat roofs
14. Moisture performance of leaky exterior walls with added insulation
15. Rainwater runoff from building facades: A review
16. Rapport Final Projet Site Internet - L'enveloppe du batiment et l'efficacit¨¦ ¨¦nerg¨¦tique
17. Review and framework for large-scale laboratory studies on wetting and drying of building envelopes
18. Study of the reduced impact of thermal bridges in two sprayed-applied polyurethane wall assemblies
19. Testing of flat roofs insulated with cellulose fiber
20. The impact of sorption history and hysteresis on moisture pattern in a wood-framed building envelope
21. The need for an integrated computer-based tool to support building envelope design
22. Use of an environmental chamber to investigate large-scale envelope specimen hygrothermal performance