Abstract
Wind dynamics, on a conventional roofing system, lift the membrane and cause fluttering, introducing stresses at the attachment locations. To identify the component of the system that has the weakest resistance against wind uplift forces, a dynamic method of evaluating roofing systems is beneficial. A vapour barrier is defined as a material of low permeance, which limits moisture transport through an assembly due to moisture diffusion. In addition, some vapour barriers can also resist the airflow movement. The objective of this paper is to investigate the changes in the wind uplift performance in a roof assembly with and without the presence of such vapour barrier. Two vapour barrier types were evaluated as components of full-scale mockups. These include polyethylene film conventionally used in low slope roof assemblies in Canada and modified bituminous surfaced reinforced film, a new product in the roofing market. Wind uplift evaluations are being carried out at the Dynamic Roofing Facility (DRF) of the National Research Council of Canada, using the SIGDERS (Special Interest Group on Dynamic Evaluation of Roofing Systems) dynamic wind test protocol. Systems with vapour barriers performed better than the systems without vapour barriers. Use of vapour barrier minimizes asymmetrical stress concentration and improves the wind rating of the mechanically attached roofing systems.
Wind dynamics, on a conventional roofing system, lift the membrane and cause fluttering, introducing stresses at the attachment locations. To identify the component of the system that has the weakest resistance against wind uplift forces, a dynamic method of evaluating roofing systems is beneficial. A vapour barrier is defined as a material of low permeance, which limits moisture transport through an assembly due to moisture diffusion. In addition, some vapour barriers can also resist the airflow movement. The objective of this paper is to investigate the changes in the wind uplift performance in a roof assembly with and without the presence of such vapour barrier. Two vapour barrier types were evaluated as components of full-scale mockups. These include polyethylene film conventionally used in low slope roof assemblies in Canada and modified bituminous surfaced reinforced film, a new product in the roofing market. Wind uplift evaluations are being carried out at the Dynamic Roofing Facility (DRF) of the National Research Council of Canada, using the SIGDERS (Special Interest Group on Dynamic Evaluation of Roofing Systems) dynamic wind test protocol. Systems with vapour barriers performed better than the systems without vapour barriers. Use of vapour barrier minimizes asymmetrical stress concentration and improves the wind rating of the mechanically attached roofing systems.
Date
2/2003
2/2003
Author(s)
Baskaran, B.A., Molleti, S., Sexton, M
Baskaran, B.A., Molleti, S., Sexton, M
Page(s)
1-16
1-16
Keyword(s)
Wind uplift, Roofing system, Vapour barrier, Dynamic testing, Fastener forces, and Failure mode
Wind uplift, Roofing system, Vapour barrier, Dynamic testing, Fastener forces, and Failure mode