Z girts are common, simple, and familiar to the cladding installation community. Their problem- they are an untested component, and create a continuous thermal break, providing poor demonstrated and modeled thermal performance. The requirements of ASHRAE Standard 90.1, the basis of the energy code, cannot be met using Z’s.
Knight Wall Systems THERMAZEE provides an effective solution that enables energy code compliance as well as a tested and engineered assembly where a Z is appropriate and desired.
Z and THERMAZEE Performance Comparison:
Continuous horizontal Z GIRTS, 24” O.C., and 4” exterior insulation yields an R-Value of 12.2, U Value 0.082, an efficiency of only 52%. DOES NOT MEET ENERGY CODE.
THERMAZEE continuous horizontal Z girts, 24” O.C., and 4” exterior insulation yields an effective assembly R-Value of 17.3, U-Value 0.058, an efficiency of 84%. MEETS ENERGY CODE.
For the 3D thermal analysis, Knight Wall used the expert services provided by Morrison-Hershfield. The CAD/FEA analysis software NX, from Siemens was used for the actual modeling. Using this software, MH had previously conducted a research project for the ASHRAE in which a 3D thermal model was developed and calibrated to within 5% of hotbox measurements. Please feel free to contact Knight Wall Systems or THOMCO for the full report which includes further modeling data and wall assemblies.