Revised ASHRAE 90.1 Standard Addresses Thermal Performance Of Metal Building Envelopes

摘要

The revised ASHRAE Standard 90.1-99, for the first time, treats metal building walls and roofs as distinct envelope elements. Maximum U-factor criteria are set based on life-cycle economics. The NAIMA three-dimensional finite element model was used to estimate the thermal performance of typical metal building envelope elements, taking into account compression of insulation at the purlins and girts as well as thermal shorts due to clips and fasteners. The resulting U-factors are published in Appendix A of the Standard and may be used to demonstrate compliance.There are many metal building insulation systems available in the industry. Performance claims generally cannot be compared directly, simply because of the various methods and assumptions made. FEA offers a cost-effective way of standardizing the evaluation, allowing contractors, architects or owners to make 'apples to apples" comparisons. The cost of each system can then be evaluated to determine the real economic value of alternative systems.