ASHRAE Mandatory Provisions for Building Envelope

Maya, do you have access to the 90.1 user's manual? This manual provides very good guidance (with diagrams) for building envelope requirements and provides much more detailed descriptions on how to comply. 1) Slab-on-grade: just what's on Earth. You have to provide insulation at the edge for some climate zones. 2) You do need to insulate the floor above the parking level. Those requirements are based on the "floors" section of Table 5.5, rather than "slab-on-grade." Consider this nonresidential, rather than semiheated. 3) When you exceed 5% skylight to roof area, you have to demonstrate compliance using either the trade-off method or whole building energy simulation. For the trade-off method, you can use Comcheck (http://www.energycodes.gov/comcheck/ez_download.stm), a program developed by the Department of Energy. You're most likely going to need to do whole building simulation for your project to meet EAp2.

For opaque assembly U-values, you do need to provide the minimum amount of insulation called for in Table 5.5 as per section 5.4.1. This is a great observation actually, as I've seen some people assume that whole building simulation allows any U-value to be used.

Roger - I disagree. Section 5.4.1 references 5.8.1.1 - 5.8.1.9, which covers things like insulation labeling. Table 5.5 only applies to the prescriptive envelope option. If you are running a model, you could, in theory, put in less insulation and still comply.

Hi Christopher, I agree with you. The Energy Cost Budget Method allows trade-offs between systems, as long as the proposed
building’s annual energy consumption remains below that of a reference building that meets
minimum requirements. The way I read the Standard, a more efficient mechanical system can compensate
for a building envelope that does not meet the prescriptive requirements.