ASHRAE 90.1-2007 Minimum Bldg Envelope Requirements

They do not have to meet the prescriptive standards for insulation levels. The Baseline (Table G3.1#5(Baseline)(c) and Proposed models would include the existing conditions.

Yes

Was your answer based on the assumption that the project would be submitted under LEED NC/MR or LEED EB-O&M?

NC since this the forum for EAp2 that it was posted under. In general if you don't touch a system in an existing building you are not required to bring it into code compliance.

To clarify the steps required under Option 1 to show what I assume must be a 5% improvement over the existing conditions (prior to any improvements), could you outline chronologically how you would proceed after creating the energy model of the pre-construction existing building ?

Not sure where your assumption comes from regarding a 5% improvement? If you don't change an existing condition, like the envelope, then it is modeled identically in both the Proposed and Baseline models.

In v3/2009, on the first page for EAp2 it calls for a 5% improvement for major renovations to existing builidings compared to the baseline (?existing energy modeling) building performance rating. My basic question is do we create an energy model based on the finished envelope (approx. 90% exist envelope, 10% new) and how must it compare to the original energy model?

The 5% improvement is not entirely over existing conditions, it is over the Appendix G Baseline model. These are very different. Your Proposed model is based on what was designed and installed in the project. Your Baseline model is based on Table G3.1#5(Baseline)(c)(f). If existing follow (f) if new follow (c).

So the baseline model is 100% existing envelope and the proposed model is proportional to the respective percentages for the existilng and new. Am I correct that only the new walls and roof must be a 5% improvement over the existing envelope walls and roof? Also, does the proposed model need to be an improvement over the baseline energy model and, if so, where is that documented? Thanks for your patience in helping clarify this.

I would appreciate any help you can offer for further clarification to my questions above. Thanks.

The envelope in both models is proportional to the respective percentages of existing and new. How to do this is spelled out in 90.1 Appendix G. For the existing portions follow Table G3.1#5(Baseline)(f). For the new follow Table G3.1#5(Baseline)(c). There is no requirement for a 5% improvement over the existing envelope. Perhaps the inclusion of the word "existing" in the credit language has you confused. This simply refers to a building renovation of an existing building. It does not refer only to the existing envelope. New construction must achieve a 10% reduction in overall energy cost and building renovations must achieve a 5% reduction. If you have a mix of both on a single project the percentage is adjusted based on the ratio of new to renovation. For example, if a project was 50% new and 50% existing the minimum energy cost reduction would be 7.5%. Yes the Proposed model needs to show a minimum improvement relative to the Baseline model. This is documented in the credit language for EAp2 and EAc1, in the Reference Guide and in 90.1 including Appendix G. It is the basis for earning the EAp2 prerequisite and earning points under option 1 for EAc1.

Thanks for the response. It cleared things up considerably. One last clarification: the new envelope requirements are in 90.1, Appendix G,Table G3.1 #5, with Exceptions a,b,c & d where applicable? Thanks again for the help.

For the Proposed model, yes that is correct. The Baseline model is spelled out in the column on the right which is what I have been referencing in my previous comments. Table G3.1#5(Baseline)(c) refers you to the appropriate Table 5.5-1 to 5.5-8 depending upon the climate zone of the project. You then select the appropriate (nonresidential, residential or semi-heated) column for your project and the use the Insulation Entirely Above Deck value for the roof, Steel-Framed Walls for the walls, Steel-Joint floors, and Unheated Slab for the Baseline model.

I took the above comments to include HVAC. Is the following true for the HVAC system for the subject building above that is 90% existing and 10% new? The energy cost for the Baseline model is based on the existing building envelope but not the existing mechanical systems. The energy model is to be per Appendix G of ASHRAE 90.1. Appendix G requires that the Baseline HVAC systems, even if HVAC systems are existing, are to be modeled based on the minimum performance requirements indicated in ASHRAE 90.1 for the Baseline HVAC system. The Baseline HVAC system types are also defined in Appendix G. The energy cost comparison is between the building energy model as renovated and the Baseline model.

You are correct. The Baseline HVAC is always the Appendix G system.