ASHRAE installations mandatory provisions in Major Renovations

I agree that you only need to meet the mandatory provisions relative to the items you change. Any unchanged system components are modeled identically.

No. Unchanged lighting and HVAC is modeled identically. If you change it then the baseline is Appendix G.

Hello, Marcus Is the following interpretation: "I agree that you only need to meet the mandatory provisions relative to the items you change. Any unchanged system components are modeled identically." the official interpretation of ASHRAE or GBCI?

See the User's Manual for 90.1-2010 on page G-24. It very clearly states existing systems are modeled identically. So ASHRAE is clear IMO. Now in future versions of 90.1 they do change this to the baseline according to Appendix G in all cases. That is also pretty clear. Unfortunately GBCI has not been so clear to its users. Apparently many LEED projects have been allowed to/told to use the Appendix G Baseline instead of modeling the systems identically. There is confusion among the reviewers on this subject and I understand it is being discussed on our next reviewer call. So I think that currently you could do either one and it should be accepted.

Hello, When alterations are to be made in existing facades (insulation installation, but retaining all structural components) how should they be modeled in the baseline building? Table G3.1, part 5, baseline building clearly states that it should not be the same as new contruction, but it is unclear for me on how it SHOULD be modeled: "Opaque assemblies used for alterations shal conform with section 5.1.3". Can someone please advise me? Thank you in advance!

For existing assemblies follow Table G3.1-5 Baseline (f) which tells you to model the existing conditions in the baseline.

Thank you Marcus! Let me be more clear about the question: Our project will be a renovation of an old warehouse (unconditioned) such that only about 20% of the exterior wals will stay (everything else will be new construction, incluiding floors, roofs, fenestration, HVAC equipments, lighting, etc...). LEED v4 Reference Guide, page 354, table 3, Existing envelope states that "(...) for an existing building (or spaces in the building) that was previously unconditioned and is renovated to include conditioning, the baseline building envelope (..) must be modeled as if the building is new construction." - This clarifies my previous question. Now my new question: knowing that only about 20% of the building's exterior walls will remain, how much can we claim our project to be a major renovation and not a new construction? This is important so that we may claim additional credits under "Optimize Energy Performance" (Major renovation with lower % cost reduction to achieve points). Thank you in advance!  

Since the building was previously not conditioned I do not think you can claim the baseline as uninsulated at all as stated in the Reference Guide. You should use the Table 5.5 minimums in the baseline.

Hi Marcus, I agree! How about my second question? May I consider the project as a Major Renovation (and not New Construction)? Thank you!

Hard to say without seeing the configuration of what was there, what will stay, and what is getting built. If you are demoing 80% of the walls, all the roofs and floors then this certainly sounds like new construction to me. If what you are saving is a mostly enclosed and distinct area then maybe you could count that part as existing. Maybe you could try to justify doing a whole building take-off (wall, windows, roof and floor area) and then claim the percentage of existing wall as the percent existing? The conservative approach would certainly be to count it all as new construction. Anything else you will need to be able to justify to the reviewer. 

Dear Marcus, Could you tell us if it is mandatory that the thermal coefficients of my building comply with table 5 - 5.3 which governs the performance of each type of envelope? I'm lost, I'm on a project outside the United States.

Could you tell us if it is mandatory that the thermal coefficients of my building comply with table 5 - 5.3 of ASHRAE 90.1 which governs the performance of each type of envelope? I'm lost, I'm on a project outside the United States.

Only the X.4 sections of 90.1 contain the mandatory provisions.