I have a heating-only warehouse (with small conditioned office) I'm modeling for C&S 2009. Based on the heating consumption in the proposed design, the warehouse space qualifies as semi-conditioned. For the Baseline I used the 5.5 envelope requirements for semi-heated space and System 9 with the required parameters: 80% efficiency and a 105deg supply temp. GBCI did not take issue with me claiming this space was semi-heated, but they did provide me with the following comment as part of their design-phase review:

"Baseline HVAC system types in Table G3.1.1.A can be modeled for conditioned spaces only, whereas semi-conditioned spaces in the Baseline model must be modeled using the HVAC system type from the actual design. Revise the Baseline model so that the HVAC systems that serve semi-heated spaces are modeled according to the actual design. Ensure that the HVAC parameters such as heating source type, heating efficiency, and fan power are modeled identically between the models. Additionally, note that heating capacity and supply air volume for the Baseline model must be auto-sized using the temperature setpoints and temperature difference from the actual design."

I do not see anything in 90.1 that says systems must be equal if the space is semi-conditioned. There is nothing to that effect in Table G3.1 (section 10). I do not see anything in G3.1.2.1 that says I have to use a different efficiency for the Baseline if it is semi-conditioned. I do not see anything in G3.1.2.8.2 (addendum dn) that says I must use the design temperature difference instead of 105deg. It certainly seems odd that some parameters must be held equal but some must be determined using the usual auto-sizing.

In addition to savings from the envelope, since I can classify this as semi-conditioned, we are benefiting from 92% efficiency heating units which use a 160deg supply air temperature. If I have to bring the Baseline up to equal these parameters, obviously we're going to lose points, so I want to avoid that.

Has anyone had a similar experience with a LEED review on this topic? After a quick search, I did not see any LEED Interpretations that seemed relevant. Can anyone point me to language in 90.1 that directs me to do what GBCI is telling me to do? Ultimately, the LEED reviewer determines what is and is not acceptable, but I do not see any justification for their comment in the ASHRAE text. Thanks for your input.