Glass in Jalousie-style

This window type will have a much greater level of infiltration.

But you can model the infiltration in the same way in the proposed model and in the baseline model, right? I think that in the future the air leakage should be considered in more detail by the standards and by the energy modelers, although it isn't easy.

I think that is correct.

We consider air tightness to be of immense importance in our climate (Vermont- very cold winters and hot, humid summers); we have received a comment from an initial project review that states: "The Room Information report indicates that a different infiltration rate was modeled between the Baseline and Proposed Case. ASHRAE Appendix G requires that schedules, outdoor air flow rates (in CFM), and all items not explicitly defined in the Baseline and Proposed Case be modeled identically in the Baseline and Proposed Case. ASHRAE 62.1 considers outside air to include infiltration. Revise the model to reflect equal air infiltration rates and schedules in the Baseline and Proposed Case. If documenting credit for improvements to air infiltration, use the exceptional calculation method to document the savings. The exceptional calculation method requires that a reasonable Baseline be identified consistent with published data and/or measured data. Additionally, for this measure, the exceptional calculation method would likely require that some form of testing be provided to verify performance in the Proposed Case." We did full envelope commissioning and testing on this project and plan to use an exceptional calculation method to gain credit for the tested infiltration of 0.9cfm50/sf of shell. The project is registered under LEED-2009 NC.

I don't think there is any complaint with your measured values for the proposed case. The issue is the selection of the baseline infiltration to establish the resulting efficiency improvement. The requirement for identical values isn't because teams don't improve the envelope but rather the difficulty in establishing a baseline. It's an important issue in many areas of the U.S.

As baseline I would consider an excellent air tightness according to some certification system. E.g., see Passive House: In terms of Airtightness, a maximum of 0.6 air changes per hour at 50 Pascals pressure (ACH50), as verified with an onsite pressure test (in both pressurized and depressurized states). http://www.passiv.de/en/02_informations/02_passive-house-requirements/02_passive-house-requirements.htm If you have local certification systems in Vermont, it might be better.

LEED projects with measured infiltration for the proposed can claim savings. The testing needs to be in accordance with ASTM E779. The Baseline is spelled out in 90.1-2013 at 0.4 cfm/sf @ 0.3 in wc.