I am wondering if anyone knows if a cleanroom return chase would be counted in the conditioned floor area for determining the primary system type for ASHRAE 90.1. There is no intent to condition this space. It is certainly not a heated or cooled space. It may be an indirectly conditioned space based on air being intentionally transferred to it, however, it is transferred purely for the purpose of maintaining a differently pressure between the cleanroom its surroundings, not to condition the chase. Any help is much appreciated. Thanks.

ASHARE 90.1's definition of a conditioned space is:

"conditioned space: a cooled space, heated space, or indirectly conditioned space defined as follows:

a. cooled space: an enclosed space within a building that is cooled by a cooling system whose sensible output
capacity exceeds 5 Btu/h·ft2 of floor area.

b. heated space: an enclosed space within a building that is heated by a heating system whose output capacity
relative to the floor area is greater than or equal to the criteria in Table 3.2.

c. indirectly conditioned space: an enclosed space within a building that is not a heated space or a cooled space, which is heated or cooled indirectly by being connected to adjacent space(s) provided:

the product of the U-factor(s) and surface area(s) of the space adjacent to connected space(s) exceeds the combined sum of the product of the U-factor(s) and surface area(s) of the space adjoining the outdoors, unconditioned spaces, and to or from semi heated spaces(e.g.,corridors)"

OR

that air from heated or cooled spaces is intentionally transferred (naturally or mechanically) into the space at a rate exceeding 3 ach (e.g., atria)."