We have not seen official guidance on this, but the LEEDuser expert consensus is "no." Each element of a building should be accounted for in either MRc1.1 or MRc1.2 and cannot be used twice. If a floor slab is reused and contributes to MRc1.1, it can therefore not also contribute towards MRc1.2. Even if it is used as a finish floor, that is not the same thing as reusing non-structural flooring under MRc1.2.

The percentage of reused existing interior building non-structural elements is calculated by area, dividing the total reused interior non-structural elements by the total area of interior non-structural elements (including new elements from additions or replacements). A calculator is provided in the documentation toolkit to facilitate this.

There is no specific way to earn LEED credit for these features. In some cases (see below), credit may be possible under MRc2.

All existing envelope and structural building elements are included. The items you do not include are interior non-structural elements, windows and non-structural roofing. If you have structural elements of the building that are considered hazardous or are otherwise structurally unsound, these can also be excluded from the calculations.

Yes. According to LEED Interpretation #998, "The approach of designing rainwater storage for a 'normal' rainfall year and providing potable water as backup is acceptable."

LEED does not distinguish what characteristics make an irrigation system "temporary." However, teams have had success by installing irrigation systems with plans to disable them in some way, such as removing sprinkler heads, cutting up pipe, or causing some other severe, if not unalterable, damage to the system.

The LEED-NC v2.2 requirements is for no more than 12 months. According to a LEED Reference Guide addendum from 7/19/2010, the time period was been increased from 12 months to 18 months for LEED 2009 projects, but USGBC has not altered the timeframe for pre-2009 projects.

Although this may contribute to reducing irrigation demand, this does not help with achieving the credit, as landscaped area in the both the baseline and design case has to be the same. Although decreasing vegetated space may be a sensible option for some projects, it is not allowed to contribute to this credit. It would not match the intent of this and other credits for LEED to include an incentive to reduce vegetated area.

No. LEED defines the scope of the credit as landscaping outside of the building footprint.

Yes.