The reference guide states that: "At the time of application, off-site energy and offsets must have actually been purchased for at least the performance period. Contracts or commitments for future purchases can meet the remainder of the 2-year requirement." Accordingly, a commitment to purchasing green power beyond the performance period is an acceptable method of meeting the 2-year criteria.

There's a compliance path for just this type of situation. As long as the property's landscaped area is equal to at least 5% of the total site area, the credit language and other documents state you are eligible for the credit. If the project is registered, check out the form in LEED Online for how to document compliance based on zero use of irrigation (and if it's not registered yet, it's a good idea to do so and always look at the LEED Online forms early on to get a full sense of the compliance and documentation options).

This isn't necessarily an easy thing to do, but a landscape architect could help you identify a rough sketch of conventional landscaping for the region, and then your landscaper could help estimate how much water per square foot they would recommend for that type of landscaping. You might also touch base with local water conservation organizations or groups promoting xeriscaping.

Yes, if 100% of the water used is from reclaimed water, graywater, or harvested rainwater, the project is eligible for all five points. Use the alternative compliance path on the LEED Online form and include an explanation of the situation along with a signed letter by the property manager, facility manager, or owner verifying the use of non-potable water.

You might be able to use Option 1 but here are the couple of constraints.

Both the baseline and actual cases must include the month of July.The LEED Reference Guide states that to capture seasonal variations, the preferred period for irrigation water use analysis is at least one full year.Option 2, the theoretical calculation, is still available to teams that have sub-metered irrigation so this might be a good alternative if you only have partial data.

If the water body can contain the rainfall event with no discharge to the sanitary sewer, then the runoff coefficient is essentially zero. If, on the other hand, the rain that falls directly into the water body raises the water level sufficiently to overflow into the sanitary sewer, the runoff coefficient is 1.0. For example, pools will often have a bit of freeboard before the water level rises enough to overflow and this will allow you to capture the rainfall, and even make up for some evaporation that would otherwise be made up using potable water.

The best place to find this type of data is typically through public agency or semi-public agencies like universities or other organizations. But if you can’t find data specific to the 2-year 24-hour storm, there is an alternative compliance path published by USGBC in the ACP Documentation Guidance for Projects Outside the U.S.

If the manufacturer publishes or can provide the runoff coefficient for your system, use that. For other surfaces where the data is not available, chose the closest surface type from the credit form and go with that.

This is mostly a judgment call and if you’re concerned about questions during the review process, a great way to make your case is with photos or with a narrative describing your methodology to determine the slope.

NOAA provides a great resource for finding information on the 2-year 24-hour storm. For some locations in the U.S., the site allows you to navigate to a specific locale and generates a table of rainfall intensities, including for the 2-year 24-hour design storm. For the other states, it lets you download isopluvial maps.