ASHRAE 90.1 - Interior Lighting Power Density (LPD)

It is your choice to follow one LPD method or the other. Most of the time in our expereince you will get more savings using the space-by-space method.

LPD is not a mandatory provision, it is a prescriptive requirement. You must comply with all mandatory provisions. Prescriptive requirements are available for trade-off. As long as you show the necessary total savings you can exceed individual prescriptive requirements.

If you do not know what the LPD is for these spaces then use the ASHRAE 90.1 values in both models.

You can claim savings if the tenant guidelines contain a LPD requirements for future tenatnt below the ASHRAE 90.1 value. See the CSv2 CIRs.

Can we have the lease document for tenant spaces state that they must be at a specific LPD and use that value in the energy model for extra savings?

Yes. You can do that. You can also require more occupancy sensors or daylight control and therefore claim savings for any measures that exceed ASHREA 90.1 standard. You will have to provided the lease documents in order to prove it.

Also can take credit for any spaces that are designed, even if they are not part of the shell and core scope.

For example, in a recent project, several spaces had been leased prior to construction. Different design team, not part of the shell and core scope, but since they had a complete lighting design already, we were able to model those spaces with the actual LPD.

One more question regarding this topic. In our CS project we are using the ASHRAE 90.1 values for both proposed and design cases. However, we will install automatic lighting controls in the tenant spaces as a part of our CS scope. Is it possible to decrease the proposed case by 10 % because of the table G3.2 even though we are using tenant neutral values?

Yes you can as long as the controls qualify.