Lighting Classification Method - Clarifications

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What 90.1 PRM Section(s) are relevant to this issue?

3.4.3 Interior Lighting - Lighting Classification Method

Explanation of issue:

A) Is the building area method to be supported in Phase I?  The analogous T-24 
approach (Complete Building Method) is not supported and is scheduled to be 
removed from the ACM.

B) Table 6 indicates that 'Tradeoffs' are not allowed when using the Building 
Area Method - what does this mean? I.e. what happens if a space in a user model 
which uses the building area method has a lighting power density greater than 
the prescribed value for that 'building type'?

Original issue reported on code.google.com by lu...@360-analytics.com on 26 Aug 2014 at 9:32

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A) Yes, building area method (BAM) needs to be supported in Phase I. 90.1 
doesn't intend to remove the building area method.

B)The Interior Lighting Power Allowance (ILPA) for a building using the BAM is 
the value stated in 90.1 2010. 
With the  space-by-space method, trade-offs are allowed between the spaces, 
i.e. the ILPA  interior lighting power allowance is the sum of the product of 
the lighting power densities for the space types from Appendix 3.4A and the 
floor areas for the corresponding spaces.

To answer your question on 'what happens' - The proposed design isn't required 
to be within any limit, so there isn't a restriction on the value that can be 
entered. In this case trade-offs aren’t applicable for performance based 
compliance.

Original comment by supriyag...@gmail.com on 29 Aug 2014 at 8:27

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Using the BAM:

Would a parking garage comprising the 2 below grade levels of an office 
building be assigned the same LPD as the rest of the office building, or would 
it be assigned the parking garage LPD?  

Similarly, would a mixed use project with 1 level of retail and 4 floors of 
residential be assigned a single 'building area type'?

Language which indicates that more than one building type can be assigned to a 
single project includes the following (though this may be left over from the 
T-24 ACM language. I can't find a basis for this this in 90.1-2010):

  - 2.1.4 - More than one building area category may be used in a building if it is a
            mixed-use facility. 
  - 3.2.2 - 'Space Classification Type' and 'Building Classification':
             For multi-use buildings, the building may be divided and a different
             building classification may be assigned to each part
  - 3.4.3 - 'Lighting Classification Method':
             Building area method can be used for building types listed in Appendix
             3.4A. Parking garage portion of the building shall be considered as a
             separate space.

According to the above rules, a mixed use project using the BAM may include 
spaces with more than one 'building area type'  In this case, if the proposed 
is simply 'as designed' and the baseline is determined from the building are 
type(s) present, trade-offs could occur between building are types.

In summary, two questions:

Can there be more than one 'building area type' assigned to a single project?

If so- how do we prevent trade-offs between different building are types?

Original comment by lu...@360-analytics.com on 29 Aug 2014 at 9:00

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90.1 2010 Section 9.5.1(d) states that multiple building area types might be 
used within a building (in case of a mixed use building). Trade-offs are 
permitted within different building area types, as long as the total ILPA is 
less than the total permitted ILPA. Trade-offs of ILPA for sections of the 
building where different methods of calculation have been used is not 
permitted. This section 9.2.2.3

To answer your questions-
1. Yes, there can be more than one 'building area type' associated with a 
building
All 3 sections listed by you- 2.1.4, 3.2.2 and 3.4.3 are applicable to 90.1
2. Parking garage would be a different building area type. It also has a 
different set of mandatory lighting control requirements. This is document in 
the PRM document 3.4.3 - Parking garage lighting controls
3. We don't need to prevent trade-offs between different BATs (90.1 2010 
Section 9.5.1). Also, trade-offs become applicable for prescriptive compliance 
approach. For performance based compliance, the proposed building LPD is 
'as-designed' and the compliance path of building area method or space-by-space 
method is only used to define the baseline building LPD for either the entire 
building (or building sections in the case of mixed-use building) or specific 
spaces.

Original comment by supriya....@pnnl.gov on 2 Sep 2014 at 4:20