WHAT IS LPD? Lighting Power Density (LPD) is the lighting power density based on area of a building, space, or outdoor area expressed in W/ft2. In short, how much artificial lighting occupants will likely use based on the design. Click here to learn more.
When establishing your project in Cove Tool it will automatically pull in LPD data based your project’s selected Cove.Tool Building Types and Energy Code. Energy Code is initially pulled from the project’s given location (address), then can be overridden per your project’s design intent. Double check with your project goals/energy codes and modify in tune-up sessions (see charts below). If lighting schedule data is available, the time of use tab can be modified to further reflect how the project will be used. Set daylight sensors and/ or occupancy sensors to what the design is pursuing. If the floor plan has good daylighting, it’s recommended to test out the EUI & utility savings impact by turning them on.
In the context of AIA 2030, the LPD goal is 25% below baseline across the GSF of 2030 projects. There is no individual project specific reduction percentage, only an overall EUI number, but lower the LPD the better the performance. Ask engineers & daylighting specialists early on for the best opportunities available to lower the LPD overall for your project.
For high level focus on LPD, only typology specific charts will be shown in this FAQ. For individual program space requirements, refer to links to respective codes. Cove Tool has provided conservative assumptions for individual spaces; please see the tables on the following pages.
FOR MULTIFAMILY PROJECTS You’ll have a breakout of LPD for the non-residential spaces and dwelling units within the project. Most codes will not specify a dwelling unit LPD, but rather a wattage level requirement. If the lighting designer or electrical engineer cannot provide an LPD on their end, use the Cove Tool default based on typology or select 0.38 as a conservative estimate per Fig 04. For a more accurate model, use the ratio method described in Fig 06. Ideally, this is a last resort as the engineer should be tasked with providing these numbers.
FOR MIXED-USE PROJECTS Use an area weighted average approach to get a total value into Cove Tool. Ideally, mixed used projects will be set up as different occupancies where users can enter the specific LPD of each overall typology vs an aggregated average. See examples below.
FIGURE 05 LPD IN UNEQUAL SPACES.
IMAGE CREDIT PATRICK CHOPSON.
STEP 1: CALCULATE ROOM AREAS
ROOM 1 AREA = 15.5 X 11 = 170.5
ROOM 2 AREA = 7.5 X 11 = 82.5
ROOM 3 AREA = 13 X 11 = 143
TOTAL AREA = 396
STEP 2: CALCULATE RATIOS
ROOM AREA RATIO = AREA OF THE ROOM/TOTAL AREA OF THE BUILDING
ROOM 1 AREA RATIO = 170.5/396 = 0.431
ROOM 2 AREA RATIO = 82.5/396 = 0.208
ROOM 3 AREA RATIO = 143/396 = 0.361
STEP 3: WEIGHTED AVERAGE LPD
LPD INTERVENTION OPPORTUNITIES
• Specifying LPD in the OPR or a % reduction factor from code.
• Specifying LED systems/fixtures.
• Add Daylighting Sensors.
• Add Occupancy Lighting sensors/timers.
• Right sizing RCP fixture layout.
• Add BMS daylight integration
• Engage in Daylighting analysis
» Orientation
» Shading
» Program/Floor plan layout
» Finish material reflectivity
» Visual Lighting Transmittance (VLT) of Glazing
CONVERSATIONS WITH CONSULTANTS It is recommended to consult with a dedicated lighting designer and electrical engineer regarding opportunities available. This is where selecting the right engineering team becomes essential. Examples of questions to ask:
• We’d like to pursue LED lighting and avoiding any mercury containing lamps, does this work for your team’s design package?
• We’re engaging in daylight studies to reduce artificial lighting needs, what is the typical cost add for daylight/occupancy sensors either per unit or per SF we can compare to utility savings? (You can add the engineer as a guest in Cove Tool)
• (Depending on size of the project) could we pursue a BMS (Building Management System) and what is the cost add/spatial modifications to the electrical rooms? Can we meter daylight systems separately?
• Do we need these many lights in the ceiling plan? Any places where we can optimize fixtures?
• How low can we go with lighting power while maintaining a well lit and productive interior space? Can we set a reasonable LPD reduction target % and implications to present to the client?
• (At specific phase checkpoints) is our LPD target on track?
CONVERSATIONS WITH OWNERS Remember to frame the cost addition of specific strategies in reference to utility savings for the client over time, this is especially helpful for owners that will retain the building for long periods of time.
Depending on the client, they will have different priorities. For educational facilities, natural daylight may be a pursuit for occupant health reasons and the benefit of natural daylighting, while a commercial office client may be more interested in the utility savings or both! Keep in mind their bottom line and present narratives/analysis that aligns with them.
If BMS systems are pursued with metering breakouts of lighting, ask the owner if LS3P can have access to the data to compare design to actual performance metrics.
For additional resources, refer to LS3P resources regarding daylighting from our EUI sessions/one-sheets.
RECOMMENDED WORKFLOWS FOR DD x UPLOAD
1. For benchmarking: refer to the latest OPR (Owner’s Project Requirements) for established thresholds.
2. If possible, provide the engineer the LPD survey created by the Design Technology team to help assist with data collection.
3. Otherwise, use one of the options below, and submit a Calculation Submission form at each phase or at least once per year, to help assist with data collection:
A. Refer to the local code standard per typology.
B. Or, use the space – by – space method as a last resort.
REFERENCE STANDARDS
• ASHRAE – 90.1 – 2007 is the baseline for 2030 AIA
• LEED
» V 4.1: ASHRAE 90.1-2016
» V 4: ASHRAE 90.1-2010
» V5: In-progress
ADDITIONAL RESOURCES
• https://www.energycodes.gov/
• https://up.codes/
ENERGY CODE STANDARDS
South Carolina (CHS, MYR, CAE, GSP):
• Commercial: 2009 IECC & ASHRAE 90.1 – 2007
• Residential: 2009 IECC
North Carolina (GSO, AVL, RDU, CLT, ILM):
• Commercial: 2015 IECC & ASHRAE 90.1-2013 with amendments
• Residential: 2015 IECC with amendments
Georgia (ATL, SAV):
• Commercial: 2015 IECC and ASHRAE 90.1-2013 with amendments
• Residential: 2015 IECC with Amendments
Florida (JAX):
• Commercial: 2021 IECC & ASHRAE 90.1 – 2019 with amendments
• Residential: 2021 IECC with amendments