Existing LIghting - Commercial Interior

John, The credit language reads: "Reduce connected lighting power density 10% below that allowed by ANSI/ASHRAE/IESNA Standard 90.1- 2007 (with errata but without addenda1) using either the Space-by-Space Method or by applying the whole building lighting power allowance to the entire tenant space." Keeping the last sentence in mind, I'd say that yes, you need to include any existing light fixtures in your overall calculations of lighting power density for the tenant space. The reasoning behind it is explainable as well, ASHRAE Lighting power density calculations assume that you're looking at all lighting in the space. There are provisions for space types that require extra lighting, such as museums and retail display lighting, but simple office lighting must meet rather draconian limits on the amount of area lighting and the amount of task lighting. Paul

We are also doing a fit-out work for our client. In addition to the general lighting in open office areas, the landlord has provided the D5 down-lights along the perimeter of the building facade. Those D5 light fittings has a separate control and are not intended for the general lighting. Are the office areas (with D5 light fixtures) eligible for additional decorative power allowance? Any advice would be appreciated. Many thanks!

Grace, Office spaces in ASHRAE 90.1 do not qualify for decorative lighting power budgets. All fixtures in the space need to be within the lighting power density allowance of the building or space type.

Thanks Paul, noted. One more clarification. Do we need to include the ballast loss in our LPD calculation? For example, 2 no of 14W with ballast loss of 5W, the total wattage to be used in calculation is 28W or (28+5)=33W? Thanks!

Grace, You should use the total fixture wattage of each fixture, which should include lamps and ballasts together. Using the nominal lamp wattage + the nominal ballast wattage is inappropriate because even "Normal Power" ballasts do not tend to drive the lamps at their full rated wattage. Your MEP engineer should be able to give you a watt value for each fixture that takes all factors into account. That's the value you should use for LPD calcs.

Paul, Thanks for your advice.

Hi, we are also doing a fit-out for a single complete floor on an office building. My question is: should the existing lighting (elevator lobby, restroom areas, stairways and corridors) be included in the lighting power density calculations (for EApr1 and EAcr1.1) even though these areas are not included in the project scope? Thanks!

Diana, It depends on how you're defining your project scope. If you're attempting to garner credit for something in the areas you specified in another credit, you must make them comply with this credit. If they're being completely ignored by the build out and ignored for the purposes of LEED, then you can leave them out. Paul

we are doing fitout for 10 floors on office building. In the project scope, we are not touching anything on the fake ceiling & lightings on each floor since we are using all the existing building's fake ceiling and lightings. Can we exclude them in the lighting calculation even though these areas are included in the project scope? But if we are relocating the existing lightings, then we have to include them in our lighting calculation, is that correct? Thanks!