Exterior Lighting Power for Non-Tradable Surfaces

Mark Benson

LEEDuser Basic Member

45 thumbs up

April 5, 2010

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Bill Swanson

Sr. Electrical Engineer

Integrated Design Solutions

LEEDuser Expert

516 thumbs up

Tue, 04/06/2010 - 13:51

Sounds like you understand it very well. The ASHRAE 90.1 Handbook describes the non-tradeable allowances as "use it or lose it". I understand your frustration. Everyone finds things they don't understand about this energy model. I can only guess why they made this as a use it or lose it allowance. Most buildings don't have much facade lighting even without ASHRAE 90.1. So why reward them with an "energy savings" for doing what they were doing anyways. And some may try to game the system. If I add 1 wall pack with some uplight over a door on a side of the building. What's to stop me from claiming the allowance for the entire wall area on that side of the building, even if the building is 100'Wide x 200'Tall. A 4000 W allowance with a single 50W MH lamp installed. Look at that. A 98.3% energy savings, I am uber green! While it's frustrating and seemingly arbitrary it won't have much affect on your overall calculations. The difference in wattage in these areas is usually pretty small in comparison to the whole buildings' lighting wattage. I doubt the difference would be noticable. The interior building allowances also have some "use it or lose it" values. Look at 9.6.2. Art exibits and retail get additional non-tradeable wattage. And the 2004 and earlier versions gave us extra wattage in rooms with computers.

Mark Benson

LEEDuser Basic Member

45 thumbs up

Tue, 04/06/2010 - 16:08

Bill, I've reviewed the ASHRAE 90.1 User's Manual and found, like you indicated, that additional interior lighting per 9.6.2 is considered "use-it-or-lose-it." However, nowhere in 90.1 or the User's Manual does it indicate that exterior lighting power on non-tradable surfaces is "use-it-or-lose-it" or has to be the same in the baseline and proposed. On the contrary, the User's Manual states in Chapter 'G', "If the proposed building does not have an exterior lighting application (for instance a parking lot that is not lighted), the baseline building shall not have the exterior lighting application either. If the lighting application exists, however, then the proposed building can take credit for a more efficient system." I agree that gaming the system is unethical and should not be allowed, but if lighting for non-tradable surfaces should be identical to prevent gaming, why not do the same for lighting on tradable surfaces? I could have one pole-mounted light in a huge parking lot and consider the entire parking lot to be lit in the baseline, showing a large amount of savings. But if it is not the intent of the lighting designer to illuminate the entire parking lot with that one light, the baseline approach would be unethical. The same goes for your hypothetical scenario with the wall-pack. If the intent is to just illuminate the door or the area just above the door, the baseline should not include the entire wall in its allowable lighting power. Finally, I agree that exterior lighting is usually not a huge component of a building's overall energy consumption. I just want to take credit where credit is due, and I believe the quote from the User's Manual above indicates that this can be done: "If the lighting application exists, however, then the proposed building can take credit for a more efficient system." Thanks for your input.