According to ASHRAE 90.1, power allowance for lighting in mall areas is 18 W/m2 (table 9.6.1). However, according to section 9.6.2 of ASHRAE 90.1, an additional lighting power of 10,8 W/m2 is allowed "when lighting is specified in addition to the general lighting for the purpose of decorative appearance". Shopping Centre mall areas are equipped, generally, with lots of lights meeting this purpose. Can we assume a power density of 28,8 W/m2 (18 + 10,8) for the mall areas of the baseline building ? Or are limited to 18 W/m2 ?

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Marcus Sheffer

LEED Fellow

7group / Energy Opportunities

LEEDuser Expert

4454 thumbs up

Thu, 11/08/2012 - 19:56

If it truly meets the definition of decorative then yes. In my mind it is decorative if you take it away and the lighting which remains meets the illumination requirements of the space. If it does not then it is at least part general lighting and no additional allowance should be used.

Bill Swanson

Sr. Electrical Engineer

Integrated Design Solutions

LEEDuser Expert

516 thumbs up

Fri, 11/09/2012 - 13:35

Also, the extra decorative allowance is "up to" 10,8 W/m2. If the light meets the definition of decorative as Marcus mentions (and controlled separately) then you can use the extra amount, up to the maximum. Maybe you only used 23,8 W/m2. You can't claim the remaining 5 W/m2 as a "savings". Your baseline and your design model will use the value of 23,8 W/m2 for that space. So, having a lot of decorative lights will show a zero energy savings, and it might allow you to meet a Code minimum. You'll be in trouble if you do this everywhere and try to meet the LEED requirement of 10% below ASHRAE.

Ricardo Sá

Director of Sustainability

Edifícios Saudáveis Consultores (503 910 767)

LEEDuser Basic Member

79 thumbs up

Tue, 11/13/2012 - 09:22

Thank you very much for your comments Marcus and Bill. The idea was to simulate the baseline building with 28,8 W/m2 (general lighting: 18 W/m2 + decorative lighting: 10,8 W/m2 = 28,8 W/m2) and to simulate the proposed design with its actual power density (general lighting: 15 W/m2 + decorative lighting: 5 W/m2 = 20 W/m2). As far as I understand for your comments I cannot do this. I can only use 23 W/m2 (general lighting: 18 W/m2 + decorative lighting: 5 W/m2 = 23 W/m2). Is this interpretation correct ? It seems very difficult for a Shopping Centre to comply with EA.p2: lighting represents 50% of the energy usage and real power densities in mall and shops are typically beyond the ASHRAE power allowances. Do you have any experience in certifying this type of buildings ? What are your recomendations ?

Marcus Sheffer

LEED Fellow

7group / Energy Opportunities

LEEDuser Expert

4454 thumbs up

Tue, 11/13/2012 - 14:58

That is how we interpret it. You only get the actual in the Proposed up to the maximum allowance for decorative lighting. Use the requirements to drive a more energy efficient lighting design - this is the real purpose behind this LEED requirement. Finding a loophole in 90.1 does not make the project more energy efficient. In my experience the 90.1 lighting allowances are easy to exceed as long as the designers understand what is required they can usually find a way to make it work. Might want to start with a "no incandescent" design criteria. While it was not a shopping center, we ran into the same issue in an office tower in Italy. The original lighting design was 20 W/m2 and once they understood the requirements they reduced it to under 10. It can be done.

Ricardo Sá

Director of Sustainability

Edifícios Saudáveis Consultores (503 910 767)

LEEDuser Basic Member

79 thumbs up

Tue, 11/13/2012 - 15:31

Thanks Marcus. I absolutely agree with you in what concerns office lighting (we are now certifying an office building that was designed with 15 W/m2 and is now bellow 7 W/m2 (tasklight strategy) ! However, lighting in shops is a different matter, its all about ambiance... In a Core & Shell project it is very difficult to impose such a restritive value to the tenants. I am still curious to see what's going on LEED Certified Shopping Centres, I really would like to know which power densities are they using.

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