Achieving the minimum Ashrea 90.1-2007 requirement for lighting power density for office space specified at 1w per square foot has been virtually impossible for my team.
The office in question is mostly divided into private offices (but this is programmatic and unchangeable) and interview with the client employees revealed expectations for 50fc levels, not an unuasual request in this geography.
This may have to do with the fact that the project is in a sunny place and people expect their interiors to be likewise highly illuminated but this is a given reality as well.
My questions are:
1) Does anyone has any experience or thoughts about the possibility to request some extra watts in order to satisfy the high lighting levels demanded assuming I am demonstrating a very good (i.e. low) watt/foot candle ratio ?
I know that a sure way to go would be task lighting, but the design of the office just does not allow me much to furniture to mount on. Anyone with a guess of whether a wall or ceiling mounted or wall or ceiling recessed luminaries assuming they are connected to an automatic shutoff and are easily adjustable will fly?
Thanks
Gahl
Paul Conrad
Energy EngineerCLEAResult Consulting
346 thumbs up
August 20, 2010 - 2:41 pm
Gahl,
As far as LEED and ASHRAE are concerned, you can't exceed the requirements. However, you DO have some options. First, consider installing occupancy sensors, Table G3.2 allows you to claim a 10% Lighting power density reduction for all areas with occupancy sensors. Similarly, you can install daylighting sensors and cut off switches to lower the amount of energy used by your system.
However, your first step needs to be education, 50 fc in an office environment is wasteful and unnecessary. You might also consider fixture placement to maintain 50 fc over work surfaces, but have darker areas on open space.
Hope this helps,
Paul
John Bauer
97 thumbs up
August 22, 2010 - 12:15 am
On existing CI fixtures which exceed the LPD, but were daylite and occupancy sensors are installed, disconneting some fixtures that do not not have an impact on the work surfaces FC might get you there in combination with the 10%. Its worth a trial run on a CI project that has already fixtures installed by the landlord.