Dear all,
We are modelling an office tower under LEED C&S 2009. The owner is NOT fitting out the offices of each floor (They are within the tenants' premises).
One of the energy efficiency measures proposed is requiring tenants to install daylight sensors in their office spaces (highly glazed facades). This will be communicated via binding tenant sales agreements.
Our query is:
Is there a chance that the GBCI asks for plan drawings showing the locations of these sensors, given that the offices will not be fitted by the owner?
Many thanks in advance!
Marcus Sheffer
LEED Fellow7group / Energy Opportunities
LEEDuser Expert
5870 thumbs up
July 16, 2012 - 11:04 am
Plans would not likely be required but a copy of the language in the sales agreement and and narrative describing how you did the modeling for it would be required.
Maya Karkour
EcoConsulting871 thumbs up
July 17, 2012 - 3:33 am
Thanks Marcus,
For the narrative part, are there specific requirements / methodologies for modelling daylight sensors, or will it be a simple narrative just describing the parameters of the sensors (e.g. lux levels and associated dimming percentages)?
Marcus Sheffer
LEED Fellow7group / Energy Opportunities
LEEDuser Expert
5870 thumbs up
July 17, 2012 - 9:20 am
Not really specific requirements, just describe what you modeled. Probably the only other parameter would be the effective daylit zone. For example, if the daylighting is coming from windows on one side of the space the effective daylighting zone is about 1.5 times the window head height. This is the only area where daylighting will be effective.
Jean Marais
b.i.g. Bechtold DesignBuilder Expert832 thumbs up
July 18, 2012 - 4:46 am
For the perscriptive method
Compliant Floor Area
CFA = bay width x 2*(Window H)
so I think the 1.5 should be 2?
Marcus Sheffer
LEED Fellow7group / Energy Opportunities
LEEDuser Expert
5870 thumbs up
July 18, 2012 - 10:01 am
Prescriptive method for EQc8.1? If so our opinion is that method has major issues and we would not recommend using it.
Our experience based on analysis and field measurements is that the 1.5 x window H is the effective daylit zone. Using 2 is a stretch as there are other factors which affect good daylighting (space reflectances, space configuration, contrast ratios, etc.). Reality is not as simple so it makes sense to er on the side of being conservative in a simplistic analysis. And in my experience most energy modeling software does pretty simplistic daylighting evaluations.
Jean Marais
b.i.g. Bechtold DesignBuilder Expert832 thumbs up
July 18, 2012 - 11:05 am
Yes. That is very true. Also, I recommend using DesignBuilder, which uses Radiance in its simulation for daylighting for the EQ8.1 credit, and can use energyplus for the daylighting used in conjuction with linear or step control for daylighing sensors for light power reduction. If using the appropriate "FullInteriorAndExteriorWithReflections" radiation mode, it is a fair approximation for modelling energy usage reductions due to daylighting measures (there are some restrictions when imploying this mode, such as non-convex zone definitions). TrnSys is also getting there, but is in my limited experience, not as user friendly.