Dear Bayanda and Paul,
As indicated by Rick, the IESNA Daylighting Metrics Committee is proposing a DA-based daylight availability/sufficiency metric. (Last that I has seen the cutoff was 50% not 55% so I am unsure what the science behind the 55% to 75% is but Rick and Lisa may be able to clarify.) We have done a pilot study in a single building comparing student assessment of a space with DA simulations and found an encouraging correlation between the two [1]. Given that the pilot study was very limited we are currently repeating the exercise with a number of schools. I expect that we will end up with 10 to 20 spaces (http://mit.edu/tito_/www/Projects/DaylitAreaStudy/DaylitAreaStudyContinued.html). Our new study will run until the end of 2012 so if you are aware of a South African school of architecture that might want to participate, feel free to have them contact me. With the results of this new study pending, I support the IESNA 50% target level for 300lux daylight autonomy based on occupancy from 6Am to 8PM.
In 2009 one of our students, Cynthia Kwan, did a nice thesis on DA distributions in 31 gymnasia and concluded a 3 tier metric for this space type [2]:
- DA <50% = low
- DA< [50% to 70%]= medium
- DA>70% = high
When it comes to DA vs. UDI I (not surprisingly) tend to favor the former mainly because (for design) I find it preferable to break daylighting into three separate metrics (availability, glare, energy) rather than combining them all in one metric which tends to be confusing to designers because then it becomes less evident how to modify the design of a space. I describe this thinking in [3]. Opinions certainly diverge on this topic.
Warm regards,
Christoph
[1] C F Reinhart and D Weissman, "The Daylit Area - Correlating architectural student assessments with current and emerging daylight availability metrics", Building and Environment, 50, pp. 155-162, 2012.
[2] C Kwan, MDesS thesis, Harvard Graduate School of Design, “Towards Climate-based Metrics: A Simulation Study of Annual Daylight levels in 31 Gymnasia”, (2009)
[3] C F Reinhart and J Wienold, "The Daylighting Dashboard - A Simulation-Based Design Analysis for Daylit Spaces", Building and Environment, 46:2, pp. 386-396, 2011.
Christoph
Christoph Reinhart
Associate Professor
Department of Architecture
Massachusetts Institute of Technology
77 Massachusetts Ave, Rm 5-418, Cambridge, MA 02139, USA
t: 617 253 7714, f: 617 253 6152, [email protected]
Sustainable Design Lab | DIVA | Daysim
From: Richard Mistrick [mailto:[email protected]]
Sent: Thursday, October 04, 2012 8:47 AM
To: DAYSIM discussion
Subject: Re: [Radiance-daysim] Daylight Autonomy Benchmarks
Bayanda,
The IES Daylight Metrics Committee has a document currently before the IESNA Board of Directors that provides some recommendations for Spatial Daylight Autonomy, which is essentially identical to the metric you have listed. It uses 300 lux and is based on research studies by Lisa Heschong of The Heschong Mahone Group. The two levels of coverage recommended are 55% coverage for acceptable and 75% coverage for a preferred level, with the time interval for the DA analysis fixed at 8AM – 6PM for all buildings. Lisa may be able to provide you with the proposed document.
Rick Mistrick
From: Bayanda Mpauli [mailto:[email protected]]
Sent: Thursday, October 04, 2012 6:49 AM
To: [email protected]
Subject: [Radiance-daysim] Daylight Autonomy Benchmarks
Dear All
I am looking for papers/research for DA thresholds related to good indoor environmental quality that can be referenced in our South African version of LEED and was wondering if anyone might be able to point me in the right direction?
The Green Building Council of South Africa is considering using Daylight Autonomy as an indicator for their Daylight Credit for the Greenstar SA Public and Education Building Tool – our version of LEED. They currently use DF. The credit falls under the Indoor and Environmental Quality section and so is about the positive impact of daylight on the occupants rather than energy savings. They have a separate glare related credit and so this does not have to be considered within this credit.
At the moment the proposal for inclusion of DA includes the following thresholds.
A DA of 80% for 160lux with
1) 1 Point awarded for 30% of the occupied area
2) 2 points awarded for 60% of the occupied area
3) 3 points awarded for 90% of the occupied area
They are trying to find out from the Green building Council of Australia (who has put the DA credit out for review in their industry and is the basis of the South Africa credtit) where the 80% and 160lux threshold has originated from and in the meantime have requested South Africa consultants to review these figures to determine what threshold would be considered appropriate and indicated of good indoor environmental daylight quality. Something to note is that the certification is for the building being handed over to tenants and it assumes no furniture nor portioning as that is not in the control of the landlord – in order for it to be representative we would be proposing quite a low reflectance floor level to try and build in at least some representation of what might happen in the space if a daylight conscious tenant fitted out the space – alternatively we might up the 160 lux threshold to something higher also to accommodate for furniture. It is currently undefined whether it be incremental or continuous DA but I think this will just impact on the threshold selected.
Ideally we would like to have the threshold based on some form of researched data already performed that can then be referenced. We are not in a position nor have the time to perform this research now. As the tools do get updated over time, it would be possible to review the figure and align it with the most current research or even review the applicability of DA itself and substitute it with future indicators that are more representative of daylight quality.
Regards,
Bayanda
BAS (UCT)
Green Star SA Accredited Professional
PJ Carew Consulting
3rd floor 71 buitengraght Cape Town 8001
tel: 021 426 4051 fax: 021 426 5050 cell: 083 335 9365
[email protected] www.pjc.co.za