Zack Rogers wrote:
This has been a very interesting thread...many good things to know, and once again Radiance shines on. I was going to comment that your dealing with a fraction of a lux difference now, there must be some sensitive objects inside your space...is this an art gallery? And your right, with the logarithmic behaviour of the eye the difference becomes even more insignificant.
Yes, it's an art gallery. An art gallery with lots of clerestory surface area that sees the exterior, and het they are asking us to see if we could specify a shade system that can get the light levels to 70 lux. That's why we have been doing all these calcs. And as many times as I say it's important to focus on the relative gains & losses with each scheme, the client still tends to focus on the numbers, which is scary in the extreme, for me.
When we got to these last galleries, because we were removing so much light, this problem with -av finally revealed itself to us. We had reached the point where the -av approximation was adding light to our model. It became evident as we hit the 1% shade region; adding more shades beyond that seemed to make no difference to the numbers. The architect called our model into question, and as he was a physics major before going into architecture, there was no convincing him that this was correct! Intuitively, I knew something had to be wrong but I couldn't put my finger on it. Physical tests at the mockup site bore out the intuition; something was wrong. So, I asked this list for help, and got some. Thanks again!
That was my image in ArchRecord a couple months ago! I'm excited someone noticed. I used the same CAD model to create the CFD image that was also in the article. It was a very interesting project, the first project I've worked on where the plants were the most important building occupant to provide light for.
Interesting! So, you were tasked with evaluating the resultant spectral makeup of the light after it had passed thru the glass, presumably to ensure photosynthesis? How did you get spectral data for all the other materials? I know Optics5 is great for glazings, but what about the other materials?
With that project and another musuem
project, I used optics 5 a lot to look at the spectral qualities of glass. Optics 5, with its new Radiance output functionality, is great!
As a matter of fact, I think I first looked at Optics5 after you mentioned it on the list, in your post about the Phipps bldg. I used it recently for a project too. It's nice to pull out a very accurate glazing spec for use in Radiance so easily. I wish there was a similar database for paint finishes, metals, etc.
One thing we learned, and anyone correct me if I'm mistaken, is that the adhesive layer in laminates almost completely eliminates ultra-violet from the spectrum. Ultra-violet, or more accurately the Krochmann factor (which is loosely related to UV and also determined by optics 5), is the main component of radiation that causes degradation of materials (artwork, furniture). I may be completely off base by now, but if you are concerned about obtaining such low light levels to minimize the footcandle-hours that fall on artwork or what not, I would look at the spectral qualities of the light you are letting in as well as they may be more effective at preventing degradation than low light levels.
It's a combo of intensity, duration of exposure, and UV filtration
(< 400nm) that we need to manage. Yes, most (not all) laminate interlayers will filter out UV and that's *always* part of any museum design strategy. There is a book, "The Museum Environment" by Garry Thompson, that gives a great overview of the UV problem as it relates to museum artifact preservation. It's actually quite interesting. Here's a link to the book's info at Amazon:
PS. Your blog is great! I had planned on doing something similar (although i typically rant and rave about politics) on my website and wasn't aware there was a name for something like that.
www.zrogers.fpcc.net - it is not nearly complete (I just had a baby boy last month!) but the home page was made entirely with Radiance!
Thanks! Yes, you'll find that it's quite a sensation these days, this business of putting up a website and blathering about whatever, out into the void of space. I like it. Most of my site is still down, I changed hosts in January and haven't had time to upload all that stuff again. Just pictures, stories and stuff. Your basic self-gratification type deal. =8-) I went to your site, but a couple of the links are not workin'. The renderings are fun, I like how the rollovers change and the change is also reflected in the water. Neat! I'll check back on it, presumably after your son starts sleeping through the night?