Hi all,
I'm doing some daylighting studies with RadianceIES with a model I've
imported from revit. The model seems to have been imported just fine.
However I'm getting very low DF-values.
The rooms I've been studying are rectangular cellular offices with about
12% of the floor area consisting of windows.
The results show that approx 5-10% the area of a working plane at 0,8 m
above the floor has a DF-value of 1.2 %.
This feels like a very low number. The window transparancy is 0,9 and all
the walls are white colored. The ceiling is white and the floor is gray.
Does anyone have a suggestion as to what might be wrong or if these values
seem ok.
Thanks in advance
Best regards
E r i k E r i k s s o n
Energy specialist and project manager
________________________________
White project & environmental management
Box 4700
116 92 STOCKHOLM
Phone: +46(0)8-402 26 77
Fax: +46 (0)8-402 25 10
Visit: ?stg?tagatan 100
http://www.white.se
We are certified according to ISO 9000 and 14 001
Erik
Try carrying out a model for one room at a time. The results tend to
be quite different.
Cheers
Paul
Sent from my iPhone
Hey,
Yeah, I've tried that. With more or less the same result.
I'm quite new to this with lighting calculations. I'm more used to energy
performance.
So I cant really say if the values are correct or not.
Best regards
E r i k E r i k s s o n
Energy specialist and project manager
________________________________
White project & environmental management
Box 4700
116 92 STOCKHOLM
Phone: +46(0)8-402 26 77
Fax: +46 (0)8-402 25 10
Visit: ?stg?tagatan 100
http://www.white.se
We are certified according to ISO 9000 and 14 001
From:
To:
Paul Carey
Erik Eriksson
Cc:
"virtual-sim at lists.onebuilding.org"
Date:
2009-09-28 17:06
Subject:
Re: [Virtual-sim] Low DF-values with Radiance
Erik
Try carrying out a model for one room at a time. The results tend to be
quite different.
Cheers
Paul
Sent from my iPhone
Hi all,
I'm doing some daylighting studies with RadianceIES with a model I've
imported from revit. The model seems to have been imported just fine.
However I'm getting very low DF-values.
The rooms I've been studying are rectangular cellular offices with about
12% of the floor area consisting of windows.
The results show that approx 5-10% the area of a working plane at 0,8 m
above the floor has a DF-value of 1.2 %.
This feels like a very low number. The window transparancy is 0,9 and all
the walls are white colored. The ceiling is white and the floor is gray.
Does anyone have a suggestion as to what might be wrong or if these values
seem ok.
Thanks in advance
Best regards
E r i k E r i k s s o n
Energy specialist and project manager
________________________________
White project & environmental management
Box 4700
116 92 STOCKHOLM
Phone: +46(0)8-402 26 77
Fax: +46 (0)8-402 25 10
Visit: ?stg?tagatan 100
http://www.white.se
We are certified according to ISO 9000 and 14 001
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Hi Erik,
I'm not familiar with the limitations/capabilities of the IES Radiance tool (still looking for a vendor in the US that can send me some kind of trial), but I may be able to offer some suggestions based on my limited daylight modeling experience:
- To clarify, is it 12% of your wall area that is windows?
- Again, not sure of the IES Radiance's operation, but when you say 'white' floors/ceiling and 'gray' floors, what reflectances are being modeled (i.e. 20/50/80%?)
- Consider the hour/month being modeled, along with the orientation and location on the globe. Perhaps you're modeling an instant in time where there is little-to-no direct sunlight on your glazing?
- I am also approaching learning daylight modeling from an energy-modeler's perspective: For daylight studies, I try to give myself an idea of what should be going on first before "crunching the numbers" by building a simple model in Google Sketchup, located/oriented on the globe, and playing with the simplified daylighting tools to see how the sun strikes the building through the year. With practice I'm sure this will become more intuitive, but until then I've learned not to rely on my intuitions!
- A general heads-up that won't solve your immediate concern: a visible transmittance (what IES Radiance calls "transparency" may be something else) of 0.9 is not unheard of, but pretty high for exterior envelope glazing... when I do daylighting/rendering studies I usually go no higher than 0.8 or so unless I have actual product specs in hand.
~Nick
NICK CATON, E.I.T.
PROJECT ENGINEER
25501 west valley parkway
olathe ks 66061
direct 913 344.0036
fax 913 345.0617
Check out our new web-site @ www.smithboucher.com
Erik/Nick
I?d agree on the glazing spec thing don?t go putting in very clear glass
unless you are very sure that it?s going to have those sorts of properties.
A check of the G value should help give you a guide to light transmittance.
Or just check out the Pilkington website or similar to give you a good idea,
their selection tool (think it?s called spectrum or something, a while since
I?ve used it) is quite good for getting some ideas of what it will be like.
In terms of the daylight studies, they should always be carried out using
the IEE overcast sky to assess daylight factors. If you want to check out
glare etc obviously use a different sky, but for DF calculations the
overcast sky should be used. The default positions of everything else in
IES should be ok once you?ve set that up as it will work out the working
plane levels based on that sky.
Nick, you should be able to download IES for a trial from their website
normally. Just email in a request for keys and they should set you up with
a trial. If you haven?t checked out DesignBuilder you might want to do that
too (30 day trial available from their website). Quite similar tool (front
end slightly more sketchup like than IES), but uses energyplus instead.
Doesn?t have the radiance link yet, but we keep pestering the guys there to
get that link in.
Regards
Paul
IES has representation in San Francisco and Boston.
http://www.iesve.com/About-us/Locations
TIM REYNOLDS, P.E., LEED AP
Associate Principal
600 108th Ave NE Suite 600 | Bellevue, WA 98004
T 425 564 8400 Ext 8431 | C 206 422 2547 | F 425 564 8517
tim.reynolds at cbengineers.com | cbengineers.com
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Thanks Tim - I somehow missed that map when I was looking for contacts a few weeks ago.
NICK CATON, E.I.T.
PROJECT ENGINEER
25501 west valley parkway
olathe ks 66061
direct 913 344.0036
fax 913 345.0617
Check out our new web-site @ www.smithboucher.com