[Equest-users] Modeling Light Shelves for Reduction inCooling/Heating Load?

Nick Caton ncaton at smithboucher.com
Mon Aug 23 15:25:52 PDT 2010


The straight answer is "yes" you may model light shelves as external
building shades for your proposed model and not get into trouble with
regard to 90.1.  You would probably not be taking credit for the full
amount of daylight incident in your spaces on an hourly basis however -
you may or may not be able to sleep at night =).

 

eQuest does not accurately model interreflected daylight, so you are
correct to assert such a model will not in and of itself accurately
account for the effects of light shelves upon your daylighting systems.
Note the values entered for surface/ground reflectance may still alter
the amount of light incident on a given window through their effects.
The effects of those shelves with regard to shading is something you can
be more confident of, however.

 

If you'd like to take better credit for light incident on your daylit
spaces, I understand some have pursued using a combination of
daysim/SPOT/excel to generate custom scheduling for use within eQuest.
I haven't traveled this road yet, but I've copied what would probably be
a worthwhile discussion below from last Janurary if you'd like to pursue
;).

 

~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 

 

From: Nilay R. Desai [mailto:ndesai at ttgcorp.com] 
Sent: Monday, August 23, 2010 4:50 PM
To: Nick Caton
Subject: RE: [Equest-users] Modeling Light Shelves for Reduction
inCooling/Heating Load?

 

Regarding day lighting simulation, unfortunately we do not have a
separate program that gives us hourly results, we are just using Ecotect
to simulate the behavior of different shading devices and light shelves.
I thought Equest might take into account the reflective properties of an
external shading device when calculating day lighting, but as I've seen
stated in the help files and archives, it doesn't look like the day
lighting benefits of light shelves can be "accurately" accounted for in
Equest. 

 

What I should have asked originally was would it be ok to model light
shelves as external building shades in reference to ASHRAE 90.1? I know
90.1 allows modeling of light shelves in the proposed model, but given
Equest's admittance to its inability to properly model light shelves,
would this method of modeling light shelves still be seen as legitimate
given the modeling limitations terminology on pg. 179 of 90.1 - 2007 (if
not for the day lighting benefits, at least the shading benefits)?

 

 

From: Otto Schwieterman [mailto:oschwieterman at fhai.com] 
Sent: Friday, January 08, 2010 8:24 AM
To: John Aulbach; Matutinovic, Luka; Nick Caton; R B
Cc: equest-users at lists.onebuilding.org
Subject: RE: [Equest-users] How does eQuest know
initialFootcandlesforDaylighting Calc?

 

Here is an alternate method to eQUEST's daylighting strategies:

 

>From my experience (and training from Marlin Addison), I believe that
eQUEST does not model daylighting with much accuracy. I believe that the
best method to handle daylighting is to run models on independent
software (DAYSIM is free) and insert the results into lighting
schedules. My general practice with lighting schedules is to force 100%
of the lights to be on when the room is occupied and during the same
occupied times, create a new schedule that shows the fraction of lights
on from the DAYSIM output. 

 

This method gives the modeler more control and flexibility with the
model and daylighting strategies. Many times we have 3 rows of lights in
a classroom and we typically force the row furthest from the window
always on when occupied so the minimum percentage of lights on during
daylighting is 33% (1/3).   

 

From: John Aulbach [mailto:jra_sac at yahoo.com] 
Sent: Thursday, January 07, 2010 12:02 PM
To: Matutinovic, Luka; Nick Caton; R B
Cc: equest-users at lists.onebuilding.org
Subject: Re: [Equest-users] How does eQuest know
initialFootcandlesforDaylighting Calc?

 

Luka:

 

That was my hope, but eQuest isn't that smart. As I was so directed by
an "unimpeachable source", there IS no footcandle level until you set it
in the Daylighting mode. eQuest then assumes that this is the level 100%
of the lights emit. Then when you allow the Daylighting mode to run,
eQuest lowers the % lighting based on how much you can gain from the
skylights, side daylighting, etc.

 

Crude but straight forward.

 

Others can add or correct..

 

John R. Aulbach, PE, CEM

Senior Energy Engineer

________________________________

Partner Energy

1990 E. Grand Avenue, El Segundo, CA 90245
W: 888-826-1216, X254| D: 310-765-7295 | F: 310-817-2745

www.ptrenergy.com <http://www.ptrenergy.com/>  | jaulbach at ptrenergy.com
<mailto:%7C%20jaulbach at ptrenergy.com> 

 

 

________________________________

From: "Matutinovic, Luka" <LMatutinovic at halsall.com>
To: Nick Caton <ncaton at smithboucher.com>; R B <slv3sat at gmail.com>; John
Aulbach <jra_sac at yahoo.com>
Cc: equest-users at lists.onebuilding.org
Sent: Thu, January 7, 2010 6:09:14 AM
Subject: RE: [Equest-users] How does eQuest know initial
FootcandlesforDaylighting Calc?

Nick,

Does this mean that there is some "baseline" fc that is provided by the
electrical lighting?  That is to say, eQuest will determine how many fc
daylight provides and satisfy the rest with some fraction of the
installed LPD?  This implies that there is a relationship between LPD
and fc, is that true and if so what is it or where could I find it?
Thanks,

Luka Matutinovic, B.A.Sc., LEED(r) AP
Green Building Consultant 

T. 416.644.0649
F. 416.487.9766  
Toll Free 1.888.425.7255
www.halsall.com <http://www.halsall.com/>  

HALSALL ASSOCIATES LTD. 
Toronto  Richmond Hill  Ottawa  Sudbury 
Burlington  Calgary  Vancouver  Dubai 

'50 Best Workplaces in Canada' 
2009 Globe and Mail
P Please consider the environment before printing this e-mail


-----Original Message-----
From: Nick Caton [mailto:ncaton at smithboucher.com] 
Sent: Wednesday, December 30, 2009 10:27 AM
To: R B; John Aulbach
Cc: equest-users at lists.onebuilding.org
Subject: Re: [Equest-users] How does eQuest know initial
FootcandlesforDaylighting Calc?

The DOE2 help files suggest, if not directly, that the sensor you are
placing is measuring ONLY "illuminance due to daylight," in isolation of
any electrical lighting in the project.  When you define a "target"
illumation level (say 30fc) at a specific point/orientation, that sensor
will plot the daylight measured in the same vector against a curve
(specified when you select dimming control options) to determine a
factor to apply to the zone's Lightig Watts/SF.

To my knowledge, eQuest in no manner whatsoever is attempting to perform
the operations of photometric software (AGI32/Visual/LightPRO/etc).

~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
<http://www.smithboucher.com/>  


-----Original Message-----
From: equest-users-bounces at lists.onebuilding.org
[mailto:equest-users-bounces at lists.onebuilding.org] On Behalf Of R B
Sent: Monday, December 28, 2009 4:44 PM
To: John Aulbach
Cc: equest-users at lists.onebuilding.org
Subject: Re: [Equest-users] How does eQuest know initial Footcandles
forDaylighting Calc?

My guess is that the tool assumes the lighting wattage that you have
gives the amount of footcandles specified. If 50% of this is from
daylight, then remaining is from 50% of the installed lighting
(translating into 50% wattage usage).
-Rohini

On 12/28/09, John Aulbach <jra_sac at yahoo.com> wrote:
> LIke the Phantom of the Opera.."A mystery never fully explained.."
>
> I have performed Daylighting savings EEMs in eQuest, where one places
a
> sensor in the space, one deliniates a minimum footcandle requirement,
and
> runs a Parametric run to determine how much lighting energy may be
saved.
>
> What is NOT clear to me is how eQuest determines what the inital
footcandle
> level is. It obviously knows the lighting fixture height (Ceilling or
> syspended) and the geometry of existing windows, etc. But I cannot
find
> where the information lies that says "eQuest assumes so many
lumens/watt of
> certain lighting."
>
> Can anyone "ILLUMINATE" me, please?
>
> Hope all had a great Christmas.
>
> John Aulbach
>
>
>
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