[Equest-users] Daylight sensor placement question

[Nick Caton]

Umesh et al,

 

I appreciate everyone's input/responses, both copied to this list and
privately!

 

I'd like to share my thoughts with you all, in response to flood of
useful advice I'm receiving =).

 

First, I want to thank and commend Umesh for bringing up something I
should have made clear (as I have in the past) - I don't personally
recommend that anybody should be trying to use eQuest as a primary tool
to determine daylighting illumination levels, except expressly to check
and fine-tune the modeled behavior.  Rest assured, I have rendered the
daylighting behavior for this particular situation many many times over
from conceptual through final design stages =).

 

eQuest is uniquely suited and capable of determining the hourly energy
behavior of a wide range of daylight harvesting controls (with its own
quirks), and through that can compare the relative energy performance of
a series of glazing/shading layouts and controls combinations... very
useful for certain situations, but one should certainly concurrently be
using photometric software fit to the task to determine interreflected
artificial and daylight behavior accurately enough to make refined
lighting & envelope system design decisions.  

 

Second, based on some conflicting advice/experiences I've received, I've
spent some further time investigating my inquiry on my own and have some
results to share:

-          A photocell located remotely from its parent space will still
measure light.  The amount measured does not necessarily change as you
move it to different zones or even outside the building perimeter
(literally outside).

-          If the parent space has no exterior windows to get daylight
from, it results in an error that stops the simulation run.

-          These behaviors combined pretty much support the notion that
photocells can only see light from their parent space's exterior
windows, and consider relative orientation/distance from the parent
space's window irrespective of whether they're actually in the space or
not.

 

I may have opened a can of worms by revealing an underlying purpose of
my original question - to model open loop photocell controls.  Allow me
to caution and clarify: eQuest's daylighting functions are currently
built on closed loop control schemes.  Modeling the hourly behavior of
open loop controls is something I have been toying with experimentally
for awhile, and probably won't ever recommend others to try within the
current version of eQuest, until I or others should work out some major
hurdles (this photocell placement workaround issue being one).  Paul
Riemer has offered some ideas regarding a "dummy wall" of sorts which
has me a bit excited... =)

 

Third, I've experimented with a variety of things to get the second set
of defined sensors to show up in the LS-M reports, but to no avail...
perhaps this is something to chalk up as one of a multitude of things to
get looked into for future eQuest updates *wink wink... ;)*?  If anyone
has seen an LS-M report for a "Ref Pnt 2," I would be sincerely
interested to examine your model, if I may, to figure out what we're
doing differently!

 

Thanks again to Umesh, Pasha, Paul R. and others for your collective
thoughts and insight!


~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: Umesh Atre [mailto:umesh at innovativedesign.net] 
Sent: Tuesday, March 30, 2010 11:15 AM
To: Nick Caton; equest-users at lists.onebuilding.org
Subject: RE: [Equest-users] Daylight sensor placement question

 

Nick,

 

Reverting back to your original email, if you are defining 2 sensors in
reference to the same space, as seen in your screenshot, 

you should get daylighting contribution calculated at both sensors.

Which does not mean that the calculated values will be accurate. Since
the primary space is your north zone, the 2nd sensor

will only be looking at the north exterior windows without any
contribution from the south or any openings on any intermediate 

interior walls.

 

I think you get the LS-M for just the first reference point. LS-G and
LV-L might be able to provide averaged numbers though. If you do

need the LS-M for the other reference point, you could reverse number
them, or define just the sensor you want, and rerun the simulation.

 

Per my past trials with using daylighting in eQUEST, footcandle levels
will be calculated at reference points placed outside

the primary space to be daylit, or for that matter even if they are
placed outside the building, as long as the primary space has

one window on an exterior wall, and sensors are tied to this space.
Outdoor sensors in this case do not measure exterior 

illumination though, which ideally would be in 1000's of footcandles. 

 

Even if you have an interior wall (or more than 1 wall) separating 2
spaces, you will get footcandle levels calculated at the other

reference points. Again, the condition seems to be that the sensors
should be defined in relation to a primary space which has

to have an exterior wall window opening. Since this does not reflect
reality, I am not sure how to approach this issue. I think all

interior walls are basically ignored for side-lighting calculations.

 

This topic has most probably been discussed here in the past, but in
short, the recommendation would be to use a separate daylighting 

program (which you are trying to avoid using I gather) to independently
calculate daylighting levels in your spaces.

 

 

 

 

 

 

________________________________

From: Nick Caton [mailto:ncaton at smithboucher.com] 
Sent: Tuesday, March 30, 2010 11:13 AM
To: Umesh Atre; equest-users at lists.onebuilding.org
Subject: RE: [Equest-users] Daylight sensor placement question

Umesh - you are understanding the layout correctly =).  

 

I could apportion some fraction of the classroom's LPD to the corridor,
and then locate a sensor in the corridor to control that resulting
fraction of lighting.  This workaround would be perfect, though it's a
bit of extra work that I'm unsure is necessary...  For all I know, these
photocells are working correctly, but I am not sure how to verify that
since the appropriate LS-M reports aren't being generated!

 

Ideally, I would like the energy model to have the photocell in the
corridor control a fraction of the lights in the classroom - if only
because it would be less work and match the true design (open loop
photocell controls).  

 

Regardless of whether this is actually working, I'd really like to know
whether photocells outside of the controlled zone, irrespective of any
relative window locations (or even better, outside of the building
perimeter) can correctly measure and report daylight, accounting for
specified building/site shades.   I understand this would be bending the
current intent of the photocells as defined in eQuest, as they're
intended to vary light levels based on closed loop controls (measuring
ambient+daylighting at the work surface in question).  This might help
bridge a gap between syncing measured/modeled daylight behavior to an
energy model to accurately approximate open loop design behavior.

 

~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: Umesh Atre [mailto:umesh at innovativedesign.net] 
Sent: Tuesday, March 30, 2010 9:26 AM
To: Nick Caton; equest-users at lists.onebuilding.org
Subject: RE: [Equest-users] Daylight sensor placement question

 

If I may ask a question:

It looks like you have the 2nd sensor located in a corridor the south
side of which is a glass wall. If I understand this correctly,

why would you not define the sensor as part of that corridor zone
instead of the north zone? 

Maybe a section or 3d of this space would help.

 

 

 

 

 

________________________________

From: equest-users-bounces at lists.onebuilding.org
[mailto:equest-users-bounces at lists.onebuilding.org] On Behalf Of Nick
Caton
Sent: Monday, March 29, 2010 11:58 AM
To: equest-users at lists.onebuilding.org
Subject: [Equest-users] Daylight sensor placement question

Hey all!

 

Daylight sensor placement question (see highlighted space in attached
screengrab for an illustration):

 

I have a classroom with North and South daylight transition windows, and
a corresponding North and South daylighting "zone."  The North side is
easy - those windows are on the envelope wall, so I'm sure the daylight
is correctly being measured/modeled within the space for the "North
zone" sensor to pick up on.

The south windows however are in an internal wall, and on the other side
is a "glass box" corridor.  Rather than pursue the fuzzy route of trying
to model daylight transitioning between zones correctly (if anyone can
fully digest the help file for INSIDE-VIS-REFL I would really appreciate
the layman's explanation), I've taken the "easy" route and located the
daylight sensor in the corridor.  This happens to conveniently match the
actual design location of the photocell.  

 

My question has two parts:

*         Can a zone's daylight sensor be located in another zone and
measure light in a remote location?  If so, are any extra steps
necessary?

*         I see my eQuest project is, on its own, generating an LS-M
report for each "Daylight Illuminance Ref Pnt 1."  What is the procedure
to generate the same reports for "Ref Pnt 2" where those occur?  

 

~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 

 

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