Hello All,
I am confused on the mandatory provision 9.4.1.1 which states that building
larger than 5000 ft2 shall have automatic control device. Does it mean
that mid-rise and high rise building cannot claim for credit in occupancy
sensors shown in Table G3.2 because their GFA is more than 5000 ft2 and only
small office can claim for this credit? I am sure I am not interpreting this
section correct since from what I read, other modelers are claiming for savings
for buildings with more than 5000 ft2 area for occupancy sensors even if
mandatory requirements states that this is required which means baseline
building will also have occupancy sensors.
Can someone correct me on this?
Thank you,
C. Jaigath
Jaigath,
Appendix G allows us to take credit for automatic controls in addition
to (beyond) what's required in 9.4.1 for minimum compliance. One of the
options here is to have programmable (time-of-day) shutoff for interior
lighting circuits, and you can infer from between Table G3.1 and G3.2 of
Appendix G that baseline models are taken to feature only such timeclock
controls for automatic shutoff. Further, it's taken that the lighting
scheduling being kept identical between the proposed and baseline
adequately reflects the minimum requirements, so you aren't supposed to
try to explicitly model the programmable shutoff.
If you have occupancy sensors throughout a building which only requires
programmable shutoff, that's an example of having automatic controls
beyond what 9.4.1 requires - and you'd get to take 10% off your proposed
LPD in all spaces where such short-term shutoff isn't already required
(per following section 9.4.1.2).
Note Table G3.2 also has a corresponding distinction between building
smaller than and larger than 5,000ft2 - offering more credit for
buildings using a means of automatic shutoff where no such controls are
even minimally required.
NICK CATON, E.I.T.
Thank you very much?Nick. I really appreciate your help on this.
?
I really got confused with this when I got a commnet recently saying that the
"baseline case per section 9.4.1.2 were not modeled" and was asked to revised
the baseline. So I ended up with no savings. This is in conflict with Table
G3.1.6 that you have pointed out which says that No automatic lighting controls
shall be modeled in the baseline building design.?
Does it mean that I am wrong when I applied also 10% savings to my baseline?
This is where?I got confused since 9.4.1.1.b?also mentions occupant sensor that
shall turn lighting off within 30?mins of occupant leaving the space.?
The hard and fast rule I follow is that baseline LPD?s are never to be messed with. Any and all credit taken for lighting controls is a deduction of LPD (or sufficiently documented schedule adjustment, I suppose) in the proposed case.
It can get confusing, but in specific spaces (i.e. classrooms), 9.4.1.2 may require occ. sensors. In such a case, I don?t take a credit in the baseline (see hard/fast rule above), but instead remove the credit otherwise taken for that space in the proposed case.
NICK CATON, E.I.T.
I actually take the credit for occ. sensor in both the baseline and proposed
case for such spaces that have a mandatory requirement for occupancy sensor
(e.g. classroom). The advantage is your total energy consumption is slightly
less, so when you are in border line cases where you are ever so slightly
less than the required percentage points for the next level of points it
helps. Much more advantageous to do it this way when you are doing a
school/university building.
Rohini Brahme, Ph.D, LEED AP
Rohini,
While it's a minor point, I'd only caution that my "hard and fast rule"
is pretty much a directly from Table G3.1.6: "No automatic lighting
controls ... shall be modeled in the baseline building design..." That
said, if I were a reviewer I wouldn't have a problem with your approach.
While modeling occ. sensors in both cases would help the EUI of the
proposed model, not modeling occ sensors in both cases will mean your
baseline and proposed HVAC systems have to deal with extra internal
loads, so presuming you have a better HVAC system in the proposed model,
I'd intuitively assume if anything a classroom-heavy school/university
might do better to not model occ. sensors in each model... I guess if
the results bear it out, go with the flow though =).
NICK CATON, E.I.T.
Rohini,
I had a review comment that addressed this. They specifically told me
not to model occupancy sensors in the baseline and only take the 10%
reduction in the proposed model for rooms that have occupancy sensors
and are not required to have occupancy sensors per ASHRAE 90.1 9.4.1.1
and 9.4.1.2.
Also read Table G3.1 No. 6-g.
We just had a pretty in-depth discussion on this internally also - local
implementations of the code (for example, Chicago Building Code) have
added some confusion. To add to what Nick said, the credits in table
G3.2 are only referenced in the lighting requirements in Table G3.1 and
are specifically listed for use in the proposed model for controls that
are not already required by the mandatory provisions of Section 9. I've
always found it ironic that a Section G3.2 doesn't exist even though a
Table G3.2 does...but I digress...here is where we arrived internally:
Section 9.4.1 has 4 main parts - Whole building control, individual
space control, exterior lighting control and additional mandatory
controls.
- 9.4.1.1 requires an automatic whole building control capable of
shutting off lighting (with override capabilities allowed) for the
entire building based on either (a) time clock signal, (b) occupancy
sensors, or (c) some other control signal (like a BMS). This applies to
all buildings over 5,000 SF.
- 9.4.1.2 requires an individual control for all spaces, either
manual or automatic. For specific space types, automatic controls are
required: classrooms (except shop classrooms, laboratory classrooms, and
preschool - 12th grade classrooms), conference/meeting rooms, and
employee lunch and break rooms UNLESS those rooms have multiscene
control in which case they are also exempt from the automatic
requirement. All other spaces are not required to have automatic
controls and can have either manual or automatic controls. In addition,
those spaces where automatic controls are mandatory are NOT required to
be connected to other automatic lighting shutoff controls (i.e. the
whole building controls required by 9.4.1.1)
- 9.4.1.3 requires photocell or astronomical time clock control
of site lighting (with some nuances, but this is a safe simplification
of the requirements).
- 9.4.1.4 requires a number of specialty lighting installations
to have controls - most applicable to LEED is the requirement for all
task lighting to have an individual control.
The way I simplified this for our engineers is the following: any and
all spaces will have 2 levels of code-required control. The first will
comply with 9.4.1.1 and the second will comply with 9.4.1.2. As an
example, for a typical private office our engineers have been using wall
devices that have an occ sensor with a manual control. If that is the
only controls that cover the private office, then the occ sensor
complies with 9.4.1.1 and the manual switch complies with 9.4.1.2; no
credit from Table G3.2 would be allowed since both control methods are
required by 9.4.1. Now, if there is a time clock in the building and
the private office were connected to the time clock with the same wall
device the situation would be different: the time clock would comply
with 9.4.1.1 and the manual switch would comply with 9.4.1.2 leaving the
occupancy sensor as an additional control, eligible in Table G3.2 for a
10% LPD credit against the PROPOSED LPD factors. For a classroom in a
community center, if the lighting is setup for multiple purposes and the
space is on the building time clock, then you just have compliance with
9.4.1.2 and 9.4.1.1 respectively. If you put in an occ sensor (some
control logic required due to the multiscene) then you can take credit
for that sensor in Table G3.2.
I'm curious what you two think of this interpretation?
We even went so far in our discussion to look literally at the way
9.4.1.1 is worded and I believe that since the word "either" does not
imply mixed compliance then any given building must comply entirely with
one of the three options, not a mix of two. Say a time clock for common
spaces with occ sensors for tenant leased space, for example, would not
comply with the most strict reading of the code. That is quite literal,
but I've had code reviewers who have read other codes that literally
before...
JEREMY R. POLING, PE, LEED AP
Jeremy,
I agree with Nick's explanation to Jaigath, below. A 10% LPD credit can
be taken in spaces that have occupancy sensors, except where occupancy
sensors are required (classrooms etc. per 9.4.1.2). It would make no
sense to allow energy savings only for spaces that have both time clock
and occupancy controls, since a space with both controls would provide
no additional energy savings over an occupancy sensor alone.
I also agree with Nick's comment to Rohini. Leave the baseline LPD alone
(turning lights off during unoccupied hours using the same schedule in
baseline and proposed) and take the 10% credit in the proposed where
applicable.
Regards,
William Bishop, PE, BEMP, LEED(r) AP
Jeremy,
Bill's condensed my thoughts very well. This logic is further supported
by Table G3.2:
If, for your "typical office" case, one needs both a local occupancy
sensor and a timeclock on the circuit to demonstrate a savings in the
proposed model, why would table G3.2 have distinct lines for "occupancy
sensor and programmable timing control" as well as simply "occupancy
sensor?" As you've noted, this table exists for the sole purpose of
doling out credit for proposed models, so there's no answer other than
one may be able to claim credit for occ. sensors without timer control.
More to the point, and as Bill notes - there's no savings gained with a
timeclock in combination with an occ. sensor that can't be achieved by
an occ. sensor alone (that's how I think of it anyway). An occ. sensor
will however save you energy over a timeclock alone as you'll achieve
shutoff periods during working hours. That's probably why the LPD
reductions in the two lines mentioned above are identical. For these
reasons, I think we can consider occ. sensors alone to be "in addition
to" the minimum automatic shutoff requirements - inferred to be a
timeclock alone. I reckon you can take the LPD credit in those spaces.
To your classroom example: Yes, I've regularly interpreted spaces like
classrooms with automatic shutoff and multi-scene controls to be
qualified for a LPD reduction due to the corresponding exemption in
9.4.1.2.
Hope that helps!
NICK CATON, E.I.T.
Nick,
Table G3.2 by itself also has to cover all possible situations, but it
is also only to provide credit for controls in addition to the mandatory
provisions. I'll explain my view on those two issues separately.
The intent of 9.4.1.1 from the 90.1 Users Manual is to ensure all
buildings "have an automatic control device that is capable of turning
off lighting in all spaces without human intervention." This ensures
energy savings when the building is unoccupied. Since occupants leave a
space during the day for various reasons, 9.4.1.2 exists to ensure that
unoccupied spaces during occupied hours have a means to save energy by
turning off the lights, either automatically or manually. In addition,
that same device (if capable) can serve as the override (for safety
reasons) to turn lighting on in the space during unoccupied hours -
another mandatory provision of 9.4.1.2. The way I read it, an occupancy
sensor alone cannot comply with both mandatory provisions because
9.4.1.2 requires an override to the automatic controls required by
9.4.1.1. If the occ sensor is installed to comply with 9.4.1.1 and no
means is provided to override the control (such as a manual switch),
then compliance with 9.4.1.2 has not been demonstrated. Once I have
satisfied 9.4.1.1 and 9.4.1.2 and only then can I look to Table G3.2 for
credit for automatic controls. That is what Table G3.1(6)(g) says.
G3.2(1) only applies to buildings less than 5,000SF and non-24-hour
operations and gives 0% credit to larger buildings. This is in line
with 9.4.1.1 that requires whole building control for buildings larger
than 5,000SF but not for those smaller. G3.2(2) and G3.2(3) provide the
exact same credit for only an occ sensor or for an occ sensor and
programmable timing device (15% for buildings less than 5,000SF and
non-24-hr, 10% for others). This "estimates" the savings from
compliance with 9.4.1.1 at approximately 5% for buildings larger than
5,000SF. The 24-hour operation comment in G3.2 is due to exception (a)
to 9.4.1.1 since whole building control is not required for 24-hour
operations.
A situation I could see using G3.2(3) would be one of the more high-tech
security systems. If the security system is tracking occupancy via
security card swipe-in/out records, then it would be capable of
determining that the building is unoccupied. It could send a signal to
a relay panel to turn of the lighting. That would comply with
9.4.1.1(c). At that point, if every space were designed with manual
controls (except the three that require automatic controls) then the
manual controls would comply with 9.4.1.2. If a time clock and
occupancy sensor were installed in addition, that would allow the credit
from G3.2; however, as you pointed out, no additional efficiency would
be gained by the combination of the two that was not achieved by the occ
sensor alone and indeed, Table G3.2 does not provide any additional
credit for installing both in this case where neither would be required
for compliance with the mandatory provisions.
I think it is an order of reading the code issue - since the mandatory
provisions come first, both 9.4.1.1 and 9.4.1.2 must be satisfied before
credit can be taken. If the building only has a time clock, in that
typical office - there needs to be a local control for compliance with
9.4.1.2. If that office has a switch that can function as an override
to the time clock AND a local control device, then that occ sensor would
indeed be eligible for the 10% credit. But if the office just has the
time clock and the occ sensor - no other devices, then I don't see any
other way that 9.4.1.2 is satisfied except by the occ sensor, meaning it
is part of the mandatory provisions and not eligible for credit under
Table G3.2.
A single occ sensor with no other controls for the lighting in a space
(in buildings larger than 5,000SF) cannot comply with 9.4.1.1, 9.4.1.2
and earn credit under Table G3.2 since table G3.2 is for controls in
addition to the minimum. Going back to the original question, I think
the issue arises somewhat from reviews only recently "cracking down" on
this part of the code...
Thoughts?
Separately, I also agree with the last comments - Baseline LPD is left
alone, always. Table G3.2 only applies to the proposed design and is a
prescriptive alternative to having to use G2.5 Exceptional Calculations.
JEREMY R. POLING, PE, LEED AP
Hi Jeremy,
No offense taken, but part of your response looks something like a straw
man argument from my end, so let me clarify my position...
When I said "occ. sensor only," I was simply referencing your typical
office case containing both an occ. sensor with manual control. I did
not intend to imply something violating 9.4.1.2. From that, I'd agree
with 95% of your post below.
I also fully agree that all mandatory provisions are to be met before
one can even begin an Appendix G performance rating model - it's plain
as day in G1.2, so let's remove that from the discussion.
We do differ in our interpretations however, and I believe I understand
where you're coming from...
Let's take a hypothetical case to illustrate:
I've developed a model for a design featuring enclosed offices with
manual control, occupancy sensors, and no timeclock. I have taken a 10%
LPD deduction in these spaces as prescribed in Table G3.2, line #2, and
have stated so in my LEED 3.0 EAp2 spreadsheet with explicit clarity.
If it's a big project, perhaps I've also uploaded a supplementary scan
of my takeoff highlighting the areas where credit for automatic controls
is/isn't being taken.
Now let's say you're my LEED reviewer, and would like to challenge my
interpretation:
You claim an occupancy sensor with manual override does not qualify for
Table G3.2's deduction because this control scheme is not (quoting
TG3.1.6.g)"...automatic lighting controls in addition to those required
for minimum code compliance under Section 9.4.1," emphasizing the
underlined phrase.
You go on to state if we were to add a timeclock to the equation, then
the design would qualify, because the timeclock would satisfy the
mandatory provisions of Section 9.4, allowing the occupancy sensor to be
classified as "in addition to."
My response:
The 90.1 User's Manual states: "The proposed building may include power
adjustment credits for occupant sensors or automatic time switches when
they are not already required by the mandatory provisions." These
occupancy sensors are not required devices, but merely one of three
options to achieve required automatic shutoff.
The only times occupancy sensors are required as a device by the
mandatory provisions are as outlined in section 9.4.1.2.a. Enclosed
offices are not on that list.
The proposed design for these offices:
1. Satisfies the requirements of providing automatic shutoff in
9.4.1.1,
2. Satisfies the requirements of space control in 9.4.1.2, and is
further not required to have a control device capable of automatic
shutoff and
3. Provides shutoff controls in addition to those required by the
above sections for a minimally compliant design.
A minimally compliant design would use the timeclock option, providing
automatic shutoff only during unoccupied hours. The proposed design
however goes beyond the minimum requirements by additionally providing
automatic shutoff during occupied hours. As such, for the context of
the Performance Rating Method prescribed in Appendix G, the proposed
design does indeed provide "automatic lighting controls in addition to
those required for minimum code compliance under section 9.4.1."
I might also point out adding a timeclock to the office circuit would
save negligible-to-zero energy and would be a waste of resources...
probably would kill a few trees or sink a few polar bear homes if you
crunch the numbers right ;). In all seriousness though, if you take
your current interpretation to the sidewalk's end, I think you'll find
you pretty much have to have redundant, functionally pointless controls
to ever demonstrate a credit via Table G3.2. I think it boils down to
whether the same device can or can't simultaneously satisfy requirements
within 9.4.1 and also provide an energy savings beyond "those required
for minimum compliance." That last phrase is not in any glossary, so
it's all up to you!
To the "cracking down" comment: I'm a diehard optimist, but I like to
think all of us (reviewers, modelers, designers, building owners) are
all doing the best we can and trying to play by the rules of the game.
The new compliance documentation for LEED v3 is definitely a
game-changer in that we must now document items we had to do only
voluntarily in the past, but despite the extra time required (who enjoys
documentation anyway?) I suppose it does level the playing field a bit
for those of us trying to do right by the rules. **
Anyway that's my take - and you're right to observe this is all
ultimately our individual views/interpretations, which may or may not
align with the reviewers... with precedents all but tossed out the
window with LEED v3, there's less for us to stand on beyond our own
logic during a review (I've found the User's Manual generally helpful
though)!
Yours,
~Nick
PS: Thanks to everyone involved for sharing their thoughts! I
sincerely enjoy these discussions and think as a group we can grow with
them. I've found historically that writing out my thoughts this way can
ultimately galvanize/refine my own positions, but also sometimes changes
my stance completely, so I enjoy it as an exercise (time allowing)! If
I'm disagreeing with anyone, it's only with complete respect for others
and to seek a better answer.
**) I'm writing this in the context of an 'ethical position statement'
of sorts regarding energy modeling in general and for LEED... may be
interesting reading to some:
http://lists.onebuilding.org/pipermail/equest-users-onebuilding.org/2010
-May/004545.html
NICK CATON, E.I.T.