I know that LEED is way more than just energy, and energy is way more
than just equipment, but just for a basis, what SEER and EER do people
have to use to get 10% better than ASHRAE 90.1 to qualify for LEED? I
also know that you don't have to use ASHRAE 90.1, but that is what I am
doing.
So, what does it take?
My shot - Residential Apartment, individual DX units, 17 SEER and 13 EER
in California CZ 12 (Mostly cooling).
Next?
--
Robert Wichert P.Eng. LEED AP BD&C
A very simple way of looking at LEED & energy, which I come back to often for discussions on that level, is to consider a building's performance like a tripod with three important legs: Lights, Mechanical, and Envelope. If any of those legs is too short, the tripod falls over.
Building on that analogy, to do 10% better than a LEED baseline, a good starting place is to have at least:
- 10% better lighting (10% lower LPD),
- 10% better HVAC & hot water heating (10% better efficiencies), and
- 10% better envelope (10% more insulation in walls/roof, 10% better windows).
For each of these, you can source the baseline/prescriptive levels from the standard of your choosing.
Overperforming in one area can sometimes make up for underperfomance in another, but with diminishing returns. Amazing HVAC equipment/design has a harder time shining when you have a poor envelope and/or the lighting designer treats LPD's as a "budget" they have to use up. For such reasons, it's advisable to always consider building performance in holistic fashion in early/broader discussions.
That's my (simple) take anyway!
NICK CATON, P.E.
My current project has very good windows, "standard" walls, you're right
about the lighting, it's right on budget (but residential doesn't really
have a budget, so the small common areas are right on budget), better
than standard roof.
I absolutely agree with you, Nick, on achieving 10% better, but all the
trades point to the others. It's kind of comical, actually.
I guess my question on this list could be rephrased, using your
approach, as "What SEER is 10% better than SEER 13?"
Robert Wichert P.Eng. LEED AP BD&C
Also the SEER only helps you while the A/C is on...meanwhile the lights are chugging along at "budgeted" rates every day eating away your 10% reduction in cooling end-use.
DSE Mobile
Robert,
SEER is a seasonal energy efficiency ratio and is unitless. It is the "cooling
output during a typical cooling-season divided by the total electric energy
input during the same period":
http://en.wikipedia.org/wiki/Seasonal_energy_efficiency_ratio. A unit with
10% or better seasonal cooling energy efficiency over a 13 SEER unit would
have a SEER rating of 14.3 or greater (1.1x13) if all other operating
parameters were held constant. See link for definitions and other
references.
Dennis
To answer the SEER question, 1.1*13 = 14.3, all things being equal. (If you're talking heatpumps, consider your HSPF's as well for the heating season.)
Again, this is all a simplified guideline for early decisionmaking, but the situation you're describing with all trades "pointing fingers" is exactly the paradigm I'm advising to kick out the door early to ensure success as a team. It's much harder to do later in the game!
Building performance is a team effort, and a team can only do as well as the weakest link. If and when someone I'm working alongside is stubbornly designing "in a bubble" to the detriment of the project, I consider it as the energy modeler's imperitive to demonstrate this to the rest of the team if necessary.
As an example: More than once I've been able to give lighting designers a big "ah-ha!" moment by showing how major even a small LPD reduction can be when mechanical and envelope designers are pulling their weight. It can also be humbling when you consider the costs implications of a 10% reduction in installed lighting wattage against the equivalent effects of getting all the premium bells and whistles for the chiller plant.
NICK CATON, P.E.
Nick,
I agree with you, and depending on what you are using as your evaluation
criteria throw in COP and other metrics as well. If you have the
opportunity of working directly with the Owners early you should help them
set an energy target for the project or help them establish energy
efficiency standards for all energy using/consuming systems and components.
A 10% improvement in your big three will not necessarily translate into a
10% improvement in total energy consumption of the whole building if that
is what Robert is trying to achieve. It is a team effort and the owner has
to be at the top of the pyramid. The owner has to be in the driver's seat
and buy into all of this in order to "burst the bubbles" of silo thinking
team members. It is, after all, the owner's money. Neither trades people
nor designers should be making decisions for the owner that the owner does
not understand or that does not meet the owners project requirements,
budget and expectations.
Dennis
I suppose the modeling software and how it treats energy might have
something to do with it too (Note to CA and TDV), but for starters the
modeling software will look at actual conditions in the particular place
where the project is located. As an absurd case, if there was no
cooling needed, an infinite SEER would show no improvement. SEER is for
"typical" and each project is not necessarily typical. For somewhere
with a high cooling demand, SEER should have a greater effect, but
cooling is only a small part of the energy budget.
I can appreciate that with "10% better walls, 10% better windows (or how
about 10% less windows), 10% lower lighting wattages, 10% more efficient
hot water, all compared to the standard, you could get 10% better using
a SEER 14.3, but I have never gotten that result. I suppose that I need
to look harder at the other legs on the stool. For me, I need SEER 17
to get to 10% better in California with a somewhat lopsided stool. I am
curious what experience others have.
The theoretical answer may be "Make everything else use 10% less energy
than standard and have a SEER 14.3 AC unit, and you're done" but to be
honest, that doesn't ever work for me.
Maybe a better question is; have you ever gotten 10% better than ASHRAE
90.1 with a 15 SEER AC system? In a real project with real people
fighting over costs, etc.?
Robert Wichert P.Eng. LEED AP BD&C
Dennis,
Not to nitpick too much, but while SEER is a ratio, it is not unitless. It's the cooling
extraction rate in BTU/hr, divided by the electricity consumption in Watts. COP is a
truly unitless number, and is smaller than the SEER by the ratio of 3.413, which is the
conversion of BTU/hr to Watts.
Joe Huang
Robert,
Simple answer is "No" - that is my point - it more than likely never will.
You have to include all of your proposed energy conservation measures that
you are likely to apply into a single model with your user and
climate/local specific schedules and profiles included to see what
the aggregated savings maybe. You can run multiple models changing only
one component to do some sensitivity analysis to see what
variables/measures may give you more dramatic changes in total energy
consumption, cost, carbon emissions, indoor comfort, life cycle cost, life
cycle assessment, etc. (which ever your client and you are using as your
decision making criteria).
As for the question regarding 10% energy reduction using 15 SEER equipment:
I've gotten 10% better energy performance using 90.1 minimum SEER compliant
equipment and effecting change in lighting power density, lighting
controls, controllable plug loads and better envelope/less infiltration,
better ventilation and properly downsizing the mechanical systems. You do
not always have to improve the mechanical efficiency of the HVAC equipment
to achieve an energy efficiency improvement target. It is a whole building
analysis that the owner's O&M behavior can have a major impact on.
Conversely, I've had bleeding edge efficiency and complexity in the energy
using systems at some facilities and the buildings perform worse than an
minimum code compliant building or a local median EUI when a custodian who
knows how to turn things off at night could have done better - when the
owner does not understand how the design team intended the building to be
operated when they made their analysis. For example, I just investigated a
net zero energy house that was donated to an international non-profit. It
has 22 SEER geothermal heat pumps, an envelope so tight it had no air
measurable leakage at 80 pascals, LED lighting, solar water heater, energy
recovery ventilator, solar PV, SIPS panel wall system, commercial grade low
e windows and a sophisticated energy monitoring system. It is built right
next to a conventionally built house, stick framed, minimum residential
code compliant construction with 13 SEER air source heat pumps. Both are
occupied by single mothers with two children. The net zero house has worse
energy performance than the code minimum house almost entirely due to
occupant behavior. I personally did not believe you could operate that
house such that it would ever consume much energy, but you can. In this
case the owner was not determined until after the house was constructed and
did not have a stake in the design and was not trained on the special
features of the house when it was offered to her. Now that she has been
educated I can see some reductions - but the house is still falling way
short of its goal of net zerobecause the owner is just unwilling to change
her lifestyle no matter what the nergy costs are.
Dennis
Man, every time I start a reply 3 more have come out, haha! I think we're all pretty much on the same page though =). This is largely written in response to Robert's most recent reply:
Applying 10% improvement to lighting/mechanical equipment/envelope is merely a strategy for achieving performance figures in the right ballpark once energy modeling begins. No more and no less. I can attest this has worked well for me in the past, but I never meant to imply "..and you're done."
This is just a means of getting the ball rolling and ensuring the important decision makers understand they have a role to play.
I agree completely regarding the limits of SEER and every other standardized efficiency rating I've worked with. Seasonal and steady state efficiencies are NEVER direct indicators of actual system consumptions, they are merely representations of performance under specific conditions. That said, they do have a useful time & place which occurs at the beginning of a project, before a more detailed analysis can be made with energy models or otherwise. SEER may or may not be an inadequate efficiency metric for your specific climate, but that doesn't change what defines your baseline equipment.
If the goal is simply to reduce heating and cooling energy consumptions of your HVAC systems by XX%, and I can't build something resembling the final design for an energy model, I simply can't offer a better answer than "improve your heating and cooling efficiencies by XX%," recognizing this alone will not get you there if your lighting consumptions and envelope performance do not do their part.
A black and white answer to what minimum performance is required of any system for any specific LEED project goal is truly unapproachable until you start the energy model that will determine the results ;).
As it happens however, I can answer Robert's most recent hypothetical almost directly: I have performed a preliminary study for a building in the vicinity of El Paso, TX using 15 SEER AHU's with energy recovery. I determined a 30% LEED improvement would have been attainable using an envelope matching 90.1 baseline constructions, but this entailed a roughly 50% LPD reduction (I would have performed the lighting design and can attest this was achievable), and a healthy laundry list of EEM's for mechanical, with a heavy service hot water equipment load helping things along.
So to wrap up, I'd say 15 SEER units absolutely can be one part of a bigger picture achieving a 10% LEED performance rating.
Apologies for the walls of text... sometimes the quick & easy answer is "there aren't any quick and easy answers!" Hope this discussion is helpful to you and yours in any case!
NICK CATON, P.E.
My two five cents - adding to the many cents already thrown in the pot.
* LEED & Appendix G at this point are based on energy cost - not raw BTUs or carbon. So the relative costs of your fuel mix will have an effect on final scores (in a place where electricity is cheap and heating fuel is not - you are likely going to have less credit for your SEER rating). I don't agree with it, but that's how the system is set up.
* The effectiveness depends on your baseline energy usage. For example - if you have a building that has very small HVAC component, even a 50% reduction won't get you to 10% overall.
* LEED addresses consumption and not efficiency (which is a good thing). So you get credit for 'driving less'. Hours that you don't need to run your HVAC = money in your pocket (the envelope leg of Nick's tripod analogy).
* It also depends on other factors like how you deliver the energy. For example - using hydronic cooling & heating will likely save you more energy than an all air system with a higher EER on the chiller. Using a waterside economizer goes back to the 'driving less' analogy. Hydronic systems are also less prone to reheat (simultaneous heating & cooling) issues that you have with all air systems.
The way I like to approach LEED projects is to go after the intent of the credits rather than the point - you'll be surprised at how often you end up with a higher LEED score when you do.
Apologies to Robert if this doesn't directly respond to the original question.
Vikram Sami, LEED AP BD+C
Thanks Vikram,
Your thoughts are right on point and resonate with my instinctive
reaction too.
Cheers!
Robert Wichert P.Eng. LEED AP BD&C
I have been following this discussion, not as an engineer or modeler, but as
someone interested in the factors influencing the financial return on energy
saving products. My concern is in the same area as Vikram Sami expressed
below but even a little deeper. Vikram rightly notes that energy costs vary
from location to location so a unit saved one place is not necessarily
comparable to another location. I would add two other factors that are very
important in an energy efficiency decision - rate structure and time of
energy saving. The bottom line is that an energy unit saved is based on both
the rate structure and the time of day that negative watt was earned.
Rate structure factors such as demand response, peak demand, and off hours
rates drive the value of reducing energy usage. Some utilities offer very
low rates at night. If you have a building element - such as our Phase
Change Material or Ice Energy's storage process - that can store energy
during the low rate hours; then this energy is available to offset demand
during a peak rate periods.
If a product can reduce the energy usage during a high rate period in a high
rate location then that energy saved should command a higher value in not
only a LEED certifications calculation but in calculating the value in an
energy modeling program for ROI.
I am not an expert on energy modeling nor do I know about all the models
available, so this comment needs to be understood from my product
perspective and most likely, my limited knowledge. It seems to me that most
models are driven by weather data. Weather data and location drive the
design of the building shell. A building is built to live and work in.
Efficiently managing the internal environment demands managing energy use
for not only the effects from the outside environment but also the comfort
and use of its occupants. I am excited about the future of building control
systems based on sensors. This trend will help solve the problems I noted
above but they do more than just save units of energy, they will save energy
at the most expensive moments.
As an MBA - not an engineer - the key here is twofold. How much energy can
I save with the package of energy saving options available to me and what is
the cost of a unit of energy when I save it.
Joe Parker
Hear! Hear!
Joe's comments about how the rate structure affects savings are worth emphasizing. These are in place by local utilities for a reason - meeting peak demands is often very costly for the utilities and they pass it on to their customers. I don't recall the details of a talk I heard at ASHRAE's last Energy Modeling Conference, but I'm pretty sure those peak power plants are also less efficient than the base power plants (which may explain part of the reason for higher peak costs). I've run a couple of energy models with and without the demand charges and have seen big differences in cost. That, in turn, has led to more diligence in representing the rate structure accurately in my models.
As a side note, a few years back I was not a fan of locally-generated (including renewable) power schemes because their efficiency was uniformly dismal and it seemed that their only reason for viability was federal government subsidies. As I've become more aware of the base / peak power big picture economics, I am reversing my opinion. Compared to running a peak power plant, it seems they can be a very viable economic solution even without subsidies.
James V Dirkes II, PE, BEMP, LEED AP
Dear all, I too have been following this very sensible discussion and now feel the need to throw my comments into the ring. So here goes:
Where are we going with all our simulation and LEED paraphernalia? It would appear that LEED compliance has turned into a numbers game and doesn't require engineering techniques but more like a cross between and MBA and an Attorney (I know what was written, but that isn't the intent of what was written). Basic engineering skills have been replaced by wizardry and unmet hours and most often than not the comparison of a base case to a proposed case are the source of the proposed savings. Why do you think the US is so slow into moving towards performance metrics? Maybe it's because the present way buildings are modeled to comply with LEED have no relationship to how buildings actually perform or more probably the liability of an engineer stating that a certain performance can be achieved based upon a simulation model and the possible shortcomings in a real building.
So what do we do? The easiest way would be to sit back and continue with what is accepted or we could look into the future and decide what import features are most required. This would most probably require a rigorous change to the current standards, but maybe that is what is required?
We are all stuck with applicable utility rates, buildings need lighting and power for equipment, we have people in buildings and architects put glass in buildings and the end result is energy and the cost of energy. Yes, there are many sources of alternative energy, but these have been relatively slow to emerge and are very costly. So if you have immense wealth one could attain a net- zero building or many 'net zero' buildings do not fully utilize lighting and equipment. So why would we require simulation models and compliance documents if we simply choose not to operate building equipment?
Peter Simmonds, Ph.D.
Great Conversation All,
I'd like to jump back in with a few more thoughts (having to jot them down
quickly - so apologize if not well organized):
First, I believe our energy codes will soon have to go to performance based
criteria if we are going to meet the "net zero energy building" goals
ASHRAE and other organizations have agreed to hit by 2030 for new
construction and major renovations. I think ASHRAE is possibly on to
something with the bEQ rating which is a rating based on a net zero target
and will help drive us toward performance based codes. Since the bEQ has
both an "as-designed" component and an "as-operated" component user/owner
behavior will have a large impact on the final outcome - which I believe
will be positive - since an owner will be incented to meet the energy
targets they established in the design phase in order to keep the rating
and, hopefully, keep the value of the property up based on its performance.
It could be a market based, engineering based way to get us to net zero
energy buildings by allowing us to be creative and innovative. I'd rather
be given a wish list of things the market wants (including a mandatory
energy target) and a fixed budget and let me be as creative as possible at
providing as many things off the wish list as is possible than be given a
wish list in the form of contract documents then receive bids (variable
cost due to bidders) and have to go through the dreaded value engineering
process where line items from the list are often eliminated without any
economic consideration to the long term effects on the building or its
energy consumption.
The marginal cost for a utility to deliver an additional kWh of capacity
that it does not have/own the generation infrastructure to make that kWh is
almost always more expensive than delivering that kWh from existing
generation capacity whether they purchase it from another company off the
grid or have to build more peaking capacity using something like a gas
turbine. I'm not sure I totally agree with Vikram on his note about LEED
being based on consumption instead of cost: Appendix G and LEED are focused
on one year's cost rather consumption rather than an efficiency standard
something like a kBtu/sf metric (although they are beginning to track such
numbers in EPA's Portfolio Manager). That's also why thermal storage can
be used to reduce the annual cost of energy consumption at a building and
actually increase consumption by shifting load to the off peak times of the
local utility to use the utility's base line generation capacity and that
is why demand side management programs and incentives by utilities are so
popular.
A global well connected eGrid could fix a lot of this by allowing excess
baseline generation capacity at night in the US to say - offset peak load
during the day in the far east (12 hour time difference) and vice versa
(can you imagine the politics and trade policies that would have to be in
place to let that happen?). We would need a good many fewer power plants in
general under this scenario.
Sorry I do not have more time to add more details right now - got to run -
hope the additional comments will generate more discussion.
Thanks,
Dennis
Weighing in from the ?outside?, I agree very much with Joe on the future of building control systems being based on sensors but I believe sensors augmented with precision, highly localized weather data - forecasts which will drive predictive control, and current and recent condition data for sensor verification and external variables not being measured.
Chuck Khuen
Classification: UNCLASSIFIED
Caveats: NONE
Energy Cost Comment-
Working for the Army, we have many similar buildings in many different locations. We once had 2 buildings each in the same climate type, designed the same, but they differed by 5 leed points when it came to energy savings. When we look into why, it turned out the only difference was utility rates.
Weather Comment-
What I have seem with a few high performance buildings is that the weather is becoming a very small factor.
Primary office building with a lot of computer equipment, well insulated roof and walls with energy recovery for outside air and a low outside wall to square footage ratio (large cubes.)
Controls Comment-
I also think that controls are one of the most crucial keys to energy savings. I have toured too many buildings when they were not occupied and the outside air dampers were 100% open. I don't have a site, but I remember one article that said most buildings could save 30% in energy just by changing how it is controlled. Less efficient equipment turned off is always more efficient that highly efficient equipment running when it doesn't need to.
John Eurek PE, LEED AP
John, you are right on target on all points!
Keep in mind, though, that weather often has a greater impact on the existing buildings that need a lot of help. They don't have the high performance envelopes and are not as likely to get a "makeover".
James V Dirkes II, PE, BEMP, LEED AP
Hi all,
I have been away from this conversation for a couple of days due to a death
in my family.
This conversation is great. I'm not sure we have ever really answered
Roberts original question though.
First - my apologies to Vikram for misquoting his statement about LEED
being cost centric in lieu of consumption focused a couple of days ago. He
is absolutely correct.
I agree with several of the thoughts in this recent thread. Stepping away
from modeling for a few thoughts. Controls, or lets say operations, are
key. We have some very sophisticated control systems installed in the field
and some pretty slick dashboards and analytic software available to look at
building use, energy efficiency, indoor air quality, indoor comfort, human
behavior and user feedback networks. Some are going so far as to measure
the heart rate and respiration rate of a person in a cubicle and begin to
inform control decisions unknown to the occupant. This is all good stuff.
However, it's my experience that many of the larger control systems rely on
legacy code and programs that are often 20 to 30 years old (nothing
necessarily wrong with that if it works). But what I've seen is the
technology is well beyond most average facility managers training to fully
utilize, it's beyond most of the control technicians installing the systems
skill sets to set up properly (when I commission a control system I often
see where the technician has pulled in literally dozens of legacy, canned
sequences and then blocked or turned off much of the code trying to meet a
specified sequence of operations, gets confused and can't hardly tell what
sequence or logic is being used to control the system at the end of the
day). In most cases the owner does not get properly trained and the
valuable, somewhat self heeling features of a lot of control systems,
alerts and notifications never even get set up.
To bring that back to modeling, much of the modeling software we use for
design cannot model most control sequences we can dream up and most
engineers are still using modeling for load design only - they write a
sequence and expect a control contractor to be able to make it work
- energy models are only being applied when a client or a rating system
require it.
To tie back to John's last comment below - 100% agreement - our local
school district, 150 buildings, 8 million sf, $11 million per year in
utilities has a dedicated energy manager and a very sophisticated facility
management system. They are beginning to save upwards of 10 to 15 percent
just by analyzing utility interval data on their larger, more energy
intensive schools, finding and turning off as much as possible when not
needed. They are doing this without energy efficiency upgrades or control
upgrades. Then they are setting energy targets, recalibrating their control
systems setting up good alerts and notifications in the system to squeeze
everything out of what they have and finally writing a strategic energy
management plan for future construction and upgrades. They are fixing their
problems and turning things off first before buying more bells and
whistles. There is something to be said for simplicity. It seems to be
working.
To Jame's point - existing buildings are at a disadvantage. With more
efficient lighting and more efficient HVAC equipment I'm seeing plug loads
and water heating use bigger pieces of the pie chart.
Thanks to everyone, and this thread can go as long as we want it to.
For me, I got three or four main points:
1. To achieve anything, all systems must achieve the same result. If
one doesn't pull its weight, well, the goal is missed. I had this
resolved on a two hour telephone call with the lighting engineers on the
project I was working on when I asked the original question. This
helped a lot and got the lighting systems pulling their share of the
load. Likewise windows, walls, roofs, and mechanical systems.
2. My experience with the same project, using Energy Pro for
modeling, shows that SEER 15 gives about 15% better building results
than SEER 13, which is to be expected from the math, but unless all the
systems achieve 15% better, well, you don't make that goal. SEER 17
does NOT give 30% better building results. More like 20% better and
again, all the systems need to pull their weight. In my climate zone
(CA central valley), more SEER does not equate linearly to more
performance. Ever higher numbers give less marginal improvement. I
believe this is also to be expected given the fact that infinite SEER
doesn't give infinite savings and all savings due to SEER require a load
to be met. I still don't have a good handle on this, but I'm getting
closer.
3. Controls are key. I just implemented a pneumatic to DDC changeout
along with some split systems for critical zones for the purpose of
shutting down the systems at night and on weekends. Big savings there.
But if the controls aren't right, well, you get the idea.
4. Process loads can eat you up. Shut them down!
5. Utility rates rule the roost. If you can use this to your
advantage, it can be a big advantage.
Great conversation, folks. Thanks for taking the time to think and reply...
Cheers from warming California - No frost this morning. Are you jealous?
Robert Wichert P.Eng. LEED AP BD&C