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A lot is at stake here
EAc1: Optimize Energy Performance is, by far, the most important credit in LEED, based on the number of points available. Up to 19 points are at stake here based on how much you’re able to reduce the project’s predicted energy cost. That large amount of points also reflects the great importance LEED places on reducing energy use and forestalling climate change1. Climate change refers to any significant change in measures of climate (such as temperature, precipitation, or wind) lasting for an extended period (decades or longer). (U.S. Environmental Protection Agency, 2008) 2.The increase in global average temperatures being caused by a buildup of CO2 and other...
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25 Comments
EAc1 Combined Heat & Power / Cogeneration
It would be very helpful to see an example of approved documentation for a combined heat & power project specifically for cogenerationThe simultaneous production of electric and thermal energy in on-site, distributed energy systems; typically, waste heat from the electricity generation process is recovered and used to heat, cool, or dehumidify building space. Neither generation of electricity without use of the byproduct heat, nor waste-heat recovery from processes other than electricity generation is included in the definition of cogeneration., such as a microturbine.
Christopher Schaffner replied Principal, The Green Engineer, LLP Feb 08 2010
Harvard Green Campus has been posting all their LEED Documentation to a public website. Within this there are several projects connected to DES, although none are using microturbines.
http://www.greencampus.harvard.edu/theresource/leed-submit/nc/
Lots of good examples there.
District energy system
If a project is connected to central plant, are you required to model step 2 using the DES, or is it an option? Can you virtually ignore the central plant? The language in your last sentence above reads "you may include..."
Christopher Schaffner replied Principal, The Green Engineer, LLP Feb 08 2010
The current DES guidance, written around LEED NCv2.2 says "Step 2 is required only for project buildings pursuing optional EAc1 points beyond the minimum number required (either zero or two points, depending on project registration date)."
As I understand it, you have to include the plant if you are going for any points under EAc1 beyond the minimum. So under LEED 2009, it's required for EAc1, but not for EAp2.
There is some confusion because the latest LEED 2009 DES guidance coming out of the TAGLEED Technical Advisory Group (TAG): Subcommittees that consist of industry experts who assist in developing credit interpretations and technical improvements to the LEED system. has not yet been approved for release by the USGBC, so stay tuned.
User electricity on Industrial buildings
Is there existing quidance or approved documentation concerning building with a large amount of production based energy use ?
We are in a situation, where the consumption in process would make up to 80-90 % of total energy use.
The basic question is:
- can you include energy saving in the process in the calculation. And if possible, how in the earth can you provide a adequate documentation ?
- can you in some bases limit the amount of process energy to a level, where minimum requirement savings are at least possible?
Christopher Schaffner replied Principal, The Green Engineer, LLP Feb 08 2010
There is currently limited guidance for projects with high process loads. You can include process energy savings in your calculations, but you need to justify VERY CLEARLY, why you feel the savings is justified. Follow the methodology for exceptional calculation measures. Data centers, waste water treatment plants and manufacturing facilities have successfully been certified using this approach.
All energy use must be included. There is currently no procedure that allows any energy consumption to be excluded.
Mike Barker replied Feb 19 2010
Are there any 2009 NC CIRs - or do 2009 CIRs only apply to projects individually ?
Also, is it acceptable to use waste heat ( say from a data centre next door ) as "free energy" ? Or must it be on-site only ?
Payback Templates
Is there an organization that has payback spreadsheets for energy efficient light fixtures? For example, if a building is designed with incandescent bulbs, is there a template out there that can calculate energy savings from upgrading to CFL1. Compact fluorescent lamp (CFL) light source in which the tube is folded or twisted into a spiral to concentrate the light output; CFLs are typically 3 to 4 times as efficient as incandescent light bulbs, and they last 8 to 10 times as long. 2. Small fluorescent lamps used as more efficient alternatives to incandescent lighting. Also called PL, CFL, Twin-Tube, or BIAX lamps. (EPA) 3. A light bulb designed to replace screw-in incandescent light bulbs; they are often found in table lamps, wall sconces, and hall and ceiling fixtures of commercial buildings with residential type lights. They combine the efficiency of fluorescent lighting with the convenience of standard incandescent bulbs. Light is produced the same way as other fluorescent lamps. Compact fluorescent bulbs have either electronic or magnetic ballasts.'s?
Bill Swanson replied Feb 08 2010
If you're doing a simple 1:1 replacement you can determine the savings yourself. Going from a 100W lamp to a 32W lamp will save 68W. The lamp is on 9 hours a day, 260 days a year. That's 159kWh a year per lamp.
There's a lot of variables to make a template. Seems too difficult to display well. You're not going to meet the LEED prerequisite for energy usage designing with only incandescent lamps. I'd suggest looking at the topic a little differently. In a watts/square foot value which is how 90.1 is set up. LEED states an office building has to be 1.0 W/sf or less for lighting. This is a pretty tight energy limit. If you could get a lighting design at 0.8 W/sf then you've saved 20% for lighting, plus a little bit in saved cooling.
There's also savings that doesn't show up in the energy calculation. Daylight harvesting, dual switching, calibrated occupancy sensors. I've seen some studies on occupancy sensors. But most LEED buildings have occupancy sensors anyways because 90.1 requires some means of automatic shutoff. If sensors are our baseline because they're required, it doesn't really calculate as a savings by having them even if they do save energy.
EAp2 vs EAc1
Please, correct me if I am wrong!
As I understand it, the energy simulation requirements of EAp2 and EAc1 are NOT identical. If I am correct, for EAp2 you:
Model the proposed design in accordance with Section 11.3 of Standard 90.1-2007 and
Model the baseline building to the building performance rating method in Appendix G.
Then, for EAc1 you:
Model the proposed design in accordance with Performance Rating (PR) Method in Appendix G of Standard 90.1-2007 and
Model the baseline building using the same PR Method as the proposed building.
Calculate the performance improvement of the proposed design compared to the baseline building.
Please tell me if this is not correct. I am not an engineer but this is my understanding of the requirements in LEED-NC 2009.
Thank you!
Christopher Schaffner replied Principal, The Green Engineer, LLP Feb 08 2010
You may be remembering how things were in older versions of LEED, but for LEED 2009, the modeling protocols are identical. Both the pre-req (EAp2) and the credit (EAc1) reference only the building performance rating method in Appendix G of 90.1-2007.
Back in the old days, you needed to use the Energy Cost Budget method to show compliance with EAp2, but used Appendix G for EAc1, although the reviewers generally let you slide on that,
eQuest energy modelling
Does anyone know how to use eQuest properly?
We are trying to simulate an office building with a VRV (variable refrigerant volume) system with heat recovery. We don't know how to input such HVAC system in the software, does anyone how to do it?
Dan Prows replied Feb 10 2010
Last data I obatined in mid-late 2009 shows that eQuest does not support VRV applications yet. These links have some info but calling eQuest direct will get you the best results (provided you can actually get someone who really knows the system).
http://lists.onebuilding.org/pipermail/equest-users-onebuilding.org/2009...
http://www.areforum.org/forums/showthread.php?p=929447
Christopher Schaffner replied Principal, The Green Engineer, LLP Feb 10 2010
There is no straight method to model VRV on eQuest. However, as with many system in eQuest, there are a few possible work arounds.
eQuest 3.63b can model variable speed compressors. By obtaining custom curves from the VRV manufacturer and inputing them in eQuest you could get valid results. This method will work only with Heat PumpA type of heating and/or cooling equipment that draws heat into a building from outside and, during the cooling season, ejects heat from the building to the outside. Heat pumps are vapor-compression refrigeration systems whose indoor/outdoor coils are used reversibly as condensers or evaporators, depending on the need for heating or cooling. In the 2003 CBECS, specific information was collected on whether the heat pump system was a packaged unit, residential-type split system, or individual room heat pump, and whether the heat pump was air source, ground source, or water source. type VRVs.
This method is described in more detail at:
http://lists.onebuilding.org/pipermail/equest-users-onebuilding.org/2009... It should work fine.
For one recent project, in the SD phase we post processed the results to adjust for VRV, based on a similar project. We modeled a standard Heat Pump system and applied delta savings on the HVAC systems energy use to the results obtained from the simulation. I was able to apply the delta because it was a similar facility and climate. This was only to get initial results, and to get a rough estimate savings - this approach would not be valid for a final LEED submission.
For the final run of the energy model, once the final design documents are out, we intend to model the system by creating custom curves from the manufacturer’s data and following the steps mentioned on the link above.
The other way to simulate VRV would be to extract hourly loads report from eQuest and then do calculations through spreadsheets after obtaining performance data from the manufacturers for the VRV systems.
As I understand it, Energy Pro and Trace are the only software packages that can currently model VRV systems directly. Energy Pro apparently has custom curves for a couple of manufacturers of VRV units.
Help needed: Process Energy / Water - 25% Default vs. Actual
We have a child care center in the SE US. We did very well on envelope, lighting, and mechanical design (53% reduction in those areas). The building has a commercial kitchen with several additional dishwashers and clothing washer/dryer combos throughout the building (kids are always hungry and messy). We are tied into a CEP using steam and chilled water. We are modeling using Trace 700.
Here is our problem:
In spite of our great performance in the "building's" performance, our energy model only shows a 21% overall improvement due to what appears to be a "weighting" issues between, HVAC/Envelope/Lighting, hot water, & plug loads (process energy).
The hot water and plug loads requirements are so high per 90.1, that these loads are 68% of the total building energy usage. As you know, design and proposed process loads must equal each other. With plug/process energy loads at 34% of the total, this hurts our overall savings average. A question was raised after reading the NC guidebook, i.e. shouldn’t we be using “25% of the baseline building energy cost” as our default process energy or are we required to use the actual loads even if they are above 25%? The guide book is unclear abouot going above 25% (you just can't go below). Obviously, if we can use 25% rather than 34% that will be a great benefit. Also, to avoid circular reference, do we model the building alone (HVAC, Service Water, & Lighting) and use 25% of that? What is the definition of "total energy cost of the baseline building?"
Also, along these same lines, we placed our hot water requirements from the kitchen and dishwashing into the service HW category. Further discussion suggested that commercial kitchen HW water use is essentially process waterProcess water is used for industrial processes and building systems such as cooling towers, boilers, and chillers. It can also refer to water used in operational processes, such as dishwashing, clothes washing, and ice making. like process water from an industrial setting and as such it should be excluded from the calcs. Is this the case? The LEED guide book just notes “service” water heating as regulated (non-process). If this water is process water, aren’t we able to exclude the process water from our energy calcs all together? We exclude these items from our water reduction calcs for good reason. Isn’t this the same?
I am probably over thinking the issue so I can use some input from anyone who has knowledge in this area. Thank you in advance.
Jean Marais replied b.i.g. bechtold INGENIEURGESELLSCHAFT MBH Feb 11 2010
In my opinion this topic needs a lot more discussion and attention. For most projects the 25% is probably based on a typical office building. Many buildings are not office buildings.
First off process energy must be equal for both baseline and design case, unless otherwise quantitively supported AND process energy must be >= 25% unless otherwise quantitively supported.
This means that for a "normal" building, you are straight away robbed of 25% of the change to put a dent in the efficiency performance improvements on your proposed design. Which means, for example if you aim for a 10% improvement you need to improve all areas other than process energy consumption by 13.33% (my math may be a little faulty, but you get the point).
In buildings that have less than 25% process loads, adding a fictious process load to achieve 25% will decrease the performace gains attributed to the other areas, due to the decreased weighting of these areas.
In buildings that have more than the required 25% process energy, decreasing the slice will increase the weight with which the other areas could contribute to the overall performace gains.
Shortly said:
decreasing process load = increased performance
increasing process load = decreased performance
Process Load Definition:
ASHRAE 90.1..."the load on a building resulting from the consuption or release of process energy." "process energy: energy consumed in support of a manufacturing , industrial, or commercial process other than conditioning spaces and maintaining comfort and amenities for the occupants of a building."
LEED: no clear definition, but includes elevators, telecom, refrigeration amongst others.
As per ASHRAE appendix G, service hot water is not included with "Receptacle and Other Loads" which according to my interperatation are the LEED process loads, because these must be equal unless otherwise supported.
Comming back to your questions:
- In a building that has substantial process loads, you should quantify design case improvements and not let baseline process loads equal design case process loads, else you're cutting out too much of the pie from which you can possibly win gains.
- Service Water Heating: ASHRAE 90.1 "heating water for domestic or commercial purposes other than space heating and process requirements." I would classify kitchen uses as "process" whether hot water or otherwise.
- You can't exclude process loads for manufacturing, so why would you be allowed to exclude process loads for kitchen.
Closing notes: In my opinion the importance is placed in improving energy savings against a "average" building of the same sort. If you were manufacturing, you would have to define a industry standard for energy consumption of that manufacturing process to quantify your "special" process energy savings.
Dan Prows replied Feb 15 2010
Thank you. I appreciate your comments and guidance.
Bill Swanson replied Feb 15 2010
The math looks right to me. In order to get 10% total calculated savings you need 13.33% energy savings in allowed areas. To get 50% savings you need 66.7% savings in allowed areas. It really makes the Achitecture 2030 Challenge difficult when you think we're already suppose to be getting 50% savings compared to the average building. Lighting and HVAC haven't changed so much that we can do everything at 1/3 of the energy. And then net zero energy in just 20 more years. On-site power can't make that much.
Jean Marais replied b.i.g. bechtold INGENIEURGESELLSCHAFT MBH Feb 16 2010
I completely agree. Many buildings (building types) will become completely imposible to certify, meaning they won't even try to be green. This outcome is even worse. A better approach may be to simply lift or add the upper certification levels, i.e. what's better than platinum?
Bill Swanson replied Feb 16 2010
Titanium level.
Diamond level.
Adamantium level.
Just throwing out ideas.
Energy model unit comparison
I was looking thru the Harvard documentation for Rockefeller Hall and I got a question. Can different energy units be used in the energy model comparing baseline to proposed design?
The model shows chilled water use for the baseline building using 347,870 kWhA kilowatt-hour is a unit of work or energy, measured as 1 kilowatt (1,000 watts) of power expended for 1 hour. One kWh is equivalent to 3,412 Btu. and the proposed design using 1,184 MBtu. Total energy saved is 0.2%. Basically zero. Yet since the savings is based on dollars the 347,870 kWh costs $60,000 and the 1,184 MBtu cost $2,000. That's a $58,000 savings for zero energy savings. The total savings for the project was $115,000. So half of the "savings" comes from a conversion of units when comparing the baseline model to the proposed model.
I'm just trying to find out if this is accurate, standard practice, or a slight of hand that they got away with. Appreciate any help.
Tristan Roberts replied Editor – LEEDuser, BuildingGreen, LLC Feb 12 2010
Bill, odd as it may seem in a situation like this, the energy savings calculations for EAp2 and EAc1 are based on energy cost savings.
It's a little bit more complex than converting from one unit to another and claiming a savings. In this situation it looks like they are switching from an electric-powerd system (with energy sold by the kwhA kilowatt-hour is a unit of work or energy, measured as 1 kilowatt (1,000 watts) of power expended for 1 hour. One kWh is equivalent to 3,412 Btu.) to a gas-powered system (with energy sold by the MBtu).
Relative to LEED, they would have to justify that the electric-powered system represents a reasonable baseline—and that they're not intentionally picking a easy target for savings.
This might not sound like a good idea in this situation, but a uniform, better method is hard to come by. Any ideas?
Bill Swanson replied Feb 12 2010
The only good, uniform method I've heard of is the one mentioned by Henry Gifford. Award temporary status based on model data and after 2 years compare actual energy information with national averages of similar buildings. The Energy Star system would be a decent benchmark since it uses building size, occupancy level and hours of operation.
If the building goes from 10 temporary points down to 2 earned points after a couple years then I'm sure the building owner will have some questions for the person doing the design or modeling. Hopefully this will reduce the manipulation of the energy models to inflate savings. And it also provides a reason for the owner to save energy when using the space. Don't crank all of the temp setting to maximum.
I agree there's no perfect system. But I can see how many software programs and forms can be manipulated. This I think is the least open to gaming and manipulation. It's possible to fudge the numbers being entered into Energy Star but a reviewer should be able to spend a couple hours to verify information.
Energy rates for energy analysis
What level of detail is required for energy calcs in regards to utility rates? For example, most utility energy charges are now fluctuating daily for both gas and electric. Some rates, depending on the service size are fluctuating Hourly!
We are using EnergyPro 5.0 and I tried to build an hourly rate schedule based on average daily rates and it exceeded the capacity of the program.
Other clients want us to use an average rate that even includes demand.
Is there a minimum standard for building a rate schedule for LEED?
Clark Denson replied Engineer, SSRCx Mar 02 2010
ASHRAE 90.1 section G2.4 allows you to use either the actual utility rate structure or state average energy rates as published by the DOE's Energy Information Administration. Either method is acceptable for LEED purposes. If the actual rate structure is too complex for your energy modeling program to simulate, you can use state averages.
If you feel that using the actual rate structure will be an advantage to your energy model, you might be able to export hourly energy demand and consumption data, post-process it in a spreadsheet program using historical or anticipated daily or hourly rates, and submit it to USGBC as an Exceptional Calculation Measure. As with all ECMs, there's no guarantee that they will accept this approach. That being said, I haven't used EnergyPro that much, so I'm not sure of its data-exporting capabilities.
Good Luck!
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