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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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90 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 Energy / Electrical Engineer, BuildingPhysics South Africa 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 ?
David Posada replied Sustainability Manager, GBD Architects Mar 25 2010
Timo, we had a manufacturing facility acheive certification where more than 90% of the facility energy use was from the process loads of the manufacturing equipment. We found a few CIRs that gave some guidance for NC2.2: EA credit 1, CIR Ruling 8/13/2007, Ruling 5/27/2008, and Ruling 2/4/2008.
All energy use, including all process loads have to be accounted for in the model. Reductions in process energy use can contribute to credit acheivement, but since it is not addressed directly by ASHRAE 90.1 we had to create a theoretical baseline for process energy use against which to compare the proposed process. It has been up to the design teams how to create a credible baseline for process loads, but some methods we've seen include comparing the proposed plant's process loads against other similar plants operated by the company, against industry averages, or a manual calculation. In one case the manual caluclation involved comparing the energy consumption of the more efficient proposed equipment with less efficient but commonly available equipment. Savings from high efficiency motors are one place to look, you may even be able to use calculations based on engineering principles that show greater efficiency of one process over another standard practice.
To compare the energy use of the baseline and proposed systems, some teams have used energy use per unit of product produced as a comparison, but reviewers have required all energy savings be converted to back annual energy cost savings. Be careful of calculations that only suggest increased annual production, as this may not be seen as producing annual energy savings. You may need to word your narrative explanation of how the process loads are modeled very thoroughly and carefully, as the assumptions or approach can be misinterpreted.
Lorey Flick replied Mar 30 2010
I recently filed a refrigerated warehouse facility where a majority of the load was process. In order to document the savings for the process load space (lighting, refrigeration), I had to provide the savings under the exceptional calculation method along with a narrative. My energy model was able to provided the modeling capability for this process load but it had to be broken out separately.
Be very clear in the template which square footage is associated with process loads so the reviewer understands why you selected system x vs y in the base design.
Lee Dingemans replied LEED AP, Wightman & Assoc. Jun 05 2010
Were can I find CIRs and sample documentation? Are they available to all? I thought I would have access to all this information after I would register a project but still I can not find any. Then I read (above) "We found a few CIRs that gave some guidance for NC2.2: EA credit 1, CIR Ruling 8/13/2007, Ruling 5/27/2008, and Ruling 2/4/2008." This made me wonder where do you find this?
Thank you,
Tristan Roberts replied Editor – LEEDuser, BuildingGreen, LLC Jun 05 2010
Lee, for more information on existing CIRs, see this page on the USGBC website. You have to be logged in to actually view them.
Existing CIRs are only applicable to pre-2009 projects, so when you see them referenced on a page like this, they're only intended as a point of general guidance.
Currently CIRs for 2009 projects are not public, and not precedent-setting. There have been some indications from GBCI that that will change, however, later this year.
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 PE, LEED AP, BETA Design 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 PE, LEED AP, BETA Design 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 PE, LEED AP, BETA Design Feb 16 2010
Titanium level.
Diamond level.
Adamantium level.
Just throwing out ideas.
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!
Revit + Ecotect
Has anyone used Revit + Ecotect for energy and carbon footprint analysis?
Jeffrey Westall replied President, Westall Architects, Inc. Mar 26 2010
I guess that would be a "no."
EA Credit 1
I have a project in which an auto repair garage is required to be ventilated at 1.5 CFM per square foot. The quantity of exhaust air is significant. In order to maintain habitable temperatures in a cold environment, there needs to be an equal amount of heated make-up air. We intend on using demand ventilation with carbon monoxide sensors to avoid operating the exhaust and make-up air systems. This type of demand ventilation is allowed by the code but not mandated. Would there be any objection to utilizing this system on the proposed model and not on the baseline model?
David Posada replied Sustainability Manager, GBD Architects Mar 25 2010
We've used demand controlled ventilation as an energy efficiency measure in the proposed model under earlier versions, so imagine it would work under 2009.
automatically controlled interior shading devices
can you forward some product sources for motorized blinds thanks
Tristan Roberts replied Editor – LEEDuser, BuildingGreen, LLC Mar 19 2010
Richard, have you checked the GreenSpec products listed in the sidebar to the right? I think we list products in this category there.
Existing Building Renovation w/ a New Addition
We're working on a 40,000 sf existing building undergoing significant interior renovations and lighting upgrades, but will be using the existing mechanical system. We will also be adding 40,000 sf with new mechanical serving the addition. Do we need to separate energy use and show minimum savings of 14% in the new addition and 7% in the renovated portion? Or do we base our overall energy cost savings for the 80,000 sf project on the percentages indicated for Existing Building Renovations?
Gwen Fuertes replied LEED Specialist, U.S. Green Building Council Apr 08 2010
Hi Carrie,
The solution is to make a "custom" EA Credit 1 point scale that is weighted between the ranges of 100% new and 100% existing buildings. [The following examples use the NC/Schools point thresholds for EAc1]. In your case, since your project will be 50% new and 50% existing, your thresholds will be the mathematical mean of the new vs existing columns per point threshold. For example, a cost savings of 10% would equate to 1 point, a cost savings of 12% would equate to 2 points, etc.
For more complex projects that don't have a clean 50/50 split, the solution would be similar but weighted based on the new vs existing ratio (e.g., if the project were 75% existing SF and 25% addition, then the 1-point threshold would be 9% cost savings, the 2-point threshold would be 11% cost savings, etc.)
This is based on a version 2 CIRCredit Interpretation Ruling. Used by design team members experiencing difficulties in the application of a LEED prerequisite or credit to a project. Typically, difficulties arise when specific issues are not directly addressed by LEED information/guide ruling, and the LEED 2009 form will automatically calculate the appropriate point threshold based on your input of the "new construction sf" and "existing renovation sf" fields.
Exterior Lighting Power for Non-Tradable Surfaces
So when calculating the Allowable Exterior Lighting Power for your Baseline energy model, there are Tradable Surfaces and Non-tradable surfaces. My question is concerned with how LEED handles lighting on Non-tradable surfaces.
It's my understanding that allowances for tradable surfaces are such that if you over-light a parking lot, you can make up for it by under-lighting a canopy. You also get to take credit for good lighting design if the sum of your installed lighting on tradable surfaces is less than the sum of allowable lighting per 90.1 table 9.4.5. For example, if you have designed 10 kW of lighting, and the allowable lighting power is 12 kW, you can show 2 kW of savings in your energy model.
For non-tradable surfaces, ASHRAE 90.1 says that you cannot compensate for overlighting a building facade by underlighting a loading dock for ambulances. I have no problem with this. What I have a problem with is the LEED Credit Form saying "Values [for Non-Tradable Surface Exterior Lighting Power] should be identical in the Baseline and Proposed Case." In other words, if a project uses super-energy-effienct lights to illuminate a building facade with 10 kW, and the allowable lighting power per Table 9.4.5 is 12 kW, I CANNOT take credit for this 2 kW savings in my energy model! Instead I have to put only 10 kW of lighting in the baseline case energy model.
This does not seem fair, nor does it seem to agree with the intent of ASHRAE 90.1. Does anyone know the USGBC's reasoning for this?
Bill Swanson replied PE, LEED AP, BETA Design Apr 06 2010
Sounds like you understand it very well. The ASHRAE 90.1 Handbook describes the non-tradeable allowances as "use it or lose it".
I understand your frustration. Everyone finds things they don't understand about this energy model. I can only guess why they made this as a use it or lose it allowance. Most buildings don't have much facade lighting even without ASHRAE 90.1. So why reward them with an "energy savings" for doing what they were doing anyways.
And some may try to game the system. If I add 1 wall pack with some uplight over a door on a side of the building. What's to stop me from claiming the allowance for the entire wall area on that side of the building, even if the building is 100'Wide x 200'Tall. A 4000 W allowance with a single 50W MH lamp installed. Look at that. A 98.3% energy savings, I am uber green!
While it's frustrating and seemingly arbitrary it won't have much affect on your overall calculations. The difference in wattage in these areas is usually pretty small in comparison to the whole buildings' lighting wattage. I doubt the difference would be noticable.
The interior building allowances also have some "use it or lose it" values. Look at 9.6.2. Art exibits and retail get additional non-tradeable wattage. And the 2004 and earlier versions gave us extra wattage in rooms with computers.
Mark Benson replied Apr 06 2010
Bill, I've reviewed the ASHRAE 90.1 User's Manual and found, like you indicated, that additional interior lighting per 9.6.2 is considered "use-it-or-lose-it." However, nowhere in 90.1 or the User's Manual does it indicate that exterior lighting power on non-tradable surfaces is "use-it-or-lose-it" or has to be the same in the baseline and proposed. On the contrary, the User's Manual states in Chapter 'G', "If the proposed building does not have an exterior lighting application (for instance a parking lot that is not lighted), the baseline building shall not have the exterior lighting application either. If the lighting application exists, however, then the proposed building can take credit for a more efficient system."
I agree that gaming the system is unethical and should not be allowed, but if lighting for non-tradable surfaces should be identical to prevent gaming, why not do the same for lighting on tradable surfaces? I could have one pole-mounted light in a huge parking lot and consider the entire parking lot to be lit in the baseline, showing a large amount of savings. But if it is not the intent of the lighting designer to illuminate the entire parking lot with that one light, the baseline approach would be unethical. The same goes for your hypothetical scenario with the wall-pack. If the intent is to just illuminate the door or the area just above the door, the baseline should not include the entire wall in its allowable lighting power.
Finally, I agree that exterior lighting is usually not a huge component of a building's overall energy consumption. I just want to take credit where credit is due, and I believe the quote from the User's Manual above indicates that this can be done: "If the lighting application exists, however, then the proposed building can take credit for a more efficient system." Thanks for your input.
Fenestration in Baseline
I need to verify what is meant by proportionally distributed. I originally understood the distribution to take the total fenestration for the building and then create a band of windows around the entire building that equals the total. Has the 2007 version made the requirement orientation specific?
Christopher Schaffner replied Principal, The Green Engineer, LLP May 04 2010
ASHRAE 90.1-2007 has made this a little easier to deal with. The requirement for the baseline case now reads says that vertical fenestration areas "shall equal that in the proposed design, or 40% of gross above grade wall area, whichever is smaller, and shall be distributed on each face of the building in the same proportions in the proposed design."
So, if your building is less than 40% glazed, baseline and proposed are equal. If you have more than 40% glazing in the proposed design, you need to reduce glazed areas proportionally on each exposure in the baseline until 40% is met.
Rotating Existing Building Renovations
Under the 90.1 Performance Rating Method (PRM), the performance of the baseline building has to be based on the average of 4 separate rotations of the baseline building. This makes sense for new construction projects, as it makes the design team consider their choice of building orientation.
In the case of a buidling that is existing, such as a 100% gut-and-renovate project, there is no opportunity to change the orientation of the building. Is it then appropriate NOT to rotate the baseline building 4 times to generate its average performance?
Christopher Schaffner replied Principal, The Green Engineer, LLP May 24 2010
To meet Appendix G requirements, you still need to rotate the baseline in the model. The rewards projects with good orientation, regardless of the project's ability to influence the outcome.
Further, I would argue that even a gut reno should be considering orientation. One might consider different glazing types or shading schemes depending on orientation. Even program elements might be impacted by orientation. Areas with high process loads might not need the winter passive solar afforded by by a south exposure, etc.
Hans Wetterlund replied Energy Analyst, WSP Jun 30 2010
We too have this experiance but unfortunately no answer. The intensions in LEED is truly missLEEDing as we can not affect the Baseline Building electricity use, the major factor, I think, to the difference between 47 % and 22 % in your exampel, Michael.
In Ashrae handbook it is stated that the calculations can be based on energy cost OR energy performance so maby therefore we can use energy performance in LEED instead of energy cost, Chris??
Tristan Roberts replied Editor – LEEDuser, BuildingGreen, LLC Jul 01 2010
LEED specifically requires use of energy cost, for better or worse.
Energy Cost
We are working on a project with a modelled energy savings of 47% when comparing BTUA unit of energy consumed by or delivered to a building. A Btu is an acronym for British thermal unit and is defined as the amount of energy required to increase the temperature of 1 pound of water by 1 degree Fahrenheit, at normal atmospheric pressure. Energy consumption is expressed in Btu to allow for consumption comparisons among fuels that are measured in different units./sf/yr. When we calculate it as LEED requires (in terms of dollars) our building energy efficiency drops to 22%. This is a result of the fact that in our location natural gas is so inexpensive and our proposed design relies more on electricity than natural gas. It seems LEED is inadvertantly encouraging the use of natural gas as an energy source. Has anyone run across this before and have any suggestions as to how to accurately represent the energy savings?
Richard Morse replied May 26 2010
We too have encountered such results, I am interested to know of any possible alternatives.
My understanding is that, for better or worse, LEED makes its measurements in dollars - presumably as a means to show demonstrable economic benefits to its implementation.
This "follow the money" approach is either brilliant or fatally flawed depending on your perspective. I for one think it's misleading, as energy savings in terms of BTUs/sf is definable, whereas the cost of the fuel is subject to constant market fluctuations.
Christopher Schaffner replied Principal, The Green Engineer, LLP May 28 2010
LEED uses energy cost because the ASHRAE standard uses energy cost. This is likely to change in the next iteration of LEED.
One thing to keep in mind is the difference between site energy and source energySource energy is the total amount of raw fuel required to operate a building; it incorporates all transmission, delivery, and production losses for a complete assessment of a building's energy use.. 1 BTUA unit of energy consumed by or delivered to a building. A Btu is an acronym for British thermal unit and is defined as the amount of energy required to increase the temperature of 1 pound of water by 1 degree Fahrenheit, at normal atmospheric pressure. Energy consumption is expressed in Btu to allow for consumption comparisons among fuels that are measured in different units. of electricity at the site typically represents about 3 BTU of fossil fuel used to generate that electricity at the source. Site energy BTUs are not an "apples to apples" comparision - 1 BTU natural gas has lower carbon emissions than 1 BTU electricity, if the the electricity is generated from fossil fuels. In an indirect way, using cost as the metric actually captures this nuance.
Hans Wetterlund replied Energy Analyst, WSP Jun 30 2010
We too have this experiance but unfortunately no answer. The intensions in LEED is truly missLEEDing as we can not affect the Baseline Building electricity use, the major factor, I think, to the difference between 47 % and 22 % in your exampel, Michael.
In Ashrae handbook it is stated that the calculations can be based on energy cost OR energy performance so maby therefore we can use energy performance in LEED instead of energy cost, Chris??
Christopher Schaffner replied Principal, The Green Engineer, LLP Jul 19 2010
Nope - it's got to be cost, at least until LEED 2012.
Energy modeling
I use Carrier HAP 4.5 for Energy Modeling, how can you model an international project if the Country you are modeling is not in the weather data base. Is it valid to use a Country or region next to it?
Christopher Schaffner replied Principal, The Green Engineer, LLP Jun 11 2010
It's generally not valid to use a country or region nearby. The weather data used should reflect the actually climate. For example, Palm Springs and Santa Monica (California) are only 100 miles apart, but it would not be correct to use the weather data for one on a project located in the other, as the climate is very different (desert vs. seacoast)
I'm not sure what format weather data HAP uses, but I imagine it is the same source info as other programs.
DOE has a complete listing of weather files for downloading. Chances are whatever you need is available there. They are often available in multiple formats.
http://apps1.eere.energy.gov/buildings/energyplus/cfm/weather_data.cfm
Xavi B replied Jun 18 2010
Thanks
DEMAND CONTROL VENTILATION AND LIGHTING CONTROL
How can I model DCV and Lighting Control into Carrier HAP 4.5. I know I can do it changing schedules. Does anyone have reference schedules or is there a way of building a real schedule to my own project?
Christopher Schaffner replied Principal, The Green Engineer, LLP Jun 11 2010
The building-sim list serve is a good place to post specific software questions.
http://lists.onebuilding.org/listinfo.cgi/bldg-sim-onebuilding.org
Christopher Schaffner replied Principal, The Green Engineer, LLP Jun 11 2010
Also, Carrier offers support to registered users of their software. You may want to contact them.
Xavi B replied Jun 18 2010
Thanks a lot
PRM baseline VS proposed building documentation
we are doing energy modeling for a mixed used tower (residential 30 flrs and office 6 floors and 5 floors parking under ground) can any one help in determining the following:
a- baseline case:
1-the envelope requirements should be residential or non residential.
2- how to model different floors in equest.
3-i m going to rotate the building as requested but how to average the values.
4-zoning in the residenatial area can it be per bedrooms or is there a preferred way.
5-what s the hvac system type to model.
6-ashare is talking about 25% factor of safety in cooling and 15 % in heating.what value shall i use in cooling load because in proposed case ashare is talking about actual equipment size (do they mean i should provide a factor of safety).
7-service water heating design shall i follow ashrae fundamental chapter or any preffered method.
8-landscape lighting is included in which section lighting or process load.
regarding proposed building:
1-automatic shades how to provide a schedule for it (residential and offices)
2-parking lighting system how to benefit from motion sensors (and same for all areas.
3-hvac system modeling using part load curves...where to get these curves.
finally can anyone provide me an actual modeling example documented and commented as here the documentationprovided when we don't have a simulation.
sorry for this long email.
regards,
tarek
Christopher Schaffner replied Principal, The Green Engineer, LLP Jul 19 2010
Let's see what we can do here:
a-baseline case
1 - envelope requirements - both! residential floors get modeled with residential envelope requirements, non-residential with non-residential
2 - modeling different floors in eQuest - easy to do, just create separate blocks in the wizard mode. Sorry, I can't give eQuest lessons here.
3 - how to average - add the results, divide by 4
4 - zoning - zoning in the base case should match actual zoning design (See Table G3.1 sections 7 & 8, of Appendix G, ASHRAE 90.1-2007)
5 - Read Section G3.1.1 - assuming the office is at least 20,000 sf, it needs to get modeled as a separate system. Depending on your heating source, you are probably System 1, for the residential areas, and System 7 for the Office.
6 - The base case systems get autosized by the program, but you are allowed to add a safety factor to their sizing. It is an input in eQuest. As you mentioned, the design case sizing is per the drawings.
7 - DHWDomestic hot water (DHW) is water used for food preparation, cleaning and sanitation and personal hygiene, but not heating. - not clear on the question - read Table G3.1, section 11 - it will answer your question.
8 - landscape lighting - you can calculate exterior lighting separately if you like - in a spreadsheet. Base case should be based on the prescriptive requirements in section 9.4.5 of 90.1
Proposed Building
1 - automatic shades - I don't remember - does eQuest allow automatic shades to be modeled? I would schedule them just like you do any other item in eQuest, but I'm not 100% sure it is in the program - I'll get back to you on that.
2 - parking garage lighting - this likely requires an exceptional calculation measure - I would do this on a spreadsheet, and be careful about documenting your assumptions.
3 - equipment curves - decent curves are already in eQuest, or you can ask the manufacturer.
whew! I'm tired.
tarek dalati replied Jul 20 2010
cristopher thank you for your reply.i hope you feel better now.
regarding the saftey factors in the proposed building.if hap is used for hvac load calculation and the factor of safety can be what ever we want.what it s usually a common practice(we usually use 10% for sensible cooling and 5 % for latent cooling and 0% heating (as no heating is required in dubai)
regards,
tarek
Christopher Schaffner replied Principal, The Green Engineer, LLP Jul 24 2010
Yes, you can size your proposed system however you like. Generally oversizing carries with it an efficiency penalty. But the base case that you compare to must be autosized by the modeling program using the safety factors described. If you can live with smaller safety factors in your proposed design, good for you - it may show improved performance compared to the base case.
Process Load -Can I call my computer room units a process load?
I have a Liebert Computer Room Unit (DX System) it has a capacity of 137.8 MBH.
It has a low efficiency (8.2 EER), the min efficiency listed on the 90/1-2007 TABLE 6.8.1B is 10.6 EER.
These types of units are designed to cool and keep humity controlled, not to be efficient. Can I call it a Process Load?
Or do you think I need to model the Proposed Building with the 8.2 EER and the Baseline Building with the 10.6 EER??
The computer room runs 24/7.
Christopher Schaffner replied Principal, The Green Engineer, LLP Jul 19 2010
I don't think you can necessarily call it a process load, but you may be able to make the case that the type of unit being used is not covered by ASHRAE, and therefore your baseline should have a lower EER.
Are you sure you are comparing at the same operating conditions? I don't understand why the "Liebert" unit performs so poorly, and if it does, why you feel compelled to use it.
DES vs purchased heat for 1! building
Hi Christopher, hi everybody,
I've juste seen the two first posts on this page but it does not help.
We are purchasing heat from a district heating plant (100% green). The USGBC's DES technical guidance is a bit confusing.
- District Energy System (DES) is defined as a central energy conversion plant and transmission and distribution system that provides thermal energy to a group of buildings (e.g., campus). Does this definition apply for one building connected to a district heating regional plant?
- Rf. EA c1. Option 1: Energy simulation. We are targeting to obtain a maximum of points. Is it correct we have to run 2 energy simulations (Building stand-alone scenario + virtual DES-equivalent plant scenario)?
- Is there any beneficial effect to use the virtual DES-equivalent plant scenario? Is there any beneficial effect to be connected to a 100% green district heating system?
Thanks in advance for your comments!
Kind regards,
Nicolas
Christopher Schaffner replied Principal, The Green Engineer, LLP Jul 28 2010
The USGBC will be issuing the new DES guidance document in the next few days. Watch for that, it will clarify and simplify things.
Your specific questions:
1) Does this definition apply for one building connected to a district heating regional plant?
Ans - yes. Anytime you are getting steam, hot water, or chilled water from a source outside your project it is considered DES.
2) Is it correct we have to run 2 energy simulations
Ans - this is the big change coming. In the new guidance you don't have to run it both ways, however, there is a cap on the number of points if you model a stand alone building. Stay tuned.
3) Is there any beneficial effect to use the virtual DES-equivalent plant scenario?
Ans - if the plant is more efficient than the code minimums, yes.
4) Is there any beneficial effect to be connected to a 100% green district heating system?
Ans - don't know what "100% green" means, but if it is more efficient than a conventional plant, it should help. If it something exceptional, be prepared to prove it to the reviewers.
Nicolas Galiotto replied M.Sc. Engineer, Ramboll Jul 28 2010
Thanks a lot Christopher. Very clear! :-)
I will watch for the new DES guidance...
Kind regards,
Nicolas
Energy Efficient Measures Prior to LEED Registration
An existing building has replaced their windows and roof in 2007, exceeding ASHRAE 90.1-2007 standards. The building is currently going through a large renovation and will be registering under LEED v3 2009. Can credit be taken in the Whole Building Energy Simulation (EAc1) for the improved thermal performance of the windows and roof even though they were replaced prior to being registered for LEED.
Thanks,
Jaimee
Marcus Sheffer replied Energy & Environmental Consultant, 7group Aug 09 2010
Since the window replacement would not be part of the scope of work of your LEED project I don't think you can claim credit for them. Unfortunately under Appendix G you will need to model the existing windows in the baseline building model (see Appendix G Table G3.1.5 Baseline (f)).
Definition of unmet load hours
What is the detailed definition of unmet load hours? It based on the thermal zone or whole building?
For example, two zones unmet the design condition at the same 1 hour, should I account 2 unmet load hours or just account 1 unmet load hour? Thanks
Tristan Roberts replied Editor – LEEDuser, BuildingGreen, LLC Aug 03 2010
I believe it is based on the whole building. If one zone has one unmet hour, that counts as one hour for the whole building. If two zones have one unmet hour at the same time, it's still one hour for the building.
Mike Liu replied ATKINS Aug 04 2010
Thanks. Basically I am agree with your opinion.
However, compare the condition 1: one zone unmet design condition and the condition2: several zone unmet design condition at the same time, the comfort level is totally different, how can the building level unmet load hours reflect this?
Help on filling out LEED online template
I am filling the LEED online template for EA p2, and I face a problem. Now I can get the building unmet load hours from eQUEST BEPS report, but I don't know how to split the heating unmet load hours and cooling unmet hours. Pls help, thanks.
Christopher Schaffner replied Principal, The Green Engineer, LLP Aug 09 2010
I believe the SS-R report in the DOE2 output will break each zone down by heating and cooling unmet hours.
Proposed HVAC System vs. Baseline System
I am having a hard time determining what type of system I should be modeling for my building in both the Proposed AND the Baseline.
Here is the deal:
The building is a Fire Station that is about 8000 sf total. 5000 sf is served by a geothermal 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. system (heating fuel = electricity), while 3000 sf is served by heating only infrared heaters. (heating fuel = gas)
I know I need to model a cooling system in the proposed case for the space with the infrared heaters even though we don't have one. I also know it needs to be the same cooling system for the proposed case as the baseline case.
So, what is the baseline system? Do I model for electric heat throughout the building even though I have gas and electric in my proposed? (since electric is the main system?) If so, my baseline system is a packaged heat pump rooftop unit.
If I am correct in selecting the baseline system, how do I model that heating only space? I almost need to have (2) systems for one space, but I don't know how to assign a single room to two different systems. I am using Trace 700 for my energy model.
Anyone have a good idea for me?
Marcus Sheffer replied Energy & Environmental Consultant, 7group Aug 09 2010
The proposed is easy - model what you are building.
The baseline looks like it should be System 4. See the note under Table G3.1.1A - "Where attributes make a building eligible for more than one baseline system type, use the predominant condition to determine the system type for the entire building."
Model the heating only space in the baseline with System 4, no need for a second system.
While you do need to model a cooling system for the uncooled area you can simply set the temperatures in that space during the cooling season to ensure that the system does not operate. Make sure the temperature settings are the same in both models.
Major renovation: HVAC system in baseline
Hi!
When you determine your building envelope for a baseline, a major renovation in an existing building, it's clear that "the baseline building design shall reflect existing conditions prior any revisions that are part of the scope of work ...".
But, the HVAC system?
I’m right if I choose the Baseline HVAC system from table 'Baseline hvac system type' in app G? Even if I have another HVAC system before the renovation? For example prior renovation a CAV system with no reheat and after the renovation a VAVVariable Air Volume (VAV) is an HVAC conservation feature that supplies varying quantities of conditioned (heated or cooled) air to different parts of a building according to the heating and cooling needs of those specific areas. system with reheat. But the modeled baseline HVAC system should be for an example a system 7 - VAV with reheat in the baseline. But the building envelop shall reflect the conditions prior renovations. I’m right? or wrong...
/Lisa
Marcus Sheffer replied Energy & Environmental Consultant, 7group Aug 09 2010
See the ASHRAE 90.1 User's Manual for guidance related to situations where the HVAC system is not being replaced.
Since it sounds like you are modifying/replacing the HVAC system you should just follow Appendix G.
You are right.
Lisa Håkansson replied Aug 10 2010
Thank you!
Yes we are replacing a new HVAC system, we keep following App G.
Lisa
Thermal bridges in the model
I can’t find anywhere how detailed the thermal brides should be calculated in the model. In the simulation program I use you can use some default values or calculate the separately in every critical construction part. Do “LEED” have any claims about it? Is it ok to use the default values for your type of building/construction?
Thanks!
Lisa
Marcus Sheffer replied Energy & Environmental Consultant, 7group Aug 09 2010
Specific and scattered thermal bridges are very difficult to model in a commercial building. Broad and general thermal bridges, like steel studs, should be modeled.
Determining the envelope U values in 90.1 should follow Appendix A. Quite often LEED projects report the U value directly through the insulation and do not de-rate these envelope components properly.
Lisa Håkansson replied Aug 10 2010
ok, Thanks!
service energy
In the LEED Letter Template, there are detailed rows to fill out energy consumption for different types of equipment that all can be categorized as "service energy" Is it allowed to fill out just one row indicating 25% or total energy consumption as service energy and not filling out the detailed rows related to service energy?
Thanks
Marcus Sheffer replied Energy & Environmental Consultant, 7group Aug 09 2010
In general you should not lump all of the "service" (also called non-regulated or process energy) uses into a single category. The LEED reviewer will want to see that all building components have been modeled and that the energy use for them is reasonable.
Also it is not the intention of the 25% rule for you to simply get your model to 25%. Model the building, including all energy uses, as accurately as you can. If you are at 25% process or more do nothing. If you are under simply explain why. Usually the best way to do so is to provide a narrative or spreadhseet showing the process energy loads and the modeling assumption used for those loads.
Photovoltaics offset energy usage
If 100% of your building energy usage is offset by a large photovoltaic array which is outside of your LEED project boundary, does this qualify for all 19 points under EAc1?
Marcus Sheffer replied Energy & Environmental Consultant, 7group Aug 10 2010
I think the answer to your question would be a definitive yes except for one word - "outside". If it qualifies under EAc2 then the answer would be yes but there has been various interpretations of what would qualify. Landfill gas from outside the boundary has qualified; PV on a campus outside the boundary has qualified; biomass outside has not qualified based on my recollection.
New District Energy Guidelines
All- check out the new guidelines published on Aug 13th by USGBC on energy credits- EAp2/EAc1- Energy Efficiency, EAp1/EAc3- Commissioning, EAc5- M&V; EAc2- On site renewable energy, EAp1/ EAc4 Refrigerant Management and EAc6 Green Power. It applies to all BD&C, ID&C and Healthcare projects. http://www.usgbc.org/ShowFile.aspx?DocumentID=7671
Green roof insulation value
We are integrating an extensive green roof in the project (7 cm of substrate) with sedum vegetation. Is there a way we can take credit for the insulation value of the roof in the energy simulation. We will have to document this so I wonder if there are any studies that we can use as a reference to document the additional insulation value of the green roof.
Mara Baum replied Sustainability Coordinator, Anshen + Allen Architects Aug 30 2010
Energy modeling of green roofs is pretty complicated business. A lot of the conventional energy saving strategies for roofs -- e.g. insulation values -- don't adequately address the real energy benefits of the green roof. In other words, it's not really about insulation. Depending on who you ask, the R-value per inch of dry soil is not very much. Other relevant issues include things like heat flux direction, peak temperature delay, evapotranspiration rates and other factors that can lead to reduction in rooftop cooling unit demand and other energy efficiencies. My understanding is that savvy engineers can incorporate these issues into their energy models.
I've made this more complicated without actually answering your question; sorry. An engineer could probably tell you more specifics. Also, I've heard that there's a green roof module for Energy Plus.
Tristan Roberts replied Editor – LEEDuser, BuildingGreen, LLC Aug 31 2010
I thought I would share what I think is a fairly frank and accurate portrayal of this issue from the esteemd John Straube, P.Eng.:
"If dirt were good insulation, they would probably sell dirt in the insulation aisle at the Home Depot. But they don’t. They sell it in the gardening section, because the R-value of dirt really sucks."
Emmanuel Pauwels replied Aug 31 2010
Thanks Mara for the comments. Now I got to find that savvy engineer...
Scott Bowman replied Principal, KJWW Engineering Consultants Sep 01 2010
This has kind of been a problem for me for some time now. There are some fundimental concepts here that do not support some of the claims made about the energy performance of vegitative roofs. Dirt has insulation quality, but is not much. The overall R value is highly dependent on moisture content, and that is a huge variable.
Do not get me wrong, there are many, many great reasons for vegitative roofs, but I do not believe energy is one of them.
Here is what we did on a project to at least get an idea of the possible savings...run a model, then determine the total load in cooling (the primary claim made) that is attributed to the roof, ie as if there was no conduction or radiation losses from the roof. That is the theoretical maximum benefit a roof can have. You will see that the overall affect is very small on most buildings, because most buildings are not dominated by roof loses.
There seems to be significant research on green roofs, and I see all sorts of data on stormwater retention and treatment, but very little on energy.
If anyone has data to the contrary, I would be the first one to read it!
Supply air temperature in Baseline
Hi!
The design flow in baseline is determined with a temperature difference of 11 C (G 3.1.2.8). This design flow and the fan power (G 3.1.2.9) will give you the specific fan power (kW/m3/s) for the AHU1.Air-handling units (AHUs) are mechanical indirect heating, ventilating, or air-conditioning systems in which the air is treated or handled by equipment located outside the rooms served, usually at a central location, and conveyed to and from the rooms by a fan and a system of distributing ducts. (NEEB, 1997 edition) 2.A type of heating and/or cooling distribution equipment that channels warm or cool air to different parts of a building. This process of channeling the conditioned air often involves drawing air over heating or cooling coils and forcing it from a central location through ducts or air-handling units. Air-handling units are hidden in the walls or ceilings, where they use steam or hot water to heat, or chilled water to cool the air inside the ductwork. baseline. If I’m right...
Q1: The minimum flow setpoint shall be 2,15 l/s,m2 ( G 3.1.13). If the designed air flow is calculated to 1,3 l/s,m2 for a baseline zone due to (G 3.1.2.8). Shall we use 2,15 l/s,m2 or 1,3 l/s,m2 as a minimum flow setpoint for baseline?
Q2. The designed air flow is calculated with a temperature difference of 11 C, (G 3.1.2.8). But shall we have that temperature difference in our energy calculations as a setpoint for both summer or winter case. Or shall we have the proposed design setpoint in baseline eg. air temperature summer 16 C and air temperature winter 18 C in both baseline and proposed design.
Thanks!
Lisa
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