[Equest-users] LEED Review Comment on U-Value Input Method

James Hansen JHANSEN at ghtltd.com
Wed Jun 22 06:24:37 PDT 2011


I did this exact comparison a few days ago for a typical high rise condo project I worked on, and came up with a 2.1% increase in energy consumption going from layer to U-value.  In a condo, the envelope has more of an impact on total annual energy consumption than an office (assuming that's what you compared Bill).  So that makes sense.  Also, considering that the point increments for EAc1 are as small as 2%, this small detail in model construction actually has the potential to change your # of LEED points fairly easily.  In other words, someone needs to determine the answer to this question once and for all.  I like the apples to apples comparison... if you have a fairly complicated façade in your proposed building, and decide to calculate the U-value and use this simplified method in your model inputs, then you should be allowed to use the simplified U-value method in your baseline.  Likewise, if you use layer construction in your proposed, it should be layer in the baseline.  The only thing we should not be allowed to do is mix and match between baseline and proposed.

 

GHT Limited
James Hansen, PE, LEED AP

Senior Associate

1010 N. Glebe Rd, Suite 200

Arlington, VA  22201-4749

703-338-5754 (Cell)

703-243-1200 (Office)

703-276-1376 (Fax)

www.ghtltd.com <http://www.ghtltd.com/> 

 

 

From: equest-users-bounces at lists.onebuilding.org [mailto:equest-users-bounces at lists.onebuilding.org] On Behalf Of Bishop, Bill
Sent: Wednesday, June 22, 2011 9:17 AM
To: eQUEST Users List
Subject: Re: [Equest-users] LEED Review Comment on U-Value Input Method

 

I haven't seen where anyone in this discussion has actually compared LAYERS to U-VALUE results for an ASHRAE "lightweight" construction, so I did a quick experiment with one of my LEED project baselines. (It was quick and easy - a lot less time than I spend on a typical forum post.) Going from LAYERS to U-VALUE increased total building energy use in the baseline by 1%. This is not insignificant, especially considering that nearly half of the building energy is lighting, plug loads and DHW which are not affected by the envelope. YMMV. [Beating dead horse now.] Doesn't make sense to use LAYERS in the Proposed and U-VALUE in the Baseline from a modeling standpoint and energy comparison, regardless of the exact wording of ASHRAE, LEED or your favorite local compliance path.

 

Bill

 

 

 

From: equest-users-bounces at lists.onebuilding.org [mailto:equest-users-bounces at lists.onebuilding.org] On Behalf Of Mark Darrall
Sent: Wednesday, June 22, 2011 6:54 AM
To: Paul Riemer; eQUEST Users List
Subject: Re: [Equest-users] LEED Review Comment on U-Value Input Method

 

As I was following this discussion, I was wondering about the difference the mass of the material layers would make, which would then dictate the suitability of LAYERS over U-VALUE. We try to use massive materials to moderate the temperature swings, store heat to radiate back into spaces...

 

My recent modeling project also had a somewhat unique exterior wall that included a CMU outer layer that had a Styrofoam infill in the cores, then furring, rigid insulation and drywall on the interior side. I didn't want to just add U-values for that...

 

Hmm...now I want to look up Trombe walls in the archive...

 

MARK DARRALL, AIA, LEED AP BD+C, NCARB
Senior Project Manager

 

 

 

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From: equest-users-bounces at lists.onebuilding.org [mailto:equest-users-bounces at lists.onebuilding.org] On Behalf Of Paul Riemer
Sent: Tuesday, June 21, 2011 5:03 PM
To: eQUEST Users List
Subject: Re: [Equest-users] LEED Review Comment on U-Value Input Method

 

I take the following info with a grain of salt but others may find them more meaningful.

 

>From the eQUEST help files:

Volume 2: Dictionary > Envelope Components > CONSTRUCTION 

TYPE

Specifies the type of construction.

LAYERS Indicates that the LAYERS keyword will be used to specify a layered construction. The program will calculate response factors for this construction. The response factors will be used in the hourly simulation to calculate the dynamic, time-delayed heat flow through the construction. Recommended for all but lightweight (low heat capacity) constructions.

 

U-VALUE Indicates that the U-VALUE keyword will be used to specify the conductance of the construction. In this case, the heat flow through the construction will be considered to be instantaneous, i.e., without time delay. Recommended only for lightweight (low heat capacity) constructions.

 

 

And from a recent LEED review comment:

EDUCATIONAL NOTES FOR FUTURE PROJECTS (Optional): 

 

Section 1.4.1A of the table does not provide descriptions for any of the Baseline and Proposed Case envelope components. Please revise the table to include the descriptions (i.e. Roof as Insulation Entirely Above Deck, Walls as Steel-Framed, etc.) for all envelope components. 

 

Paul Riemer, PE, LEED AP 

DUNHAM

 

From: equest-users-bounces at lists.onebuilding.org [mailto:equest-users-bounces at lists.onebuilding.org] On Behalf Of Eric O'Neill
Sent: Tuesday, June 21, 2011 3:52 PM
To: Carol Gardner
Cc: eQUEST Users List
Subject: Re: [Equest-users] LEED Review Comment on U-Value Input Method

 

Well, perhaps I'm nitpicking, but I see two distinct statements here.

 

1.       "shall conform with the following common, lightweight assembly type"
AND

2.       "shall match the appropriate assembly maximum U-factors in Tables 5.5-1 through 5.5-8"

 

If a baseline model does not meet both requirements, it doesn't pass, right? 

 

A mass construction, to me, meets both requirements. Just because it has mass does not mean that it doesn't match the assembly U-factors. 

 

However, I feel that a U-value only wall meets #2, but doesn't meet #1. My original point was that U-value only constructions don't conform with lightweight assembly types because lightweight constructions, by definition, have some mass (or else they'd be no-weight, right?). ASHRAE has provided examples of "light constructions" in the Fundamentals book as steel constructions without brick or concrete, so that tells me that lightweight doesn't imply no mass.

 

But I'll confess that I'm only going on instinct and what I feel is the spirit of the code as Bruce described. It is not terribly explicit, so I understand your position and it could probably be argued both ways until the cows come home. I'd just hate to be on the wrong end of it when the final review came through...

 

Eric

 

From: Carol Gardner [mailto:cmg750 at gmail.com] 
Sent: Tuesday, June 21, 2011 2:46 PM
To: Eric O'Neill
Cc: Robby Oylear; Bishop, Bill; Bruce Easterbrook; eQUEST Users List
Subject: Re: [Equest-users] LEED Review Comment on U-Value Input Method

 

First of all, as a former energy code reviewer, 2 years for Oregon and about 5 for the City of Portland, it was my responsibility to interpret the intent of the code when the language or application was unclear. That explains why I respond to the word "shall" so strongly. 

When I read "shall conform with the following common, lightweight assembly type" which for walls is stated to be steel framed walls, and "shall match the appropriate assembly maximum U-factors in Tables 5.5-1 through 5.5-8", I assume I am being directed to use the Prescriptive assembly U-factor provided on the Building Energy Requirements table for my climate zone in Chapter 5.

I did a bit of research to see if there was information in the past versions of the standard and in the User's Manuals. What I found was that prior to the adoption of Appendix G, the requirement was to model with the Prescriptive assembly U-factors as well as to match the heat capacity in each case: proposed and design. This meant that if the proposed wall was steel framed then the baseline must be too and credit could not be taken for added mass or changes in framing.

After the adoption of Appendix G and the Energy Cost Budget Method in 2004 things changed a bit. At that point the direction in the User's Manual states that the baseline building is assumed to be steel framed no matter what the construction of the proposed building. If the proposed building uses added mass, or wood framing or beneficial constructions it is credited to the building. The baseline building shall comply with the applicable prescriptive requirements for steel-framed walls, i.e the Prescriptive assembly U-factor  for steel framed walls on Table 5 for your climate zone..

So, I do not see a mandate, or an implication even, to specify the baseline building walls using layers. Rather I see a clear instruction to use the Prescriptive Path U-value for the baseline and to take credit for any improvements in the proposed building walls. I don't think this is "gaming the system" at all. It is sad but true that many buildings being built today just meet the minimum prescriptive requirement. I have even seen some that didn't. If a building owner is willing to lay out the extra money for a better wall, why shouldn't he/she get credit for it?

Stepping off my soap box,

Carol

On Tue, Jun 21, 2011 at 8:55 AM, Eric O'Neill <ELO at michaelsenergy.com> wrote:

Robby, 

 

I see your point. However, I'm curious how many wall assembly types you can think of that meet the criteria they discuss in that section (and whether their different themal delay properties would impact the project):

 

·         Lightweight (I assume this means no brick exteriors)

·         Common

·         Steel Framed

·         R-13 + R-7.5ci (for instance, depending on climate zone)

 

Now, I'm not saying they couldn't be more explicit. You're absolutely right that they could be. However, I could fairly easily justify steel siding, 1.5 inches of polystyrene, steel framed wall with batt insulation and a gyp board finish. Maybe small changes like vinyl siding or an equivalent level of spray foam insulation would have marginally different time delay properties, but I'm guessing they would be negligible based on the information found in the chapter I previously cited.

 

Eric

 

From: Robby Oylear [mailto:robbyoylear at gmail.com] 

Sent: Tuesday, June 21, 2011 10:12 AM

To: Eric O'Neill; Bishop, Bill; Carol Gardner; Bruce Easterbrook; eQUEST Users List


Subject: Re: [Equest-users] LEED Review Comment on U-Value Input Method

 

While I agree that modeling the baseline with some level of light mass should be done to get more accurate results, it's difficult to understand why 90.1 would not specify a mass value to model. The definition of a baseline is a minimum value for comparison.  How can LEED reviewers judge whether or not you're taking the appropriate credit for thermal mass when the baseline building done by one modeler will have a different mass value than one done by another modeler?

 

Values that are vague and undefined (process loads or lighting plug loads in residential for example) are typically left the same between both models.  This allows for the factor to be accounted for, but provides no credit to the proposed model.  The same could be done for thermal mass, to account for it in both models, but not provide credit.  Without a defined baseline, I don't see how one can justify whether or not they've modeled the correct "lightweight" assembly mass value.

 

-Robby

On Mon, Jun 20, 2011 at 9:47 AM, Eric O'Neill <ELO at michaelsenergy.com> wrote:

I think some confusion stems from the definition of "lightweight". The fundamentals book discusses light and heavy constructions in the radiant time series, and defines a few examples in table 22, ch 30 (2005 handbook - NonRes Cooling and Heating Load Calcs, Radiant Time Series Method). Light constructions are steel sidings, 2 inches of insulation, an airspace, and gyp board. It also defines medium and heavy, with brick and heavyweight concrete, respectively. 

 

So when they say lightweight, I believe they're referring to something similar. I don't believe "lightweight" is intended to mean "no-weight" for the reasons Bruce described. It seems to me they're giving design teams the opportunity to take advantage of a heavy exterior construction if it reduces the peaks. They do ask that they conform with the lightweight assemblies, which, in my opinion, just a U-value does not.

 

Eric

 

From: equest-users-bounces at lists.onebuilding.org [mailto:equest-users-bounces at lists.onebuilding.org] On Behalf Of Bishop, Bill
Sent: Monday, June 20, 2011 11:01 AM
To: Carol Gardner; Bruce Easterbrook
Cc: eQUEST Users List


Subject: Re: [Equest-users] LEED Review Comment on U-Value Input Method

 

Carol,

As we noted earlier in this thread, we can't find an explicit requirement that layer-by-layer be used. It is strongly implied for at least the proposed in Appendix G, and it is good practice for several reasons as Bruce describes below. From the 90.1 User's Manual - "The general rule for the baseline building run is that all inputs must be identical to the proposed design run, except for those features that are allowed to differ." It seems logical to extend this general rule to input methods as well as inputs. Would you accept the modeling results if the proposed building was done in TRACE while the baseline was done in eQUEST?

Bilbo

 

 

From: Carol Gardner [mailto:cmg750 at gmail.com] 
Sent: Monday, June 20, 2011 11:30 AM
To: Bruce Easterbrook
Cc: Bishop, Bill; Pasha Korber-Gonzalez; eQUEST Users List
Subject: Re: [Equest-users] LEED Review Comment on U-Value Input Method

 

I guess we'll have to agree to disagree. 

 

Bilizebub: could you point out the section in LEED or Std 90 that says that walls must both be layer by layer. Thanks.

 

 

On Mon, Jun 20, 2011 at 7:01 AM, Bruce Easterbrook <bruce5 at bellnet.ca> wrote:

I think what is being forgotten is "intent", and the accuracy of your model.  So for intent the desire of the powers that be is that smart design be used to reduce the energy consumption of buildings.  You should not be manipulating the "system" to take credit for something which is not really a credit.  Your model should be as accurate as you can possibly make it with reasonable effort.  U-value construction is not accurate, all buildings have mass.  Mass serves to shave peaks.  When you have a building modelled with no mass as soon as the sun hits it you will have a cooling load.  With U-value construction the heat hitting the building is immediately loaded on to the cooling system at 100%.  This doesn't happen in reality and you will oversize your cooling system.  Therefore you have designed an inefficient system, you are costing your client money because they have to buy and operate a bigger cooling system than required.  Logic and good modelling dictate you account for mass.  The baseline is a "standard" building construction in use at this time and that is defined, "lightweight steel construction".  You don't get credit for the mass of this building.  However if you start adding mass strategically to further load shift your peaks you should be able to take credit for that.  Besides U-value construction is the old school, brute force technique when energy was cheap and we used spread sheets and calculators.  eQuest allows us to accurately predict the mass effect of a building and we have the computing power to run this program sitting on our desk.  A good modeller is required to use all the tools at their disposal to create the best base model they can so that the project people can assess different techniques to reduce the energy usage of the building and the economic costs of doing this.  I think it is pretty obvious the evaluator will reject a model not done layer by layer.  They can't easily check the base construction, the U-value method is not accurate and they are overloaded.  So it's file 13 and on to the next project.
Bruce Easterbrook P.Eng.
Abode Engineering 


On 20/06/2011 09:03 AM, Bishop, Bill wrote: 

Like Pasha mentioned, if you use layer-by-layer method in the proposed, you should use the same method in the baseline, unless you want to argue that "lightweight" requires the use of the U-value construction method. I don't see what advantage that serves, other than helping you avoid the time of creating baseline envelope constructions. While "lightweight" is not defined in 90.1, the baseline layer materials and thicknesses are described in A3, so if you use the layer-by-layer method for both baseline and proposed, and if there is a difference in the overall mass of each wall construction, the modeling output will reflect that difference. Both baseline and proposed constructions will have "mass", and if the proposed construction is optimized, there will be energy savings.

 

The eQUEST help menu item for "EXTERIOR-WALL  and ROOF" states that using LAYERS rather than U-VALUE can result in greater computational time, but gives more accurate results. Computational time is at the bottom of my eQUEST concerns. I have not compared modeling results of LAYERS vs. U-VALUE. Delayed construction appears to be required by Appendix G, is supposedly more accurate, and I don't see a good reason not to use it.

 

Billzebub

 

Error! Filename not specified.

 

From: equest-users-bounces at lists.onebuilding.org [mailto:equest-users-bounces at lists.onebuilding.org] On Behalf Of Pasha Korber-Gonzalez
Sent: Saturday, June 18, 2011 4:39 PM
To: eQUEST Users List
Subject: Re: [Equest-users] LEED Review Comment on U-Value Input Method

 

Following the other comments on this, I am confused and worried too that if they are requiring to simulate mass in the baseline, then how could we use Mass constructions as "passive" design strategies and take credit for this type of ECM?

 

Directly from what I was reading in the 2007 code: Table G3.1.5-Baseline Building Enevelope

Opaque Assemblies.  Opaque assemblies used for new building or additions shall conform with the following common, lightweight assembly types and shall match the appropriate assembly maximum U-factors in Tables 5.5-1 through 5.5-8:

 

Doesn't the reference to "lightweight" assemblies mean that you don't have to account for thermal lags (massing)?   This has always been my interpretation.  Therefore, when it comes to modeling the U-values for the assemblies with the U-value method versus the layer method would be acceptable for your baseline simulations.  Where there is no requirement to show any type of massing effects it shouldn't matter if you choose to use the U-value input method or the layer-by-layer method.

 

But--it is important for the simulator to understand that when using eQuest (I can't speak for other simulation tools); the input method has to be matched in both the baseline and proposed.  You can't choose U-value input for the baseline and layer-by-layer for the proposed, you have to use the "apples-to-apples" approach for both models.

 

It will be a big issue if GBCI mandates that we have to use only layer-by-layer inputs for compliance where Appendix G is clearly stating that there is no need to account for thermal lag in the baseline building as it states "lightweight" construction.  Any type of thermal lag characteristics in lightweight construction are negligible to the performance of such constructions as required by Appendix G baseline inputs.

 

pkg

 

 



 

On Fri, Jun 17, 2011 at 3:23 PM, Carol Gardner <cmg750 at gmail.com> wrote:

I'll bite. What extends it to the baseline? I still see that it just says to credit it to the proposed building. Wasn't this language created to guide people to the fact that even if mass was added to a steel framed building it still fell under the "steel framed" category and not the mass? 

 

On Fri, Jun 17, 2011 at 2:07 PM, Bishop, Bill <wbishop at pathfinder-ea.com> wrote:

Another piece of the puzzle. >From the 90.1 User's Manual, section on Baseline Building Opaque Assemblies (p.G14 in 2004 ed.):

"The baseline building is assumed to be steel framed no matter what the construction of the proposed building. If the proposed building has thermal mass in the exterior construction and this is a benefit in a particular climate, then the mass is credited in the building performance rating method."

 

So delayed construction is the de facto method for modeling the proposed envelope, and by extension, the baseline.

 

Bill

 

Error! Filename not specified.

 

From: equest-users-bounces at lists.onebuilding.org [mailto:equest-users-bounces at lists.onebuilding.org] On Behalf Of Carol Gardner
Sent: Friday, June 17, 2011 4:40 PM
To: Daniel Knapp
Cc: equest-users at lists.onebuilding.org


Subject: Re: [Equest-users] LEED Review Comment on U-Value Input Method

 

But the Simulation General Requirements are for the simulation model itself and it's capabilities, they do not address the simulation inputs.

I think this section of the code is what governs this issue:

Opaque Assemblies. Opaque assemblies used for new buildings or additions shall conform with the following common, lightweight assembly types and shall match the appropriate assembly maximum U-factors in Tables 5.5-1 through 5.5-8:

But I disagree with Guarav's interpretation for these reasons. The use of the word assemblies might "suggest" the need to model the whole structure but the use of "lightweight" in the sentence, and it's location after the word shall, is the key. Those U-values in Tables 5.5-1 through 5.5-8 are for lightweight construction. Lightweight construction is not delayed construction. The Standard 90 committee even gave us a variety of wall types to select from on those tables so that we would have an appropriate assembly maximum U-factor to use.

Anyway, that's my interpretation.

Carol

On Fri, Jun 17, 2011 at 9:24 AM, Daniel Knapp <danielk at arborus.ca> wrote:


FYI, Simulation General Requirements as laid out in 11.2 of the 90.1 User's Manual specifically call for the treatment of Thermal Mass Effects in the Minimum Modeling Capabilities.  (see 11.1.2.3 and as already mentioned G2.2.1.c) and notes that "A building's ability to absorb and hold heat varies with its *type of construction* and with its system and ventilation characteristics.  This affects the timing and magnitude of loads handled by the HVAC system.  Simulation programs must be able to model these effects".



On 2011-06-16, at 7:15 PM, Mehta, Gaurav wrote:

> Michael,
>
> Agreed, appendix G does not specifically states that one needs to model delayed construction. However, going by the semantics used in Appendix G, one can conclude that delayed construction should be used. Consider the following:
>
> Table G3.1-5 Building Envelope, under Baseline Building Performance, part (b) Opaque Assemblies: states that Opaque assemblies......shall confirm with the following common, lightweight assembly types and shall match the appropriate assembly U-factors.....
>
> **The use of the term 'assemblies' suggests the need to model the whole assembly rather than only the U-factor**
>
> To answer your other question, how do you know what comprises of the baseline opaque assembly, I'll suggest use Appendix A. For example, for steel framed walls, see section A3.3.1 General, you'll find the assembly layers that you can use to model the baseline above grade walls. Similarly, you can use respective sections for roof, floor, etc. to determine the baseline assembly layers.
>
> If I remember correctly, somebody in the past has been kind enough to post the baseline assemblies that can be copied to the inp file (or imported into the inp file). Search the archives.
>
> Furthermore, eQUEST has an extensive library of materials that one can use, which includes the thickens, specific heat and density of the material. You can create your own materials by using the ASHRAE Handbook of fundamentals, chapter 26 (2009).
>
>
> Thanks.
>
> Best regards,
>
> Gaurav
>
> Gaurav Mehta, LEED® AP BD+C
> Sustainable Building Analyst
> Stantec
> 1932 First Avenue Suite 307
> Seattle WA 98101
> Ph: (206) 770-7779
> Fx:  (206) 770-5941
> Gaurav.Mehta at stantec.com
> www.stantec.com <http://www.stantec.com/> 
>
> The content of this email is the confidential property of Stantec and should not be copied, modified, retransmitted, or used for any purpose except with Stantec's written authorization. If you are not the intended recipient, please delete all copies and notify us immediately.
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> -----Original Message-----
> From: equest-users-bounces at lists.onebuilding.org [mailto:equest-users-bounces at lists.onebuilding.org] On Behalf Of James Hansen
> Sent: Thursday, June 16, 2011 3:09 PM
> To: Bishop, Bill; Michael Mantai; equest-users at lists.onebuilding.org
> Subject: Re: [Equest-users] LEED Review Comment on U-Value Input Method
>
> Michael, I'd advise that you email the project coordinator (or whatever GBCI calls the "head" of a project review team).  Usually they will answer relatively quick and easy questions so that you don't have to risk improperly addressing a comment.
>
> Ask them where in Appendix G it specifically requires the time delayed method be used.
>
> GHT Limited
> James Hansen, PE, LEED AP
> Senior Associate
> 1010 N. Glebe Rd, Suite 200
> Arlington, VA  22201-4749
> 703-338-5754 (Cell)
> 703-243-1200 (Office)
> 703-276-1376 (Fax)
> www.ghtltd.com <http://www.ghtltd.com/> 
>
>
> -----Original Message-----
> From: equest-users-bounces at lists.onebuilding.org [mailto:equest-users-bounces at lists.onebuilding.org] On Behalf Of Bishop, Bill
> Sent: Thursday, June 16, 2011 4:22 PM
> To: Michael Mantai; equest-users at lists.onebuilding.org
> Subject: Re: [Equest-users] LEED Review Comment on U-Value Input Method
>
> Michael,
>
> My understanding has always been that delayed construction should be
> used, though I can't find exact wording in Appendix G that requires it
> other than G2.2.1(c). For other components/layers of steel-framed walls,
> look to A3.3.1, and to Table A3.3 for assembly U-Factors for different
> stud spacing. You should be pretty close to the required U-Factor if you
> use the correct materials and thicknesses from A3.3. Yes, you may need
> to tweak a layer or two to get the construction to match the U-Factor
> exactly. As described in other posts, once you create these
> constructions for the baseline, copy them for future models.
>
> Regards,
> Bill
>
> -----Original Message-----
> From: equest-users-bounces at lists.onebuilding.org
> [mailto:equest-users-bounces at lists.onebuilding.org] On Behalf Of Michael
> Mantai
> Sent: Thursday, June 16, 2011 4:00 PM
> To: equest-users at lists.onebuilding.org
> Subject: [Equest-users] LEED Review Comment on U-Value Input Method
>
> We received the following comment on recent LEED review:
>
> "The simulation input screenshots, provided in the EAc1 modeling
> narrative
> report, indicate that the exterior wall and roof constructions were
> modeled
> as QUICK surface type (U Value Input specification method), which does
> not
> account for the time delayed heat flow through the constructions as
> required
> by Section G2.2.1(c). Revise the Proposed and Baseline models so the
> exterior walls and roof surface types are modeled as DELAYED (Layer
> Input
> specification method) with the thermal mass effects of the constructions
> taken into consideration. In addition, provide a revised LV I report for
> each model reflecting the changes."
>
> Section G2.2.1(c) describes modeling software requirements, but I don't
> see
> anywhere else in Appendix G that specifies that thermal mass effects
> have to
> be included in the baseline model.
>
> Previous review comments on other projects have led me to believe that
> U-value input was the correct method to set up the baseline model.
>
> If I revise the model to input each layer, what layers do I input?
> 90.1-2007 Appendix G states to use steel-framed walls, and the Tables
> provide minimum R-value for insulation and overall assembly U-value.
> But it
> does not appear to provide such other items as stud spacing, sheathing,
> or
> even what material is on the outside of the building (for exterior
> walls).
> Has anyone else had this type of comment before or are you using the
> layer
> input method for baseline models?  It seems that if I need to specify
> layers, the resultant U-value should equal exactly the minimum U-value
> per
> the 90.1 tables.  That would lead me to believe that there might be
> different combinations of layers that result in the same U-values but
> result
> in different energy use in the baseline, and obviously I would want to
> have
> the highest energy use for LEED purposes.
>
>
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-
Daniel Knapp, PhD, LEED® AP O+M
danielk at arborus.ca

Arborus Consulting
Energy Strategies for the Built Environment
www.arborus.ca <http://www.arborus.ca/> 
76 Chamberlain Avenue
Ottawa, ON, K1S 1V9
Phone: (613) 234-7178 ext. 113
Fax: (613) 234-0740




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Carol Gardner PE


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-- 
Carol Gardner PE

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