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

[Carol Gardner]

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****
>
> ** **
>
> [image: Signature in jpg form]****
>
> ** **
>
> *From:* equest-users-bounces at lists.onebuilding.org [
> mailto:equest-users-bounces at lists.onebuilding.org<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****
>
>  ****
>
> [image: Signature in jpg form]****
>
>  ****
>
> *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
> >
> > The content of this email is the confidential property of Stantec and
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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
> >
> >
> > -----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
> 76 Chamberlain Avenue
> Ottawa, ON, K1S 1V9
> Phone: (613) 234-7178 ext. 113
> Fax: (613) 234-0740****
>
>
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>
> --
> Carol Gardner PE****
>
>
>
> ****
>
> --
> Carol Gardner PE****
>
>
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-- 
Carol Gardner PE
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