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

[Daniel Knapp]

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
> 
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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 (UValue Input specification method), which does
> not
> account for the timedelayed 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 LVI 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
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