[Equest-users] LEED Review Comment for Appendix A constructions

Maria Karpman maria.karpman at karpmanconsulting.net
Fri Apr 12 07:33:19 PDT 2013


Pasha,

 

Appendix A is referenced by 90.1 Section 5.5.3. It is not a new rule, and must be used for determining thermal properties of the proposed designs because many simulation tools including eQUEST cannot capture two-dimensional heat transfer (thermal bridging) of the specified constructions. Thermal bridging is an especially big factor for steel-frame constructions, where calculating overall U-value of wall assembly using weighted average properties of frame and cavity sections (parallel path method) can distort result by factor of 2+ compared to the tables provided in Appendix A (such as Table A3.3 or A9.2B). Note that Thermal bridging is accounted for in Tables 5.5-x which list the baseline constructions. For example, for climate zone 5 (Table 5.5-5) minimum insulation R-value of steel-framed walls in non-residential spaces is R-13 cavity plus R-7.5 continuous. If we do not account for thermal bridging, then the overall R-value of insulation in the cavity portion of the wall is R-20.5, and we’d expect that overall surface U-value (not accounting for gypsum board, siding, air, etc.) would be somewhere around 1/20.5=0.049 because cavity section is very wide compared to frame section. However the equivalent Assembly Maximum for the surface is U-0.064, which is what you‘d get if you use tables in Appendix A to calculate thermal properties of frame/cavity portion of the wall assembly instead of parallel path method. There is a nice discussion on that in 90.1 User Manual. 

 

Good luck with your project,

 

Maria

 

From: equest-users-bounces at lists.onebuilding.org [mailto:equest-users-bounces at lists.onebuilding.org] On Behalf Of PKConsulting
Sent: Friday, April 12, 2013 8:55 AM
To: Cam Fitzgerald
Cc: eQUEST Users List
Subject: Re: [Equest-users] LEED Review Comment for Appendix A constructions

 

Thanks Cam,   I couldn't find where it reads this in Table g3.1,   Could you give me a page reference please?   I need to provide my client with this reference info for their future projects.

 

Also can you explain why this hasn't been addressed on LEED projects in the past?   This is the first time I have received this comment on any of my LEED submissions.

 

Thanks,

Pasha

Sent from my iPhone


On Apr 12, 2013, at 5:45 AM, "Cam Fitzgerald" <cam at energyopportunities.com> wrote:

Good morning, Pasha,

 

Appendix G primarily provides very specific guidance for building the appropriate Baseline model to use as a benchmark to calculate the projected energy savings for your Proposed building as designed. Most of the guidance in Table G3.1 for the Proposed model indicates it must be modeled as designed. This is where appendix A comes in for the Proposed constructions. U-values  may only be calculated using the inverse of the sum of the R-values if each layer is continuous (e.g. uninterrupted by other materials such as steel studs or joists). Appendix A provides tables with the effective U-values for various common heterogeneous constructions. Depending on the construction, the overall U-value for the assembly can vary significantly from the U-value calculated by summing the U-value of the major components. The Appendix A assembly performance must be used for the Proposed constructions to accurately reflect performance of the building envelope. Hope this helps.

 

Have a great day!

 

Cam Fitzgerald

 

Energy Opportunities/a 7group company

 

 

 

From:  <mailto:equest-users-bounces at lists.onebuilding.org> equest-users-bounces at lists.onebuilding.org [ <mailto:equest-users-bounces at lists.onebuilding.org> mailto:equest-users-bounces at lists.onebuilding.org] On Behalf Of Pasha Korber-Gonzalez
Sent: Thursday, April 11, 2013 6:00 PM
To: eQUEST Users List
Subject: [Equest-users] LEED Review Comment for Appendix A constructions

 

Hi --  hopefully others have run into this before.    We have a review comment that suggests that we need to revise our Proposed Construction performance values by reference of Appendix A constructions from 90.1 standard.

 

This is a new comment which I have not experienced LEED Reviewers addressing on past projects, and it seems to be in line with the release of the new Table 1.4 that is so interactive and also requires reference to Appendix A tables for proposed construction performance values.

 

I have re-read Appendix G and cannot find any required reference to using Appendix A performance values for proposed construction except for Fenestration that is Not NFRC rated.     Where does it state the requirement to use Appendix A values for all of the proposed envelope construction values??   Why is GBCI implementing this now, and it was never a factor before?

 

I need some education on this one please, I couldn't find any specific references on my own.

 

Thanks!

 

Pasha

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