[Equest-users] Window U Value

Mon Aug 1 08:06:52 PDT 2016

Hello Sefa,

This is a timely question - I needed this as a reminder for a couple active projects!

Anytime the SIM reports are unintuitive/confusing - be sure you're aware of the following resource: Help > Tutorials and Reference > Detailed Simulation Reports Summary

Here, there are a number of clarifying notes concerning report LV-D specifically.  To your case, if all frame widths are set to zero, then the difference between inputs and these outputs will be the OA film coefficient for a 7.5 mph (summer) windspeed:

See the table located here in the DOE-2 help files for further information/documentation: Volume 2: Dictionary > Envelope Components > GLASS-TYPE > GLASS-CONDUCTANCE (Table 11)

In summary, do not equate the GLASS-CONDUCTANCE input with the assembly U-value, when using simplified glass type inputs.  

If you want to effect U-0.9 for the entire assembly, enter 1.23 for glass conductance in simplified window properties inputs.  LV-D should then report 0.9 as the assembly U-value.

At one point - I performed a curve-fit to find the coefficients to interpolate the above-cited table and shared with the list - see the email thread and image copied below.  Until assembly U-value becomes an input option for Simplified glass type inputs (feature-request, developers!), you could also calculate/automate GLASS-CONDUCTANCE with the following expression, referencing a global parameter:

0.2535*#PA("ASSEMBLY-UVALUE")**3+0.101*#PA("ASSEMBLY-UVALUE")**2+1.0852*#PA("ASSEMBLY-UVALUE")-0.0117

~Nick

Nick Caton, P.E.

  Senior Energy Engineer
  Energy and Sustainability Services
  North America Operations
  Schneider Electric

D  913.564.6361 
M  785.410.3317 
E  nicholas.caton at schneider-electric.com <mailto:nicholas.caton at schneider-electric.com> 
F  913.564.6380

15200 Santa Fe Trail Drive
Suite 204
Lenexa, KS 66219
United States

-----Original Message-----
From: Equest-users [mailto:equest-users-bounces at lists.onebuilding.org] On Behalf Of Sefa Sahin via Equest-users
Sent: Monday, August 01, 2016 8:47 AM
To: equest-users at lists.onebuilding.org
Subject: [Equest-users] Window U Value

Dear All,

I am trying to model window with 0.9 U-value. When I use 0.9 U value on model, LV-D reports shows 0.709 U value (frame with = 0 ). What is the reason it ? Please find attached files.

Thanks for all replies,

Sefa Sahin

From: Nicholas Caton [mailto:ncaton at catonenergy.com] 
Sent: Tuesday, December 23, 2014 3:43 PM
To: Jones, Christopher; Omar ElRawy; equest
Subject: RE: [Equest-users] Exterior Air Film - glazing

Chris:

After backtracking to the old glossary... I've learned something today!  You are absolutely right, and thank you for pressing the point!

I had the mistaken impression the U-values prescribed by 90.1 were exclusive of air films, analogous to GLASS-CONDUCTANCE.  The LV-D reports, inclusive of the exterior air film (assuming a 7.5mph wind), actually ought match the prescribed gross assembly U-factor.  I'll be updating some of my personal resources!

For anyone else interested, here shared are coefficients for a curve matching the DOE2 reference for converting between the two:

Omar,  I'll leave it to you to decide how to proceed.  I have (successfully enough) addressed the exact same commentary multiple times by simply illustrating my inputs matched the prescribed values.  My heart was in the right place, but I (and perhaps my reviewers) did not realize the disconnect with the output reports was not simply a matter of an erroneous inclusion of air films.  I will be changing my ways moving forward, personally!

Kind regards, and happy holidays to everyone on the list!

~Nick

NICK CATON, P.E.
Owner

Caton Energy Consulting
  1150 N. 192nd St., #4-202

  Shoreline, WA 98133
  office:  785.410.3317

www.catonenergy.com

From: Jones, Christopher [mailto:cjones at halsall.com] 
Sent: Tuesday, December 23, 2014 5:33 AM
To: Nicholas Caton; Omar ElRawy; equest
Subject: RE: [Equest-users] Exterior Air Film - glazing

Nick,

Would you not agree that one should define the glazing Conductance in the eQuest input, not the glazing U-value?  That way the .sim file reported glazing U-value is closer to what is expected?  

Christopher Jones, P.Eng. 
Tel: 416.644.4226 * Toll Free: 1.888.425.7255 x 527

From: Nicholas Caton [mailto:ncaton at catonenergy.com] 
Sent: Monday, December 22, 2014 4:46 PM
To: Jones, Christopher; Omar ElRawy; equest
Subject: RE: [Equest-users] Exterior Air Film

The LV-D reports (and others touching on windows/constructions) do indeed include an exterior air film.  I don't know of a way to change that.

A quick screengrab of your (correct) inputs and a one-line explanation of that fact is probably your most expedient path forward for a LEED review response.

~Nick

NICK CATON, P.E.
Owner

Caton Energy Consulting
  1150 N. 192nd St., #4-202

  Shoreline, WA 98133
  office:  785.410.3317

www.catonenergy.com

From: Equest-users [mailto:equest-users-bounces at lists.onebuilding.org] On Behalf Of Jones, Christopher
Sent: Monday, December 22, 2014 8:23 AM
To: Omar ElRawy; equest
Subject: Re: [Equest-users] Exterior Air Film

For glazing, you have to enter the GLASS-CONDUCTANCE into eQuest, not the glazing U-value.  See page 65 in the DOE22Vol2-Dictionary reference manual available for download at doe2.com.

Christopher Jones, P.Eng. 
Tel: 416.644.4226 * Toll Free: 1.888.425.7255 x 527

From: Equest-users [mailto:equest-users-bounces at lists.onebuilding.org] On Behalf Of Omar ElRawy
Sent: Monday, December 22, 2014 7:28 AM
To: equest
Subject: [Equest-users] Exterior Air Film

Dear all,

            I have a problem reporting baseline case for LEED submission, where the exterior walls and windows U-values in Report LV-D appears less than the ASHRAE G 90.1 values that I did enter to the model, and this is (as I think) because eQuest adds the exterior air-film effect to the assembly during the run. 

My question is that; can I disable this eQuest calculation to see my input directly in LV-D report or not?

Thanks,

Omar ElRawy, LEED AP BD+C
LEED Project Manager
EA Sustainable Building Consultants
http://www.ea-buildingconsultants.com/ <http://www.ea-buildingconsultants.com/> 

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