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Inquiry regarding modeling vapor barriers (like Tyvex) and analyzing building energy performance

Anonymous

Inquiry regarding modeling vapor barriers (like Tyvex) and analyzing building energy performance

Anonymous
Not applicable

Hi All!  I have a rather simple question.  I am modeling a single family home with standard stick-frame construction.  I have the vapor/water barrier modeled as a 'membrane layer' (0 thickness) with 'air infiltration barrier' as the material.  When I run the energy analyses, I am not seeing a difference in building energy results when I wrap at inserts/ends versus no wrapping.  I would think that the detail of wrapping at inserts/ends would improve energy performance so I am beginning to think that I am not modeling this layer correctly.  Perhaps I am wrong and the energy data is acceptable.  I should note that I am uploading my Revit project in Green Building Studio to collect the energy performance results.  I appreciate any suggestions or insights!  Thank you in advance.  Helen 

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ToanDN
Consultant
Consultant

@Anonymous wrote:

Hi All!  I have a rather simple question.  I am modeling a single family home with standard stick-frame construction.  I have the vapor/water barrier modeled as a 'membrane layer' (0 thickness) with 'air infiltration barrier' as the material.  When I run the energy analyses, I am not seeing a difference in building energy results when I wrap at inserts/ends versus no wrapping.  I would think that the detail of wrapping at inserts/ends would improve energy performance so I am beginning to think that I am not modeling this layer correctly.  Perhaps I am wrong and the energy data is acceptable.  I should note that I am uploading my Revit project in Green Building Studio to collect the energy performance results.  I appreciate any suggestions or insights!  Thank you in advance.  Helen 


I believe component layer wrapping does not affect energy calculations, only floor plan view presentation.  

barthbradley
Consultant
Consultant
Accepted solution

@Anonymous wrote:

 When I run the energy analyses, I am not seeing a difference in building energy results when I wrap at inserts/ends versus no wrapping.  


 

Curious question. Why would expect the results to be affected by wall wrapping?  

Anonymous
Not applicable

Hey thanks @Anonymousbradley for setting that inquiry clear and checking that for me.  I expected a tighter building envelope would prevent heat/cold from escaping from the home, therefore reducing any unnecessary energy loss.  I am modeling affordable housing for my graduate research and the contractors have taken extra time to seal, tape and otherwise wrap any openings/corners/inserts etc in the buildings.  Thought it might reflect in the modeling.  Appreciate your help!   

RDAOU
Mentor
Mentor

@Anonymous 

 

Although Wall wraps (ends/inserts) is a 3D component, the Energy Analysis tool uses only the Analytical Surface of the wall which does not include the lateral and the top/bottom faces  (ie: wrapped ends/inserts) 

 

  • Unless the model has major modeling issues and/or leaks, the cold bridge / water tightness of the model can be optimized/accounted for by adjusting the Analytical Surface resolution and Space resolution 

Should you run the simulation on the same project (once with wrapped walls and once without) and compare results on insight, would would clearly notice that the results are the same

 

 

 

 

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Anonymous
Not applicable
Hi @RDAOU, thank you! Yes, there is no difference. @Anonymous pointed that out and I have since moved on. I appreciate your follow up. Seriously though, do you all get paid to respond to these questions? It is definitely a life saver for me. Thank you.
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barthbradley
Consultant
Consultant

@Anonymous wrote:
Seriously though, do you all get paid to respond to these questions? 

 

Nope. We don't even get a Christmas card from them. This is a Users Forum.  In other words, we're "Used" by Autodesk.  he, he.     

 

 

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