[Equest-users] Building Walls

[Maria Karpman]

Here is an abstract from eQUEST Help (Volume 1: Basics
<mk:@MSITStore:C:\Users\Maria\Documents\eQUEST%203-64%20Data\Help\DOE-2.chm:
:/Docs/volume1basics.htm>  > Envelope Components
<mk:@MSITStore:C:\Users\Maria\Documents\eQUEST%203-64%20Data\Help\DOE-2.chm:
:/Docs/envelopecomponents.htm> ) that supports Nick's theory: 

 

".The outside air film coefficient of an exterior wall or roof should not be
specified as a layer because it is calculated by the LOADS program as a
function of surface roughness and wind speed. "

 

Maria

 

From: equest-users-bounces at lists.onebuilding.org
[mailto:equest-users-bounces at lists.onebuilding.org] On Behalf Of Nick Caton
Sent: Wednesday, September 12, 2012 12:23 PM
To: Dahlstrom, Aaron; Peter Hillermann; equest-users at lists.onebuilding.org
Subject: Re: [Equest-users] Building Walls

 

I can add a probable bit of method to the madness for those concerned:

 

The reason exterior air film is not entered as a static property, nor
reported lumped in with the constructions' overall assembly U-values, is
because it's actually a variable property.  

 

The reference I have handy (Table 5-12, 2001 Fundamentals) lists multiple
resistance values for moving air (at various speeds) and still air (for
various surface orientations and directions of heat flow).  

 

I take it as implicit that eQuest/DOE2 models this variable contribution
from the exterior air film in consideration of the hourly windspeed data
available from the weather file, so presenting any single value could be
misleading.  I've had to make that clarification a few times for those
scrutinizing the construction reports without the eQuest detailed simulation
reports reference handy ;).

 

Hope that helps a bit!

 

~Nick

cid:489575314 at 22072009-0ABB

 

NICK CATON, P.E.

SENIOR ENGINEER

 

Smith & Boucher Engineers

25501 west valley parkway, suite 200

olathe, ks 66061

direct 913.344.0036

fax 913.345.0617

www.smithboucher.com 

 

From: equest-users-bounces at lists.onebuilding.org
[mailto:equest-users-bounces at lists.onebuilding.org] On Behalf Of Dahlstrom,
Aaron
Sent: Monday, September 10, 2012 4:20 PM
To: Peter Hillermann; equest-users at lists.onebuilding.org
Subject: Re: [Equest-users] Building Walls

 

Peter - 

 

We've noticed the identical issue. Another way of stating it - the sequence
of layers input for the baseline and the proposed should EXCLUDE
contributions from air film. eQUEST adds the interior air film as a separate
entry under the Layers tab.

 



 

 

ASHRAE's regulations for baseline constructions include the contribution of
the exterior air film at a specified windspeed. As far as I can tell, this
is how the u-value displayed on the LV-D report is calculated. (Report says
"includes exterior air film").

 

However, we have noticed that the value displayed inside eQUEST as
"calculated u-value" does not match the u-value from the LV-D. My theory is
that the item shown in eQUEST includes the interior air film but not the
exterior air film. (From Vol 2 dictionary, under CONSTRUCTION:U-VALUE - "For
exterior surfaces, equals the overall conductance of the surface including
the inside air film but excluding the outside air film.")

 



 

I'm just learning about this issue, so any wisdom from more experienced
folks would be welcome!

 

Aaron

 

Aaron Dahlstrom , PE, LEEDR AP

In Posse - A subsidiary of AKF| 1500 Walnut Street, Suite 1414,
Philadelphia, PA 19102 

d: 215-282-6753| m: | In Posse: 215-282-6800| AKF: 215-735-7290

e: ADahlstrom at in-posse.com | in posse web: www.in-posse.com
<http://www.in-posse.com/>  | akf web: www.akfgroup.com
<http://www.akfgroup.com/> 

 

 

 

From: equest-users-bounces at lists.onebuilding.org
[mailto:equest-users-bounces at lists.onebuilding.org] On Behalf Of Peter
Hillermann
Sent: Monday, September 10, 2012 2:02 PM
To: equest-users at lists.onebuilding.org
Subject: [Equest-users] Building Walls

 

To All:

 

A general piece of information I got from our engineer when we had done the
energy model for LEED and something to look out for. He let me know that in
the baseline for wall construction to make sure you add in the air film
(inside and out) otherwise LEED has an issue with your submission.

 

Our exact comment was this:

The Baseline Case roof and exterior wall U-values reported in Table 1.4.1A
(U-0.048 and U-0.065, respectively) are

inconsistent with the U-values reported in the LV-D report (U-0.054 and
U-0.063, respectively). Please ensure consistency

across construction drawings, software summaries, and the EAp2 Template.

 

Hope it helps.

 

I also don't know if anyone has this summarized, because I used the baseline
walls from this forum that someone had posted and that was the response.

 

PS: Thank you to this forum, we ended up getting LEED Certified.

 

Thanks,

 

PETER HILLERMANN

 

peterh at westallarchitects.com

 

westall

architects

3404 pierce drive

chamblee, georgia 30341

 

o 770.458.4113

c 678.898.2936

 

westallarchitects.com

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