[Equest-users] Modelling multilayer thick wall in eQUEST

Joe Huang yjhuang at whiteboxtechnologies.com
Thu May 15 11:28:44 PDT 2014


I don't think modeling the wall in another way will overcome the problem of  "Wall too 
thick", which indicates that DOE-2 is not able to derive a common ratio for the wall 
response factors after 100 time steps.  Please check your inputs to make sure that they're 
correct, and if so, then your wall construction is simply too massive or has  too much 
thermal discontinuity (?) across the layers, like concrete, insulation, concrete, 
insulation, etc.  for DOE-2 to handle.  You can model the wall as a pure resistance layer, 
but then it would have no thermal mass at all. Better to play around with the material 
properties, esp. the specific-heat, until the error goes away.


Joe Huang
White Box Technologies, Inc.
346 Rheem Blvd., Suite 108D
Moraga CA 94556
yjhuang at whiteboxtechnologies.com
http://weather.whiteboxtechnologies.com for simulation-ready weather data
(o) (925)388-0265
(c) (510)928-2683
"building energy simulations at your fingertips"

On 5/15/2014 10:53 AM, Chris Baker wrote:
> The easiest way to do this I think is in the DD wizard.  I have a big wall buildup also 
> - similar at least.
> First of all, remember if you have multiple kinds of exterior wall buildup you want to 
> draw separate shells for those areas.  For example, my current project has a part of the 
> building that is 2X6 exterior walls because it was added later on to a 8" cmu exterior 
> wall building.
> The shells just get drawn separately and you can specify the layup in the design 
> development wizard for each.
> The easiest way to do this, from what I've seen, is to first calculate the R-value of 
> the system and any EIFS layers you may have added.
> When you specify the exterior walls in the design development wizard show your 
> construction (CMU, 2x6, whatever it is)  and get as close as the wizard will let you to 
> the actual wall system.
> Then you need to make sure the R-rating of the final wall system in equest is the same 
> or similar to the R-rating of the wall you have at your building.  This will make sure 
> that the energy simulations are at least in the ballpark- based on overall construction 
> type and R-value.
> The same will work for Roof construction too.  Get as close as you can to the actual 
> roof layup in the wizard.  Then get close to what the R-value is for the foam.
> If the R-value of the system is more than what you can see in the insulation dropdown 
> menus, just add "additional insulation" and use that dropdown menu to add more.
> This is all done on Sheet 3 of the design development wizard.
> On sheet 4 is Your vertical wall construction type/ insulation and ceiling finish & 
> insulation so don't forget about that either.  Remember to show any insulation here that 
> you may have at ceiling level.
> Chris Baker
> CCI CAD Drafter
> Fort Wainwright, Alaska
> *From:*Equest-users [mailto:equest-users-bounces at lists.onebuilding.org] *On Behalf Of 
> *Prasad S Wani
> *Sent:* Sunday, May 11, 2014 10:22 PM
> *To:* equest-users at lists.onebuilding.org
> *Subject:* [Equest-users] Modelling multilayer thick wall in eQUEST
> Dear All,
> Can anybody please tell how to model multilayer wall (thick concrete+ air gap +thick 
> concrete + other materials ) in eQUEST ?
> I tried eQUEST option of layered construction, but error occurs "Wall is too thick".
> Is there any other method to model it ?
> Thank you in advance.
> Regards
> Prasad
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