[Equest-users] Error - Wall is too thick or too dense

[Keith Swartz]

Prasad,

I used Nick's technique when I encountered the same error a few years ago, except I didn't bother adjusting the density of the insulation. I was evaluating insulation thicknesses on an underground wall. If I remember right, the maximum thickness of a wall in eQUEST is 20 inches, and for an underground wall eQUEST uses 12 of those inches for soil, so I had 8 inches left to play with. Since I was comparing insulation thicknesses of 2" and 3" I made the concrete 5" thick in the model, even though the actual concrete thickness was more.

The results from that model were kind of interesting. The additional insulation was beneficial for rooms that were heated only, but not for rooms that were cooled. The relatively cool wall must help with cooling more than it hurts with heating. Adding insulation reduces that free cooling.

Keith Swartz, PE, BEMP, LEED AP
Senior Energy Engineer | Energy Center of Wisconsin | Madison.Chicago.Minneapolis
608.210.7123 | www.ecw.org<http://www.ecw.org/>

From: Nick Caton [mailto:ncaton at smithboucher.com]
Sent: Tuesday, July 29, 2014 9:09 AM
To: Prasad S Wani; equest-users at lists.onebuilding.org
Subject: Re: [Equest-users] Error - Wall is too thick or too dense

Hi Prasad,

Reducing your air gap would make the overall wall construction more dense... so if that eliminates the error message, then the error must be rooted in your wall construction exceeding some maximum thickness.  I have run into this on much thicker constructions before involving large amounts of concrete, but 1.2 ft seems within a range of constructions I've successfully modeled without such errors as well.

Are you leveraging custom (not library) wall materials and/or have you modified any of the library material density entries, specifically?  If so, I'd double check your inputs/units, but if that's not the issue, I would suggest reducing thickness of your concrete layer to a point that the "maximum construction thickness error" does not occur, and increasing its material density per unit depth (thickness) in turn to achieve the same net mass for that construction layer.

[cid:image001.jpg at 01CFAB46.6128FBD0]

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 [mailto:equest-users-bounces at lists.onebuilding.org] On Behalf Of Prasad S Wani
Sent: Tuesday, July 29, 2014 7:49 AM
To: equest-users at lists.onebuilding.org
Subject: [Equest-users] Error - Wall is too thick or too dense

Dear All,

I am modelling a multilayer wall consisting of materials - Cement Plaster, Medium weight concrete and Air.

The total wall thickness is ~ 1.2 ft. However, a simulation error is obtained - "Wall is too thick or too dense".

Error persisted even when total wall thickness was increased by increasing air gap thickness.

However, error did not occur when air gap thickness was reduced.

It appears that reducing air gap reduces density of the wall (density varies directly with air gap).

Kindly inform whether there is a method in eQUEST by which such simulation error (Wall is too thick or too dense) can be nullified.

Thanks in advance.

Regards
Prasad
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