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Net wall area in OpenStudio and/or EnergyPlus

asked 2015-10-03 21:39:01 -0500

Ery Djunaedy's avatar

updated 2020-01-27 18:48:09 -0500

I just realized that the envelope summary in EnergyPlus does not include the nett area of the walls. Only gross area is reported, i.e. the wall area without windows. Anybody knows where the nett area of the walls is reported? Is there a user-script for this in OpenStudio? Thanks.

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answered 2015-10-04 17:14:41 -0500

I think you can find it in the html reports in the "input verification" part it which is one of the first reports. I know it shows both gross wall area and window area so you could calculate it from that.

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Input verification in HTML only list the overall surface area per zone, gross wall vs window. I did not explain that the reason for this question is to use the EPlus summary result as the basis of OTTV calculation. Simply a table with list of surfaces (and sub-surfaces), orientation, nett area, U-value, SHGC (if applicable).

Ery Djunaedy's avatar Ery Djunaedy  ( 2015-10-05 06:45:50 -0500 )edit

Envelope Summary lists all exterior opaque and fenestration surfaces, but just as cross vs. net area. But the fenestration surfaces do have a column for parent surface, which would add in getting a net area calculation.

David Goldwasser's avatar David Goldwasser  ( 2015-10-05 09:40:45 -0500 )edit

David: yes, the HTML table does have the parent surface information. The problem is that we have to do it manually, i.e. for every window we need to identify the opaque surface, and then subtract the gross area. This is very tedious job. I cannot make a query for the HTML tables like I can in SQL.

Ery Djunaedy's avatar Ery Djunaedy  ( 2015-10-05 17:59:04 -0500 )edit

I am not sure if this helps but you can open the html file as an excel file, then you can set up the appropriate formulas and it is all done automatically.

Annie Marston's avatar Annie Marston  ( 2015-10-06 08:27:28 -0500 )edit

answered 2015-10-04 19:09:17 -0500

updated 2015-10-04 19:14:14 -0500

The Envelope Table of the standard results report in OpenStudio 1.9 gives the total area by exterior construction. This uses net vs. gross wall area for the calculation. It doesn't list every surface, but does show a surface count. If you need to see each surface use @Annie Marston's suggestion. If you wanted a detailed report on each surface in OpenStudio you could write a measure for that using the surface.netArea method.

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Wow, v1.9 .. I am teaching v1.8 using v1.7 installed in my computer. I guess I need to skip v1.8. And from the sound of it, it does not give what I want. Write a measure?!! This is my one biggest grievances against OpenStudio: the developers are very easy to suggest "write your own measure" like every other Joe down the road can type in Ruby. May be it is easy. But back in the day when "Add Output Variable" was just released, I tried to come up with "Add Meter". I thought it was going to be easy, but I managed to mangle the code.

Ery Djunaedy's avatar Ery Djunaedy  ( 2015-10-05 06:57:59 -0500 )edit

With OpenStudio 1.7.5 or later you can download the new results measure from BCL. The only difference with 1.9.0 is that it is pre-installed.

David Goldwasser's avatar David Goldwasser  ( 2015-10-05 09:42:47 -0500 )edit

answered 2015-10-05 07:25:18 -0500

Ery Djunaedy's avatar

It turned out that such table exists: in the SQL file. If you ask for a SQL report in EPlus (OpenStudio default), you will have SQL output. For whatever reason, the information I need is reported here and only here. And the best part is: it is not reported through ResultsViewer in OpenStudio.

To access the data, we need to use sqlite3, and the following SQL code will extract the right information:

drop view if exists SurfaceList;
CREATE VIEW IF NOT EXISTS SurfaceList AS SELECT Surfaces.*, Constructions.Name, Constructions.Uvalue FROM Surfaces INNER JOIN Constructions ON ( Constructions.ConstructionIndex = Surfaces.ConstructionIndex );
select * From SurfaceList;
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Is the tabular data should appear in the html file that comes out of EnergyPlus? The ResultsViewer application is for time series data out of the SQL file. For example if you reported hourly surface temperatures.

David Goldwasser's avatar David Goldwasser  ( 2015-10-05 09:45:08 -0500 )edit

Nope, it does not appear in the HTML summary report. I simply need to nett area or the walls, and it appears ONLY in this SQL table.

Ery Djunaedy's avatar Ery Djunaedy  ( 2015-10-05 18:02:36 -0500 )edit

Uurrghh, just when you thought you have a perfect solution! It turned out the the SQL table does not contain any SHGC information. Well, don't you love EnergyPlus. It throws around the results in bits and pieces here and there, that you need to assemble it yourself. May be this is a new result measure that OpenStudio can assemble.

Ery Djunaedy's avatar Ery Djunaedy  ( 2015-10-05 18:05:42 -0500 )edit

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Asked: 2015-10-03 21:39:01 -0500

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Last updated: Oct 05 '15