Question-and-Answer Resource for the Building Energy Modeling Community
Get s tarted with the Help page
Ask Your Question
4

Change U-Value of Construction during the simulation with EPLUS

asked 2015-12-10 11:59:40 -0600

updated 2017-06-02 18:24:38 -0600

What is the solution to change construction properties (in this case u-value) during the simulation in EnergyPlus? Is it possible to assign a schedule to construction properties?

PS: This question is originally posted here by Christian Kongsgaard.

edit retag flag offensive close merge delete

2 Answers

Sort by » oldest newest most voted
4

answered 2015-12-10 13:04:37 -0600

updated 2015-12-10 13:09:57 -0600

I have never done it but I think one solution would be to create as many constructions as you want your u-value to vary and write an EMS program that changes the construction assigned to a particular surfaces using the Construction State Actuator based on, for instance, a schedule.

EDIT: Here is more info from the EMS Application Guide

An actuator is available for controlling the construction assigned to a surface that can be useful for modeling dynamic technologies for thermal envelopes. These actuators are called “Surface” and have a control type “Construction State.” This actuator is used in conjunction with the input object called EnergyManagementSystem:ConstructionIndexVariable. Each Construction object defined in an input file has an index that points to where the data for that construction are stored in the program’s internal data structures. The EnergyManagementSystem:ConstructionIndexVariable input object is used to create and fill a global Erl variable with the value that points to the specific construction named in the object. The Erl variable is what you assign to the construction state actuator’s variable to override the construction assigned to a particular surface. When the actuator is set to Null, the surface reverts to the Construction originally referenced by the surface in the input file. Using the surface construction state actuator brings with it a high degree of risk when it comes to modeling thermal heat capacity and transient heat transfer in opaque surfaces. If this actuator is used inappropriately, for example to assign different constructions, to a single surface, that have radically different heat storage capacities, then the heat transfer modeling results may not be physically accurate. When a construction state is overridden using this actuator, the thermal history data that evolved while using the previous construction are reused for the new construction. When this actuator is used, the program attempts to detect if incompatible constructions are being assigned. In some cases it issues a warning and allows the assignments to proceed, in others it warns and doesn’t allow the assignment to proceed. If the original construction assigned to a surface has internal source/sink (defined using Construction:InternalSource) then any assignments to the surface must also be internal source constructions. If using the heat transfer algorithm called ConductionFiniteDifference, then the constructions must have the same number of finite difference nodes or the assignment is not allowed. The construction state actuator cannot be used in conjunction with the heat transfer algorithms called ConductionFiniteDifferenceSimplified or CombinedHeatAndMoistureFiniteElement

edit flag offensive delete link more

Comments

Thanks @Jeremy! I was hoping for an easier solution but if EMS is the only way then I will give it a try. Thanks again.

Mostapha Roudsari gravatar image Mostapha Roudsari  ( 2015-12-11 10:42:16 -0600 )edit
-1

answered 2015-12-12 15:49:34 -0600

Hossam Wefki gravatar image

You can at diva for grasshopper but for the same construction For example Red wall with different thickness

edit flag offensive delete link more

Comments

Hossam. I think you're answering a different question. This question is not about changing the construction u-value/thickness for the whole simulation. It's about changing the values during the simulation at each timestep.

Mostapha Roudsari gravatar image Mostapha Roudsari  ( 2015-12-13 09:31:01 -0600 )edit

ok sorry But i need to know what is the value of changing u value for each timestep?

Hossam Wefki gravatar image Hossam Wefki  ( 2015-12-14 00:49:30 -0600 )edit

hi, you managed to write a program to change the EMS uvalue during the simulation?

MartinaRomeo gravatar image MartinaRomeo  ( 2016-12-06 05:21:23 -0600 )edit

Your Answer

Please start posting anonymously - your entry will be published after you log in or create a new account.

Add Answer

 

Question Tools

2 followers

Stats

Asked: 2015-12-10 11:59:40 -0600

Seen: 453 times

Last updated: Dec 10 '15